International Poultry Production — Volume 16 Number 4 27

Classical deficiency signs andnon specific parameters (forexample, lowered produc-

tion and reproduction rates) areassociated with vitamin deficienciesor excesses. Vitamin nutritionshould no longer be consideredimportant only for preventing defi-ciency signs but also for optimisinganimal health, productivity andproduct quality.What quantities of supplementalvitamins should be provided to poul-try diets? One suggestion would beto meet vitamin requirements basedon the National Research Council orother agency nutrient recommenda-tions. A second choice would be toprovide higher levels as recom-mended by poultry industry groups.This article attempts first to dispelthe concept that only meeting NRCrequirements will provide poultryoptimum production and healthprotection. Some poultry industrygroups are recommending optimumvitamin supplementation.

Intake of vitamins

Vitamin dietary intake and utilisationis influenced by many factors, includ-ing particular feed ingredients, bio-availability, harvesting, processing,storage, feed intake, antagonists,least cost feed formulations andother factors.lAAggrroonnoommiicc eeffffeeccttss aanndd hhaarrvveessttiinnggccoonnddiittiioonnss..Vitamin levels will vary in feed ingre-dients because of crop location, fer-tilisation, plant genetics, plantdisease and weather. Harvestingconditions often play a major role inthe vitamin content of many feed-stuffs. Vitamin content of corn isdrastically reduced when harvestmonths are not conducive to fullripening. In one study, vitamin Eactivity in blight corn was 59% lowerthan in sound corn and activity ofthe vitamin in lightweight corn aver-aged 21% lower than in sound corn.The rate of oxidation of naturaltocopherol was higher in high mois-ture corn than in low moisture corndue to increased peroxidation of thelipid.lPPrroocceessssiinngg aanndd ssttoorraaggee eeffffeeccttss..

Many vitamins are delicate sub-stances that can suffer loss of activitydue to unfavourable circumstancesencountered during processing orstorage of premixes and feeds.Stress factors for vitamins includehumidity, pressure (pelleting), fric-tion (abrasion), heat, light, oxida-tion-reduction, rancidity, traceminerals, pH and interactions withother vitamins, carriers, enzymesand feed additives. Humidity is theprimary factor that can decrease thestability of vitamins in premixes andfeedstuffs. Humidity augments thenegative effects exerted by cholinechloride, trace elements and otherchemical reactions that are not

found in dry feed. Corn is oftendried rapidly under high tempera-tures, resulting in losses of vitamin Eactivity and other heat sensitive vita-mins. When corn was artificiallydried for 40 minutes at 88°C, lossesof α-tocopherol averaged 19% andwhen corn was dried for 54 minutesat 107°C, losses averaged 41%.After three months of storage, thevitamin A retention was 88% underlow temperature and low humidity,86% under high temperature andlow humidity and 2% under hightemperature and high humidity.Humidity was significantly morestressful than temperature. Vitaminsthat undergo friction or are mixed

and stored with minerals are subjectto loss of potency. Friction is animportant factor because it erodesthe coating that protects several vit-amins and reduces vitamin crystalsto a smaller particle size. Hazards tovitamins from minerals are abrasionand direct destruction by certaintrace elements, particularly copper,zinc and iron; manganese and sele-nium are the least reactive.Some vitamins are destroyed bylight. Riboflavin is stable to most fac-tors involved in processing; how-ever, it is readily destroyed by eithervisible or ultraviolet light. Vitamin B6,vitamin C and folacin can also bedestroyed by light. While pelletinggenerally improves the value ofenergy and protein carriers in a feed,this is not true for most vitamins.During pelleting of feeds, four ele-ments destructive for a number ofvitamins are applied in combinedaction: friction, heat, pressure andhumidity. Increasing the pelletingtemperature or conditioning timegenerally enhances redox reactionsand destroys vitamins. Vitamins A,D3, K3, C and thiamin are most likelyto show stability problems in pel-leted feeds. Feed manufacturershave increased pelleting tempera-tures for all animal feeds in order tocontrol salmonella organisms andincrease digestibility and are usingsteam pelleting, prepelleting condi-tioners and feed expanders, whichlead to increased vitamin degrada-tion. Table 1 shows typical losses ofcommercial form vitamins under arange of pelleting conditions.lRReedduucceedd ffeeeedd iinnttaakkee..When feed intake is reduced, vita-min allowances should be adjustedto ensure adequate vitamin intakefor optimum performance.Restricting feed intake practicesand/or improved feed conversionwill decrease dietary intake of allnutrients, including vitamins.Restricted feeding of broilerbreeders and turkey breeder hensmay result in marginal vitamin intakeif diets are not adequately fortified.Reduced feed intake may also resultfrom stress and disease.Use of high energy feeds, such asfats, to provide diets with greater

Optimum vitaminnutrition for poultry

by Lee R. McDowell, Department of Animal Sciences, University of Florida, Gainesville, Florida 32611, USAand Nelson E. Ward, DSM Nutritional Products Inc, 45 Waterview Boulevard, Parsippany, NJ 07054, USA.

