Body composition in vivo. VI. The composition of ewes during prolonged undernutrition

Abstract

Ten Border Leicester x Merino ewes were divided into two groups on the basis of a initial calculation of their body composition. Group 1 comprised a group of six moderately fat ewes (fat content < 25% body weight), and group 2 four very fat ewes (fat content >40% body weight). The ewes were undernourished by feeding progressively diminishing quantities of a mixture of lucerne chaff and oats (1:1) until group 1 had lost 38.7 and group 2 33.7% of their initial weight in 150–200 days. Feed intakes and wool growth of the sheep were recorded and calculations were made of the body composition in terms of total body water, fat, protein, and ash as undernutrition progressed. Thiocyanate spaces, haematocrit values, and plasma, blood, and red cell volumes were also measured. Generally the ewes in group 1 exhibited a starvation syndrome which was characterized by the gradual depletion of the fat and protein reserves of the body until fat reserves had been almost completely used. Thiocyanate spaces in these ewes expanded relative to body weight, and the circulatory parameters showed a progressive shrinkage of the red cell volume while plasma volume was maintained. The ewes in group 2 differed markedly in their reaction to undernutrition in that three out of the four passed, after a time, into a phase of inappetence and died while still in a very fat condition.