Baumann T A, Lardy G P, Caton J S, Anderson V L
Department of Animal and Range Sciences, North Dakota State University, Fargo 58105, USA.
J Anim Sci. 2004 Sep;82(9):2667-78. doi: 10.2527/2004.8292667x.
Two trials were conducted to determine the effect of energy source (ENG) and ruminally degradable protein (RDP) on lactating cow performance and intake and digestion in beef steers. In Trial 1, 78 cow-calf pairs were used in a 2 x 2 factorial design to determine the effect of ENG (corn or soyhulls; SH) and RDP (with our without sunflower meal) to a forage diet for lactating beef cows. The basal diet consisted of 75% grass hay (11.5% CP) and 25% wheat straw (7.4% CP). Supplement treatments and predicted RDP balances were corn (-415 g of RDP/d); SH (-260 g of RDP/d); corn plus RDP (0 g of RDP/d); or SH plus RDP (0 g of RDP/d). Data were analyzed as a split-plot in time, with pen as the experimental unit (two pens per treatment). No interaction between ENG and RDP was present (P > 0.08) for any response variable. No differences (P > 0.39) due to ENG or RDP were noted for BW, BCS, or milk yield; however, final calf weight tended to increase with ENG (P = 0.06). In Trial 2, a 5 x 5 Latin square was used to determine effects of ENG and RDP on intake and digestion in steers (686 +/- 51 kg BW). Treatments were arranged as a 2 x 2 plus one factorial and comprised a control (CON; grass hay, 7% CP), grass hay plus 0.4% BW SH, grass hay plus 0.4% BW SH and 0.15% BW sunflower meal, grass hay plus 0.4% BW corn, and grass hay plus 0.4% BW corn and 0.2% BW sunflower meal. Preplanned contrasts included main effects of ENG and RDP, ENG x RDP interaction, and CON vs. supplemented (SUP) treatments. Supplementation increased total DMI compared with CON (P = 0.001), but forage DMI was greater (P = 0.001) for CON than for SUP. An ENG x RDP interaction occurred for forage DMI (P = 0.02); addition of RDP to corn decreased forage intake, whereas addition of RDP to SH had no effect. There was an ENG x RDP interaction (P = 0.001) for ruminal pH; pH tended to increase with RDP addition to SH (P = 0.07), but decreased with RDP addition to corn (P = 0.001). Supplementation increased ruminal ammonia compared with CON (P = 0.001). Likewise, RDP increased ruminal ammonia (P = 0.001). An interaction occurred for OM disappearance (OMD; P = 0.01). The RDP addition to SH numerically decreased OMD (P = 0.23), whereas RDP addition to corn numerically increased OMD (P = 0.14). Intake and digestion seem to respond differently to RDP addition depending on supplemental energy source. Both corn or SH seem to be suitable supplements for the quality of forage used in this trial. Addition of supplemental protein did not improve cow or calf performance.
进行了两项试验，以确定能量来源（ENG）和瘤胃可降解蛋白（RDP）对泌乳奶牛生产性能以及肉牛采食量和消化率的影响。在试验1中，78对母牛-犊牛采用2×2析因设计，以确定ENG（玉米或大豆皮；SH）和RDP（添加或不添加向日葵粕）对泌乳肉牛饲粮的影响。基础饲粮由75%的禾本科干草（粗蛋白含量11.5%）和25%的小麦秸秆（粗蛋白含量7.4%）组成。补充处理及预测的RDP平衡为：玉米（-415克RDP/天）；SH（-260克RDP/天）；玉米加RDP（0克RDP/天）；或SH加RDP（0克RDP/天）。数据按时间裂区分析，以栏为试验单位（每个处理两个栏）。对于任何反应变量，ENG和RDP之间均不存在交互作用（P>0.08）。对于体重、体况评分或产奶量，未发现因ENG或RDP导致的差异（P>0.39）；然而，最终犊牛体重随ENG有增加趋势（P=0.06）。在试验2中，采用5×5拉丁方设计来确定ENG和RDP对肉牛（体重686±51千克）采食量和消化率的影响。处理按2×2加一析因排列，包括对照（CON；禾本科干草，粗蛋白含量7%）、禾本科干草加0.4%体重的SH、禾本科干草加0.4%体重的SH和0.15%体重的向日葵粕、禾本科干草加0.4%体重的玉米，以及禾本科干草加0.4%体重的玉米和0.2%体重的向日葵粕。预先计划的对比包括ENG和RDP的主效应、ENG×RDP交互作用，以及CON与补充（SUP）处理的对比。与CON相比，补充饲粮增加了总干物质采食量（DMI）（P=0.001），但CON的饲草DMI高于SUP（P=0.001）。饲草DMI存在ENG×RDP交互作用（P=0.02）；向玉米中添加RDP降低了饲草采食量，而向SH中添加RDP则无影响。瘤胃pH存在ENG×RDP交互作用（P=0.001）；向SH中添加RDP时pH有增加趋势（P=0.07），但向玉米中添加RDP时pH降低（P=0.001）。与CON相比，补充饲粮增加了瘤胃氨含量（P=0.001）。同样，RDP增加了瘤胃氨含量（P=0.001）。有机物消失率（OMD）存在交互作用（P=0.01）。向SH中添加RDP使OMD数值上降低（P=0.23），而向玉米中添加RDP使OMD数值上增加（P=0.14）。采食量和消化率对添加RDP的反应似乎因补充能量来源而异。玉米或SH似乎都是本试验所用饲草质量的合适补充物。添加补充蛋白质并未改善母牛或犊牛的生产性能。
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