The University of Reading

Veterinary Epidemiology and Economics Research Unit Department of Agriculture

An Epidemiological Survey of Vitamin E Deficiency in the UK Sheep Flock

Project LS3401

S. Roderick

March 2001

A report to the Department of Environment, Food and Rural Affairs (DEFRA)

Veterinary Epidemiology and Economics and Research Unit, Department of Agriculture, The University of Reading, RG6 6AT

Tel: 0118 9264888

Acknowledgement

I wish to thank Nick Taylor and Tony Wilsmore at VEERU for their assistance in survey design and data analysis and Steve Morris for his invaluable help with mapping the data. David Garwes (DEFRA), Leslie Stubbings (sheep consultant), Brian Merrell (ADAS Redesdale), Owen Davies (ADAS Pwllpeirian), and Chris Trower (veterinary practitioner) provided very useful comments during the questionnaire piloting stage. Leslie Stubbings also kindly offered constructive comments on the first draft of this report. In particular, I would like to thank John Thorley, Chris Lloyd and staff at the National Sheep Association for their support and for their hard work in ensuring that the questionnaires were posted to NSA members. I am extremely grateful to those NSA members and veterinary surgeons that took the time to complete and return questionnaires. This study was funded by DEFRA. The study was completed at the Veterinary Epidemiology and Economics Research Unit (VEERU). The author is now based at the Organic Studies Centre, Duchy College, Cornwall.

Executive Summary

• The overall objective of the study was to investigate the extent of the problem of vitamin E deficiency in the UK sheep flock and to identify some of the key determinants.

• A survey of 10,156 members of the National Sheep Association was conducted by means of

a pre-tested postal questionnaire, during August 2000. A “useful” response rate of 26.42% was achieved. This represents approximately 5% of the pre-FMD UK sheep population.

• To support data from the sheep farmer survey, 1,000 veterinary practices registered with the

Royal College of Veterinary Surgeons (RCVS) as having sheep farmer clients, were surveyed be means of a pre-tested postal questionnaire, during August 2000. Of 1000 posted questionnaires, a useful response rate of 24.9% was achieved.

• The sheep farmer survey covered farms with a total of at least 1,072,147 breeding ewes

(2,666 respondents who completed details of breeding ewe numbers). The average flock size was 402 breeding ewes. The majority of responding farms were lowland farms (54.73%). 21.5% were hill farms and 22.8% were upland farms.

• Four distinct indicators of a potential vitamin E deficiency were used in the survey to identify

the extent of the condition in sheep flocks. These were: − Observation of White Muscle Disease (WMD); − Farm selenium deficiency status, based on farmer knowledge; − Diagnosis of vitamin E deficiency by veterinarian or VI centre; and − Observation by farmers of “typical” signs of vitamin E deficiency.

• The proportion of farmers reporting WMD on farms known to be selenium deficient was 6.33 times greater than the proportion on farms reporting WMD and claiming not to be selenium deficient. 9.9% (257) of responding farmers had had a vitamin E deficiency confirmed in their flock.

• 54.9% of respondents observed at least one typical sign of vitamin E deficiency in at least

one age category of lamb. 25.5% of respondents observed at least two signs in at least one age category of lamb. The occurrence of the sudden death of lambs was the most commonly observed sign. The incidence appeared more frequently in lambs between 3 weeks and weaning. Deteriorating condition in lambs over 3 weeks and lethargy and stiffness in lambs to 3 weeks were also more frequently observed than other signs.

• Approximately 50% of all respondents administered some form of vitamin E/selenium

supplementation. Supplementation of lambs of more than one month was the most common strategy applied, with supplementation of ewes mid and late pregnancy being the most common approach to the supplementation of ewes. Some producers were supplementing more than one category of animal. The use of anthelmintics with added selenium was by far the most common method of supplementation, although supplemented feeds were also commonly used

• On average, 37.0% of those that indicated the presence of WMD in their flocks also

recognised typical signs of vitamin E deficiency. This was significantly higher than in those flocks where respondents claimed not to have WMD.

• Respondents that reported lambs suffering with WMD were estimated to be 2.4 times more

likely to recognise at least one typical sign of vitamin E deficiency than those with flocks

that apparently did not suffer WMD. These results clearly illustrate that the recognition of “typical” signs provides a good indicator of the risk of WMD.

• Farms were divided into four categories of risk, based upon whether they were selenium

deficient or not, whether the presence of WMD had been observed and whether vitamin E deficiency had been confirmed in the flock. 20.68% of flocks were considered as high risk, 17.18% as medium risk, 50.02% as low risk and 12.12% of unknown risk.

• Using the survey data describing whether or not farms were known to be in a selenium

deficient area, the sample area was divided into four categories, depending on the proportion of selenium deficient farms (Very High Proportion, High Proportion, Medium Proportion and Low Proportion). The differences between the proportions for each category were statistically significant. A map of the categories was produced.

• 76% of respondents either wintered some (19%) or all (56%) of their flocks. A significantly

higher proportion of respondents who housed ewes indicated that they had WMD in their flocks. There was also a large difference between those farms that house all and those that house only part of their flocks.

• The length of time ewes were housed pre-lambing appeared to influence the risk of detecting

signs typical of vitamin E deficiency, with ewes housed for more than 4 weeks being at a greater risk than ewes housed for less than 4 weeks.

• A definite trend of decreasing use of hay and increasing use of silage and straw was observed

with increasing period of housing pre-lambing. A direct comparison of the rate of WMD between flocks fed and not fed on straw indicated that those fed on straw were more likely to have WMD. The same trend was seen with those feeding silage to housed ewes. This effect was not seen with hay.

• Ewes outwintered on silage were shown to be statistically, at a significantly greater risk of

producing lambs that suffered WMD as compared to those not fed silage. No effect of feeding hay to out-wintered ewes was observed.

• Anecdotal evidence from veterinarians suggested a link between vitamin E deficiency and

fast-growing breeds of sheep. The survey was unable to provide evidence to support this hypothesis.

• No effect of month of lambing or stage of lambing season on vitamin E deficiency was

detected. • There was insufficient data to provide any evidence of an association between organic

farming methods and vitamin E deficiency. • The survey data provided evidence that flocks at risk of vitamin E deficiency were more

likely to suffer stillbirths and abortion. • An indication of an association between vitamin E deficiency and reduced resistance to

infection was provided by data indicating that lambs of all age categories that suffered diarrhoea were more likely to have WMD.

• Further studies are required to support and quantify the trends identified in this study,

particularly regarding the influence of feeding, housing and breeding on vitamin E

deficiency. It is recommended that these be completed on case-study farms, identified from the survey responses.

• Although using “typical” signs as a method of identifying vitamin E deficiency appeared to

match expected trends in this condition, more accurate diagnostic procedures are required to validate the observed trends.

• It is recommended that an economic analysis of the impact of vitamin E deficiency and

control should be implemented to assess the impact on flock efficiency and the potential cost-benefit of supplementation strategies.

• Decision support and risk assessments tools are required to enable effective targeting of

vitamin E supplementation. It is recommended that the risk categories identified in this study be further refined and adapted for this purpose.

TABLE OF CONTENTS

Page 1. OBJECTIVES AND BACKGROUND 11.1. Objective 11.2. Background 12. METHODOLOGY 32.1. Sheep farmer survey 32.2. Veterinary practitioner survey 32.3. Response rates 33. DESCRIPTION OF SURVEYED FARMS 44. INDICATORS OF VITAMIN E DEFICIENCY 54.1. White Muscle Disease 54.2. Selenium deficiency 64.3. The relationship between WMD and selenium deficiency 84.4. Selenium and vitamin E deficiency 84.5. Diagnosis of vitamin E deficiency by veterinarian or VI Centre 94.6. Vitamin E deficiency: control strategies 104.7. “Typical” signs of vitamin E deficiency 114.8. The recognition of “typical” signs of vitamin E deficiency 124.9. Within flock incidence of “typical” signs of vitamin E deficiency 134.10. Relationship between WMD, selenium deficiency, diagnosis of vitamin E deficiency

and the observation of “typical” signs 14

4.11. Combining key indicators to define deficiency risk 154.12. Relationship between risk and recognition of “typical” signs 165. ANALYSIS OF FACTORS INFLUENCING VITAMIN E DEFICIENCY 185.1. Geographical factors 185.2. Housing 205.3. Feeding 225.4. Breeds 265.5. Litter size 275.6. Month of lambing 275.7. Stage of lambing season 285.8. Climatic factors 285.9. Organic farming methods 285.10. Use of fertilisers 296. PRODUCTION LOSSES ASSOCIATED WITH VITAMIN E DEFICIENCY 296.1. Abortion 296.2. Stillbirths 306.3. Mortality rates 306.4. Incidence of diarrhoea in lambs 317. RECOMMENDATIONS 328. REFERENCES 34

APPENDIX

LIST OF TABLES Table Title Page 1. A regional breakdown of farm survey responses 3 2. Description of sheep farms covered by surveyed veterinary practices 4 3. Distribution of farm types covered by the surveyed veterinary practices (%) 4 4. Distribution of surveyed farms by farm type and flock size 4 5. Farms by Less Favoured Area status 5 6. Observation of White Muscle Disease in Lowland, Upland and Hill flocks (% of

survey responses) 5

7. Frequency of WMD by age category (% of flocks indicating WMD as a problem) 6 8. Distribution of selenium deficient farms between farm types (%) 6 9. The relationship between selenium deficiency and WMD (% of total survey

responses) 8

10. The relationship between selenium deficiency and WMD (estimates of relative risk) 8 11. Percentage of surveyed veterinary practice that observe vitamin E deficiency not

associated with selenium deficiency 9

12. Relationship between selenium deficient farms and confirmed vitamin E deficiency in sheep (%)

9

13. The prevalence of vitamin E deficiency in sheep flocks covered by surveyed veterinary practices (% of practices)

9

14. Vitamin E/selenium supplementation (% of flocks) 10 15. Timing of vitamin E/selenium supplementation practices (% of farms that

supplement) 10

16. Details of vitamin E/selenium supplementation products (% of farms that supplement)

10

17. “Typical” signs of vitamin E deficiency and other conditions which may also be associated with these signs

11

18. Frequency of observation of “typical” signs of vitamin E deficiency (% of respondents)

12

19. Distribution of the number of “typical” signs observed in a single flock (%) 13 20. Flock incidence of one or more “typical” signs of vitamin E deficiency

(% of all flocks) 13

21. Relationship between the recognition of “typical” signs of vitamin E Deficiency and WMD (% of farms recognising “typical” signs)

14

22. The relationship between WMD in lambs and the recognition of at least one “typical” sign of vitamin E deficiency (average of all lamb age groups)

14

23. Risk estimates describing the relationship between WMD in lambs and recognition of at least one “typical” sign of vitamin E deficiency (four age groups)

15

24. Categories of vitamin E deficiency indicators 15 25. Definition and magnitude of deficiency risk categories 16 26. Distribution of responses to recognition of at least one typical sign across risk

categories 16

27. Distribution of responses to recognition of at least two typical signs across risk categories

16

28. Relationship between areas with very high, high, medium and low proportion of farms with selenium deficiency and WMD

18

29. Relationship between WMD and selenium deficiency in the four categories of selenium deficient areas

20

30. Distribution of hill, upland and lowland farms between the vitamin E deficiency risk categories (% of respondents of each farm type)

