The prediction of the body composition of hill sheep from body weight, red cell volume and tritiated water space

Abstract

SummaryThe use of body weight, red cell volume and tritiated water space in the prediction of the body water, body-fat and soft tissue protein contents of hill sheep was investigated. Sixteen Blackface sheep, ranging in age from 2½ to 6½ years, were used before mating in November when in peak body condition and 21, of similar age distribution, were used in mid-lactation in June when in very poor body condition. Mean fat concentrations in the empty body were 188 and 28 g/kg in November and June, respectively.Body weight alone accounted for 46 and 14% of the variation in body-fat content in November and June, respectively. The inclusion of red cell volume as a second independent variate did not improve the efficiency of the prediction equations. When tritiated water space and body weight were used 77% of the variation in body-fat content was accounted for in both November and June. Separate equations for the November and June groups gave the most accurate estimate of body-fat content, but it was concluded that for most practical purposes a single relationship would be sufficiently accurate. Soft tissue protein content was best described as a simple function of body weight.The application of prediction equations from the literature to the present populations of sheep led to overestimates of body-fat content by up to 100%. It is suggested that prediction equations need to be specific to the experimental conditions operating or to the particular population under study.