In vivo prediction with tritiated water of chemical and dissectible components of the dressed carcass of sheep growing at different rates

Abstract

Two groups of Border Leicester x Merino wether weaner sheep were given a concentrate ration either ad libitum or at 60% ad libitum. Mean growth rates were 255 and 136 g/day respectively. Animals were slaughtered at predetermined liveweights over the range 20–45 kg after a 30 hr fast, during which tritiated water (TOH) space was measured. The right half-carcass was dissected into fat, muscle and bone, and the left half-carcass was minced and analysed for chemical components (fat, protein, ash, water and energy).

The relationships between the weight of carcass components and carcass weight were examined by regression analysis and were similar for both groups. Relationships between the weight of dissected fat, muscle and bone and chemical fat, protein and ash respectively were also determined.

The chemical and dissected composition of the carcass could be predicted accurately from fleecefree fasted liveweight. The addition of TOH space to the regression equation improved the prediction of dissected and chemical fat and energy. The most accurate equation for bone included liveweight and age. It is suggested that tritiated water has only limited application in the prediction of dressed carcass composition in vivo.