Energy intake, nitrogen balance and water influx of Dorper sheep when consuming different diets

Abstract

Dorper sheep are well adapted to arid areas and inhabit extreme deserts. We hypothesised that these sheep would have low energy and nitrogen requirements, allowing them to be raised in these areas. We measured energy intake, N requirement and water influx of Dorpers (body mass = 40 kg) that were offered either lucerne hay (17·5% crude protein), lucerne hay plus wheat straw or wheat straw (3·25% crude protein) and water ad libitum. Dry matter digestibility and apparent digestible energy as a per cent of gross energy were 67·7% and 66·1%, respectively, for lucerne hay, and 46·5% and 50·7%, respectively, for wheat straw. Dorpers gained body mass and were in positive N balance on lucerne hay, lost body mass but were in positive N balance on lucerne hay plus wheat straw and lost body mass and were in negative N balance on wheat straw. Metabolisable energy intake was 925 kJ kg–0·75 day–1 on lucerne hay, 706 kJ kg–0·75 day–1 on lucerne hay plus straw, and 420 kJ kg–0·75 day–1 on wheat straw. Apparent N digestibility of Dorper was 76·9%, 68·1% and –24·3% for lucerne hay, lucerne hay plus wheat straw and wheat straw, respectively, and their water influxes on these respective diets were 3·74 1 day–1, 3·17 1 day–1 and 1·68 1 day–1. Energy and N requirements of Dorpers were similar to many sheep breeds and greater than a number of desert sheep and desert herbivores. We concluded that Dorpers did not appear to have special physiological adaptations of low energy and nitrogen requirements.