Abstract:
Under ad libitum feeding conditions, injected acetate disappeared more slowly from the blood of sheep fed on a diet of low protein oaten chaff than when 6% casein was added to the diet. Only 2 days after the sheep were changed from the high to the low protein diet, the rate of disappearance of injected acetate dropped considerably. An equally rapid rise occurred when the sheep were changed from the low to the high protein diet. After receiving casein per duodenum for 3 days, sheep fed ad libitum on low quality oaten chaff improved in their ability to cope with injected acetate.Propionate tolerance was rapidly improved when sheep were transferred from a low quality oaten chaff diet to one supplemented with casein, each offered ad libitum. The changes in ability to cope with acetate load are discussed in relation to possible mechanisms concerned, and a physiological mechanism of regulating voluntary feed intake is suggested. It is emphasized that further investigations are needed of the effect(s) of the nature of the diet upon the sheep's ability to utilize the metabolizable energy at ad libitum intake, particularly upon the avenues and efficiency of acetate utilization.