Continued on page 29

VViittaammiinn 117700°°FF 118800°°FF 119900°°FF 220000°°FF((7777°°CC)) ((8822°°CC)) ((8888°°CC)) ((9933°°CC))

A beadlet 90-100 90-100 90-95 85-90D3 beadlet 90-100 90-100 90-95 85-90E acetate 90-100 90-100 90-95 80-90E spray dry 90-100 90-100 90-95 85-90K (menadione 50-60 40-50 40-50 35-40sodium bisulphite)K (menadione 80-90 70-80 65-75 65-75nicotinamide bisulphite)Thiamin monohydrate 90-100 90-100 90-95 85-90Thiamin HCl 90-100 85-95 85-95 70-80Riboflavin 90-100 90-100 90-95 85-90Pyridoxine 90-100 90-100 90-95 80-90Vitamin B12 90-100 80-90 70-85 60-80Ca Pantothenate 90-100 90-100 90-95 85-90Niacin 90-100 90-100 90-95 85-90Niacinamide 90-100 90-100 90-95 85-90Folic acid 90-100 85-90 80-90 70-80Biotin 90-100 90-100 90-95 85-90Vitamin C 50-80 40-70 30-60 20-40ethycelluloseVitamin C phosphorylated 90-100 90-100 90-95 90-95Estimates based on 20-30 second conditioning time (Ward, 2005).

Table 1. Range in estimated stability of vitamin products at differentpelleting temperatures.

VViittaammiinn lleevveell BBooddyy wweeiigghhtt ((kkgg)) FF//GG MMoorrttaalliittyy ((%%))

NRC 2.186d 2.219d 11.0c

Low 25% 2.382c 2.069c 8.7b

Average 2.436b 2.023b 7.4a

High 25% 2.454ab 2.014ab 7.6ab

High 25 + 25% 2.463a 1.999a 7.4a

Ward, 1994, aPerformance averaged across three stress levels (minimal, moderate, rela-tively high) bP<0.05 within column.

Table 2. Performance of broilers at 51 days of age as affected by vita-min levela.

International Poultry Production — Volume 16 Number 4 29

nutrient density for higher animalperformance requires a higher vita-min concentration in feeds. Poultryspecies provided diets ad libitumconsume quantities sufficient tomeet energy requirements.Thus, vitamin fortification must beincreased for high energy dietsbecause animals will consume lesstotal feed. Feed consumption wascompared in broilers receivingmetabolisable energy ranging from2,800-3,550kcal/kg of feed. Feedand vitamin consumption were each19.1% lower in broilers consumingthe diet with greater energy densitycompared to those consuming thelowest energy diet.Ambient temperature also has animportant influence on diet con-sumption, as animals consumegreater quantities during cold tem-peratures and reduced amounts as aresult of heat stress. Vitamins, aswell as other nutrients must, there-fore, be adjusted to reflect changingdietary consumption.lVViittaammiinn vvaarriiaabbiilliittyy aanndd iinnssuuffffiicciieennttaannaallyyssiiss..Tables of feed composition demon-strate the lack of complete vitamininformation, with vitamin levels vary-ing widely within a given feedstuff.Variability of vitamin contentwithin ingredients is generally largeand difficult to quantify and antici-pate. It is well recognised that vita-min levels shown in tables of vitamincomposition of feedstuffs representaverage values and that actual vita-min content of each feedstuff variesover a fairly wide range. Feed table averages are often oflittle value in predicting individualcontent of feed- stuffs or bioavail-ability of vitamins. Vitamin E contentof 42 varieties of corn varied from11.1-36.4 IU per kg, a 3.3 fold differ-ence. For 65 samples of corn, biotinvaried between 0.012-0.072ppm, asix fold difference.lVViittaammiinn bbiiooaavvaaiillaabbiilliittyy..Even accurate feedstuff analyses ofvitamin concentrations do not pro-vide bioavailability data needed forcertain vitamins. Bound forms of vit-amins in natural ingredients oftenare unavailable to animals.Bioavailability of choline, niacin andvitamin B6 is adequate in some feedsbut limited or variable in others. Forexample, bioavailability of choline is100% in corn but varies from 60-75% in soybean meal; that of niacinis 100% in soybean meal but zero inwheat and sorghum and varies from0-30% in corn; that of vitamin B6 is65% in soybean meal and variesfrom 45-56% in corn. For alfalfameal, corn, cottonseed meal andsoybean meal, bioavailability ofbiotin is estimated at 100%.However, biotin availability is vari-able for other feedstuffs, for exam-ple, 20-50% in barley, 62% in corngluten meal, 30% in fish meal, 20-60% in sorghum, 32% in oats and 0-62% in wheat.

