Chapter-07 104

FEEDING TRIALS ON DOGS FOR PALATABILITY

AND DIGESTIBILITY STUDIES

Chapter-07 105

1. INTRODUCTION

In addition to various parameters palatability and digestibility are important issues in

canine nutrition as they determine the consumption and utilization of the food, which finally

decide the health of the animal. The health of the animal depends on the nutritional adequacy

of their foods and studies on palatability and digestibility help to identify the nutritional

requirements of the pet food.

Dogs have extra taste buds than cats. In both species the sense of flavor is used to test

the palatability of food and to stimulate secretion from the salivary glands, the stomach and

sometimes the pancreas. Both dogs and cats usually reject food with a bitter taste. Dogs,

however, can taste a sweet sensation better than cats and also detect salty flavors at very low

concentrations. Cats experience many amino acids as salty and can associate them with

animal proteins.

To understand and evaluate the nutritional and palatability effects of pet food

containing extruded soybean, experiments were planned as outlined below.

I. Criteria for product evaluation

II. Palatability studies

III. Digestibility studies

I. CRITERIA FOR PRODUCT EVALUATION

Product effectiveness studies are generally carried out to evaluate the impact of

specific changes done in new pet food. The changes may be due to variations in the

nutritional parameters or variations in any other quality parameters like palatability or

digestibility. To ensure the new products performance focused parameters are considered

during product development study. The preference/palatability tests and digestibility tests are

the key tests to qualify the new product for release into the market.

Chapter-07 106

Unprocessed soybeans contain many antinutritive factors as discussed in Chapter 01.

The impairment of these anti-nutritive factors by extrusion process and their relative levels

are discussed in Chapter-04. After extrusion the extruded soybean was included in pet food

formulations. Different pet food formulations were done and extruded as pellets and the

details are discussed in chapter-05 and chapter-03 respectively.

II. PALATABILITY STUDIES

Preference studies are normally done to understand the inclination or likeliness of the

dog or cat towards the pet food. Palatability is a complex dimension, which includes the

animals, breed, palatants in the product, reaction/response by animals and observations by

formulators/manufactures. Palatability is one of the important aspects for any food

formulator during product development. Even though feeding trials are no longer required

for a food to meet the requirements for labeling a food "complete and balanced," palatability

studies are required during developing a new pet food. "Preference" and "acceptance" are

specific measurement techniques to assist in the investigation of assumed pleasant or

unpleasant sensations of food intake.

A. Preference test

The two-bowl preference test measures "choice" between a pair of test foods that are

fed simultaneously side by side. The results of a two-bowl preference test may indicate that

animals distinctly prefer one of the foods, thus the preferred food would be termed more

"palatable".

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B. Acceptance test

The one-bowl or monadic method quantifies food acceptance. In most cases this

technique is less sensitive' than the two-pan method. Palatability or preference for a food

substance depends upon mainly from the following points.

Olfactory appeal or freshness of the product

Taste (as it affects taste buds)

Size and texture of the product which includes crunchiness, chewyness, plasticity and

mouth feel

Nature of the ingredients

- Dosage and nutritional requirement of the product

Moisture content

Whatever the objectives of a new product may be, the palatability testing in the early

stages is made through the comparison between two products. Commonly accepted methods

of measuring palatability require calculating a quantitative score based on relative intake of

two samples in the target animals like pets. The feeding protocols for the animals, data

collection, analysis and comparison are generally associated with feeding trials. In animal

palatability tests, the end results are generally expressed as 'better than,' 'worse than,' or

'equal' when two different product samples are selected for palatability testing.

C. Palatability test protocol:

i. Twelve healthy dogs (9 crossbred and 3 native) were selected and housed

separately for palatability studies for twenty days,

ii. Dogs were acclimatized for two bowl tests and for daily feeding schedules such

as time, quantity and place,

iii. The known quantity of two pet foods was offered ad libitum simultaneously to 12

adult dogs in separate bowls along with water,

iv. Overall, each pet food consumption was recorded with the swiping of diets in the

bowls every day.

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VI.

The acceptance of the pet food under test was determined as average consumption

for the test period

The preference of the pet food was calculated based on the first approach to one

of the food out of two foods served to the dog.

