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Study on effect of feeding extruded soybean food on reproductive hormone profile in pet dogs.


Nutrition plays a complex and controversial role in Animal health. Today, the animal feed industry worldwide is becoming increasingly dependent upon vegetable protein sources. There are many hundreds of these bioactive plant chemicals found in dietary sources of fruits, vegetables, legumes, whole grains, nuts, seeds, herbs and spices. Isoflavones are a class of organic compounds and biomolecules related to the flavonoids [11]. Increasing consumer awareness of soybean as a healthy food ingredient has led to a tremendous growth in sales of soy isoflavone-enriched foods and dietary supplements [12]. Although the active components of soy proteins have not been clearly determined, a large number of studies have reported that isoflavones are the most beneficial group of soy components. Phytochemicals such as isoflavones occur naturally in plants and mostly in soybeans. Phytochemicals are bioactive compounds and are non-nutritive, as they do not play any nutritional role. They act as phytoestrogens in mammals. Isoflavones have the ability to behave as estrogen mimics, but also have other important non-hormonal properties that have attracted the attention of many investigators [13]. After ingestion soybean isoflavones are hydrolyzed by intestinal glucosidases, which releases the aglycones, daidzein, genistein and glycitein. These may be absorbed or further metabolized to many specific metabolites, including equol and p-ethylpheno [1,9]. As indicated in fig-O1 and 02, the two primary

Isoflavones that are found in soybean foods are daidzein [4,7-dihydroxyisoflavone] and genistein (4', 5,7-trihydroxyisoflavone) and their respective glucosides, genistein (fig-O1) and daidzein (fig-02). Soybean foods typically contain more genistein than daidzein, although this ratio varies among different soybean products. Isoflavones have received a great deal of research on non-hormonal properties especially for possible cancer and heart disease-preventive properties [3]. Though much attention by researchers was given to its beneficial effects, not much work was focused on phytoestrogens and its pseudo estrogenic activity [13] in pets when soybean is incorporated in pet foods. The objective of this study was to evaluate the use of extruded soybean in pet food formulations and its implications on dog's reproductivity.

Hence the studies were planned to understand the possible effects of extruded soybean enriched pet food feeding trials on dogs.




The determinations of concentrations of hormones in biological fluids including plasma, urine, saliva and feces have been useful in determining the reproductive status of animals'. Although there are a number of factors that influence hormone concentrations, the hormone fluctuations do happen due to nature of food intake.

Experimental Details

The feeding trials for 'pet food with extruded soyabean' was conducted on six adult cross- bred dogs aged approximately 30 months. The dogs ranged from 12 to 25 kilograms in body weight. This study was approved by the Institutional Animal Ethics Committee and all the dogs were cared for according to the principles outlined in the "CPCSEA GUIDELINES FOR LABORATORY ANIMAL FACILITY" & NIH Guide for the Care and Use of Laboratory Animals (NRC, 1985 (18)).

A. Study protocol

(i) Six healthy dogs of three male and three female were selected and housed separately.

(ii) 400 gram of pet food enriched with extruded soybean was offered simultaneously to all adult dogs in separate bowls along with water for a period of 52 weeks.

(iii) Before and after the trial period the dogs were examined for physical health condition.

(iv) The blood was collected 14 and serum seperated before taking for hormone analysis.

Testosterone levels in male dogs, progesterone and estrogen levels in female dogs were tested and the hormone levels of experimental dogs are compared with normal values.

B. Composition of the diet

A typical pet food formula consists of the following specifications and ingredients and the formulations are done as per regular maintenance diet [15,16,17] for dogs. The pet food formulation was done using the ingredients as mentioned in table-02 and to meet the product specifications indicated in table-O1. The ingredients such as extruded soybean, poultry byproduct meal, ground wheat, ground rice, rice bran, corn gluten meal, vitamin, mineral and salt mix were used to in the formulation. Ground wheat and rice were incorporated as starch additives, rice bran as source of fibre, soybean, poultry byproduct meal and corn gluten meal as protein sources. The composition of this formula was extruded and fed to the dogs to assess the effect of extruded soybean pet food on pets' re-productivity.

Feeding data


In this food interaction study, the mean average consumption of Pet food was 353g/day/dog as indicated in table-04. During feeding programme dogs maintained normal health and weight.