Many of the earlier establishedrequirements for poultry reliedheavily on purified feed ingredients.Swine data showed that responsesto vitamins may differ depending onwhether vitamins are being added toa purified or natural diet.Requirements of the pig for niacin,riboflavin and pantothenic acid wereconsiderably higher on a natural dietthan requirements established ear-lier from experiments using purifieddiets. This shows that resultsobtained with purified diets mustalso be verified with natural dietsand that bioavailability of vitaminsmay be greater in purified diets.lCCoommppuutteerriisseedd lleeaasstt ccoosstt ffeeeedd ffoorr--mmuullaattiioonnss..Vitamins are not usually entered asspecifications in computerised feedformulations. Therefore, vitamin richfeedstuffs – such as alfalfa, distiller’ssolubles or grains; brewer’s grains;fermentation products and meat,milk and fish byproducts – are oftenexcluded or reduced when leastcost feed formulations are com-puted. The resulting least cost dietconsisting of a grain and soybeanmeal is usually lower in vitamins thana more complex one containingmore costly vitamin rich feeds.

Vitamin requirements

There are many factors affecting vit-amin requirements and vitamin utili-sation.lPPhhyyssiioollooggiiccaall mmaakkee--uupp aanndd pprroodduucc--ttiioonn ffuunnccttiioonn..Vitamin needs of animals andhumans depend greatly on theirphysiological make-up, age, health,and nutritional status and function,such as producing meat or eggs.Breeder hens have higher vitaminrequirements for optimum hatcha-bility, since vitamin requirements foregg production are generally lessthan that for egg hatchability.Higher levels of vitamins A, D3 andE are needed in breeder hen dietsthan in feeds for rapidly growingbroilers. Selection for faster growth

rate may allow animals to reachmuch higher weights at muchyounger ages with less feed con-sumed. Since genetic potential hasimproved at the rate of 0.8% feedconversion yearly and most of theNRC vitamin requirement data is20-40 years old, vitamin require-ments determined several decadesago may not apply to today's poul-try.To compare the potential effectsof stress conditions on vitaminrequirements, Ward, fed five levelsof vitamins to 9,600 broilers over a42 day period: NRC, low 25% indus-try, average industry, high 25%industry and high 25 + 25%.Birds were subjected to three lev-els of stress (minimum, moderateand relatively high) based on differ-ent levels of coccidia, E. coli, place-ment density and nutritional plane.The results showed that as degreeof stress increased, bird perfor-mance declined. Furthermore,although the highest level of vitaminsdid not completely overcome thedetrimental effect of stress, clearlythe higher levels of vitamins didimprove performance over thelower levels (Tables 2-4).lDDiisseeaassee oorr aaddvveerrssee eennvviirroonnmmeennttaallccoonnddiittiioonnss..Intensified production increasesstress and subclinical disease levelconditions because of higher densi-ties of animals in confined areas. Sellet al. suggested that NRC levels ofvitamin E are probably sufficient forgrazing turkeys that are ‘free of dis-ease’. Stress and disease conditionsin animals increase the basic require-ment for certain vitamins. A numberof studies indicate that nutrient lev-els that are adequate for growth andegg production may not be ade-quate for normal immunity and formaximising the animal's resistance todisease. Higher than recommendedlevels of vitamin A to layer chickensunder heat stress was beneficial tolaying performance and immunefunction. High levels of vitamin Emaintained antibody production inchicks.

Supplementing the diets of liveturkeys with vitamin E can reducethe chance of transmission ofListeria monocytogenes, a majorhuman bacterial food bornepathogen found in poultry.Turkeys supplemented daily withvitamin E (100-200IU) had elevatedlevels of several types of lympho-cytes (T-cells) when infected withListeria monocytogenes. Therefore,vitamin E stimulates live turkeys’immune responses (via lympho-cytes) and enhances clearance of themicro-organism from the gut.Diseases or parasites affecting thegastrointestinal tract will reduceintestinal absorption of vitamins,both from dietary sources and thosesynthesised by micro-organisms. Ifthey cause diarrhoea or vomitingthis will also decrease intestinalabsorption and increase needs.Vitamin A deficiency is often seenin heavily parasitised animals thatsupposedly were receiving an ade-quate amount of the vitamin.Mycotoxins are known to causedigestive disturbances such as vomit-ing and diarrhoea as well as internalbleeding and interfere with absorp-tion of dietary vitamins A, D, E andK.In broiler chickens mouldy corn(mycotoxins) has been associatedwith deficiencies of vitamins D (rick-ets) and E (encephalomalacia) inspite of the fact that these vitaminswere supplemented at levelsregarded as satisfactory.Mortality from fowl typhoid(Salmonella gallinarum) was reducedin chicks fed vitamin levels greaterthan normal. Vitamin E supplemen-tation at a high level decreased chickmortality due to Escherichia colichallenge from 40-5%. Coccidiosisproduces a triple stress on vitamin Krequirements as follows:• Coccidiosis reduces feed intake,thereby reducing vitamin K intake.• Coccidiosis injures the intestinaltract and reduces absorption of thevitamin.• Treatment with sulfaquinoxaline orother coccidiostats causes anincreased requirement for vitamin K.The current NRC vitamin Krequirement for growing chicks is0.5mg per kg of diet. It was con-cluded that as much as 8mg of vita-min K per kg of diet was needed forchicks with coccidiosis.lHHeeaatt ssttrreessss.The decreased nutrient intake bypoultry at high temperatures alsohas repercussions on the intake ofvitamins and also affects metabolismsuch as for vitamin A, E and C whichplay important roles in performanceand immune function.Supplementation of these vitaminsis helpful for maintaining perfor-mance and immune function of heatstressed birds. High dietary vitaminE provided to broilers reduced neg-ative effects of heat stress (32°C).Vitamins A (15,000mg/kg) + E

