饲粮能量和蛋白质水平对荷斯坦公牛生长育肥性能及血液生化指标的影响

Effects of Dietary Energy and Protein Levels on Growing-Fattening Performance and Blood Biochemical Indicators of Holstein Bulls

本试验旨在研究饲粮不同能量和蛋白质水平对荷斯坦公牛生长育肥性能及血液生化指标的影响，筛选出荷斯坦公牛生长育肥期适宜的饲粮营养水平参数。选取4～5月龄体重（约180 kg）相近的健康荷斯坦公牛30头，随机分为Ⅰ（低能量低蛋白质水平饲粮）、Ⅱ（中能量中蛋白质水平饲粮）和Ⅲ组（高能量高蛋白质水平饲粮），每组10头。试验期362 d。结果表明：1）与Ⅰ组相比，Ⅲ组日增重（DG）显著提高（P＜0．05），Ⅱ组DG有增加的趋势（P＞0．05）。Ⅲ组的料重比低于Ⅰ和Ⅱ组（P＞0．05）。2）Ⅲ组血液中葡萄糖含量和生长激素含量比Ⅰ组显著提高（P＜0．05），尿素氮含量比Ⅰ组显著降低（P＜0．05），Ⅱ和Ⅲ组之间无显著差异（P＞0．05）。3）粗蛋白质和粗脂肪的表观消化率随饲粮能量和蛋白质水平的提高而增加，Ⅲ组显著高于Ⅰ组（P＜0．05）。综上，依据荷斯坦公牛代谢体重（ W0．75，kg）和DG（ kg）推算出荷斯坦公牛生长育肥期（180～500 kg 体重阶段）产奶净能[ NEL， MJ／（ d ·头）]和小肠可消化粗蛋白质[IDCP，g／（d·头）]需要量的计算公式分别为：NEL＝0．57W0．75＋1．02DG（R2＝0．9368）；IDCP＝2．65W0．75＋202．03DG（ R2＝0．8929）。

The objective of this study was to evaluate the effects of different dietary energy and protein levels on growing-fattening performance and blood biochemical indicators of Holstein bulls to select the most appro-priate levels of nutrition parameters. Thirty Holstein bulls （ weighted about 180 kg, aged 4 to 5 months） were allocated into three groups with ten bulls in each group. The three groups were provided with different nutrition-al level diets： low energy and protein levels diet （ group Ⅰ） , medium energy and protein levels diet （ groupⅡ） and high energy and protein levels diet （ group Ⅲ） . The experiment lasted for 362 days. The results showed as follows：1） compared with groupⅠ, daily gain （ DG） in groupⅢwas significantly increased （ P〈0.05） and that in group Ⅱ had an increasing trend （P〉0.05）, while feed/gain in group Ⅲ was decreased compared with that in groups Ⅰ and Ⅱ （ P〉0.05） . 2） The contents of blood glucose and growth hormone in group Ⅲwere significantly increased compared with those in groupⅠ（ P〈0.05） , but no significant difference was found between groups Ⅱ and Ⅲ （ P〉0.05） . The content of blood urea nitrogen in group Ⅲ was signifi-cantly decreased compared with that in groupⅠ （ P〈0.05） . 3） With the increasing of dietary energy and pro-tein levels, apparent digestibility of crude protein and crude fat was raised, and group Ⅲ was significantly higher than groupⅠ（P〈0.05）. According to above results, net energy for lactation [NEL, MJ/（d·head）] and small intestinal digestible crude protein （IDCP） requirements [g/（d·head）] of growing-fattening Hol-stein bulls （weighted 180 to 500 kg） are calculated based on metabolic weight （W0.75, kg） and DG （kg） as follows： NEL=0.57W0.75＋1.02DG （R2=0.936 8）; IDCP=2.65W0.75＋202.03DG （R2=0.892 9）.