20

31. Description of housing strategies in surveyed sheep flocks 20

LIST OF TABLES Table Title Page 32. Distribution of pre-lambing housing periods in surveyed sheep flocks 21 33. Distribution of periods of housing lambs in surveyed sheep flocks 21 34. Relationship between housing and WMD 21 35. Relationship between observation of WMD and post-lambing housing for flocks

housed for more than 4 weeks pre-lambing (% of flocks). 22

36. Feeds given to housed and outdoor flocks (% of flocks) 23 37. Feeding practices in ewes housed pre-lambing (% of flocks) 24 38. Relationship between creep feeding of lambs and the period of housing after

lambing. 24

39. Lamb flocks receiving a creep feed whilst grazing 24 40. Relationship between feeding of housed ewes with various forages and concentrate

feeds and WMD (% of flocks with WMD) 26

41. Influence of breed on the observation of “typical” signs of vitamin E deficiency 26 42. Distribution of lambing month on surveyed farms (%) 27 43. Responses to the question “Did you get as many lambs born this year as expected” 27 44. Survey respondents reasons for lower than expected number of lambs born 28 45. Incidence of abortion in surveyed flocks 29 46. Relationship between annual incidence of abortion and vitamin E risk (%) 30 47. Relationship between annual incidence of abortion and recognition of two or more

“typical” signs (%) 30

48. Relationship between WMD and the incidence of stillbirths (%) 30 49. Estimated lamb mortality rates (first 7 days) for Hill, Upland and Lowland (flocks of

more than 50 breeding ewes) 31

50. Distribution of surveyed flocks and age groups that regularly suffer diarrhoea 31 51. Relationship between diarrhoea in lambs and the presence of WMD 32 52. Relationship between the recognition of “typical” signs of deficiency and the

presence of diarrhoea (%) 32

LIST OF FIGURES Figure Title Page 1 Map of distribution of surveyed farms 7 2 Schematic representation of vitamin E deficiency risk groups 17 3 Map showing the distribution of areas with a very high, high, medium and low

proportion of farms with selenium deficiency 19

LIST OF APPENDICES

Appendix 1 The Producer Questionnaire

Appendix 2 The Veterinary Practitioner Questionnaire

Appendix 3 Typical clinical signs of vitamin E deficiency observed by veterinarians

1. OBJECTIVES AND BACKGROUND 1.1 Objective The overall objective of the study was to investigate the extent of the problem of vitamin E deficiency in the UK sheep flock and to identify some of the key determinants. 1.2 Background The extent of Vitamin E deficiency in the UK sheep flock is not well understood. A recent DEFRA (then MAFF) workshop held to discuss the vitamin E requirements of sheep identified the greater demands for higher performance as being a multi-factorial contributor to the changes in the vitamin E status of the UK sheep flock. If this were the case, this represents an important animal welfare and economic concern to producers, consumers and retailers. An epidemiological study to quantify the problem and to attempt to identify pre-disposing factors was a key recommendation of the workshop. The main function of vitamin E in the animal is as a biological antioxidant. Changing production conditions may be resulting in an increase in oxidative stress in animals, which in turn increases the potential for vitamin E deficiency. These conditions include: • Changes in feeding management, such as:

Higher levels of polyunsaturated fats in sheep diets requiring correspondingly increased levels of dietary vitamin E;

A change in diets from those with naturally high levels of vitamin E (e.g. grass) to diets with lower levels (e.g. straw); and

The processing and storage of feeds that may result in reduction of natural vitamin E levels;

• Breeds and breeding practices, such as: Genetic changes and breed improvements aimed at faster growth and leaner carcasses

may result in smaller fat depots available for vitamin E storage. The individual animal and flock health status, the levels of veterinary input and care and general levels of shepherding and management may also be contributory factors. Acute deficiency of vitamin E results in muscle degeneration (muscular dystrophy or white muscle disease), a condition manifested by difficulty in standing, trembling and staggering. In sheep, the condition is generally seen in young, growing lambs. There is also evidence that deficiency can result in loss of vigour in new born lambs, and a reduction in growth rate. There are also associations with reduced immunity and a role in the incidence of some key conditions, such as mastitis. There are important economic considerations beside potentially large production losses. The quality of meat, particularly the oxidative stability associated with keeping quality, is reduced under conditions of vitamin E deficiency. Increased levels of polyunsaturated fatty acids in diets require correspondingly increased levels of vitamin E to avoid a reduction in the shelf life of meat. Vitamin E and selenium have complementary, but independent roles in the protection of cells against the damaging effects of lipid peroxides and free radicals produced during normal metabolism. Tissues or cells which undergo rapid increases in oxidative metabolism, such as muscle (skeletal, cardiac or respiratory) and blood cells (e.g. erythrocytes, phagocytes and lymphocytes) are particularly susceptible to damage in the event of a deficiency in one or both of these antioxidants. The most commonly recognized condition of vitamin E/selenium deficiency is the myodegenerative syndrome. The condition is most commonly referred to as white muscle disease (WMD) because of the pale appearance of the body muscles and heart. WMD is most 1

prevalent in animals up to 6 months of age and signs can vary widely from lambs with mild stiffness and discomfort (often mistaken for joint ill) to those that lie down and are unwilling to move, or even collapse when driven. Sometimes breathing difficulties may be observed when the muscles controlling breathing are involved (Jones, 1993). Adverse weather conditions and stress may affect the occurrence and/or severity of WMD (Greig and Hunter, 1980). It is also claimed that deficiencies of vitamin E and/or selenium can impair productivity through their effects on growth and/or reproduction (Kott et al., 1983). In the latter case, the overall effect is often reflected in poorer lambing rates (Mudd and Mackie, 1973). Pregnant ewes, which are severely deficient in vitamin E and/or selenium, may produce stillborn or weakly lambs, which only survive for a few days before dying of acute heart failure (Hamliri et al., 1990). Vitamin E deficiency has been implicated with the death of embryos in early pregnancy, although reports are conflicting (Niekerk et al., 1996; Suttle et al., 1991; UK, North of Scotland College of Agriculture, 1981; Vipond, 1984). Vitamin E supplementation of ewes in late pregnancy was found to significantly increase lamb vigour and growth rates, but had no effect on lamb survival rate (Merrell, 1999). Vitamin E is synthesised by plants but not by animals. Grass normally contains adequate levels of vitamin E but lush spring grass may contain high levels of polyunsaturated fatty acids (PUFAs). When eaten by the animal, these PUFAs are converted into the toxic peroxides referred to earlier (Suttle et al., 1991). Forage crops, such as rape or kale are a good source of vitamin E, as is grass silage. Root crops are poor sources and many hay crops may also be low in vitamin E (Greig and Hunter, 1980). The maturity and storage of feed materials affect their vitamin E content. Cereals contain moderate levels of vitamin E but the use of propionic acid or caustic soda to preserve moist grain rapidly destroys the vitamin (Bradley et al., 1986; Watson et al., 1988). Recently, research has partly focused on increasing the shelf life of meat through increased oxidative stability by supplementing animals with vitamin E before slaughter (Guidera et al., 1997). Optimising the fatty acid composition of sheep meat by increasing the amount of unsaturated fatty acids will reduce the oxidative stability. The oxidative stability may be increased by supplementing animals with vitamin E. However, recent work reported by Chikunya et al. (1999) indicated problems when feeding a polyunsaturated fatty acid rich diet to lambs supplemented with vitamin E. Both vitamin E supplemented and unsupplemented groups showed evidence of white muscle disease post-mortem. Despite the apparent importance of vitamin E deficiency to the UK sheep industry, the vitamin E status of the national flock is not known. Over recent years, emphasis has been placed more on identification of areas deficient in selenium, and strategies to overcome sub-optimal selenium levels. Although vitamin E and selenium are closely associated, there is little data reflecting the geographical link between vitamin E deficiency and the areas of known selenium deficiency. There are no cheap, reliable vitamin E assays available and most of the information results from controlled vitamin E supplementation studies and observations of clinically affected animals under selenium sufficiency. The need to conduct an epidemiological study to quantify the problem, and to look for predisposing conditions, was one of the key recommendations of a DEFRA (then MAFF) workshop on this subject. Although recording and monitoring may allow a measure of the incidence of acute deficiency, the extent of sub-acute or chronic deficiency cannot be easily established. 2. METHODOLOGY Postal surveys of sheep farmers and veterinary practitioners were conducted. Data collected in the farmer survey were analysed with the objective of describing the epidemiology of vitamin E deficiency and identifying pre-disposing factors. Qualitative and quantitative data from the 2

veterinary practitioner survey were used to direct and support the analysis of the farmer survey, and as an aid to the assessment of the results obtained from the analysis. 2.1 Sheep farmer survey A survey of 10,156 members of the National Sheep Association (NSA) was conducted by means of a pre-tested postal questionnaire, during August 2000. 2.2 Veterinary practitioner survey A survey of 1,000 veterinary practices registered with the Royal College of Veterinary Surgeons (RCVS) as having sheep farmer clients, were surveyed be means of a pre-tested questionnaire during August 2000. 2.3 Response rates Farmer survey 2,752 responses were returned (a response rate of 27.10%). Of these, 2,686 were considered “useful” responses, in that they contained data suitable for analysis. This is a useful response rate of 26.45%. It was possible to examine this response rate on a regional basis (Table 1). The regions are divided into those supplied by the NSA to describe the sample surveyed. Further details of the population sampled were not available. Table 1 A regional breakdown of farm survey responses

Region County Sample surveyed

Percentage of all

farms (%)

“Useful” response rate (%)

Scotland All of Scotland 1,398 13.77 24.07 Northern Cumbria, Durham, Humberside,

Lancashire, Northumberland, North Yorks, West Yorks.

1,669 16.43 30.37

Wales and Borders

All of Wales, Gloucestershire, Herefordshire, Worcestershire, Shropshire, Warwickshire, West Midlands

2,962 29.17 25.01

Central Cheshire, Derbyshire, Leicestershire, Lincolnshire, Nottinghamshire, Staffordshire, South Yorkshire

804 7.92 26.10

Eastern Bedfordshire, Cambridgeshire, Essex, Hertfordshire, Norfolk, Northamptonshire, Suffolk

537 5.29 27.49

South East

Berkshire, Buckinghamshire, Hampshire, Kent, Isle of Wight, London, Oxford, West Sussex, East Sussex, Wiltshire

1,309 12.89 26.08

South West

Devon, Dorset, Somerset, Avon, Cornwall

1,477 14.54 30.37

Total 10,156 100.00 26.45 Northern Ireland*

All of Northern Ireland NA 57 farmers responded. No data on the original population surveyed

3

Veterinary practice survey Of 1,000 posted questionnaires, 249 useable responses were received. This is a useful response rate of 24.9%. A further 15 responses were received from veterinary practices that no longer have sheep farmer clients. The responses can be divided into categories describing the approximate percentage of farmer clients that keep sheep. Data on number of flocks covered by each practice were also collected (Table 2). Table 3 describes practices by type of sheep system covered by the practice (%). The majority of practices had at least some clients with lowland flocks (spring lambing and early lambing indoors). Table 2 Description of sheep farms covered by surveyed veterinary practices Percentage of farmer

clients that keep sheep

n % of practices Average number of flocks

Total number of flocks

<10% 74 29.8 11 766 10-25% 54 21.8 44 2313 25-50% 44 17.7 87 3578 50-75% 39 15.7 119 4171 >75% 37 14.9 194 6986

All practices 248 100.0 76 17,814 Table 3 Distribution of farm types covered by the surveyed veterinary practices (%) Frequency

Hill Upland Lowland spring

lambing

Lowland early

lambing indoor

Lowland early

lambing outdoor

Predominantly 13.3 11.6 40.6 8.8 5.6 Some 21.3 27.7 34.9 37.8 20.5 Few 6.0 6.0 10.0 32.5 21.3 None 59.4 54.6 14.5 20.9 52.6 Practices with (n) 101 113 213 197 118 Overall % 40.6 45.4 85.5 79.1 47.4 3. DESCRIPTION OF SURVEYED FARMS Surveyed farms were categorised as being hill, upland or lowland (Table 4) and by their Less Favoured Area (LFA) status (Table 5). The majority of farms surveyed were lowland farms (54.73%) Table 4 Distribution of surveyed farms by farm type and flock size Farm Type Number of flocks Total breeding ewes Average breeding

flock Lowland 1,459 395,468 271 Hill 574 409,546 713 Upland 607 261,218 430 No classification 26 (46)* 5,915 228 Overall 2,666 107,2147 402 NB: Farms classified as being of more than one type are classed here as hill if they also have upland and/or lowland areas, and as upland if they also have lowland areas. *Twenty farms provided no classification details and no data on breeding ewe numbers.

