Some aspects of protein nutrition and its relation to wool growth and body weight changes in the sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University

Abstract

Early studies involving dietary protein level effects on wool growth (Fraser and Roberts, 1933; Slen and Whiting, 1952; Ferguson, 1959) noted that over a wide range, dietary protein level remains relatively independent of wool growth rate. These observations led to the conclusion that once minimum protein levels were met, dietary protein was no longer a major factor limiting wool growth (Ferguson, 1959). For some time dietary protein has been known to be involved in a complex series of biochemical reactions within the rumen (reviewed by Barnett and Reid, 1961). Host notable of the reactions related to this study are those involved with deacination and fermentation of protein by the rumen microorganisns. After considering results of protein level experiments, knowledge of rumen microbial action on protein, and work with sheep indicating that nitrogen retention was increased by abomasal or duodenal protein infusions (Cuthbertson and Chalmers, 1950), Reis and Schinckel (1961) decided to by-pass rumen action by administering casein supplements through an abomasal cannula. The effect of "by-passed" protein supplements on wool growth rate was then assessed. Following supplementation, wool growth rate increased by 41 to 77%. These results suggested that protein nutrition is a major factor limiting wool growth.