Modelling and predicting fat deposition rates in various South African sheep crosses using ultrasound technology

Abstract

Producers require an accurate predictive tool that can determine the optimal point of slaughter based on fat depth. The modelling of fat deposition with a simple mathematical model could supply in this need. Dohne Merino and Merino ewes were crossed with Dorper, Dormer and Ile de France rams and the crossbred offspring reared under optimal growth circumstances until one year of age. Fat deposition of lambs of both sexes were monitored from 80–360 days using ultrasound and the data subsequently fitted to various equations and evaluated for goodness of fit. A linear fitting of fat depth to age (R2 > 0.77) and live weight (R2 > 0.56) were deemed to provide the best fit. The slope parameters of the equations indicated that ewes deposited fat faster than rams and that Dorper crosses had the highest fat deposition rate. An attempt was also made to model loin muscle growth, but the model fit was adjudged to be unsatisfactory.