4

Table 5 Farms by Less Favoured Area status N % Less favoured area 1146 42.9 Part LFA 105 3.9 Non-LFA 1415 53.0 2666 4. INDICATORS OF VITAMIN E DEFICIENCY Four distinct indicators of a potential vitamin E deficiency were used in the survey to identify the extent of the condition in sheep flocks. These were: • Observation of White Muscle Disease (WMD) by the farmer; • Farm selenium deficiency status, based on farmer knowledge; • Diagnosis of vitamin E deficiency by veterinarian or VI centre; and • Observation by farmers of “typical” signs of vitamin E deficiency (from a pre-selected list of

signs). 4.1 White Muscle Disease White Muscle Disease in Sheep Four hundred and eighteen farmers indicated that they had observed cases of White Muscle Disease (WMD) (also referred to as Muscular Dystrophy or Stiff Lamb Disease). These are described in terms of farm type in Table 6. Producers indicating that WMD was a problem on their farm were asked to indicate the extent of the problem (not a problem; rarely a problem, not very often a problem, frequently a problem) amongst four age categories of lamb. The results from the 418 producers who had indicated WMD as a problem are shown in Table7. Table 6 Observation of White Muscle Disease in Lowland, Upland and Hill flocks

(% of survey responses) Lowland Upland Hill All farms

Yes 12.73 19.83 18.59 15.61 No 63.72 55.83 58.06 60.71

Don't know 15.72 17.04 17.27 16.37 No response 7.83 7.30 6.09 7.32

With regard to WMD, although the number of farms in the lowlands that recognise this as a problem was lower than the other two farm type categories, this difference is not as large as that observed for selenium deficiency (section 4.2). These data from this sub-section of the questionnaire are characterised by the low response rate to the question i.e those who indicated a problem did not generally complete details on the frequency of the problem. This factor, coupled with the data from those that did respond, may indicate that generally WMD was not seen as a significant problem, and when it did occur it was rare or not very often and occurred mainly in older lambs.

5

Table 7 Frequency of WMD by age category (% of flocks indicating WMD as a problem)

Lambs less than 1 week

Lambs 1 to 3 weeks

Lambs 3 weeks to weaning

Weaned lambs

Rarely 7.42 8.13 9.09 10.05 Not Very Often 4.31 9.57 11.00 11.00

Frequently 1.20 2.63 4.55 4.55 Total 12.92 20.33 24.64 25.60

White Muscle Disease in Cattle In response to a question referring to the presence of WMD in calves, 2,032 producers responded. Of these 9.8% had seen WMD in calves, 59.0% had not and a further 31% kept no cattle. Examining the data from farms that kept cattle, the percentage reporting WMD was 14.2%. 4.2 Selenium Deficiency Vitamin E deficiency is known to be associated with selenium deficiency. Thirty one percent of respondents indicated that their farms were in selenium deficient areas. The distribution of these farms is shown in Figure 1. A further 46.34% indicated that they did not know whether their farms were in selenium deficient areas. The distribution of the selenium deficient sample between hill, lowland and upland farms is described in Table 8. Table 8 Distribution of selenium deficient farms between farm types (%)

Hill Lowland Upland All farms Yes 42.25 21.68 43.37 31.17 No 17.55 26.65 17.20 22.49

Don't know 40.20 51.67 39.43 46.34 Whilst the situation in the hills and uplands were similar with respect to the percentage of these farms in selenium deficient areas (43.4% and 42.5% respectively), the rate in the lowlands (21.7%) was significantly lower. The percentage of “don’t know” responses was high in all three farm-type categories, and was particularly high amongst the responses from lowland producers.

6

Figure 1 Map of distribution of surveyed farms (selenium deficient farms marked as black dots)

7

4.3 The relationship between WMD and Selenium deficiency Although at least 66% of farms with a WMD problem occurred on farms with a known selenium deficiency, 51% of selenium deficient farms claimed that they did not have a WMD problem. The data in Table 9 suggest that there are farms that suffer WMD that is not associated with selenium deficiency (approximately 10% of selenium deficient cases) and that many farms in selenium deficient areas could be adopting preventive measures against WMD. Table 9 The relationship between selenium deficiency and WMD

(% of total survey responses) Do your lambs suffer from WMD? (%)

Selenium deficient?

Yes No Don't Know No response Total

Yes 10.24 14.59 3.91 2.42 4.34 No 1.15 16.57 1.75 1.19 29.82 Don't know 3.95 28.03 10.46 2.12 21.51 No response 0.22 1.53 0.19 2.05 44.32 Total 15.56 60.72 16.31 7.78 N = 2686 These data can be simplified to “Yes” and “No” responses to estimate relative risk of WMD associated with selenium deficiency (Table 10) Table 10 The relationship between selenium deficiency and WMD

(estimates of relative risk) Do your lambs suffer from WMD? Selenium deficiency? Yes (n) No (n) Total (n) Risk estimate %Yes (n) 275 392 667 41.2% No (n) 31 445 476 6.5% Total (n) 306 837 1143 26.8% From these data, the relative risk is 6.33 (95% CI of 4.45 to 9.00). So, the proportion of farmers reporting WMD on farms known to be selenium deficient is 6.33 times greater than the proportion on farms with WMD that are not deficient (χ2 = 277 with 1df; p<0.001). The attributable fraction estimate, or the percentage of WMD cases in selenium deficient areas ‘attributable’ to selenium deficiency, is 84.2% (95% CI of 77.5% to 88.9%). This assumes that all the cases of WMD on non-selenium deficient farms were the result of factors other than selenium, and that all of these farms were actually not selenium deficient. The population attributable fraction, or the percentage of WMD in the whole population of responding farms which is attributable to selenium deficiency, is 75.7% (95% CI are 69.7% to 79.9%). 4.4 Selenium and vitamin E deficiency Veterinary practitioners were asked whether a vitamin E deficiency syndrome not associated with selenium deficiency occurred in their practices. 15% indicated that there were flocks that fell into this category, with the majority of cases being associated with selenium. Based on the description of farm clients described in Table 3, Table 11 indicates the percentage of veterinary practices that observe vitamin E deficiency that is not associated with selenium deficiency.

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Table 11 Percentage of surveyed veterinary practice that observe vitamin E deficiency not associated with selenium deficiency

Number of clients % with non selenium vitamin E deficient cases

Hill flocks 101 7.92 Upland flocks 113 9.73 Lowland/spring lambing flocks 213 11.27 Lowland, early lambing flocks (indoor) 197 8.63 Lowland, early lambing flocks (outdoor) 118 4.24 4.5 Diagnosis of vitamin E deficiency by veterinarian or VI Centre The sheep farmers surveyed were asked if they had had cases of vitamin E deficiency diagnosed by a veterinarian or Veterinary Investigation (VI) Centre. Two hundred and fifty seven (257 or 9.9%) of 2,597 farms who responded to this question, had had a vitamin E deficiency confirmed. Examining these data along with data reflecting the selenium status of responding farms, perhaps the most interesting result was that 8.3% of flocks that had received confirmation of a vitamin E deficiency also claimed not to be in a selenium deficient area. A further 14.6% were unsure as to whether the farm was deficient (Table 12). The trend on lowland, hill and upland farms was 67.6%, 87.7% and 79.7% of confirmed vitamin E deficiency, respectively, occurring on farms with a recognised selenium deficiency Table 12 Relationship between selenium deficient farms and confirmed vitamin E

deficiency in sheep (%) Is your farm selenium deficient?

Vitamin E deficiency diagnosed

Vitamin E deficiency not

diagnosed

All responding farms

Yes 77.08 25.67 30.84 No 8.30 24.35 22.73 Don't know 14.62 49.98 46.42 N = 2516 The relative risk estimate for these data is 7.52 (95% CI is 5.70 to 9.94; χ2 = 286 with 1df; p<0.001), with an attributable fraction of 86.7% (95% CI of 82.4% to 89.9%). The population attributable fraction is 66.8% (95% CI is 63.5% to 69.3%).

The survey of veterinary practices provided data on the percentage of flocks within a practice that may be considered as deficient in vitamin E. These data indicate that generally, the condition is considered to occur in a small percentage of flocks covered by sheep practices. The number of practices which have a large number of afflicted flocks tend to occur in areas where sheep production predominates (Table 13). Table 13 The prevalence of vitamin E deficiency in sheep flocks covered by surveyed

veterinary practices (% of practices) Prevalence All practices Practices with > 75% sheep clients>50% flocks 3.21 8.11 26-50% flocks 9.24 16.22 5-25% flocks 16.87 24.32 <5% flocks 22.89 29.73 None 41.37 18.92 Don't know 6.43 2.7 N 249 37 9

4.6 Vitamin E deficiency: control strategies Of 2,503 producers responding to questions referring to control strategies, approximately 50% administered some form of vitamin E/selenium supplementation (Table 14). Table 14 Vitamin E/selenium supplementation (% of flocks) Do you ever give vitamin E/selenium supplementation to sheep?

%

Yes, to all sheep 29.01 Yes, to ewes only 8.51 Yes, to lambs only 12.70 No 49.78 An indication of the supplementation strategy, with regard to the type of animal and timing of the supplementation, is given in Table 15. These data show that supplementation of lambs of more than one month is the most common strategy, with supplementation mid and late pregnancy being the most common approach to the supplementation of ewes. It is clear that some producers are supplementing more than one category of animal. The use of anthelmintics with added selenium was by far the most common method of supplementation (Table 16). 35% of producers indicated that they used other methods of supplementation, including selenium bullets, land application, various trace element drenches and injections and supplemented concentrate feeds and feed blocks. Table 15 Timing of vitamin E/selenium supplementation practices (% of farms that

supplement) Timing of supplementation % Ewes pre-tupping/early pregnancy 15.59 Ewes mid pregnancy 15.35 Ewes before lambing 36.83 Lambs at birth 6.44 Lambs in first month 15.59 Lambs more than 1month 50.59 N 1257 Table 16 Details of vitamin E/selenium supplementation products (% of farms that

supplement) Product % Anthelmintic with added selenium 70.48 Other oral/injectable forms of selenium and vitamin E 34.42 N 1257 Seventy nine percent of producers who indicated that they had observed lambs with WMD used a vitamin E/selenium supplementation. Forty four percent of those who did not see WMD used a supplement, whilst 46% of those not knowing if they had WMD used a supplement. These data perhaps reflect the widespread use of supplemented anthelmintics, even outside areas with a selenium deficiency problem. All of the commercial products available are also supplemented with cobalt. The survey of veterinary practitioners revealed that 43.37% of practices prescribe prophylaxis for vitamin E/selenium deficiency. This increases to 55% when practices that have more than

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10% of sheep farmer clients were analysed. Of the practices that have more than 75% of sheep farmer clients, 65% of these regularly prescribe prophylactic measures. Of practices that do prescribe preventive measures, 59% place equal importance on vitamin E and selenium, whilst 24% see selenium as more important and 11% view vitamin E as more important. Sixty two percent concentrated prophylactic efforts on both ewes and lambs, whilst 27% focus specifically on prevention in lambs and 10% specifically on ewes. With regard to the timing of preventive measures, most veterinarians that treated ewes tended to do this during mid and late pregnancy. There was an even spread between lambs of various ages with regard to the timing of treating lambs, although the trend was for more treatment of young lambs. 4.7 “Typical” signs of vitamin E deficiency In both farmer and veterinarian surveys, data were collected on “typical” signs associated with vitamin E deficiency in sheep. In the farmer survey, these data referred to the occurrence of “typical” signs. The survey of veterinary practices requested respondents to record typical clinical signs observed in the practice. Farmer survey The “typical” signs reported by Stubbings (1999) were adopted and adapted for use in the questionnaire. In addition, the occurrence of sudden death was included following recommendations from key informant consultation. For four age groups of lamb, respondents were asked to tick a box alongside each sign if these had been observed in their flocks over the last five years. The “typical signs” included are shown in Table 17, along with a list of other conditions which may also be associated with these signs. Table 17 “Typical” signs of vitamin E deficiency and other conditions which may

also be associated with these signs “Typical” signs of vitamin E deficiency Other conditions potentially associated with

these signs • Deteriorating condition/decline in growth

rate

• Reduced appetite • Lethargic, stiff and reluctant to move

Navel/joint ill, watery mouth, hypothermia/starvation

• Grey, dull dirty coats Border disease (with tremors) • Droopy ears, hollow sides • Rag-doll-like and wobbly Swayback. Daft lamb disease • Sudden death Depends on frequency and detail of

observation The age categories covered were: Lambs less than 1 week old; Lambs from 1 to 3 weeks old; Lambs 3 weeks to weaning; Weaned lambs.

