Comparison of three methods for the in vivo estimation of body composition in dairy ewes

Abstract

Three methods for estimating in vivo body fat in sheep, by the assessment of body water using the deuterium oxide (Ddilution technique, adipose cell size (ACS) measurement and body condition scoring (BCS), were studied in mature ewes and compared to results obtained after slaughter and chemical analyses. Twenty Lacaune dairy ewes were slaughtered at three stages of lactation (30 days (n = 8), 60 days (n = 8) and 110 days (n = 4)), with a mean body weight (BW) of 72.7 ± 7.6 kg, 16.0 t 4.7 kg of body lipids (LIP) and 42.7 ± 3.8 kg of total body water. Body fatness ranged from 10.3 to 28.8 % of empty body weight. Although the ewes were relatively fat, the mean adipose cell volume of subcutaneous pericaudal or sternal adipose tissue (209 or 287 pl, respec- tively) was in the lower range of previously reported values, while cells from omental adipose tissue had a larger mean volume (804 pl) than has been previously reported. Due to differences in the frame of ewes, prediction of body lipids through D,O, ACS and BCS was improved by including body weight in the model. The best equations using ACS were obtained with subcutaneous fat tissues (sternal tissue: residual coefficient of variation (rCV) = 13.9 % and pericaudal: rCV = 17.8 %), fol- lowed by internal tissue (omental: rCV = 19.5 %). The rCVs of the prediction of body lipids with these in vivo methods were in general agreement with published works on cattle or sheep i.e. D 8.8 %, pericaudal ACS: 13.9 % and BCS: 16.7 %. The interest and limitations of the methods studied are dis- cussed in terms of different experimental objectives and constraints. (© Elsevier / Inra)