D. Results

Table-01: Palatability comparison between Pet food with raw soybean RS-01 and Pet food with extruded soy bean ES-01(cha pter-05).

Dog No.

Breed Age (months)

Average food consumption (g/day)

Dog No.

Breed Age (months)

RS ES-01 1 C/B 8 25 350' 2 C/B 8 26 349' 3 C/B 8 0 370' 4 C/B 8 10 345' 5 C/B 48 35 320' 6 Native 18 45 345' 7 Native 16 5 365' 8 Native 14 15 355' 9 C/B 20 20 365' 10 C/B 21 25 342' 11 C/B 25 16 350' 12 C/B 30 20 360'

Average consumption (g/dog/day) 20 351' Average consumption % 05.30 94.60

Preference % 00 100

Chapter-07 109

Table-02: Palatability comparison between Pet food with 15% extruded soybean (ES-01) and Ft jt food with 3C '% extruded so ybean (ES -02).

Dog No.

Breed Age (months)

Average food consumption (g/day)

Dog No.

Breed Age (months)

ES-01 ES-02 1 C/B 8 240 250

2 C/B 8 249 249

3 C/B 8 265 270 4 C/B 8 245 255

5 C/B 48 220 270

6 Native 18 245 255 7 Native 16 240 250 8 Native 14 260 243 9 C/B 13 250 265

10 C/B 13 250 245 11 C/B 25 225 270

12 C/B 30 260 240 Average consumption (g/dog/day) 245 255 Average consumption % 49 51 Preference % 55 45

The comparison of palatability results in table-01 indicated that the average pet food-

RS consumption was 20.1 gram/day/dog with 5.3% total consumption levels compared to pet

food ES-01 consumption of 351 gram/day/dog with 94.6% total consumption.

The palatability comparison of pet foods with 15 and 30% in table-02 indicated that

the average consumption of pet food-ES-01 was 245 gram/day/dog with 49% total

consumption levels compared to pet food ES-02 consumption of 25 5 gram/day/dog with 51%

total consumption.

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E. Discussion

The data in table-01 and table-02 indicated that pet food with extruded

soybean was preferred 100% over pet food with raw soybean indicating off flavor in pet food

RS. This is also supported by 94.6% consumption levels of pet food ES-01 compared to pet

food RS with 5.3% consumption levels. There is clear indication that soybean, if not

extruded to impair undesirable compounds such as lipase would contribute to off flavours in

soybean products. This observation supports the earlier inspections made by JM Dust and

Trivedi^ that palatability can be influenced by flavour, food texture, size and shape. This is

evidenced with the preference of dogs to pet food with extruded soybean indicating the

absence of unpalatable flavours. This is further confirmed with the trial data as indicated in

table-02 where it is demonstrated that both pet foods ES-01 and ES-02 were preferred at the

ratio of 55:45. This indicates that there is similarity in palatability of pet food containing

extruded soybean. The preference for the pet food with extruded soybean emphasizes the

need for the treatment of soybean by extrusion at 120-140°C to improve its nutritive values.

III. DIGESTIBILITY STUDIES

Generally the rate of the catabolism of a protein is determined'' by two factors,

namely by the rate of its digestion and by that of its absorption as both factors are considered

as inherent parts of protein quality. Digestibility studies are done to evaluate the product

efficacy, which can be either for maintenance, growth, body condition or any other

observations. Usually digestibility trials involve an experiment by which the amount of

nutrients actually digested and absorbed from a measured amount of food consumed by

animal is determined. The digestibility depends on various parameters like; age of the dog,

type of food, level of cooking or gelatinization in the given food and type of ingredients used

for the preparation of food etc. The following study data explains the digestibility levels of

pet food with extruded soybean.

A. Digestibility study protocol:

1. Determination of nutrient value of the pet food by in-vitro analyses^ for crude protein,

crude fibre, crude fat, NFE and the total digestible nutrients.

2. Randomization of dogs was done and the dogs were acclimatized for daily feeding

schedules such as time, quantity and place, atleast 5 days prior to actual

experimentation.

3. The observation for daily food intake and leftover was recorded during

acclimatization and collection period.

4. The fecal samples were collected on daily basis for 5 days and placed into labeled

plastic bags. Samples were frozen as they were collected.