Veterinarian survey The surveyed veterinarians used similar descriptions to describe the signs of vitamin E deficiency. A full list of the comments received are presented in Appendix 1. An interesting example is presented as Case Study 1.

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Case Study 1 Veterinary practice in Midlands area with approximately 35 sheep-keeping clients, predominantly lowland, spring lambing flock with some early lambing, fully housed flocks. 5-25% of flocks may be deficient. Majority associated with selenium deficiency. Some lowland spring lambing flocks have been observed as being vitamin E deficient but not selenium deficient. Vitamin E deficiency seen following aftermath grazing. Both selenium and vitamin E prophylactic treatment normally offered to lambs at 1 to 4 weeks. “In a recent case - 25% of lambs 8-12 weeks of age developed mild lameness/stiffness in left fore (in 100% of those affected it was left fore)- this progressed in a number to increased weakness/collapse and sternal recumbency. Recovery was seen within 48 hours of vitesel injection. Why always left fore?” 4.8 The recognition of “typical” signs of vitamin E deficiency 1,475 (54.9%) of respondents observed at least one sign in at least one age category of lamb. Six hundred and eighty seven (25.5%) respondents observed at least two signs in any one category of lamb. One hundred and seventy four (6.5%) respondents observed at least one of the signs in all categories of lamb. The results in Table18 show clearly that the occurrence of the sudden death of lambs was the most commonly observed sign. However, it was also pointed out by respondents in both surveys that sudden death may be associated with many conditions, and that the frequency and detail of observation influences whether or not a death is observed as sudden. There were also clear differences between age groups in the percentage of flocks showing these signs. The incidence appeared more frequently in lambs between 3 weeks and weaning. Deteriorating condition in lambs over 3 weeks and lethargy and stiffness in lambs to 3 weeks were also more frequently observed than other signs. Table 18 Frequency of observation of “typical” signs of vitamin E deficiency

(% of respondents) Age category of lamb

Less than 1 week old

From 1 to 3 weeks

3 weeks to weaning

Weaned lambs

Deteriorating condition/decline in growth rate

3.23 4.97 14.99 11.39

Reduced appetite 3.00 2.11 2.93 2.67 Lethargic, stiff and reluctant to move 4.58 8.09 5.19 3.12 Grey, dull dirty coat 0.45 1.00 5.34 3.93 Droopy ears, hollow sides 3.15 2.30 5.38 3.67 Rag-doll-like and wobbly 4.16 2.34 3.38 1.37 Sudden Death 11.29 10.57 24.11 15.80 Flocks were categorised according to the number of “typical” signs observed for each of the four categories of lamb (Table 19)

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Table 19 Distribution of the number of “typical” signs observed in a single flock (%) Age category of lamb Number of signs observed Less than 1

week old From 1 to 3

weeks 3 weeks to weaning

Weaned lambs

No “typical” signs 80.82 79.15 64.65 73.96 One only 13.06 14.58 20.59 17.03 Two 3.89 4.19 8.57 5.53 Three 1.19 0.96 3.49 1.78 Four 0.41 0.63 1.45 0.89 Five 0.33 0.15 0.63 0.30 Six 0.07 0.07 0.22 0.15 Seven 0.22 0.26 0.41 0.37 One or more sign observed 19.18 20.85 35.35 26.04 Two or more signs observed

6.14 6.29 14.85 9.05

4.9 Within flock incidence of “typical” signs of vitamin E deficiency The approximate incidence of these signs within a flock was investigated by asking respondents who had observed these signs to indicate the approximate percentage of lambs that were afflicted. Again these data were categorised by age. The categories used to assess incidence were: None; Just a few lambs (less than 10%); More than a few but less than half (10-50%); More than half of lambs (50-80%); Almost all of the lambs (more than 80%)

The results (Table 20) show that when they occurred, observation of these signs tended to occur at levels of less than 10% of the flock. Table 20 Flock incidence of one or more “typical” signs of vitamin E deficiency

(% of all flocks) less than 10% 10-50% 50-80% More than

80% 0-1 weeks 18.62 0.63 0 0 1-3 weeks 20.29 0.60 0 0 3 weeks to wean 33.10 1.90 0.45 0 Weaned 23.60 1.49 0.52 0.45 4.10 Relationship between WMD, selenium deficiency, diagnosis of vitamin E deficiency and the observation of “typical” signs A comparison of the percentage of respondents that indicated the presence of at least one of the typical vitamin E deficiency signs was made between those that recognise WMD in their flocks and those that did not (Table 21). These data clearly demonstrate that a higher percentage of those with lambs that suffered WMD also recognised some of the typical vitamin E deficiency signs.

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Table 21 Relationship between the recognition of “typical” signs of vitamin E deficiency and WMD (% of farms recognising “typical” signs)

Do your lambs suffer with WMD? Age category of lamb Yes no don't know did not respond0-1 weeks 25.36 16.31 28.31 10.05 1-3 weeks 35.89 14.96 31.96 13.40 3 weeks to wean 52.15 29.12 49.77 20.10 Weaned 34.69 21.89 38.58 14.83 Average 37.02 20.57 37.16 14.59 On average, 37.0% of those that indicated “yes” to the presence of WMD also recognised typical signs. This value was 20.6% in those that responded “no”. It is interesting to note that a similar result to the “yes” group was achieved in the “don’t know” group. This may suggest that either the proportion of farms with WMD is higher than that indicated by the data, or that similar disease conditions are occurring in the “don’t know” group. Lambs 3 weeks to weaning appeared to be the most commonly affected by these signs. In Table 22 the risk estimates for all age groups are given only for farmers who replied “yes” and “no” to WMD. Table 22 The relationship between WMD in lambs and the recognition of at least one

“typical” sign of vitamin E deficiency (average of all lamb age groups) Do you see one or more “typical” signs?

Do you see WMD in lambs? Yes No Total % of yes responses

Yes (n) 321 97 418 76.8 No (n) 757 874 1631 46.4 Total (n) 1078 971 2049 52.6 Relative risk 1.65 Attributable risk 39.6% Population attributable risk 11.8% Chi2 (1df) 123 (p<0.001) A similar trend was seen for all age groups of calves. The risk estimates are given in Table 23. When examining the risk parameters, the age category with the largest relative risk value is lambs aged 1 to 3 weeks. In this case, respondents with lambs that suffer WMD are 2.4 times more likely to recognise at least one typical sign of vitamin E deficiency than flocks with lambs that do not suffer WMD. These results clearly illustrate that the recognition of “typical” signs provides a good indicator of the risk of WMD.

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Table 23 Risk estimates describing the relationship between WMD in lambs and recognition of at least one “typical” sign of vitamin E deficiency (four age groups)

Do you see one or more “typical” signs? Do you see WMD in lambs? Lambs 0-1

week Lambs 1 – 3

weeks Lambs 3 weeks

to weaning Weaned lambs

Yes (% of yes responses) 25.4 35.9 52.2 34.7 No (% of yes responses) 16.3 15.0 29.1 21.9 Total (% of yes responses) 18.2 19.2 33.8 24.5 Relative risk 1.55 2.40 1.79 1.58 Attributable risk (%) 35.7 58.3 44.2 36.9 Population attributable risk (%)

10.2 22.2 13.9 10.7

Chi2 (1df) 18.34 (p<0.001)

93.8 (p<0.001)

78.84 (p<0.001)

29.47 (p<0.001)

4.11 Combining key indicators to define deficiency risk The data reflecting the various deficiency indicators were combined to produce a number of categories of data that may be used in an analysis of influential variables. Farms were divided into nine deficiency status categories (Table 24). These can be further summarised into farms that were confirmed deficient (high risk), medium and low risk. A further category can be classed as being of unknown risk. Table 25 gives estimates of the number of surveyed flocks that fall into these risk categories and the total population of ewes at risk in each category. Figure 2 demonstrates these risk categories schematically. Table 24 Categories of vitamin E deficiency indicators Deficiency status N % 1 Farms that are selenium deficient and recognise a WMD

problem or have had vitamin E deficiency diagnosed 357 13.87

2 Farms that are not selenium deficient but recognise a WMD problem or have had vitamin E deficiency diagnosed

47 1.83

3 Farms that don't know whether they are selenium deficient but recognise a WMD problem or have had vitamin E deficiency diagnosed

128 4.97

4 Farms that are selenium deficient and do not recognise a WMD problem and have not had vitamin E deficiency diagnosed

351 13.64

5 Farms that are selenium deficient and do not know whether they have a WMD problem and have not had vitamin E deficiency diagnosed

91 3.54

6 Farms that are not selenium deficient and do not know whether they have a WMD problem and have not had vitamin E deficiency diagnosed

43 1.67

7 Farms that do not know whether they are selenium deficient and do not know whether they have a WMD problem and have not had vitamin E deficiency diagnosed

269 10.45

8 Farms that don't know whether they are selenium deficient and do not recognise a WMD problem

805 31.29

9 Farms that are not selenium deficient and do not have a recognised WMD problem and have not had vitamin E deficiency diagnosed

482 18.73

Total 2573

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Table 25 Definition and magnitude of deficiency risk categories Risk category Deficiency

category Number of farms % Breeding ewes

High risk 1,2,3 532 20.68 277,549 Medium risk 4,5 442 17.18 210,329 Low risk 8,9 1287 50.02 358,784 Unknown risk 6,7 312 12.12 91,518 Total 2573 4.12 Relationship between risk and recognition of “typical” signs The percentage of farms recognising at least one and at least two typical signs of vitamin E deficiency were compared across risk groups (Table 26 and 27). The trend for both levels of “typical” sign recognition was for a declining percentage across risk groups, with the highest level of recognition in the high risk group and lowest in the low risk group. These differences were statistically significant, again indicating clearly that the recognition of “typical” signs provides a good indicator of the risk of WMD. Table 26 Distribution of responses to recognition of at least one typical sign across risk

categories Risk category Number of farms

recognising typical signs

Total farms %

High risk 388 532 72.93 Medium risk 296 485 61.03 Low risk 559 1287 43.43 Unknown risk 189 269 70.26 N 1432 2573 55.65 Table 27 Distribution of responses to recognition of at least two typical signs across

risk categories Risk category Number of farms

recognising typical signs

Total farms %

High risk 200 532 37.59 Medium risk 140 485 28.87 Low risk 221 1287 17.17 Unknown risk 112 269 41.64 N 673 2573 26.16 Perhaps the most interesting result is the high level of recognition in the unknown risk group. For both levels of recognition (one or more and two or more), the percentage was similar to the high risk category of farms.