Continued from page 27

Continued on page 30

VViittaammiinn lleevveell MMiinniimmaall MMooddeerraattee RReellaattiivveellyy hhiigghh

NRC 2.138cd 2.284f 2.234e

Low 25% 2.025b 2.032b 2.150d

Average 1.958a 2.005b 2.105c

High 25% 1.959a 1.950a 2.121cd

High 25 + 25% 1.927a 1.963a 2.121cd

Ward, 1994, aP<0.05 within column.

Table 4. Feed conversion of broilers at 51 days of age as affected bystress and vitamin levela.

VViittaammiinn lleevveell MMiinniimmaall MMooddeerraattee RReellaattiivveellyy hhiigghh

NRC 2.395cd 2.075i 2.088i

Low 25% 2.548b 2.424ef 2.174h

Average 2.583a 2.483cde 2.241g

High 25% 2.600a 2.485c 2.275f

High 25 + 25% 2.610a 2.494c 2.286def

Ward, 1994, aP<0.05 within column.

Table 3. Body weight of broilers at 51 days of age as affected by stressand vitamin levela.

VViittaammiinnss CCoonnttrrooll ((mmgg//kkgg))aa OOVVNN ((mmgg//kkgg))bb

Vitamin A (retinol) 13,000 IU 12,500 IUVitamin D3 2,600 IU 4,000 IUVitamin E (alpha-tocopherol) 18.90 225.00Vitamin K3 (menadione) 2.20 4.00Thiamin 1.40 3.00Riboflavin 6.20 9.00Vitamin B6 3.00 6.00Vitamin B12 21.20 40.00Niacin 33.00 60.00Pantothenic acid 10.40 15.00Folic acid 0.68 2.00Biotin 0.07 0.25Vitamin C 0 100aAverage vitamin concentrations used in Spanish broiler operations.bOptimum vitamin nutrition, increased vitamin fortification.

Table 5. Composition of experimental vitamin premixes for determin-ing the nutritive value of broiler meat.

30 International Poultry Production — Volume 16 Number 4

(250 mg/kg) reduced heat stressrelated decreases in broilers. Bothvitamins E (65mg/kg) and C(1,000mg/kg) enhanced in vitro lym-phocyte proliferative responses ofheat stressed hens. High dietary supplemental vitaminE (250mg/kg) is beneficial to eggproduction at high temperatures.Broilers under heat stress conditionsfound increased levels of vitamin E(100-200IU/kg) to improve live per-formance of birds, as well as thedigestibility of crude protein, etherextract and gross energy.Optimum responses in growth,feed efficiency and/or liveability inbroilers under heat stress seem tooccur with supplements of vitaminC. For laying hens under stress,there are improvements in liveabil-ity, food intake, egg production andegg quality with vitamin C concen-trations in the range of 250-400mg/kg. Production responses inpoultry confirm that dietary supple-mentation with vitamin C generallyonly benefits birds under stress.lVViittaammiinn aannttaaggoonniissttss..Vitamin antagonists (antimetabo-lites) interfere with the activity ofvarious vitamins. The antagonistcould cleave the metabolite mole-cule and render it inactive, as occurswith thiaminase and thiamin; it couldcomplex with the metabolite, withsimilar results, as happens betweenavidin and biotin; or by reason ofstructural similarity it could occupyreaction sites and, thereby, denythem to the metabolite, as withdicumarol and vitamin K.The presence of vitamin antago-nists in animal and human dietsshould be considered in adjustingvitamin allowances, as most vitaminshave antagonists that reduce theirutilisation. Some common antago-nists are as follows:

• Thiaminase, found in raw fish andsome feedstuffs, is a thiamin antago-nist.• Dicumarol, found in certain plants,interferes with blood clotting byblocking the action of vitamin K.• Avidin, found in raw egg white,and streptavidin, from Streptomycesmolds, are biotin antimetabolites.• Rancid fats inactivate biotin anddestroy vitamins A, D, and E andpossibly others.• Mycotoxins increase requirementsfor fat soluble and other vitamins(for example, biotin, folic acid andpossibly others).lUUssee ooff aannttiimmiiccrroobbiiaall ddrruuggss..Some antimicrobial drugs willincrease vitamin needs of animals byaltering intestinal microflora andinhibiting synthesis of certain vita-mins. Certain sulphonamides mayincrease requirements of biotin,folacin, vitamin K and possibly oth-ers when intestinal synthesis isreduced.lLLeevveellss ooff ootthheerr nnuuttrriieennttss iinn tthheeddiieett..The level of fat in the diet affects

absorption of the fat soluble vita-mins A, D, E and K, as well as therequirement for vitamin E and possi-bly other vitamins. Fat soluble vita-mins may fail to be absorbed ifdigestion of fat is impaired.Polyunsaturated fatty acids (PUFA)and oxidised sources of fats caninfluence individual vitaminallowances. For example, highdietary PUFA increases the vitamin Erequirements by 3IU per g of PUFA. Many interrelationships of vitaminswith other nutrients exist and,therefore, affect requirements. Forexample, prominent interrelation-ships exist for vitamin E with sele-nium, vitamin D with calcium andphosphorus, choline with methion-ine, and for niacin with tryptophan.

