Effects of pasture inclusion of mimosa on growth by sheep and goats co-grazing grass/forb pastures

Effects of mimosa alley-cropped in grass/forb pastures on growth performance of co-grazing sheep and goat wethers were determined. Eighteen sheep (Katahdin) and eighteen goats (>= 75% Boer blood), with BW of 22+/-0.3 and 21+/-0.2 kg, respectively, and age of 4 to 5 months were used. Wethers grazed 0.4-ha pastures of grasses and forbs for 16 weeks. Three pastures with alley-cropped mimosa (W) and three without (WO) were divided into four paddocks for 2-week rotational grazing. Based on mimosa leaf mass at the beginning of grazing periods and animal days, daily consumption of mimosa leaf DM averaged 47 g per animal, although mimosa leaf harvest was complete long before the end of the grazing periods. Mimosa leaf samples averaged 2.81, 37.8, and 85.9% N, NDF and in vitro true DM digestibility (IVDMD), respectively. Forage mass (grass and forbs) was similar between treatments before (2928 and 2695 kg/ha) and after grazing (1507 and 1452 kg/ha) for WO and W, respectively. Pre-grazed forage concentrations of N (1.25 and 1.24%), NDF (64.5 and 63.8%) and IVDMD (52.9 and 56.2%) for WO and W, respectively, were similar between treatments, as was also true post-grazing. ADG was numerically greater (P=0.17) for W vs. WO (70 vs. 51 g/d; SE=7.7). In summary, alley-cropped mimosa increased nutritive value of the forage available for consumption. Nonetheless, mimosa had limited effect on growth performance of co-grazing sheep and goats perhaps because of decreasing mimosa leaf availability as 2-week grazing periods advanced or overall relatively low intake of mimosa leaf.