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Figure 2 Schematic representation of vitamin E deficiency risk groups

Yes Don’t knowNo

WMD RECOGNISED and/or

VITAMIN E DEFICIENCY DIAGNOSED

SELENIUM DEFICIENCY RECOGNISED

Don’t know

No Yes Don’t know

No Yes Don’t know

No Yes

1 2 3 4 5 6 7 8

LOW RISK HIGH RISK MEDIUM RISK UNKNOWN RISK

9

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5. ANALYSIS OF FACTORS INFLUENCING VITAMIN E DEFICIENCY 5.1 Geographical factors The most important geographical factors that influence vitamin E deficiency are likely to be associated with selenium deficiency. The strong association between WMD, vitamin E deficiency and selenium deficiency has been demonstrated earlier in the report. Detailed maps of selenium deficiency were not available from the Soil Survey and Land Research Centre (SSLRC). The SSLRC has an incomplete data-set for total topsoil selenium which comprises around 1000 - 1500 sample points covering random parts of the country. A detailed analysis of samples from a 5 km grid is currently being completed. Correlation of values with other soil properties on a reliable basis would be infeasible (D.Thompson, pers.comm). Although the major selenium deficient areas of the country are well recognised, less widespread pockets of deficiency exist in certain areas. Using the survey data describing whether or not farms were known to be in a selenium deficient area, the sample area, excluding Shetland (incomplete postcode dataset) was divided into four categories depending on the proportion of selenium deficient farms (Very High Proportion, High Proportion, Medium Proportion and Low Proportion). The differences between the mean selenium deficiency rate values for each category are statistically significant. The distribution of the categories is demonstrated in Figure 3. The proportion in each category that claim selenium deficiency and recognise WMD is shown in Table 28. Table 28 Relationship between areas with very high, high, medium and low

proportion of farms with selenium deficiency and WMD Proportion of selenium deficient farms

Number of farms

Number recognising

selenium deficiency

Percentage of recognised selenium

deficiency (%)

Percentage of farms claiming

to recognise WMD(%)

Low 332 32 9.64 11.66 Medium 1181 261 22.10 14.55 High 695 322 46.33 19.82 Very High 174 121 69.54 31.10 Overall 2382 736 30.90 16.84 The rates of WMD recognition by respondents, in each category were compared. The WMD recognition rate is significantly lower than the selenium deficiency rate in the medium, high and very high proportion categories. The trend between regional categories in the overall WMD recognition rate is similar to the trend in selenium deficiency. In the low selenium proportion category, the rate of WMD recognition is higher than the percentage of farms with a recognised selenium deficiency. Overall, only 1.42% of farms recognise a WMD problem, but do not recognise a selenium deficiency. This suggests that the difference between the low proportion category and other categories is the percentage of farms where the selenium deficiency status is not known. Alternatively, these could be farms that suffer WMD and are not selenium deficient. Of farms that recognise WMD, there were significant differences between the four regions, in the percentages that fall into the three selenium deficiency catgories (Yes, No, Don’t Know) (Table 29)

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Figure 3 Map showing the distribution of areas with a very high, high, medium and low proportion of farms with selenium deficiency

19

Selenium Deficiency categories

(Proportion of selenium deficient farms)

Very high proportion (70%)

High proportion (46%)

Medium proportion (22%)

Low proportion (10%)

Table 29 Relationship between WMD and selenium deficiency in the four categories of

selenium deficient areas Proportion of farms with selenium deficiency

Total number of farms

recognising WMD

% from selenium

deficient farms

% from farms with no

selenium deficiency

% from farms where selenium deficiency status

is not known Low 36 30.56 16.67 52.78 Medium 168 59.52 7.14 33.33 High 132 79.55 7.58 12.88 Very High 51 86.27 3.92 9.80 Overall 387 67.18 7.75 25.06 These data suggest that farms in the “Don’t Know” category within the low proportion of selenium deficiency areas are either not deficient in selenium, or are located in smaller sub-regional pockets of deficiency. Although there are no real differences between selenium deficient areas in the proportion of flocks considered deficient, there are differences between areas in the proportion that are considered as being within high and medium risk categories. A higher risk of vitamin E deficiency is associated with farms in the selenium deficient areas. The influence of farm type was tested, indicating that significantly more lowland farms were classed as being of low risk than in the hills and uplands. This result is confounded by the higher proportion of hill and upland farms found in selenium deficient areas. Fifty one percent (51.26%) of hill and 50.26% of upland farms are considered as being of high or medium risk as compared with 30.56% in lowland flocks (Table 30). Table 30 Distribution of hill, upland and lowland farms between the vitamin E

deficiency risk categories (% of respondents of each farm type) Deficiency risk category Hill Upland Lowland All High risk 26.98 24.96 16.45 20.71 Medium risk 24.28 25.30 14.10 18.90 Low risk 39.75 40.17 58.05 49.94 Unknown risk 8.99 9.57 11.40 10.45 N 556 585 1404 2545 5.2 Housing With regard to the winter housing of ewes, 76% of respondents either wintered some (19%) or all (56%) of their flocks. There were differences between farm type, with housing being more common in the lowlands (Table 31). The data indicated that there was a tendency towards housing of larger flocks. Table 31 Description of housing strategies in surveyed sheep flocks

System Housed Not housed Part flock housed

N

Lowland 71.35 17.80 10.85 1466 Hill 25.39 40.17 34.43 575 Upland 49.51 24.34 26.15 608

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For those flocks that are housed, there was an even distribution of the length of time that ewes are housed pre-lambing (Table 32). Table 32 Distribution of pre-lambing housing periods in surveyed sheep flocks

Pre-lambing housing period Number of flocks

% of flocks

1-7 days 294 14.67 1-2 weeks 344 17.17 2-4 weeks 413 20.61 4-6 weeks 371 18.51 6-8 weeks 364 18.16

More than 8 weeks 218 10.88 Total 2004 The majority of respondents (65%) housed lambs for no more than a week after lambing (Table 33). Table 33 Distribution of periods of housing lambs in surveyed sheep flocks

Period of lamb housing Number of flocks

% of flocks

1-2 days 568 27.93 2-7 days 758 37.27

1-2 weeks 243 11.95 2-4 weeks 241 11.85

More than 4 weeks 196 9.64 Lambs never go out 28 1.38

Total 2034 There was no real difference between the various ewe-housing periods and the proportion of flocks that kept lambs indoors for up to a week. Only 3% of housed flocks kept ewes housed for more than 4 weeks pre-lambing and their lambs housed for more than 4 weeks post-lambing. A significantly higher proportion of respondents who housed ewes indicated that they had WMD in their flocks (relative rate = 1.7; χ2 = 16.6; p<0.0001) (Table 34). There was a very large difference between the two groups in the percentage that indicated they did not know whether they had WMD. There was a much clear distinction within flocks that definitely did not house as to whether the condition was present or not. Table 34 Relationship between housing and WMD Are ewes housed? Flocks with

WMD (n) Flocks with no

WMD (n) Total (n) Percentage of

flocks with WMD (%)

All or part of flock (n) 336 1553 1889 17.8 Not housed (n) 56 480 536 10.5 Total 392 2033 2425 16.2 There was also a large difference between those farms that house all and those that house only part of the flock. This may be explained when comparing the housing period post-lambing in the flocks that were housed for more than 4 weeks pre-lambing. More than 90% of the part-housed flocks are housed post-lambing for less than 2 weeks, compared to 64% in the all-housed flocks

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(Table 35). Observations from veterinarians suggested that deficiency is a particular problem with in-wintered ewes and lambs reared indoors. Clinical signs were reported by a number of veterinarians as occurring in 2-4 week old lambs following turnout. It may also be the case that the ewes that are housed in the part-housed flocks may be more susceptible in that they are likely to be pedigree ewes of a fast-growing breed (potentially a pre-disposing factor), ewe-lambs or multiple-lamb bearing ewes. Table 35 Relationship between observation of WMD and post-lambing housing for

flocks housed for more than 4 weeks pre-lambing (% of flocks). Period housed post-lambing All housed Some flocks housed 0-2 weeks 63.94 90.83 2 to 4 weeks 24.93 5.96 more than 4 weeks 11.13 3.21 N 710 280 Respondents who had observed typical signs of vitamin E deficiency were asked whether they had observed the influence of housing on the occurrence of these signs. Of 610 respondents that housed ewes and observed typical signs, 36.0% felt that the signs were more likely to occur when lambs were born indoors, as compared to only 6.9% who felt that outdoor lambing was more of a problem. 57.0% did not observe any housing effect. Furthermore, 22.9% of a sub-sample of 480 felt that the signs occurred more often after housing had been introduced. Only 8.1% felt that housing at improved the incidence of these signs. 69.0% did not view the introduction of housing as influencing the problem. Housing and the lack of fresh herbage and straw based diets were noted by some veterinarians as being important pre-disposing factors. It has already been shown that the proportion of flocks that feed straw is higher in those that house for long periods pre-lambing. A hypothesis that ewes housed on a diet containing straw were more likely to be deficient in vitamin E was tested. The difference in the proportion of respondents who saw two or more signs in ewes housed and fed on straw, although small, was greater than those not feeding straw (28.64% and 21.65% respectively). This difference is statistically significant (p<0.05). The length of time ewes were housed appears to influence the risk of WMD-like signs in lambs. Considering lambs released from housing within two weeks of lambing, the rate of observation of two or more typical signs of vitamin E deficiency was significantly greater in flocks that had housed ewes for more than four weeks pre-lambing (34.5%), compared to ewes housed for less than 4 weeks (25.4%). 5.3 Feeding A section of the questionnaire was dedicated to feeding strategies. These data were analysed in relation to the various vitamin E deficiency indicators. Questions referring to winter feeding practices were divided into housed and out-wintered sections. A recurring trend in the responses was for respondents who kept ewes housed for some of the lambing period to leave blank the section on feeds given to ewes whilst outdoors. As a consequence, meaningful descriptions from these farms was not possible. The data presented in Table 36 describes feeds given to flocks that were entirely outdoor and feeds given to flocks during housing. Examining the data received from farms that did not house ewes, the majority (71%) fed hay and purchased concentrates (65%), either in isolation or in

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combination with other feeds. A similar trend was noted in housed flocks, including those that did not house all ewes. Table 36 Feeds given to housed and outdoor flocks (% of flocks) Feed Outdoor Indoor Hay 70.88 67.48 Straw 4.01 22.96 Silage 24.81 35.49 Haylage 8.32 12.33 Turnips/Swedes 9.40 3.06 Kale/Rape 2.16 0.29 Purchased concentrates

