Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Animal, Dairy, and Veterinary Sciences


J. O. Anderson


Chick feeding tests were conducted to study the effects of dietary imbalances among the three branched chain amino acids on growth rate. All diets fed in these tests contained about 18% protein. The indispensable amino acids (IAA) were found in two of the diets fed in the proportions found by Dobson et al. (1964) to be well balanced. One of the diets had all IAA at 85% of these balanced levels while the other had them all at 125% of these levels. The tests involved reducing the isoleucine, leucine and valine levels in the high IAA diet to the low levels in all combinations.

Growth rates were similar with the diets containing all ten IAA at the low levels, all ten at the high levels, or seven at the high levels and isoleucine, leucine and valine at the low levels. Generally, when only one or two of these three were reduced to the low levels, growth rates were lower. Thus there appeared to be a three-way interaction among these amino acids with the reduction in weight gain being the result of an imbalance and not of a deficiency. The changes in growth rate noted when the leucine level was reduced indicated that the leucine level in Dobson's balanced diet was relatively high; the isoleucine level appeared to be relatively low. The interaction between leucine and valine appeared to be more significant than the other two two-way interactions.

The effect of dietary level of these amino acids on the branched chain amino acid transaminase (BAT) activity in the liver and kidneys was determined. The differences noted were inconsistent. There tended to be a slightly higher activity in chicks fed the high levels of these amino acids, but the differences certainly were not as great as the changes in arginase activity reported by others when imbalanced diets were fed.

Chicks fed the diet low in valine and high in the other nine IAA were selected for fast or slow growth on this diet. They were raised to maturity and produced eggs that were hatched for feeding tests with the diets containing different levels of the branched chain amino acids. Only a limited number of chicks from the two strains were hatched. Performance of the chicks was similar to that of their parents when fed the low valine diet.