Ultrasound measurements of perirenal fat thickness to estimate the body condition of reproducing rabbit does in different physiological states.

Abstract

Sixty New-Zealand×Californian multiparous rabbit does were used to evaluate the capability of a computerized ultrasound system to estimate changes in body condition at different physiological states: parturition, 21st day of lactation, weaning and 28th day of gestation. Perirenal fat weight and carcass energy concentration were significantly correlated with live weight (r = 0.58 and 0.49, respectively; P<0.001) and ultrasound measurement of perirenal fat thickness (r = 0.51 and 0.45; P<0.001). The inclusion of quadratic and cubic terms of the perirenal fat thickness as independent variables significantly increased the coefficient of determination and lowered the residual standard deviation of the models, based on the live weight of the animals, to estimate the perirenal fat weight and the carcass energy concentration (P<0.01). However, these general models tended to overestimate the perirenal fat weight and the body energy concentration of lean animals (<50 g of perirenal fat weight or 8.0 MJ kg-1 of carcass energy concentration). When specific multiple regression equations for predicting perirenal fat weight and body energy of multiparous does were developed in function of their physiological state, prediction accuracy of equations improved for rabbits at parturition (R2 = 0.72 and 0.67), 21 days of lactation (R2 = 0.84 and 0.67) and weaning (R2 = 0.76 and 0.65). No model was able to predict either perirenal fat weight or carcass energy concentration of the multiparous rabbit does at 28th day of gestation. In conclusion, excluding animals in late gestation, ultrasound measurement of perirenal fat thickness seems to be a useful technique for in vivo estimation of the body condition of reproducing multiparous rabbit does.