5. Fecal sample scoring was done based on the following scale

Table-03: Fecal evaluation score'

Nature of the stool Fecal Hard, dry pellets 1 hard, formed, dry stool that remains firm and soft

2

soft, formed, moist 3 soft, unformed stool that assumes shape of container and is pudding­like

4

watery, liquid that can be poured 5

6. Fecal samples were analysed for moisture (fresh) and pooled fecal samples for

nutrient value (dry) example; crude protein, crude fibre, crude fat. NFE and the total

digestible nutrients.

7. Proximate analysis was done for pet food and digestibility nutrient study was

planned as per the method followed by Blackburn and Southgate'

8. ME values are calculated as per AAFCO quantitative methods.

9. Digestibility co-efficient, Total digestible nutrients were calculated

Chapter-07 112

B. Digestibility results:

Table-04: Experimental animal details

Dog No. Breed Age

(months)

B.Wt

(kg)

Food

(g/day)

1 C/B 8 11.6 200

2 C/B 8 12.1 200

3 C/B 8 12.8 213

4 C/B 8 11 190

5 Native 48 17 260

6 Native 18 14.3 225

7 C/B 16 15 250

8 C/B 14 15 225

9 C/B 13 14 245

10 C/B 13 14.5 255

Average - 15.4 13.73 226.3

Table 05: Pre-trial investigation results -Pet food

Proximate Principle Found

Moisture % 4.402

Crude Protein % 33.97

Crude Fibre % 1.50

Crude Fat % 16.735

Ash % 5.90

NFE % 37.493

Dry Matter% 95.598

Gross Energy (Cal/g) 4.71

Metabolizable Energy (Cal/g) 3.92

Chapter-07 113

Table 06: Post-trial investigation results: Chemical composition in excreta

No. Parameter Average value Found

1 Digestible Dry Matter (DDM) % 56.99 ±3.469

2 Digestible Crude Protein (DCP) % 21.48 ±1.725

3 Digestible Crude Fibre (DCF) % -2.471 ±0.762

4 Digestible NFE (DNFE) % 43.41 ±3.506

5 Digestible ether extract (DEE) % 15.27 ±0.41

6 Total Digestible nutrients (TDN) % 96.76 ±3.064

7 Actual GE utilized Cal/g 2.897 ±0.146

8 Actual GE excreted Cal/g 1.813±0.146

9 % of GE utilized 61.5±3.10

10 % GE excreted 38.5 ±8.041

11 Metabolizable Energy (ME) K.cal/kg 3531 ± 122.43

12. Fecal score 2.5-3.5

Out of 16.735% of ether extract estimated, 15.27% is digestible with 91.25%

utilization. Estimated crude protein was 33.97% with approximately 26% utilization,

indicating protein digestibility coefficient of 76%. The Total Carbohydrates estimated

was 43.40%. out of which approximately 41% is digestible with 94.33% utilization. Out

of 4.71 cal of gross energy calculated per gram of food, 2.897 cal/g was absorbed

(61.5%) and 1.813 cal/g (38.5%) excreted in the feces. The metabolizable energy

calculated from the fecal matter is approximately 3530 Kcal/kg of food. Fecal output

score was 2.5 to 3.5.

Chapter-07 114

C. Discussion:

Out often dogs, eight dogs maintained a stable body weight during digestibility trial. The

details of the dogs are given table-04. The large variation in breed of the dogs made it

difficult to determine any real differences between the breeds so the data were grouped

together. The determination was done for nutrient profile of the experimental pet food and

excreta and data is indicated in table-05 and 06. It is shown that approximately 60% of the

Dry Matter is digestible with 40% excretion.

Variation in protein quality and amino acid availability among major protein ingredients

and the response to varying levels of inclusion and processing conditions, their availability

may be variable among animal meals. Out of 16.735% of ether extract estimated, 15.27% is

digestible with 91.25%) utilization. Out of 33.97% crude protein estimated, approximately

26%) is utilized, therefore protein digestibility coefficient is 76%). These values are similar to

the observations made by J. M. Dust' for various ingredients and their digestibility

coefficients in pet food. He discussed that chemical composition and quality of alternative

protein sources differ greatly among ingredients within the same category. These

observations are also supported by G. C. Fahey, Jr .̂ and H. S. Hussein'^ where it was

discussed that alternative raw materials in pet food tend to vary in their nutrient availability

and hence their implications in pet food. Since, the nutrient availability gets influenced by

process conditons", maintaining optimum condhions during processing are very critical. By

extrusion technology (chapter-04), the antinutritive and undesirable compounds of soybean

are inactivated. The Pet food containing such extruded soybean resulted in better palatability

compared to the diet containing raw soybean. During digestibility studies it was observed

normal fecal score and volume. Hence, extruded soybean can be used in pet food

formulations as the antinutritive factors and undesirable compounds are impaired by

extrusion process (chapter-04).

