Drought-Stressed Soybean Supplementation for Beef Cows1

Three experiments were conducted to determine the effects of supplementation with whole or rolled drought-stressed soybeans (DSSB) on performance of beef cows. Experiment 1 involved the inclusion of DSSB as a winter supplement for gestating spring-calving cows. Cows grazed abundant dormant native tall-grass prairie pasture and were individually fed 1 of 4 treatment supplements for 88 d prior to onset of parturition. Treatments for Exp. 1 were 1) 0.91 kg/d whole soybeans; 2) 0.91 kg/d rolled soybeans; 3) 1.26 kg/d of soybean meal and soybean hulls; and 4) no supplement (NCON). Experiment 2 was a 4 × 4 Latin square digestibility study with the same supplemental treatments as Exp. 1. Experiment 3 involved lactating fall-calving cows and heifers that had ad libitum access to Bermudagrass hay and were individually fed 1 of 3 treatments for 100 d through the winter. Treatments for Exp. 3 were 1) 0.91 kg/d whole soybeans; 2) 0.91 kg/d rolled soybeans; and 3) no supplement (NCON). All 3 groups of supplemented cows in Exp. 1 maintained BW and BCS compared with severe losses of BW and BCS among NCON cows (P < 0.05). Similarly, calves nursing NCON cows weighed 18 kg less than calves from supplemented cows at weaning (P < 0.05). No differences among treatments were detected for pregnancy rates. Dry matter intake was 31% greater for the supplemented treatments compared with NCON (P < 0.05) in Exp. 2. Supplementation also tended to increase total tract apparent DM digestibility (P = 0.14) and ADF digestibility (P = 0.10). In Exp. 3, cow BW were not affected by treatment during or after the supplementation period. There was a trend (P = 0.10) for supplemented cows to better maintain BCS during the supplementation period. Calves nursing supplemented cows tended to gain at a faster rate (P = 0.08) during the supplementation period compared with NCON calves. Pregnancy rates were not affected by treatments. This research indicates that DSSB can be an effective winter protein supplement for beef cows, and that the processing of the soybeans does not affect cow and calf performance or pregnancy rates.