Feeding Sorghum to Increase the Value of Sheep in Feedlots

Abstract

High prices for sheep meat and the need for year-round supply means that grain feeding of sheep will continue as an important component of sheep production. Grain feeding low body weight lambs and cast-for-age (CFA) sheep from pastoral areas of eastern Australia at the end of the growing season can enable critical carcase weight grades to be achieved, sometimes doubling market returns. In parts of Australia sorghum grain is a cheaper alternative to other cereal grains but its use and nutritive value in sheep feeding systems is not well understood. This paper describes results from four experiments conducted by the Sheep CRC to investigate sorghum grain as a major component of diets fed to lambs and CFA ewes and wethers. The experiments involved comparisons of diets based on sorghum with a winter cereal grain and with commercial feed pellets, investigated the effects of various processing methods (whole grain, cracked, steam flaked and expandat®) and the effect of feeding sorghum grain with and without additional true protein and non-protein-nitrogen (NPN) sources. Growth, feed conversion, carcase performance and digestion parameters were measured. There were higher concentrations of starch in the faeces of sheep fed unprocessed sorghum grain (ca. 18 - 31 % of faecal OM) than when steam-processed grain was fed (4 % of faecal OM) to older sheep. Although steam flaking increased the digestibility of sorghum starch by CFA sheep it appears that the benefits of processing do not justify the costs. Substituting true protein sources for NPN did not significantly increase performance of CFA ewes.