Chapter-07 115

As discussed by G. M. Clapper et al ,̂ that fecal bulk and flatulence are the greatest

concerns in recommending the soy product inclusion in pet food. In contrast to his

observations, as indicated in table-06, the fecal volume and flatulence were observed normal

with fecal score^ of 2.5 to 3.5 during pet food feeding trials. This score indicates that fecal

matter is hard, formed, dry stool that remains firm and soft and moist. This is due to

formulations of pet food with extruded soybean protein and optimum pet food extrusion

conditions.

2. Conclusion

Soybean processing technologies such as extrusion aids in increased availability of all

nutrients due to impairment of antinutritive and undesirable compounds. The digestibility

score and the improvement in palatability of pet food containing soybean protein indicate

that extruded soybean can be used in pet food diets as nutritive and economical ingredient.

Thereby it is inferred that extruded soy protein when formulated with other protein sources

that has balancing amino acids can give an economical source of highly available and reliable

quality protein to the pets.

Chapter-07 116

References:

1. Anonymous: Guido schroeder, the concept of palatability and digestibility and

assessments by means of trials. Companion animal nutrition,

2. J. M. Dust C. M. Grieshop*, C. M. Parsons*, L. K. Karr-Lilientha 1*, C. S.

Schasteent, J. D. Quigley, lllj, N. R. Merchen*, and G. C. Fahey, Jr. *1 Chemical

composition, protein quality, palatability, and digestibility of alternative protein

sources for dogs *University of Illinois at Urbana-Champaign, Urbana 61801;

tNovus International, Inc., St. Charles, MO 63304; and JAPC, Ankeny, lA 50021

3. Trivedi, N., J. Hutton, and L. Boone. 2000. Useable data: How to translate the results

derived from palatability testing. Petfood Ind. 42:42-44.

4. Donald D. Van Slyke and George F. White., the relation between the digestibility and

the retention of ingested proteins., the journal of biological chemistry, 1991, page 219

-229.

5. G. M. Clapper. C. M. Grieshop, N. R. Merchen, J. C. Russett, J. L. Brent, Jr., and G.

C. Fahey, Jr., Ileal and total tract nutrient digestibilities and fecal characteristics of

dogs as affected by soybean protein inclusion in dry, extruded diets J. Anim. Sci.

2001,79:1523-1532

6. AOAC. Official Methods of Analysis. Assoc. Offic. Anal. Chem., 1995, Washington,

DC.

7. N.A. Blackburn, D.A.T. Southgate A.R.C, Food Research Institute, Norwich, UK,

protein digestibility and absorption: effects of fibre,

and the extent of individual variation. Item 3.2.4 of the Provisional Agenda, Joint

FAO/WHO/UNU Expert Consultation on

Energy and Protein Requirements. 1981.

8. Banerjee. G.C. A Text Book of Animal Husbandry, 8th edition, 1999,631-653.

9. G. C. Fahey, Jr. and H. S. Hussein.. The nutritional value of alternative raw materials

used in petfood. Proc. Petfood Forum, 1997. pp. 12-24.

10. H. S. Hussein and G. C. Fahey, Jr. Nutrition research with petfood implications.

Proc. Petfood Forum, 1997. pp. 26-43.

Chapter-07 117

ll.Jurgen Zentek, Sonja Fricke, Marion Hewicker-Trautwein, Britt Ehinger, Gunter

Amtsberg and Christoph Baums 2004, Dietary Protein Source and Manufacturing

Processes Affect Macronutrient Digestibility, Fecal Consistency, and Presence of

Fecal Clostridium perfringens in Adult Dogs-'= The American Society for

Nutritional Sciences J. Nutr. 134:2158S-2161S, August.