Optimum allowances

The NRC requirements for a vita-min are usually close to minimumlevels required to prevent deficiencysigns and for conditions of healthand adequate performance, pro-

vided sufficient amounts of all othernutrients are supplied.Most nutritionists usually considerNRC requirements for vitamins tobe close to minimum requirementssufficient to prevent clinical defi-ciency signs and they may beadjusted upward according to expe-rience within the industry in situa-tions where a higher level ofvitamins is needed.Commercial supplementation lev-els of most vitamins for poultryoften reflect stresses encounteredunder production practices. Over90% of the broilers, turkeys and lay-ing hens were included in a broadsurvey of vitamin supplementationrates; levels for most vitamins weresubstantially higher than NRC. The1993 supplementation values werenot found to change much in a morerecent survey, with the exceptionthat vitamin E levels virtually dou-bled.Allowances of a vitamin are thosetotal levels from all sources fed tocompensate for factors influencingvitamin needs of animals. Theseinfluencing factors include:lThose that may lead to inadequatelevels of the vitamin in the diet.lThose that may affect the animal’sability to utilise the vitamin undercommercial production conditions.The higher the allowance thegreater is the extent to which it maycompensate for the influencing fac-tors. Thus, under commercial pro-duction conditions, vitaminallowances higher than NRCrequirements may be needed toallow optimum performance.Generally, the optimum supple-mentation level is the vitamin con-centration that achieves the bestgrowth rate, feed utilisation andhealth (including immune compe-tency) and provides adequate bodyreserves. Barroeta et al. defines

Continued from page 29

International Poultry Production — Volume 16 Number 4 31

optimum vitamin nutrition as ‘vita-min levels above minimum require-ments to optimise genetic potentialand improve immune status in thebird, leading to an improvement inproduction and egg quality’.The concept of optimum vitaminnutrition under commercial produc-tion conditions is illustrated in Fig. 1.The marginal zone in Fig. 1 repre-sents vitamin levels that are lowerthan requirements that may predis-pose animals to deficiency.The requirement zones are mini-mum vitamin quantities that areneeded to prevent deficiency signs,but may lead to suboptimum perfor-mance even though animals appearnormal. The optimum allowances inFig. 1 permit animals to achieve theirfull genetic potential for optimumperformance. In the excess zone,vitamin levels range from levels stillsafe, but uneconomical, to concen-trations that may produce toxiceffects. Usually only vitamins A andD, under practical feeding conditionspose the possibility of toxicity prob-lems.Optimum allowances of any vita-

min are depicted as a range in Fig. 1because factors influencing vitaminneeds are highly variable and opti-mum allowances to allow maximumresponse may vary from animal toanimal of the same species.It should be emphasised that subacute deficiencies can exist althoughthe actual deficiency signs do notappear. Such borderline deficienciesare both the most costly and themost difficult to cope with and oftengo unnoticed and unrectified, yetthey may result in poor and expen-sive gains, impaired reproduction ordepressed production. Also, under farm conditions, onewill usually not find a single vitamindeficiency. Instead, deficiencies areusually a combination of factors, andoften deficiency signs will not beclear cut.If the NRC minimum requirementfor a vitamin is the level that barelyprevents clinical deficiency signs,then this level moves in relationshipto the level required for optimumproduction responses. This meansthat if a greater quantity of a vitaminis required for an optimum response(because of the influencing factors),a greater quantity would also berequired to prevent deficiency signs(Fig. 2).Optimum poultry performancerequired under modern commercialconditions cannot be obtained byfortifying diets to just meet minimumvitamin requirements.Establishment of adequate mar-

gins of safety must provide for thosefactors that may increase certaindietary vitamin requirements and forvariability in active vitamin potenciesand availability within individual feedingredients. The actual minimum nutritionalrequirement for vitamins is difficultto access as it is most often deter-

mined under favourable experimen-tal conditions. In 1994, the NRCreported the most recent vitaminrequirements for chickens. These were determined underoptimal rearing conditions, thereby,implying that these levels should beincreased under ‘field conditions’.Supplementation allowances needto reflect different management sys-tems and be high enough to allowfor fluctuation in environmental tem-peratures, energy content of feed orother factors that influence feedconsumption. Riboflavin and other vitamins playan important role in skin develop-ment, tensile strength and healingrates. A deficiency in riboflavin canslow epithelialisation of wounds by4-5 days, reduce collagen content by25%, and decrease tensile strengthof wounds by 45%. Riboflavin defi-ciency can increase skin homocys-teine by 2-4 fold, which ultimatelyimpairs the cross link formation ofcollagen. Marginal field deficiencies ofriboflavin could increase skin tearsand cause longer healing times, andultimately increase costly down-grades. Vitamin requirements for