64.71 78.74

Home mixed cereals 8.47 18.16 Straight barley 4.78 4.13 Sugar beet 30.35 20.19 Other feeds 21.73 11.89 N 649 2060 Of the “other” feeds given to housed ewes, the most common were molasses (17% of other feeds), fodder beet (14%), feed-blocks (13%), oats (9%), maize gluten (9%), liquid feed (7%) and soya (7%). Since none of the these feeds were named as feed options in the questionnaire, these data can only be considered as representing the minimum level of use within the sample. In solely outdoor flocks, 48% of other feeds were feed-blocks. Seventy seven percent of housed and 76% of non-housed flocks used mineral supplementation in the form of a salt-lick, in-feed mineral or mineral block. A definite trend of decreasing use of hay and increasing use of silage and straw was observed with increasing period of housing pre-lambing (Table 37). Whilst the feeding of hay was predominant (83%) in flocks housed for less than a week, for those housed for more than 8 weeks, half of the flocks were receiving hay and half receiving silage. There were obviously flocks that were receiving combinations of forage. The feeding of purchased concentrates was very common (average across all housed categories was 78%) with little variation between flocks. Fifty five percent of housed flocks also gave creep feed to lambs during the housing period. Twenty percent of those who only house some of the flock gave a creep feed. The percentage of lamb flocks that are fed creep increases with the period that they are housed (Table 38) In the hills and uplands, the majority of flocks did not receive creep feed whilst grazing, whilst in the lowlands this practice was more common. Most creep feed was given to lambs early in the season (Table 39)

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Table 37 Feeding practices in ewes housed pre-lambing (% of flocks) Housing period pre-lambing 1-7 days 1-2 weeks 2-4 weeks 4-6 weeks 6-8 weeks More than 8

weeks Forage feeds

Hay 82.99 79.36 70.94 61.73 54.12 48.17 Silage 22.45 27.91 31.72 39.89 48.08 50.00 Straw 15.65 18.02 23.73 27.76 24.18 30.28

Haylage 9.86 11.05 13.08 15.09 12.64 12.84 Swedes/turnips 5.78 4.07 3.39 2.43 0.82 0.92

Concentrate feeds Purchased

concentrates 74.49 76.45 80.63 81.94 80.22 76.61

Sugar beet 23.81 22.38 19.13 21.29 18.41 14.22 Home-mixed

cereals 17.01 22.09 18.89 16.98 16.76 18.81

Barley 6.12 3.20 4.12 6.20 2.75 2.29 Supplementation

Mineral blocks 42.86 46.22 44.79 43.13 33.52 31.65 In-feed minerals 31.97 32.56 33.90 36.12 40.66 49.54

Salt licks 10.20 14.83 16.95 16.17 13.19 12.84 No supplementation 24.49 19.48 20.34 17.52 24.45 18.35 Table 38 Relationship between creep feeding of lambs and the period of housing after

lambing. Period of lamb housing

Number of flocks % of lamb flocks receiving creep feed

1-2 days 26 5.87 2-7 days 75 11.57 1-2 weeks 66 29.20 2-4 weeks 165 72.69 More than 4 weeks 179 93.72 Lambs never go out 27 100.00 Total 538 Table 39 Lamb flocks receiving a creep feed whilst grazing Creep feed

throughout growing period*

Only early season creep

feed

No creep feed

Hill 9.25 17.17 73.58 Upland 9.36 24.96 65.68 Lowland 20.59 37.67 41.74 Overall 15.6 30.41 53.99 * a small percentage only fed creep during the late fattening period

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With regard to the influence of feeding on vitamin E deficiency, this factor was mentioned more frequently than any other in the survey of veterinary practices. A selection of comments from this survey are presented below: • “Straw based diets are the worst. The situation is also worse since reduction in fishmeal

based protein to pregnant/milking ewes?” • “Has increased with feeding of home-grown cereals” • “Seen when fed home grown feed after a bad i.e. damp harvest” • “Association with certain pastures, and/or poor winter diet i.e. straw or poorly conserved

silage/hay” • “Home grown food implications. Grazing on poor pasture” • “The feed merchants have this last year added extra vitamin E in the ration so this has

helped together with us treating the selenium deficiencies” • “High cereal/sugar beets diets in show sheep” • “Ewes in late pregnancy on straw based rations and concentrate with little vitamin E added -

daily intake of vitamin E likely to be low” • “It would seem that our incidence (recognition) of vitamin E deficiency in sheep lags behind

that of cattle. Could this reflect greater tolerance of the condition in sheep or the usual trend to feed sheep the best of hay/silage and the worst to cattle?”

• “since feed manufacturers have put more vitamin E in ewe rations, survival rates and lamb thriftiness have improved”

• “Only 1 case in last 5 years. This was in early lambing Charolais flock fed moist grain from a silo and protein/mineral pellets”

• “Since feed manufacturers have put more vitamin E in ewe rations, survival rates and lamb thriftiness have improved”

• “Most clients provide lamb creep feed pellets with coccidiostat -presumably this provides adequate intake”

• “Seen on aftermath grazing” • “Most flocks receive some concentrates at lambing and we assume this controls/prevents the

occurrence of vitamin E/Selenium deficiency” • “Was seen with prop-corn barley - treated with propionic acid, when this was a fashion” • “Turning sheep into housed animals (like cattle) makes the incidence more because of silage

feeding. Barley concentrates treated with propionic acid can be a problem” • “Straw and root -based diets” • “Most examples of deficiency are seen where forage conversation is poor.” • “The main case was home produced cereal treated with propionic acid with what was

thought to be adequate vitamin E levels but baseline levels may be too low and need to be reassessed.”

• “Lack of hay/silage in winter diet, with straw given as alternative” • “Housing - no access to fresh herbage” The analysis of the influence of feeding on vitamin E deficiency was limited by the attention to detail possible in a postal survey of this kind. Furthermore, the impact of feeding practices is, in turn, influenced by supplementation practices and confounded by housing (see previous section). A direct comparison of the rate of WMD between flocks fed and not fed on straw indicated that those fed on straw were more likely to have WMD. Although the difference is small, the effect is statistically significant. The same trend was seen with those feeding silage to housed ewes. A non-statistically significant trend of higher WMD rate in housed flocks fed barley was also observed (Table 40). This analysis was completed on a small sample of flocks that received

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barley. No effect on WMD was noted with the feeding of ewes with hay and the feeding of ewes with purchased concentrates. Table 40 Relationship between feeding of housed ewes with various forages and

concentrate feeds and WMD (% of flocks with WMD) Feed used Feed not used Chi2 p-value

Straw 24.4 19.6 4.33 <0.05 Silage 23.6 19.2 4.77 <0.05 Barley 28.4 20.1 2.7 =0.10 Hay 20.2 10.6 NS Purchased concentrate 20.2 20.7 NS Perhaps the strongest relationship observed in out-wintered sheep was seen with ewes fed silage. The percentage of ewes fed silage that suffered WMD was 28.1% compared with a 13.7% in flocks not fed silage (Chi2 = 12.74 with 1 df; p<0.0001). No effect of feeding hay was observed. 5.4 Breeds More than 430 breeds, crossbreeds and strains of sheep were recorded, with most farms keeping at least two breeds/crossbreeds and many keeping multiple breeds/crossbreeds. Respondents who had observed typical signs of vitamin E deficiency were asked whether they had observed the influence of breed. 16% noted a breed effect (Table 41). Those that did observe this effect were asked which breed suffered the most. Precise analysis of these responses was not possible, given the great variation in breeds and crossbreds reported. A trend indicated that lambs born to Suffolk and Texel sires were more susceptible. However, caution should be applied in assessing these responses, as these breeds were also the most prevalent within the surveyed sample. Within flock confounding factors are also important sources of bias as is the probability that fast growing breeds are more likely to be housed. Table 41 Influence of breed on the observation of “typical” signs of vitamin E

deficiency % of flocks recognising “typical”

signs of vitamin E deficiency Observed signs in a particular breed 15.79 No breed influence observed 69.09 Only one breed kept 15.11 Some respondents to the veterinary practice survey indicated that fast growing breeds, such as the Suffolk, Texel and Charolais, were more at risk from vitamin E deficiency than other slower growing breeds. Well-muscled lambs were also noted to be more susceptible. To test these breed effects, the deficiency indicators were used to test differences between flocks that contained at least on of these fast growing breeds and those that did not. In each of these tests a breed effect was not detected, indicating that breed appeared to have little relationship to the presence of WMD in a flock. However, these results should be treated with caution, as there are a number of confounding factors, including the presence of other breeds. Some veterinarians also noted flocks with rapid growing pedigree breeds were more at risk. Although some producers indicated that they kept pedigree flocks, these details were too inconsistent to use pedigree as a variable. However, it was possible to select single breed flocks (dam and sire) of the Charolais, Texel and Suffolk breeds. There were 162 (6% of the surveyed

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sample) purebred flocks of these breeds. Again, these data did not show any differences in the proportion of flocks that had WMD, or had had vitamin E deficiency diagnosed, as compared with the entire survey population. There was also the same proportional distribution between vitamin E risk categories. 5.5 Litter size Respondents who had observed typical signs of vitamin E deficiency were asked whether they had observed the influence of litter size. Of those observing typical signs, 43.1% of respondents indicated that multiple births (twins or more) were most likely to suffer these signs. 50.4% did not see any litter size effect and only 6.4 % felt that singles suffered most frequently. The veterinary survey included a number of responses suggesting that a stiff lamb syndrome is most often seen in the fastest growing lambs, which are most frequently singles. One comment suggested that ewes with singles have more milk and hence the lambs tend to eat less solids that would provide the vitamin E supplementation they required. 5.6 Month of lambing Data reflecting season of lambing are presented in Table 42. These data show clearly that March and April were the most common lambing season, although both lowland and upland flocks tended to lamb over longer periods, or had two or more distinct lambing seasons. Table 42 Distribution of lambing month on surveyed farms (%) Lowland Hill Upland All Nov-Dec 10.01 1.40 2.81 6.48 Jan-Feb 49.38 12.04 28.55 36.48 Mar-April 77.57 93.19 91.09 84.07 May-June 4.66 24.26 8.25 9.75 N 1458 573 606 2637 Twenty six percent of respondents indicated that they got less lambs born than they expected (Table 43). Table 43 Responses to the question “Did you get as many lambs born this year as

expected” Response categories % As expected 63.78 More than expected 10.19 Less than expected 24.08 Much less than expected 1.95 N 2620 There were no real differences in the response rates between lambing seasons. Of the 2,620 responses to this question, 870 (33%) provided detail of why the number of lambs born was lower than expected. This was a higher proportion than that indicating that they got less lambs than expected. This was a consequence of some general comments being made with regard to lambing performance. A breakdown of responses is given in Table 44.

