H.A. Boekholt

1. Broiler chickens were fed 60-100% of recommended energy intakes to study the effects of energy restriction on protein and fat retention. 2. At an energy retention of 179 kJ/kg W0.75 d, only protein was retained. At higher energy intakes, each increment in retention had a rather constant composition: about 85% energy in fat and 15% in protein. At lower energy intakes body fat was mobilised whereas protein was deposited. 3. The efficiencies of energy retention in protein and fat were estimated to be 0.66 and 0.86 respectively. 4. The rather constant composition of additional retained energy after additional energy supply provides an explanation for a linear relationship between energy intake and energy retention.

Two cows, with fistulae in the rumen, proximal duodenum and distal ileum, were given diets varying in protein quality and quantity. Daily N intake/cow ranged from 149 to 330 g with lysine contents of 2.7 to 5.7 g/16 g N. The ammonia N constituted 2 to 9% of the N in duodenal contents and less than 2% of the N in the feedstuff, ileal contents and faeces. The proportion of alpha -amino N in non-ammonia N was greater in duodenal contents than in ileal contents and in faeces. The disappearance of non-ammonia N and alpha -amino N from the small intestine with different diets averaged 65% and 70% of the amounts in duodenal contents. (Abstract retrieved from CAB Abstracts by CABI’s permission)