STEP-UP PROTEIN SUPPLEMENTATION FOR BEEF-COWS GRAZING DORMANT, TALLGRASS PRAIRIE

Protein supplementation contributes significantly to expenses of maintaining pregnant beef cows (Bos taurus) on winter range. Two experiments evaluated winter supplementation schemes for grazing beef cows. Dehydrated alfalfa (Medicago sativa L.) pellets (DEHY) or soybean [Glycine max (L.) Merr.] meal/sorghum [Sorghum bicolor (L.) Moench.] grain (SS) supplements were fed during the third trimester of gestation. In Exp. 1, treatments were: (i) 5.3 lb/head/d DEHY, (ii) 3.7 lb/head/d SS; (iii) 3.8 lb/head/d DEHY, and (iv) DEHY averaging 3.7 lb/head/d across the supplementation period but fed in increasing amounts with advancing gestation (step-fed). In Exp. 2, the two supplements were each used with two feeding methods: level- or step-feeding (as in Exp. 1). Amounts fed averaged 5.8, 5.7, 4.3, and 4.2 lb/head/d for level-fed DEHY, step-fed DEHY, level-fed SS, and step-fed SS. In Exp. 1, weight loss to within 48 h postpartum was less for 5.3 DEHY (-123 lb) than for 3.7 SS (-157 lb), 3.8 DEHY (-171 lb), or step-fed DEHY (-181 lb), and cumulative body condition (BC) change was less for 5.3 DEHY (-0.38) and 3.7 SS (-0.43) than for 3.8 DEHY (-0.76) or step-fed DEHY (-0.86). In Exp. 2, weight loss to within 48 h postpartum was less for DEHY groups than for SS groups and was unaffected by feeding method (-104, -109, -161, and -155 lb for level-fed DEHY, step-fed DEHY, level-fed SS, and step-fed SS). A supplement type x method interaction occurred for BC change (-0.20, -0.26, -0.49, and -0.19 for level-fed DEHY, step-fed DEHY, level-fed SS, and step-fed SS). Treatments did not affect subsequent reproductive performance in either experiment. Although caution is advised in extrapolating these results to cows in poor condition, step-feeding does not appear to offer significant benefits over level-feeding for cows calving in moderate body condition.