Carcass composition of lambs including a method of assessment using tritiated water in vivo

Abstract

AbstractTwenty-four Suffolk cross lambs, the progeny of three sires, were reared artificially under standardized conditions and slaughtered at 40 kg live weight.The tritiated water technique as a means of estimating carcass composition in vivo was evaluated and carcass composition was established using both physical dissection and chemical analysis. Live-weight gain of the lambs from weaning was 389 g/day but the carcasses were lean. Dissected fat, lean and bone percentages were 20·5, 58·4 and 18·9 respectively. Differences between progeny groups were non-significant.Fat percentage was the most variable body component, although lower than in many other reported studies. The CV for dissected fat was 15·2% and for chemically analysed fat 15·9%. The correlation between estimates for the two methods was high (r = 0·90) despite there being quantities of other constituents in the dissected fat. It was not possible to demonstrate any relationship between reciprocal of tritiated water count and fat percentage or any other measurement of the composition of the whole carcass. Other measurements made on the live animal, such as fasted live weight and ultrasonic determinations of fat thickness and area of m. longissimus dor si were also not related to carcass composition.It is concluded that neither tritiated water count nor any of the other measurements of the live animal would be sufficiently accurate to be of value in performance testing.