Escape protein and weaning effects on calves grazing meadow regrowth

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 nursin g during the duration of the trial. Supplementation treatments were no supp lement or supplemental undegraded intake protein (UIP). An 80:20 (dry matte r 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 su pplement daily whereas supplemented weaned calves received 0.91 kg of suppl ement daily. Weaned and nursing calves grazed subirrigated meadow regrowth throughout the trial. The trials were conducted from 17 October to 18 Novem ber 1995 and 5 September to 1 November 1996. Milk intake was measured by th e weigh-suckle-weigh technique. Diet samples collected from ruminally cannu lated calves after rumen evacuation averaged 12.5% crude protein and 54.8% in vitro organic matter digestibility. No supplementation x weaning managem ent interactions were detected (P > 0.18). Nursing calves had greater weigh t gains (0.95 vs. 0.59 kg day(-1); P = 0.001) and lower forage intakes (2.3 6 vs. 2.96 kg day(-1); P 0.009) than weaned calves. Supplementation with un degraded intake protein increased (P = 0.03) daily gains of calves compared to nonsupplemented calves 0.88 vs 0.66 kg day(-1), respectively. Forage in take 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 per centage 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 supplem ented 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.