Anderson L P, Paterson J A, Ansotegui R P, Cecava M, Schmutz W
Department Animal and Range Sciences, Montana State University, Bozeman 59717, USA.
J Anim Sci. 2001 Aug;79(8):2224-32. doi: 10.2527/2001.7982224x.
Two 60-d experiments were conducted to evaluate the effects of supplementing degradable (DIP) and(or) undegradable (UIP) intake protein on the performance of lactating first-calf heifers. Diets were formulated to meet the requirements for either DIP, metabolizable protein (MP), or both when diets contained low-quality grass hay and an efficiency of microbial protein synthesis estimate of 10%. In Exp. 1, 32 individually fed first-calf heifers (avg 395 kg) were allotted to a 2 x 2 factorial arrangement of treatments (main effects of DIP, MP, and DIP x MP interaction) 1 d after calving. Cows consumed a basal diet of chopped crested wheat grass hay (4.3% CP, 67% DIP) ad libitum. Supplemental DIP and UIP were supplied by varying the ratios of soybean meal (75% DIP) and a heat-treated, protected soybean meal (70% UIP). Cow weight gain was better (P < 0.01) when adequate DIP was supplied than when DIP was deficient. However, calf weight gain was not increased by supplementing the cow with DIP. Supplemental UIP did not (P > 0.40) improve cow or calf weight gain. Blood urea N levels were higher (P < 0.01) for cows receiving supplemental DIP and UIP. However, milk production estimates were similar among treatments, as were digestibilities of OM and ADF. Nitrogen digestibility was greater when supplemental DIP was fed, but providing additional UIP did not (P = 0.15) change N digestibilities. Experiment 2 evaluated similar supplements using the same experimental design to determine changes in cow and calf weight gain, body condition score, and pregnancy rate. Seventy-two first-calf heifers (avg 441 kg) were allotted to supplement treatments 1 d after calving and were fed grass hay (5% CP, 53% DIP, 10% microbial efficiency) for ad libitum consumption for 60 d. Supplements were individually fed three times/week. Varying the ratios of soybean meal, heat-treated soybean meal, and corn gluten meal provided additional DIP and UIP. Unlike in Exp. 1, supplemental UIP improved (P < 0.05) cow weight gain. Calves from dams supplemented with DIP gained 5 kg more weight after 60 d than calves from dams deficient in DIP. Pregnancy rates in the fall were similar (P = 0.90) among treatments. These data suggest that DIP was more limiting in Exp. 1 than was UIP. Supplementing UIP in Exp. 2 improved cow weight gains but did not improve calf gains. Data suggest that the efficiency of microbial protein synthesis for this forage-based diet was probably less than 10%.
进行了两项为期60天的试验，以评估补充可降解摄入蛋白（DIP）和（或）不可降解摄入蛋白（UIP）对初产哺乳母牛生产性能的影响。当日粮含有低质量禾本科干草且微生物蛋白合成效率估计为10%时，日粮配方满足DIP、代谢蛋白（MP）或两者的需求。在试验1中，32头个体饲养的初产母牛（平均体重395千克）在产犊后1天被分配到2×2析因试验设计的处理组（DIP、MP的主效应以及DIP×MP的交互作用）。母牛自由采食切碎的小麦草干草基础日粮（粗蛋白含量4.3%，DIP含量67%）。通过改变豆粕（DIP含量75%）和热处理过的包被豆粕（UIP含量70%）的比例来提供额外的DIP和UIP。提供充足DIP时母牛体重增加情况优于DIP不足时（P<0.01）。然而，给母牛补充DIP并没有增加犊牛体重。补充UIP对母牛或犊牛体重增加没有影响（P>0.40）。补充DIP和UIP的母牛血尿素氮水平更高（P<0.01）。然而，各处理间的产奶量估计值、有机物和酸性洗涤纤维的消化率相似。饲喂额外DIP时氮消化率更高，但提供额外UIP并没有改变氮消化率（P=0.15）。试验2采用相同的试验设计评估类似的补充剂，以确定母牛和犊牛体重增加、体况评分和妊娠率的变化。72头初产母牛（平均体重441千克）在产犊后1天被分配到各补充剂处理组，自由采食禾本科干草（粗蛋白含量5%，DIP含量53%，微生物效率10%）60天。补充剂每周单独饲喂3次。通过改变豆粕、热处理豆粕和玉米蛋白粉的比例来提供额外的DIP和UIP。与试验1不同，补充UIP提高了母牛体重增加（P<0.05）。补充DIP的母牛所产犊牛在60天后比未补充DIP的母牛所产犊牛多增重5千克。秋季各处理间妊娠率相似（P = 0.90）。这些数据表明，在试验1中DIP比UIP的限制作用更大。在试验2中补充UIP提高了母牛体重增加，但未提高犊牛体重增加。数据表明，这种以牧草为基础的日粮的微生物蛋白合成效率可能低于10%。
