Steer responses to increasing proportions of legume when fed switchgrass hay1

Switchgrass (Panicum virgatum L.; SG) may have CP below recommended concentrations for feeding ruminants that limit animal performance when cut as hay and fed as the sole diet. Three experiments were conducted to determine the influence of white clover (Trifolium repens. L.) at 0, 15, and 30% of DM (Exp. 1), or alfalfa (Medicago sativa L.) at 0, 25, and 50% of DM with either headed SG (Exp. 2) or vegetative SG (Exp. 3) on steer DMI (kg/100 kg of BW) and DM digestion (g/kg). Eating behavior (Exp. 1) and masticated feed characteristics (Exp. 2 and 3) were also examined. Steer (Bos taurus L.) DM digestion of SG (Exp. 1) increased linearly (P < 0.01) from 544 g/kg on SG to 584 g/kg when clover composed 30% of the offered diet. However, steer DMI of headed SG (Exp. 2) was 1.61 kg/100 kg of BW with a DM digestion of 480 g/kg when fed alone, and both increased linearly (P < 0.01) to 2.68 kg/100 kg of BW and 578 g/kg, respectively, when alfalfa composed 50% of the offered diet. The DM digestion of vegetative SG (Exp. 3) increased linearly (P = 0.09) from 541 when fed alone to 575 g/kg when alfalfa composed 50% of the offered diet. The CP of masticated feed (Exp. 2 and 3) increased linearly (P < 0.01) and NDF decreased linearly (P < 0.01) with increasing alfalfa. Perennial legumes can be a useful source of CP in SG hay diets.