As indicated in table-03, the pet food consumption was recorded minimum of 345 g/day for dog No. 6 (native breed) and maximum of 363 g/day for dog No. 3 (cross bred) for whole feeding trial period of 52 weeks. As indicated in table-05, the testosterone levels in serum samples varied between 173 to 368 lug/dl for male dogs. In female dogs the progesterone levels varied between 0.67 to 4.76 qg/ml and estradiol levels remained constant at <10 ng/ml.


As indicated in Table-05, it was demonstrated that feeding of pet food did not influence the main sex hormones in serum of the dogs indicating that Pet food containing extruded soybean may not influence the serum progesterone, estrogen and testosterone levels. This discussion further supports the earlier studies of W. Gregory Dr., Urbana [12] where they demonstrated the negative or no effect of soy protein in rat reproductive system. The progesterone and estrogen levels of dogs are in normal range of 0.67 to 4.76 igg/ml and <10 bg/ml respectively as indicated in table-06 and as discussed by Foster & Smith, Inc [8]. and Hase M. [9]. The serum testosterone levels are in the range of 173 to 368 ng/dl. Testosterone levels in dogs' range [1] from 10l00ng/dl during normal seasons. However, the range may increase depending upon peak reproductive seasons and climatic conditions. The results indicated that testosterone levels are similar to the values as observed in normal healthy dogs.


The objective of this study was to evaluate the use of extruded soybean in pet food formulations and its implications on dog's fertility profile. It is indicated through hormone serum levels that the main sex hormone were not affected by feeding the pet food containing extruded soybean for 52 weeks. Hence extruded soybean can be used in pet food formulations.


[1] Axelson M, Sjovall J, Gustafsson B, Setchell KDR. 1984, Soya- A dietary source of the non-steroidal oestrogen equol in humans and animals. J Endocrin, 102:49-56.

[2] Anne Patterson RD

[3] Setchell KDR, Adlercreutz H. Mammalian lignans and phyto-oestrogens. Recent Studies on their formation, metabolism and biological role in health and disease. In: Rowland IA, ed. The Role of Gut Microflora in Toxicity and Cancer. New York: Academic Press 1988:315-345.

[4] Liu, K. Chemistry and nutritional value of soybean components. Ch. 2. In "Soybeans: Chemistry, Technology, and Utilization ". Aspen Publishers, Inc. Frederick, Md, 1997, pp 25-113.

[5] Liener, I. E. Implications of antinutritional components in soybean foods. Critical Reviews in food Science and Nutrition 1994, 34:31-67.

[6] Kakade, M., N. Simons, I. Liener, and J. Lambert. Biochemical and nutritional assessment of different varieties of soybeans. J. Agr. Food Chem. 1972, 20:87-90.

[7] Mounts, T. L., Wolf, W. J., and Martinez, W. H.. Processing and Utilization. Soybeans: Improvement, Production, and Uses (J. R. Wilcox, Editor). Agronomy Monographs No. 16. Amer. Soc. Agronomy, Madison, Wi., U.S.A,1987.

[8] Anonymous: Foster & Smith, Inc Hormone Levels: Determining Breeding Times and Whelping Dates,

[9] Hase M, Hori T, Kawakami E, Tsutsui T, Mar, Plasma LH and progesterone levels before and after ovulation and observation of ovarian follicles by ultrasonographic diagnosis system in dogs, J. Vet. Med Sci, 2000, 62(3): 2438.

[10] Kaufman PB, Duke JA, Brielmann H, Boik J, Hoyt JE. 1997, "A comparative survey of leguminous plants as sources of the isoflavones genistein and daidzein Implications for human nutrition and health" J Altern Compl Med 3:7-12

[11] M. UZZAN AND T.P. LABUZA, Critical Issues in R&D of Soy Isoflavoneenriched Foods and Dietary Supplements, 2004, JOURNAL OF FOOD SCIENCE CRH77 Vol. 69, Nr. 3.

[12] Setchell KDR, Borriello SP, Hulme P, Axelson M. 1984, Non-steroidal estrogens of dietary origin: possible roles in hormone-dependent disease. Am J Clin Nutr, 40:569-578.

[13] S. J. Delaney,. H. Kass, Q. R. Rogers, A. J. Fascetti, Plasma and whole blood taurine in normal dogs of varying size fed commercially prepared food Journal of Animal Physiology and Animal Nutrition, 2003, 87 (5-6), 236-244.

