Department of Animal Science, Texas A&M University, College Station 77843.
J Anim Sci. 2012 Jul;90(7):2324-30. doi: 10.2527/jas.2011-4782. Epub 2012 Jan 27.
Minimal quantities of ruminally degradable protein from supplements may improve supplement use efficiency of ruminants grazing dormant forages. In Exp. 1, N retention, ruminal NH(3), serum urea N, and NDF digestibility were evaluated for 12 ruminally cannulated cows (Bos spp.) in an incomplete Latin Square design with 3 periods of 42 d each. Cows were fed weeping lovegrass [Eragrostis curvula (Schrad.) Nees] hay (4.1% CP, 75% NDF, OM basis) at 1.3 % BW/d and offered 1 of 3 sources of CP [urea, cottonseed (Gossypium spp.) meal (CSM); or 50% blood meal and 50% feather meal combination (BFM)] fed to supply 0, 40, 80, or 160 g/d of CP. Beginning on d 22 of supplementation, ruminal contents and serum samples were collected at -2, 0, 3, 6, 9, 12, 18, 24, 30, 36, and 48 h relative to the morning offering of hay. On Day 24, feces and urine were collected for 72 h. In Exp. 2, 4 ruminally cannulated steers were used in a replicated 4 by 4 Latin Square to evaluate use of supplements differing in quantity and ruminal CP degradability. Steers were fed 6.8 kg/d chopped sudangrass [Sorghum bicolor (L.) Moench nothosubsp. drummondii (Steud.) de Wet ex Davidse] hay (3.7% CP, 74% NDF on OM basis) and supplemented with 56 g/d of a salt mineral mix (CON); CON + 28 g/d blood meal + 28 g/d feather meal (BFM); CON + 98 g/d CSM (LCS); or CON + 392 g/d CSM (HCS). Treatments provided 0, 40, 40, or 160 g/d of CP for CON, BFM, LCS, and HCS respectively. In Exp. 1, N use and total tract NDF digestibility were not affected by protein sources or amounts (P ≥ 0.18). Ruminal NH(3) concentrations exhibited a quadratic response over time for UREA (P < 0.05) and was greater with increasing inclusion of urea (P < 0.05); whereas BFM or CSM did not differ (P > 0.05) by amount or across time. In Exp. 2, supplementation had a tendency (P = 0.09) to increase DM disappearance. Supplementation also increased (P < 0.01) serum glucose concentrations; however, no difference (P ≥ 0.28) was found between supplements. Serum urea N and ruminal NH(3) concentrations were increased (P ≤ 0.01) in steers fed HCS. Feeding low quantities of a high-RUP supplement maintained rumen function without negatively affecting DM or NDF digestibility of a low-quality forage diet.
在 Exp.1 中，12 头瘤胃被瘘管的奶牛（Bos spp.）采用不完全拉丁方设计，每个周期 42 天，分为 3 个周期，评估了奶牛的氮保留、瘤胃 NH3、血清尿素氮和 NDF 消化率。奶牛以 1.3%体重的速度喂食垂序草（Eragrostis curvula (Schrad.) Nees）干草（4.1%CP，75%NDF，OM 基础），并提供 3 种 CP 来源之一[尿素、棉籽（Gossypium spp.）粉（CSM）；或 50%血粉和 50%羽毛粉组合（BFM）]，以提供 0、40、80 或 160 g/d CP。从补充的第 22 天开始，相对于早上提供的干草，在 -2、0、3、6、9、12、18、24、30、36 和 48 h 时收集瘤胃液和血清样本。在第 24 天，收集了 72 h 的粪便和尿液。在 Exp.2 中，4 头瘤胃被瘘管的牛采用复制的 4×4 拉丁方设计，以评估不同数量和瘤胃 CP 降解性的补充料的利用情况。牛以 6.8 kg/d 的切碎的苏丹草（Sorghum bicolor (L.) Moench nothosubsp. drummondii (Steud.) de Wet ex Davidse）干草（3.7%CP，74%NDF，基于 OM）为食，并补充 56 g/d 的盐矿混合物（CON）；CON+28 g/d 血粉+28 g/d 羽毛粉（BFM）；CON+98 g/d CSM（LCS）；或 CON+392 g/d CSM（HCS）。CON、BFM、LCS 和 HCS 组分别提供 0、40、40 或 160 g/d CP。在 Exp.1 中，蛋白质来源或数量对氮的利用和全肠道 NDF 消化率没有影响（P≥0.18）。瘤胃 NH3 浓度随时间呈二次反应，对 UREA （P<0.05），随着尿素添加量的增加而增加（P<0.05）；而 BFM 或 CSM 则没有差异（P>0.05）。在 Exp.2 中，补充剂有增加（P=0.09）DM 消失的趋势。补充剂还增加了（P<0.01）血清葡萄糖浓度；然而，补充剂之间没有差异（P≥0.28）。HCS 组的血清尿素氮和瘤胃 NH3 浓度升高（P≤0.01）。饲喂低数量的高 RUP 补充剂可维持瘤胃功能，而不会对低质量饲草的 DM 或 NDF 消化率产生负面影响。
