Undegraded intake protein supplementation: I. Effects on forage utilization and performance of periparturient beef cows fed low-quality hay

Hereford x Angus cows (n = 36; initial wt = 568 +/- 59 kg) were used to eva luate effects of undegradable intake protein (UIP) supplementation on forag e utilization and performance of beef cows fed low-quality hay. Treatments were control (unsupplemented) or one of three protein supplements. Suppleme nts were fed at 1.3 kg DM/d and included UIP at low, medium, or high levels (53, 223, or 412 g UIP/kg supplement DM, respectively). Supplements were f ormulated to be isocaloric (1.77 Meal NEm/kg) and to contain equal amounts of degradable intake protein (DIP; 211 g DIP/kg supplement DM). Intake of f orage was measured daily during six 7-d collection periods, which approxima ted mo 7, 8, and 9 of gestation and mo 1, 2, and 3 of lactation. Prairie ha y (5.8% CP) was offered daily for ad libitum consumption. Cows were weighed and condition-scored on d 7 of each period. Supplemented cows had greater (P = .01) total organic matter intake (g/kg BW) compared with control anima ls during gestation. Forage organic matter intake (g/kg BW) was greater (P less than or equal to .02) for control cows than for supplemented cows duri ng lactation. Digestion of OM and NDF was lower (P < .10) for control than for supplemented cows. Body weight of supplemented cows was greater (P = .0 1) than that of control cows on four of six weigh dates. Supplemental UIP d id not affect (P > .10) cow body weight or condition score. Body condition scores of supplemented cows were higher (P = .02) during mo 9 of gestation and during mo 3 of lactation compared with controls. Reproductive performan ce was similar (P > .10) among treatment groups, and there were few differe nces in calf performance. These data were interpreted to suggest that suppl emental protein can increase total tract OM and NDF digestion by beef cows and increase body weight. Increasing the level of UIP in the supplement had little effect on forage utilization or animal performance.