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Table 44 Survey respondents reasons for lower than expected number of lambs born % of farms with less than

expected lambs* % of all responding farms

Ewes were mated too late 5.43 1.41 Ewes were too fat at mating 21.26 5.53 Ewes in poor condition at mating

18.77 4.89

There was an abortion problem 28.73** 5.95 Don’t know the reason 28.89 7.52 Other reasons 57.48 14.96 N 682 2620 * some farms gave more than one response ** includes counts of abortion that were included under the “other reasons” category Poor weather was cited in 22% of “other” reasons for lambing performance being lower than expected. This can be further defined as poor weather at tupping (8.8%), during winter generally (7.6%) and at lambing (4.8%). Poor tup performance or inadequate tup:ewe ratio (10.1%), poor ewe health or disease (6.9%), failure to flush ewes (5.9%), too many ewe lambs (4.8%) and too many old ewes (4.8%) were also important reasons cited for reduced performance. Mineral deficiency (specific and non-specific) accounted for 4.8% of “other” responses. Failure of AI, change of breed and stress-related factors were also significant responses. Season of lambing was analysed as a potential pre-disposing factor influencing vitamin E deficiency. No relationship was noted between WMD and November to December lambing, January to February lambing and March to April lambing. However, lambs born in May to June were shown to be more likely to have WMD (23%) than other flocks (16%). These data are probably confounded by farm type factors, with late lambing and selenium deficiency most often occurring in the hills and uplands. 5.7 Stage of lambing season Respondents who had observed typical signs of vitamin E deficiency were asked whether they had observed the influence of stage of the lambing season. Eight hundred and forty respondents completed this question. Twenty four percent (23.8%), 10.7% and 10.0% indicated that late, middle or early lambing season influence the incidence of typical signs, respectively. Fifty six percent (55.9%) did not observe any stage of lambing effect. 5.8 Climatic factors There was no conclusive evidence from the farmer survey to show direct climatic factors. There may be an indirect association with climatic factors that result in poor quality forages with low vitamin E levels e.g damp harvesting conditions. Comments from veterinarians regarding the pre-disposing climatic factors associated with white muscle disease included: “Always occurs in April after a cold snap”; In a selenium deficient area: “We see problems in the spring and on good grass in the summer”; and “Wet weather exacerbates the problem”. 5.9 Organic farming methods Concern has been expressed that vitamin E deficiency could become a problem in organic flocks and herds (MAFF, 1999). Mineral and vitamin deficiencies in organic systems tend to be, as in conventional systems, a regional problem associated with hill and upland farms and are normally treated using conventional methods of supplementation (Roderick and Hovi, 1999). There were

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insufficient organic, or in-conversion, farms within the surveyed sample to draw firm conclusions on the impact of this method of production on the incidence of vitamin E deficiency. Only one veterinarian suggested an increase in organic farming practices could lead to an increased incidence of deficiency. 5.10 Use of fertilisers Fertilisers and their use were not included as a variable in the producer survey. One of the veterinarians surveyed reported that vitamin E deficiency was seen more frequently on farms with high nitrogen fertiliser use. A number of producers and veterinarians reported success in the use of pasture applications of selenium, and other trace elements, in deficient areas. One veterinarian commented that “Several clients have moved to fertilisers containing Selenium and have noted a marked improvement in productivity”. The application of seaweed dressings to soil was also reported to have improved a deficiency situation. 6. PRODUCTION LOSSES ASSOCIATED WITH VITAMIN E DEFICIENCY 6.1 Abortion Although abortion was not included as a “typical” sign in the survey of sheep farmers, infertility and stillbirths were mentioned as possible indicators of deficiency by a number of respondents in the veterinarian survey e.g. “ewes may present with "uterine inertia" type dystokia, resulting in stillborn lambs”. Also, a loss in condition of ewes suffering deficiency may result in an increased rate of aborted foetuses. A summary of responses on the incidence and rate of abortion in surveyed flocks are shown in Table 45 Table 45 Incidence of abortion in surveyed flocks

% No abortion 30.22 < 1% of flock 38.84 1-2 % of flock 22.01 >2% of flock 8.93 The level of abortion in flocks was used as a variable in the analysis of vitamin E deficiency “risk”. Results from farms in the high risk category indicate that these farms have a significantly higher level of abortion than other farms (Table 46). The general trend was of a greater level of abortion amongst the high risk groups, and declining with level of risk. These data give a good indication that a higher proportion of farms at risk of vitamin E deficiency are likely to suffer abortion in their flocks, and at a higher rate. Again, these data may be confounded by farm type, i.e. more selenium deficient farms found in the hills and uplands where it may be expected that abortion levels are higher.

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Table 46 Relationship between annual incidence of abortion and vitamin E risk (%) Risk category No abortion <1% flock

aborting 1-2% of flock

aborting >2 % of flock

aborting N

High risk 15.18 42.51 27.33 14.98 494 Medium risk 24.42 42.56 23.49 9.53 430 Low risk 40.05 36.07 17.56 6.31 1156 Unknown risk 25.73 39.42 27.39 7.47 241 N 2321 The abortion rates in flocks demonstrating two or more typical signs were also compared with those not showing signs. A similar trend was observed to the analysis described in Table 46, with those showing signs more likely to abort and at higher levels (Table 47). Table 47 Relationship between annual incidence of abortion and recognition of two or

more “typical” signs (%) Annual incidence of abortion Flocks with two or more

typical signs Flocks not showing typical

signs No abortion 17.33 35.11 0-1% 42.29 37.64 1-2% 26.71 20.11 >2% 13.67 7.13 N 629 1780 6.2 Stillbirths Stillbirths, and early lamb deaths, are considered to be typical signs of vitamin E deficiency. The flock survey gave strong evidence that flocks with WMD were more likely to suffer stillbirths than those without WMD, and that the frequency within flocks was higher. The differences between the rates in the “yes” and “don’t know” flocks are statistically, significantly greater than that in the “No” group (Table 48). As with other analyses a similar trend between “don’t know”and “yes” flocks is evident. This result may suggest that many respondents who responded “don’t know” may have WMD in their flocks. Table 48 Relationship between WMD and the incidence of stillbirths (%) Presence of WMD

No stillbirths

Stillbirths but not very often

Frequent stillbirths

n

Yes 29.23 66.18 4.59 414 No 47.47 51.53 1.00 1599 Don’t know 29.63 65.74 4.63 432 All 41.23 56.52 2.25 2445 6.3 Mortality rates Data were collected reflecting the number of lambs born alive and the number of lambs that died during the first 7 days of life. From these data, mortality rates were estimated (the definition of mortality rate in this case being the rate of death in the first week per 100 lambs born alive). Overall, the lamb mortality rate estimated from 2,536 flocks, including those flocks with no mortalities, was 5.66%. In order to eliminate the effect of no mortalities in small flocks, an estimate of the average mortality rate for flocks of more than 50 breeding ewes was made (Table 49). The standard deviation within each sub-sample suggests large variation with the groups. The accuracy of these data should be treated with caution for a number of reasons; primarily the absence of formal records on most farms. On hill farms it is particularly difficult to record lamb losses in flocks that lamb outdoors.

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Table 49 Estimated lamb mortality rates (first 7 days) for Hill, Upland and Lowland (flocks of more than 50 breeding ewes)

Flock Type Lamb mortality (to 7 days) %

Number of flocks Standard deviation

Hill 5.21 485 3.83 Upland 5.74 475 4.27 Lowland 5.54 979 5.17 Overall 5.50 1939 4.65 6.4 Incidence of diarrhoea in lambs Respondents to the producer survey were asked whether lambs of a range of ages regularly suffered diarrhoea. A total of 691 respondents (25.4%) indicated that this was a regular problem in at least one age class of lamb. The incidence of “scours” was more common in older lambs (Table 50), particularly from 3 weeks to weaning. At this age, this is normally associated with coccidiosis. Table 50 Distribution of surveyed flocks and age groups that regularly suffer

diarrhoea First Week Week 1To3 Week 3 To

Weaning Post-Weaning

Number of flocks (n) 114 149 330 260 % of flocks 4.24 5.55 12.29 9.68 Common causes of diarrhoea

E.coli CryptosporidiaRotavirus

Coccidia Nematodirus and other

PGEs A number of veterinarians noted a decreased resistance to infection as a consequence of vitamin E deficiency. To test this hypothesis, the percentage of respondents indicating that both diarrhoea and WMD was a problem in lambs was compared with the percentage indicating WMD but no diarrhoea problem. Four age categories of lamb were tested. The results (Table 51) indicate a significant effect in lambs less than 1 week, 1 to 3 weeks and 3 weeks to weaning, with all of these showing a higher percentage of WMD farms amongst those observing a problem with diarrhoea. These results give an indication that those animals suffering with WMD may be more susceptible to infections associated with diarrhoea. One veterinarian reported an apparent decline in response to anthelmintics in deficient lambs. The relationship between diarrhoea and the recognition of at least two “typical” signs in each of four age categories gives an even more dramatic result, with all age groups showing a positive relationship between the two conditions (Table 52). Some caution must be applied here, as this relationship may be one of association i.e the signs may be typical of diarrhoea.

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Table 51 Relationship between diarrhoea in lambs and the presence of WMD WMD present With diarrhoea Without diarrhoea Lambs 0-1 week Yes (%) 31.0 19.9 Chi2 6.33 p-value <0.05 Relative risk 1.56 Lambs 1-3 weeks Yes (%) 37.8 19.4 Chi2 22.27 p-value <0.001 Relative risk 1.96 Lambs 3 weeks to weaning Yes (%) 30.5 19.1 Chi2 17.14 p-value <0.001 Relative risk 1.60 Lambs Post-weaning Yes (%) 26.2 19.8 Chi2 4.33 p-value <0.001 Relative risk 1.32 Table 52 Relationship between the recognition of “typical” signs of deficiency and the

presence of diarrhoea (%) Flocks with two or

more "typical" signs and diarrhoea

No "typical" signs, lambs with diarrhoea

Lambs 0 -1 week 13.33 3.63 Lambs 1- 3weeks 19.53 4.59

Lambs 3 weeks to weaning 29.57 9.23 Lambs post-weaning 27.16 7.91

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7. RECOMMENDATIONS This study has provided information describing the epidemiology of vitamin E deficiency in the UK sheep flock. Determining factors, such as those associated with selenium deficiency, housing and feeding have been identified. However, given the nature of postal surveys of this type, quantification of the impact of these effects could not be accurately evaluated. In order to quantify and sharpen knowledge of the effect of these factors on the vitamin E status of sheep, further, more detailed studies are required. This would be best achieved using selected case-studies from the survey sample. This would allow more detailed assessment of factors, such as the effect of forage quality and feed composition. As a consequence of confounding factors and insufficient data, assessments of the impact of some variables were not possible. For example, there is anecdotal evidence of fast growing breeds being more susceptible to vitamin E deficiency. It was not possible to support this with statistical evidence from the data available. Studies to support this evidence require monitoring under controlled conditions. Other potential determinants of deficiency, supported by anecdotal evidence but not statistical analysis, also require more detailed and controlled study. Results from this study were based largely on the respondents’ perception of the presence of otherwise of “typical” signs of deficiency. Although this methodology appeared to match expected trends, particularly with regard to the incidence in selenium deficient areas, more accurate diagnostic procedures are required to validate the observed trends. The survey indicated that there could be a strong relationship between vitamin E and selenium deficiency and certain critical components of economic efficiency, such as increased mortality caused by the sudden death of lambs, increased rates of abortion and stillbirths and reduced growth rates in lambs. Evidence of a reduced immunity to infection also suggests indirect production losses associated with deficiency. Using the survey data as a base-line, a more detailed economic analysis of the potential impact of deficiency, supplementation and other methods of control is now required. The risk factors identified, such as length of winter housing of ewes and the type of winter forage fed, as well as the soil selenium status of the farm, suggest that supplementation should be targeted. A basic model for the assessment of risk of vitamin E deficiency was developed from the survey data. This process of risk assessment needs further advancement, so as to provide a tool for producers and veterinarians to improve the targeting of control strategies. It is recommended that the risk categories identified in this study be further refined and adapted for this purpose.

