IFAS/Range Cattle Research and Education Center, University of Florida, Ona, FL.
Department of Animal Science, Texas A&M University, College Station, TX.
J Anim Sci. 2018 Dec 3;96(12):5112-5123. doi: 10.1093/jas/sky374.
Two experiments evaluated the effects of concentrate amount and monensin inclusion on growth and physiological parameters of early-weaned beef calves consuming warm-season grasses in drylot (Exp. 1) and pastures (Exp. 2). In both experiments, treatments consisted of two concentrate DM amounts (1 or 2% of BW) and two inclusion rates of monensin (0 or 20 mg of monensin/kg of total DM intake). In Exp. 1, 48 Angus × Brahman crossbred early-weaned (EW) beef calves (initial age = 90 ± 13 d; initial BW = 83 ± 12 kg) were distributed in 12 drylot pens (four calves per pen; three pens per treatment) and provided stargrass (Cynodon nlemfuensis) hay (9% CP and 52% IVDOM) at amounts to ensure 10% DM refusals for 56 d. In Exp. 2, 36 Angus × Brahman crossbred EW heifer calves (initial BW = 171 ± 15 kg) were randomly allocated into one of 12 bahiagrass (Paspalum notatum) pastures on a continuous and fixed stocking rate (1 ha and three heifers per pasture; three pastures per treatment) and received daily supplementation of their respective treatments for 84 d. In both experiments, effects of monensin inclusion × concentrate amount were not detected for any variable (P ≥ 0.14), but overall ADG and plasma IGF-1 concentrations were greater (P ≤ 0.05), whereas fecal coccidia egg counts tended (P = 0.09; Exp. 1) or were less (P = 0.05; Exp. 2) for calves offered concentrate with vs. without monensin inclusion. Calves offered concentrate at 2% of BW had greater (P ≤ 0.05) overall ADG (Exps. 1 and 2), herbage mass (Exp. 2 only), in vivo apparent digestibility, total DMI and plasma concentrations of glucose and IGF-1 (Exp. 1 only), less forage DM intake (Exp. 1 only), and no effects on fecal coccidia egg counts (Exps. 1 and 2) compared to calves offered concentrate at 1% of BW. Increasing concentrate amount is an effective management practice to increase ADG and decrease forage DMI in early-weaned calves consuming warm-season grasses, whereas the decrease in fecal coccidia egg count and additional ADG provide evidence that monensin should be supplied to early-weaned calves grazing warm-season pastures and receiving concentrate at 1% of BW or above.
两个实验评估了浓缩物的数量和莫能菌素的添加对在干草场(实验 1)和牧场上(实验 2)食用暖季草的早期断奶肉牛的生长和生理参数的影响。在两个实验中,处理包括两种浓缩物 DM 量(BW 的 1%或 2%)和两种莫能菌素添加率(总 DM 摄入量的 0 或 20mg 莫能菌素/kg)。在实验 1 中,48 头安格斯×婆罗门杂交早期断奶(EW)肉牛(初始年龄=90±13d;初始 BW=83±12kg)被分配到 12 个干草场围栏(每栏 4 头;每处理 3 栏),并提供了星状草(Cynodon nlemfuensis)干草(9%CP 和 52%IVDOM),以确保 56 天内有 10%的 DM 被拒绝。在实验 2 中,36 头安格斯×婆罗门杂交早期断奶(EW)小母牛(初始 BW=171±15kg)被随机分配到 12 个巴哈草(Paspalum notatum)牧场上的一个连续和固定的饲养率(每公顷和每牧场三头小母牛;每处理三个牧场),并在 84 天内每天补充各自的处理。在两个实验中,莫能菌素添加×浓缩物量对任何变量都没有影响(P≥0.14),但总体 ADG 和血浆 IGF-1 浓度更高(P≤0.05),而粪便球虫卵计数则倾向于(P=0.09;实验 1)或较少(P=0.05;实验 2)对于提供浓缩物和不提供浓缩物的小母牛。与提供 1% BW 浓缩物的小母牛相比,提供 2% BW 浓缩物的小母牛具有更高的总体 ADG(实验 1 和 2)、牧草质量(仅实验 2)、体内表观消化率、总 DMI 和血糖和 IGF-1 的血浆浓度(仅实验 1)、更少的牧草 DM 摄入量(仅实验 1),粪便球虫卵计数无影响(实验 1 和 2)。与提供 1% BW 浓缩物的小母牛相比,增加浓缩物的量是提高早期断奶肉牛暖季草采食量和降低牧草 DM 摄入量的有效管理措施,而粪便球虫卵计数的减少和额外的 ADG 提供了证据,即莫能菌素应供应给放牧暖季牧场并接受 1% BW 或以上浓缩物的早期断奶小母牛。