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Growth and Reproductive Performance of Bulls and Heifers Fed Purified and Natural Diets. III. Blood Proteins, Glucose, Amino Acids and Hair Amino Acid Analysis (42–210 Days of Age)¹

U. S. Department of Agriculture

Abstract

Thirty-one bull and heifer calves were weaned onto purified diets containing either urea or isolated soy protein or a natural diet at 84 days of age. Blood glucose and protein were determined at 42 and 84 days of age, plasma free amino acids at 42, 84 and 210 days of age and the amino acid content of hair was determined at 210 days of age.

Calves fed the urea purified diet had significantly greater quantities of beta globulin than calves fed the isolated soy protein purified diet. Blood glucose significantly decreased from 42 to 84 days in calves fed the purified diets but increased slightly in calves fed the natural diet.

Blood plasma free amino acid patterns of the calves at 42 days of age were similar but differed significantly at 84 and 210 days of age. The concentration of the "essential amino acids" was markedly depressed in calves fed the urea purified diet compared to calves fed the protein containing diets. The concentrations of threonine, phenylalanine, valine, leucine, isoleucine, cystine, hydroxyproline and tyrosine were especially low, whereas the urea and serine concentrations were especially high in calves fed the urea purified diet compared to calves fed the isolated soy protein purified diet. Methionine and lysine concentrations appeared low but serine and glycine concentrations were high in calves fed the isolated soy purified diet compared to the natural diet.

Cystine concentration was low, whereas methionine concentration was high in the hair of calves fed the urea purified diet compared to the hair obtained from calves fed the protein containing diets at 210 days of age.

¹ The authors gratefully acknowledge the assistance of Dr. M. L. Crandall for the veterinary services performed in the care of the calves and for obtaining the blood samples.

² Animal Husbandry Research Division, A.R.S., Beltsville, Maryland.

³ Biometrical Services, A.R.S., Beltsville, Maryland.