Dry matter intake and digestibility of temperate pastures supplemented with sorghum grain in wethers and heifers

Abstract

The aim of this study was to evaluate the effect of sorghum grain supplementation on total and forage dry matter (DM) intake and digestibility of wethers and heifers consuming temperate pasture. Twenty four Corriedale x Milchschaf wethers and 24 crossbred heifers fed temperate pasture were non-supplemented or supplemented with sorghum grain at 5, 10 or 15 g/kg body weight (BW). Offered and refused feed were measured for 11 days and faeces voided were recorded daily during five days. Samples of feeds and faeces were collected daily and analyzed for DM. Supplement inclusion led to an inverse response in both species. Total dry matter intake (TDMI) of supplemented wethers was 20% lower than non-supplemented ones. Forage dry matter intake (FDMI) averaged 40% less in supplemented groups than in non-supplemented ones. Heifers receiving the supplement had 23% more TDMI but 10% less FDMI than non-supplemented, and lower FDMI was observed as supplementation increased. Dry matter digestibility (DMD) was 0.69 for wethers and 0.65 for heifers, with no differences between treatments. When the results from all animals were analyzed together, no differences on TDMI, lower FDMI and higher DMD were observed for the supplemented groups. In conclusion, sorghum grain supplementation affected TDMI differently in the two species, reducing TDMI in wethers and increasing TDMI in heifers. Supplementation reduced FDMI, the reduction being higher in wethers than in heifers. Dry matter digestibility of supplemented diets was higher, probably due to grain digestibility.