egg production as suggested by theNRC have changed little over thelast 30-50 years. However, during this time periodlayer feed conversion rates havedramatically improved by approxi-mately 40% based on a higher eggmass production (approximately30%) and lower feed consumption(approximately 10%). Broiler vitamin requirements havelikewise changed little in recentyears. However, for the last 30years broiler feed conversion rateshave improved dramatically, morethan 20%, due to a much higherbody weight in a shorter productionperiod. On the other hand, modernbroiler production systems oftenplace animals under high stress con-ditions so that an optimum level ofvitamins in feed is essential to allowbirds to achieve their full potentialwhile maintaining good health.Although NRC poultry vitaminrequirements have changed little inthe last 30-50 years, the poultryindustry has more closely attemptedto recommend higher supplementa-tion levels for poultry diets. Theindustry vitamin average allowanceshave increased significantly (30-

500%) to keep pace with greatergenetic potential, faster growthrates, better feed efficiency, poorerquality ingredients, larger poultryhouses and generally higher diseaselevels, all of which caused increasedstress. A reasonable amount of logicwould suggest that vitamin require-ments determined decades ago maynot apply to today’s poultry feeds.

Recent research

A trial was done to study the effectsof two different vitamin levels inbroiler diets on production parame-ters, vitamin deposition in meat andmeat quality. One diet containedaverage vitamin concentrations usedin Spanish broiler operations vs opti-mum vitamin nutrition (OVN) levelsas recommended by DSM, formerlyRoche Vitamins (Table 5).Breast meat was also analysed forvitamin content and oxidative stabil-ity (Thiobarbituric reactant sub-stance, TBARS). As an additionaltreatment effect, broilers were alsosubjected to density stress condi-tions (12.7 vs 16.4 animals/m2).Chickens fed the higher OVNdiets were significantly heavier(increased final weight by 2.7%), atemore and obtained better averagedaily gains than those receiving moretypical vitamin concentrations.High density stress conditionsreduced gains with OVN birds bestcounteracting this stress. Breast lipidoxidation was reduced by the OVNpremix. Higher levels of vitamins E,thiamin and pantothenic acid inbreast meat resulted from the OVNdiets. Research from France alsoevaluated OVN diets on broiler per-formance. The OVN premix produced a sig-nificant improvement in growth andfeed efficiency throughout the entirerearing process. Higher vitaminsimproved the weight and fillet andbird to cook/live carcase yield. With the OVN diet, vitamin E wasdramatically increased in meat (forexample, in fillets 12.5 vs 5.4mg/kg). Optimum vitamin nutrition levelswere tested in Spain to evaluate thevalue of additional vitamins for layinghens. Compared to the average vita-min concentrations provided tohens in the Spanish feed industry,eggs from OVN treated hens hadsignificantly higher concentrations ofvitamins A, E, thiamin, riboflavin,pantothenic acid, biotin, folic acidand vitamin B12. In addition toimproving the nutritive value of eggs,lipid oxidation of eggs from hens fedOVN were not statistically affected,but showed numerically lowerTBAR values (0.274 vs 0.301mmol/g)than hens fed control diets. The vitamin D3 metabolite, 25-hydroxy vitamin D3 (25-OHD3), wasused as part of an OVN investiga-tion to evaluate egg productionparameters and egg quality com-

Continued on page 33

TToottaall vviittaammiinn lleevveell ffrroomm aallll ssoouurrcceess iinn ffeeeeddAAlllloowwaanncceess

aa bb cc dd ee

AAvveerraaggee aanniimmaall rreessppoonnssee

MMaarrggiinnaall

RReeqquuiirreemmeennttss((pprreevveennttddeeffiicciieennccyy)) OOppttiimmuumm EExxcceessss

Fig. 1. Optimum vitamin nutrition for animals under commercial pro-duction conditions. Allowances are for total vitamin levels from allsources fed to compensate for factors affecting animals’ vitaminneeds.

TToottaall vviittaammiinn lleevveell ffrroomm aallll ssoouurrcceess iinn ffeeeedd

NNRRCC rreeqquuiirreemmeenntt IInnfflluueenncciinngg ffaaccttoorrssAAlllloowwaanncceess

aa bb cc

AAvveerraaggee aanniimmaall rreessppoonnssee

MMaarrggiinnaall

SSttrreessss

OOppttiimmuumm

OOtthheerrss

NNuuttrriieenntt iinntteerr--rreellaattiioonnsshhiippss

SSttaabbiilliittyy

BBiiooaavvaaiillaabbiilliittyy

DDiieett ccoommppoossiittiioonn

BBiioollooggiiccaall vvaarriiaattiioonnss

PPaarraassiitteess

IInnffeeccttiioouuss ddiisseeaasseess

Fig. 2. Optimum vitamin nutrition for animals under commercial pro-duction conditions and influencing factors.

