Escape protein and weaning effects on calves grazing meadow regrowth

Abstract

Forty spring-born calves grazing subirrigated meadow regrowth after haying in July were assigned to 2 weaning and 2 supplementation treatments in fall of 1995 and 1996. Weaning treatments were weaning on 1 September or nursing during the duration of the trial. Supplementation treatments were no supplement or supplemental undegraded intake protein (UIP). An 80:20 (dry matter basis) blend of sulfite liquor treated soybean meal and feather meal was the source of undegraded intake protein (undegraded intake protein = 45% of supplement dry matter). Supplemented nursing calves received 0.50 kg of supplement daily whereas supplemented weaned calves received 0.91 kg of supplement daily. Weaned and nursing calves grazed subirrigated meadow regrowth throughout the trial. The trials were conducted from 17 October to 18 November 1995 and 5 September to 4 November 1996. Milk intake was measured by the weigh-suckle-weigh technique. Diet samples collected from ruminally cannulated calves after rumen evacuation averaged 12.5% crude protein and 54.8% in vitro organic matter digestibility. No supplementation x weaning management interactions were detected (P > 0.18). Nursing calves had greater weight gains (0.95 vs. 0.59 kg day(-1); P = 0.001) and lower forage intakes (2.36 vs. 2.96 kg day(-1); P = 0.009) than weaned calves. Supplementation with undegraded intake protein increased (P = 0.03) daily gains of calves compared to nonsupplemented calves 0.88 vs 0.66 kg day(-1), respectively. Forage intake as a percentage of body weight tended to be higher in non-supplemented calves (P = 0.09). However, total intake (forage plus supplement) as a percentage of body weight tended to be higher in supplemented calves (P = 0.14). Total intake (kg day(-1)) was greater (P = 0.01) for calves supplemented with undegraded intake protein. Milk intake did not differ between supplemented and unsupplemented calves (P > 0.52). We concluded that subirrigated meadow regrowth forage was limiting in metabolizable protein and that milk represents an important source of metabolizable protein for grazing calves.