[14] BIS (Bureau of Indian Standards), August 1987, Indian standard Specification for Dog feeds, IS 11968-1986, page 4-5, Appendix-A, Clause 2.4.

[15] Drs. Foster & Smith, Inc. 2007, Protein Requirements for Good Nutrition, (AAFCO nutrient profile) Veterinary & Aquatic Services Department,

[16] AAFCO: Association of American Feed Control Officials Incorporated. Official Publication 2001. Atlanta:

[17] Joannou GE, Kelly GE, Reeder AY, Waring MA, Nelson C. A urinary profile study of dietary phytoestrogens. The identification and mode of metabolism of new isoflavonoids. J Steroid Biochem Molec Biol 1995;54:167-184

[18] NRC. 1985a. Guide for the Care and Use of Laboratory Animals,Publication no. 85-23 (rev.). National Institutes of Health, Bethesda, MD

B. Purushotham *, PM Radhakrishna (1), BS. Sherigara (2) and Shiva Kumar (1)

Department of Post Graduate Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, Shimoga-577 451

* Tetragon Chemie Pvt. Ltd., IS 40, KHB colony, Yelahanka New Town, Bangalore-560106 Corresponding Author Email:

(1) Research and Development Centre, Tetragon Chemie Pvt. Ltd., Bangalore

[2) Industrial chemistry, Kuvempu university
Table 01: Maintenance diet specifications for adult dog.

Constituent %   Specification

Moisture        10.00
Crude protein   24.00
Crude fat       08.00
Crude fibre     05.00

Table 02: Pet food formulations.

Sl. No.   Ingredients                        Quantity
                                             (in %)

1.        Extruded soybean                   31
2.        Ground wheat                       36
3.        Ground rice                        5
4.        Rice bran                          2
5.        Poultry by product meal            15
6.        Corn gluten meal                   5
7.        Additives                          0.5
8.        Vitamins, Minerals and salt mix.   5

Table 03: Pet food feeding with average consumption details.

Dog            Age        Daily average food consumption
No.   Breed    (months)   (g/day)


                          I     II    III   IV    V     VI

1     C/B      8          350   340   361   346   355   365
2     C/B      8          349   352   370   352   352   353
3     C/B      8          370   365   375   367   365   365
4     C/B      8          345   355   365   345   355   355
5     C/B      48         350   360   340   367   340   320
6     Native   18         345   347   350   347   367   347

Dog   Daily average food consumption
No.   (g/day)


      VII   VIII   IX    X     XI    X1I

1     355   346    357   360   355   356
2     353   354    359   344   350   369
3     364   354    360   345   365   366
4     344   340    355   343   358   357
5     365   354    350   356   349   349
6     335   357    335   335   348   330

C/B= Cross Bred breed

Table 04: Average mean consumption of pet food.

Dog   Breed    Age        Mean average
No.            (months)   consumption g

1     C/B      8          353.83
2     C/B      8          354.75
3     C/B      8          363.41
4     C/B      8          351.41
5     C/B      48         350.00
6     Native   18         345.25

Total mean consumption    353.00

C/B= Cross Bred breed

Table 05: Hormone levels in experimental dogs after feeding trials.

Dog   Dog      Age (months)   Found value
                              Testosterone   Progesterone   Estradiol
                              ng/dl          ng/ml          ng/ml

1     C/B      8              358.67         --             --
2     C/B      8              173.99         --             --
3     C/B      8              368.63         --             --
4     C/B      8              --             4.76           <10
5     C/B      48             --             1.24           <10
6     Native   18             --             0.67           <10

C/B= Cross Bred breed

Table 06: Progesterone and estrogen levels for breeding. *

Day             Estrogen   Progesterone Level
                Level      (ng/ml)

-3 day          High       < 1
-2 day          Moderate   2-3
-1 day          Low        3-4
0 (ovulation)   Low        5
+1 day          --         > 5
+2 day          --         > 5
+3 day          --         > 5
+2-3 weeks      --         10-80
+62 day +/- 1   --         2
+63 +/- 1       --         1

* Foster & Smith, Inc Hormone Levels: Determining Breeding Times
and Whelping Dates,
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Article Details
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Author:Purushotham, B.; Radhakrishna, P.M.; Sherigara, B.S.; Kumar, Shiva
Publication:International Journal of Biotechnology & Biochemistry
Article Type:Report
Geographic Code:9INDI
Date:Sep 1, 2009
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