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REFERENCES Allison, R.D.,Laven, R.A (2000) Effects of vitamin E supplementation on the health and fertility of dairy cows: a review. Veterinary Record 147: 703-708. Bradley, R. Anderson, P. H. Wilesmith, J. W. (1986) Changing patterns of nutritional myodegeneration (white muscle disease) in cattle and sheep in the period 1975-1985 in Great Britain. Proceedings of the 6th International Conference on Production Disease in Farm Animals, Belfast. Pp. 248-251. Chikunya et al (1997) Reference details not known. Chikunya, S., Wachira, A., Sinclair, L.A., Wilkinson, R.G., Demirel.G., Enser, M and Wood, J.D. (1999). Vitamin E Research on Growing Lambs. In: Vitamin E Requirements in Sheep. An invited workshop to discuss current needs. Harper Adams University College, 29 June, 1999. Greig, A. Hunter, A. R. (1980) Nutritional myopathy in feeding hoggs. Veterinary Record 107: 3, 62-63. Hamliri, A. Olson, W. G. Johnson, D. W. Kessabi, M. (1990) Evaluation of biochemical evidence of congenital nutritional myopathy in two-week prepartum fetuses from selenium-deficient ewes. American Journal of Veterinary Research 51: 7, 1112-1115. Jones (1993) Lameness in Sheep.The Moredun Foundation News Sheet. Kott, R. W. Ruttle, J. L. Southward, G. M. (1983) Effects of vitamin E and selenium injections on reproduction and preweaning lamb survival in ewes consuming diets marginally deficient in selenium. Journal of Animal Science 57: 3, 553-558. MAFF (1999). Vitamin E Requirements in Sheep. An invited workshop to discuss current needs. Harper Adams University College, 29 June, 1999. Livestock Science and Biotechnology Unit, Chief Scientist’s Group, MAFF. Merrel, B (1999) Effects of supplementing ewes with Vitamin E in late pregnancy on sheep performance. In: Vitamin E Requirements in Sheep. An invited workshop to discuss current needs. Harper Adams University College, 29 June, 1999. Mudd, A. J. Mackie, I. L. (1973) The influence of vitamin E and selenium on ewe prolificacy. Veterinary Record 93: 7, 197-199. Niekerk, F. E. van. Cloete, S. W. P. Heine, E. W. P. Merwe, G. D. van der. Wellington, A. Plessis, S. S. du. Bekker, D. (1996) The effect of selenium supplementation during the early post-mating period on embryonic survival in sheep. Journal of the South African Veterinary Association 67: 4, 209-213. Roderick, S and Hovi, M. (1999) Animal Health and Welfare in Organic Livestock Systems: Identification of Constraints and Priorities. A report to MAFF (contract ref: OF0172) Suttle, N. F. Linklater, K. A. Jones, D. G. (1991) Disorders Related to Trace Element Deficiencies. In: Diseases of Sheep. 2nd edition. Ed.W. B. Martin and I. D. Aitken. pp. 238-250. Blackwell Scientific Publications, Oxford.

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UK, North of Scotland College of Agriculture (1981) Effect of selenium/vitamin E supplementation prior to mating on ewe fertility in commercial flocks. UK, North of Scotland College of Agriculture: Research investigations and field trials 1979-80. Aberdeen, UK. Pp.23. Vipond, J. E. (1984) Effects of a single oral dose of a commercial selenium cobalt and vitamin preparation on ewe fertility. Veterinary Record 114: 21, 519-521. Watson, M. J. Judson, G. J. Harrigan, K. E. Caple, I. W. (1988) Vitamin E deficiency and myopathy in neonatal lambs of ewes fed wheat-based diets for two months. Proceedings of the Nutrition Society of Australia 13: 93.

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APPENDIX 1

The Producer Questionnaire

APPENDIX 2

The Veterinary Practitioner Questionnaire

APPENDIX 3

Typical clinical signs of vitamin E deficiency observed by veterinarians (Comments extracted from questionnaire returns)

"Slow" lambs born to low vitamin E status dams - supplying high levels vitamin E in last 6 weeks of pregnancy makes a dramatic difference. Ill thrift in growing lambs >10 weeks 2-4 weeks old fast growing lambs – limb stiffness, falling over, usually associated with a cold snap in the weather Clinical signs are normally stiff lambs. Laboratory confirmation of Vitamin E/Selenium deficiency has been inconclusive but the lambs seem to respond well to Dystocel and long acting penicillin which we have taken to be indicative of deficiency. One farm has seen benefit of Selenium supplemented feed. Collapsing lambs at turnout Dead lambs at birth, early lamb deaths, stiff gait, recumbant Do not see signs Ewes – dystokia, ewes not dispelling foetus without intervention - low Selenium. Treatment leads to improvement. Lambs - poor growth, poor immune system, vulnerable to disease - low Selenium .Treatment leads to improvement Infertility in ewes - usually after Copper and Cobalt deficiency Failure to stand, lambs bright but collapse on hind limbs after minimal exercise. Ewes also collapse and unable to stand Failure to thrive First 2 weeks of life, muscular tremor while standing soon becoming recumbent. Flaccidity of body, otherwise normal. Condition often responds to vitamin E injections. Usually just a few lambs in a flock affected. Seems to affect the same flock each year. Flacid paralysis in lambs. Weakness in lambs General ill-thrift, poor resistance to common infections. Parasitism. Rarely "white muscle" Ill thrift Ill thrift in lambs and chronic scour Ill thrift, occasional WMD Ill thrift. WMD In a recent case - 25% of lambs 8-12 weeks of age developed mild lameness/stiffness in left fore (in 100% of those affected it was left fore)- this progressed in a number to increased weakness/collapse and sternal recumbency. Recovery was seen within 48 hours of vitesel injection. Why always left fore? In extreme cases - lambs look like little pigs Inco-ordination, off hind limbs, ill-thrift Indoor lambs - scouring, lack of weight. Outdoor lambs unthrifty, lack of weight gain Infertility, poorer lamb birth weight/weakly lambs, stiff young and growing lambs Infertility. Ill thrift. WMD Lambs are weak, have pounding hearts, easily catch pneumonia, not growing/thriving well, sudden death very common - post mortem enlarged hearts Lambs born dead Lambs greater than 4 weeks develop muscular stiffness, "lameness" and weakness Lambs showing muscular weakness Lambs slow to suckle, lethargic, need encouragement to rise, lazy slow gait. More severe cases show dyspnoea. Majority are large well muscled lambs Lambs stiff and recumbent Lethargy at birth. Lowered resistance to general infection. Stiffness in older lambs

Low blood vitamin E is occasionally picked up when samples are taken for other trace elements Low fertility. Stiff lamb disease. Poor doing near finishing Mainly muscular dystrophy, recumbancy Mainly poor growth in grwoing lambs. Occasionally hear problems/leg problem in young lambs muscle wasting, stiff lamb unable to rise Muscle weakness in young and growing lambs, occasionally heart failure Muscle weakness, stiffness to recumbency, Diagnosis is difficult. Diagnosis improved with analysis of BUCK low plasma VitE Muscular dystrophy. Infertility, poor growth rates, recumbent ewe Muscular stiffness, poor immune response to infections, poor fertility Myopathy in lambs Neonatal lamb problems Never proven it bur presumed ewes that keep falling over hind legs, weak and ataxic. When treated with vitenium those ewes sometimes recover. No diagnosed cases in recent years None seen None seen. Many farmers confuse spinal abscesses with vitamin E/selenium deficiency and are convinced they have deficiency. All blood tests we have done on lambs have proved negative for vit E /Sel deficiency Not diagnosed in last 3- 4 years Poor fertility in flocks on AI/ET Poor fertility, WMD, Pneumonia Poor lamb viability and poor lamb growth Poor neonatal survivability, protracted lambing. Ill thrift in fattening lambs Poor reproductive performance, fewer lambs per ewe, weak and stillborn lambs, unthrifty lambs, slow to rise and suckle, higher incidence of watery mouth, etc. True WMD in Beltex and heavily muscled breeds Possible cause of weak lambs in unfed hill flocks Posterior paresis in young lambs Predominantly lambs born to deficient ewes. Gait problems, knuckling of front legs Predominantly muscle stiffness Primarily failure of lambs to survive. Some classical WMD symptoms Racing heart/hanging shoulder blades/slow to stand/poor suckers. Therefore possibly low colostrum levels- more scour - more pneumonia, more navel infection Recumbency, weakness, sudden death Reluctance to get up and walk, stiffness Respiratory distress, stiff lambs, mild paraplegia, ill-thrift, poor resistance Signs of nutritional muscular dystrophy Slow to suckle, weakly. Unthrifty post weaning. Liver rupture? Some infertility. Large weak lambs that will not suck and get up in first 24 hourse of life. Also some ruptured livers with vitamin E alone Sometimes white muscle, sometimes weak ill thrift Stiff gait in growing lambs Stiff gait, white muscle type syndrome. A variety is sudden death type syndrome - heart muscle problem Stiff lamb Stiff lamb

Stiff lamb disease Stiff lamb disease Poor growth rates Sudden death in lambs pushed for showing Stiff lambs Stiff lambs, poor suck reflex, non-vital after birth with failure to get up. Poor thriving and muscular waekness in older lambs (Selenium deficiency only) Stiff lambs. Ewes with dyspnoaea and ill thrift Stiff lambs. Muscular lameness. Unable to stand at 1-3 weeks. Decreased resistance to infection. Reproductive performance in ewes. Retained placenta and post parturient metritisStiffness of lambs stiffness, going off legs Stiffness/reluctance to walk Stillbirths, weak lambs, fading lambs, ill-thrift Subclinical problem associated with blood testing on farms where cattle are infertile owing to selenium deficiency and calves suffer neonatal scouring and death Sudden death + nervous signs in young lambs Sudden death in lambs just turned out Sudden death/stiffness Tends to be muscular weakness in week old lambs - can often be difficult to disassociate from joint ill. Tends to be profound lumbar muscle weakness in many cases. Ewes may present with "uterine inertia" type dystokia, resulting in stillborn lambs The birth of weak lambs Unthrifty lambs Usually found on a routine blood sampling Usually non-specific ill-thrift/dullness. Diagnosis mainly be improvement post Selenium even though blood samples are in the "normal" range Usually only in lambs. Unable to rise or else very stiff. Often < 1 week old. Most keep sucking the ewe, although soem have reduced appetite. Temperature normal. Vitamin E deficiency (as separate from vitamin E/Selenium deficiency) was observed a few years ago, particularly in some upland/hill Welsh Mountain flocks in the year following a very dry summer/autumn (with some burning of exposed hill pastures) We used to see nutritional muscular dystrophy - generally early signs Weak and still born lambs Weak ill-thriven lambs. Poor fertility in ewes Weak lambs Weak lambs (neonates) Weak lambs at birth. Fat lambs not finishing. Lambs collapsing. Associated with low lambing percentage Weak lambs with obvious WMD on post mortem Weak lambs, dull, stupid. Low conception rate in ewes Weak lambs, some off legs, poor resistance to disease, poor growth rates weak legs, sudden death Weakly lambs at birth. Unable to raise heads. Scapula raised above spinal cord. Sudden death. Protracted lambing - dead lambs. Ewes lying down, no response to calcium but respond to vitamin E an dphosphorus. Weakly lambs not as viable and lively - definite improvement after vitamin E prophyalxis. Have also tried to improve immune problems in lambs with watery mouth/joint ill but had only limited success - sucking/viability definitely improved.

Weakly lambs, die soon after birth. WMD in older lambs - not seen recently Weakly, pale lambs - some anaemia. More prone to other neonatal disease - joint ill, coccidiosis, etc Weakness and recumbancy in young lambs. Diagnosis on ck values >1000iu (and often a lot higher). It is not economic to send blood samples away to differentiate vitamin E and Se. Weakness in hind legs, ill thriving, poor suckling, increase in occurrence of watery mouth Weakness, ill thrift and death Weakness, inability to rise in post-natal period. Complication has been joint ill in at least two flocks. Both flocks early lamb indoors. Weakness, lethargy, lameness/stiffness Weakness, poor thrift Weakness, reluctance to stand, pneumonic signs Weakness/muscular dystrophy/stiff lambs/death White muscle disease - young growing lambs going off legs. Front legs tend to be affected first. Sometimes neonates unable to stand up and not copper - WMD WMD in lambs, limb weakness, ill thrift. In ewes- poor lambs, poor colostrum, ill thrift WMD in lambs. Poor conception rates WMD, ill thrift, weak lambs WMD,-stiff lamb, swollen muscle, bradycardia, breathing difficulties