International Poultry Production — Volume 16 Number 4 33

pared to the control of the averagevitamin concentrations used in theSpanish egg production industry.Vitamin D in the OVN diet wasprovided as 1,500 IU/kg D3 and1,500 IU/kg of 25-OHD3 (commer-cial name Hy-D). Using a combina-tion of OVN + Hy-D resulted in adramatic increase of performanceparameters for laying hens (Table 6).Hens receiving OVN + Hy-D signifi-cantly improved production at afavourable cost (cost to benefit ratioof 1:9).Production parameters were asfollows:l55% benefit from higher layingrate.l24% benefit from bigger egg size.l15% benefit from lower feedintake.l6% benefit from less broken eggs.There was also better egg qualitywith lower susceptibility to oxida-tion in fresh and 28 day stored eggsand lower egg weight losses afterstoring eggs for 21 days at roomtemperature.A study with turkeys evaluated theimpact of 25-OHD3 (Hy-D) as a par-tial substitute for vitamin D3 in twolevels of vitamin dosage, control(typical vitamin levels) or OVN (anenhanced dose of 13 vitamins).During the first part of the experi-ment the birds receiving anenhanced vitamin dose (OVN), andparticularly without Hy-D, grow bet-ter. However, after 12 weeks thedietary dosage of Hy-D for theheavy turkeys, made it possible,whatever the vitamin dose, toachieve growth, bone developmentand body constitution and toimprove percentage of fillets.

Conclusions

Optimum concentrations of vitaminsin poultry diets allow today’s poultryto perform to their genetic poten-tial. Vitamin requirements estab-lished decades ago do not take intoaccount the modern geneticallysuperior birds with increasedgrowth, egg production and im-

proved feed efficiency.Vitamin intake per unit of output iscontinually declining. The yearlydecline for layers is around 1% peregg produced, while for broilers hasbeen 0.6-0.8% per kg body gain.Also vitamin allowances today needto take into account modern man-agement procedures that increasebird densities and stress conditionsfor the producing birds. Vitamins areimportant for maintaining optimumimmune response. Higher levels ofvitamins (for example, vitamins A, Eand C) have been shown to increaseoverall health by improving diseaseresistance as a result of improvedimmunity.Optimum vitamin nutrition fromrecent studies with broilers haveshown increased growth, feed effi-ciency, increased oxidative stabilityof meat and better resistance to highdensity stress conditions. For layinghens OVN diets increased eggweights, number of large eggs, lowerpercentage of broken eggs, higherpercentage of lay and improved feedefficiency.A higher level of vitamin E is par-ticularly important for improvinglipid stability in meat. Supra-nutritionsupplementation of vitamin E (400mg/kg) was highly effective atinhibiting the lipid oxidation devel-opment in all raw products includingbreast, thigh muscle and skin.Likewise, this same high level ofvitamin E was much more effectiveat reducing the lipid oxidation ofcooked chicken patties than controldietary vitamin E (400 vs 33mg/kg).

Beneficial effects of vitamin E are notrestricted to lipid protection, and ithas also been demonstrated thatthey protect proteins present inturkey meat from oxidation pro-voked by different oxidation meth-ods.The most common bone diseasesof economic importance to thepoultry industry are tibial dyschon-droplasia (TD) and rickets. TheNRC recommends 200-300IU vita-min D3/kg feed to broilers andbreeders. However, studies with dif-ferent classes of poultry have shownbenefits from considerably higherdietary concentrations of the vita-min. Atencio et al., indicates that2800-3000IU vitamin D3 should bepresent in the diets of broiler breed-ers for maximum production andthe requirement may be higher foroptimum body ash of progency.Chicks fed 3,200IU vitamin D3/kgfeed had the highest body weightand tibia ash and the lowest TD andapproximate rickets incidences.Fritts and Waldroup, observed adecrease in TD incidence and sever-ity by supplementing vitamin D3 upto 4,000IU/kg in diets of broilerchicks.McCormack et al reported that10,000IU of vitamin D3/kg of dietcan prevent TD almost completely.It is suggested that the activity of thevitamin D metabolite 25-OHD3 isalmost twice that of vitamin D3. Itwould seem logical to use 25-OHD3

alone or in combination with vitaminD3 for improved supplementationprogrammes. Research indicated

Continued from page 31 that 25-OHD3 was effective toreduce TD in broilers, when Ca wasless than 0.85%.Optimum vitamin nutrition pro-grammes have used 3,000IU/kg ofvitamin D (0.5 D3 and 0.5 25-OHD3)to evaluate egg production parame-ters. Hens that receive the OVN(including 25-OHD3) had greatlyimproved laying rate and egg size,reduced broken eggs, better feedefficiency and lowered susceptibilityto oxidation of fresh and storedeggs. Turkeys receiving 25-OHD3

