Effect of genetic line on energy and nitrogen metabolism during late gestation in twin-pregnant ewes fed restrictedly

Abstract

Nitrogen and energy metabolism were measured in balance and respiration experiments performed seven weeks before expected lambing in twenty twin-pregnant ewes from two genetic lines: high average daily gain (Gain) and slaughter quality (Lean). Ewes were grouped according to liveweight (LW): heavier (Heavy) and lighter (Light) than the average for the genetic line. All animals were fed restrictedly, about 70 % of their energy requirements. Selection for slaughter quality rather than high daily gain increased apparent crude protein digestibility (77.9 vs 81.1% for Gain and Lean, respectively, P<0.05), but neither genetic line nor LW affected other parameters of quantitative nitrogen and energy metabolism.