Corn silage versus grain sorghum silage as a supplement to growing steers grazing high quality pastures: Effects on performance and ruminal fermentation

Supplementation with corn silage (CS) or grain sorghum silage (SS) on average daily gain (ADG), rate of subcutaneous fat deposition (RFD) and ruminal fermentation characteristics were evaluated in 42 Angus × Hereford steers (187 ± 26 kg) grazing high quality pastures. Steers were assigned to one of three treatments in a randomized design being; TP, fresh pasture (700 g/kg grass and 300 g/kg legumes) fed ad libitum; TCS or TSS, with restricted pasture plus CS or SS, both finely chopped and rolled at dough grain stage, representing 400 g/kg of the total diet on DM basis, respectively. Two paddocks per treatment and 7 steers per paddock were used. Average daily gain was not affected by treatments (mean = 0.939 kg/day), but RFD was lower (P<0.03) for TSS versus TP steers. Dry matter intake was similar among treatments (mean = 6.99 kg/day), being silage intake 2.8 kg DM/(steer day) in supplemental treatments. Ruminal pH was similar among treatments (mean = 6.7), but NH3N concentration was lower (P<0.01) for TSS versus TP. Total VFA concentrations, molar proportions of acetate (A), propionate (P), n-butyrate and A:P ratio were not affected by supplementation. Silage supplementation resulted in increased stocking rates, from 2.45 in TP to 4.66 (TCS and TSS) steers/ha, and live weight production from 260 for TP to 469 (TCS) and 483 (TSS) kg/ha. Grain sorghum silage can replace corn silage to supplement growing steers without detrimental effects on performance and ruminal fermentation, thus being a good alternative in marginal areas where corn production is agronomically uncertain.