(Hy-D) were able to achieve growthwith good bone development, with-out lameness disorders.Not only does the OVN improvepoultry production and health, like-wise human nutrition for those con-suming poultry products isbenefited. An egg can provide any-where from 100% of human require-ments for vitamin K to only 0.3% ofrequirements for niacin. Higher lev-els of vitamins E, thiamin and pan-tothenic acid were determined inbroiler meat for birds receivingOVN.In addition to having poultry meatwith higher vitamin content, OVNcan even more dramatically increasevitamin content of eggs. The recentOVN studies with laying hensresulted in significantly higher eggconcentrations of vitamin A, E, thi-amin, riboflavin, pantothenic acid,biotin, folic acid and vitamin B12.Sheehy et al., showed a linear rela-tionship between diet α-tocopheroland its accumulation in muscle.Additionally, research confirms theability to elevate folic acid in eggs.Enrichment of eggs with folate ispossible when dietary folic acid lev-els are increased. The NRC require-ment for folic acid is 0.25mg/kg ofdiet. Folic acid in eggs can beincreased approximately three foldby increasing dietary folic acid to 2-4mg/kg.Eggs are among the few potentnatural sources of vitamin D forhumans. Recent research has indi-cated that vitamin D3 content ofeggs can also be further increased bysupplementing hen feed with vitamin

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CCoonnttrrooll OOVVNN ++ DDiiffffeerreennccee HHyy--DD ((%%))

Egg weight (g) 65.88 66.36 + 0.7XL eggs (%) 7.5 10.1 + 25.4Broken eggs (%) 1.43 1.14 - 20.3Daily feed intake (g/d) 117.2 114.5 - 2.3Lay (%) 80.2 82.4 + 2.7Egg mass (g/d) 52.84 54.68 + 3.5Cumulative feed conversion 2.218 2.094 - 5.6

Table 6. Performance parameters of laying hens (41-67 weeks of age)fed average vitamin supplementation concentrations (control) com-pared to those receiving Optimum Vitamin Nutrition and 25 hydroxycholecalciferol (Hy-D).

34 International Poultry Production — Volume 16 Number 4

D3. For groups of hens that received6,000 or 15,000IU/kg feed, eggyolk, vitamin D3 ranged from 9.1 to13.6 and from 25.3 to 33.7µg/100g,respectively.It is important to realise that vita-min content of eggs today is lowerthan it was in 1995. Feeding thesame levels of vitamins, Pérez-Vendrell et al reported vitamin A,vitamin E and vitamin B12 decreasingby 25.1, 37.5 and 33.0% comparedto the concentrations in 1995.The reason for lower vitamin con-tent in recent years is likely due toimprovement of layer feed conver-sion as a result of better poultrygenetics and management.Obviously, a lower total feedintake due to improved feed effi-ciency will make less quantities ofvitamins available to be transferredto eggs. This would apply to produc-tion of poultry meat as well. Greaterfeed efficiency limits the amount ofvitamins transferred to meat.Therefore, poultry diets now needhigher levels of dietary vitamins tojust have the same nutritional valueas in the past.For the purpose of cost reduction,there is the ‘false economy’ conceptthat vitamins should be removedfrom finisher diets. However,Gwyther et al reported that NRCvitamin recommendations weremuch too low to maintain broiler

performance. This study indicatedthat broiler vitamin requirementsexceed those recommended by theNRC and that the elimination of vit-amin supplementation from broilerdiets would severely impair perfor-mance. Withdrawal of riboflavin from thediet during the last weeks of a fin-

isher diet reduced content in thebreast muscle by 37%. Teeter and Deyhim eliminated vit-amins and/or minerals from broilerdiets for the last 21 days of life, dur-ing which time the birds wereexposed to heat stress.There was significant reduction in

live bird and carcase performance.

Performance tended to be poorestwhen the diet contained added traceminerals and no added vitamins, sug-gesting oxidation of the vitaminsalready present. n

References are available from the authors on request.

SummarylVitamin requirements (for example, NRC) established decades ago have changed little and do not reflect greatlyimproved genetic selection and changes in management procedures of modern poultry operations.

lVitamin supplementation allowances need to be set at levels that reflect different management systems that arehigh enough to take care of fluctuations in environmental temperatures, energy content of feed and influencing fac-tors (for example, infectious diseases, stress, parasites, biological variations, diet composition, bioavailability andnutrient interrelationships) that might influence feed composition or vitamin requirements.

lTo allow poultry to express their genetic potential and to account for not always ideal farm management condi-tions, optimum levels of vitamins are necessary. Top poultry industry leaders recognise the need for optimum vita-min nutrition (OVN).

lPerformance benefits from OVN diets for meat production include increased growth, feed efficiency, oxidative sta-bility of meat, resistance to high density stress and prevention of bone problems with vitamin D3 and/or 25-OHD3.For laying hens OVN diets improve all phases of egg production (for example, increased egg numbers, egg weights,percentage lay and increased feed efficiency).

lEggs and meat are excellent sources of bioavailable vitamins. Due to lower feed intakes, as a result of improvedfeed efficiency, vitamin levels have decreased in meat and eggs in recent years. Use of OVN concentrations in poultryfeeds will improve human nutrition as poultry products will be a dependable source of bioavailable vitamins.

l‘Risk versus benefits economics’ should be considered in reviewing and adjusting the vitamin fortification of poultryrations. The cost of fortifying the ration with the essential vitamins and increasing vitamin fortification levels should beweighed against the risk of losses from vitamin deficiency conditions and sub-optimum performance. For the modernsuccessful poultry operation, OVN is essential.

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