不同蛋白质水平高精料饲粮对荷斯坦奶公牛育肥性能、养分表观消化率及血清生化指标的影响

Effects of High Concentrate Diets with Different Protein Levels on Fattening Performance,Nutrient Apparent Digestibility and Serum Biochemical Indices of Holstein Bulls

本试验旨在研究不同蛋白质水平高精料饲粮对荷斯坦奶公牛生长性能、养分表观消化率及血清生化指标的影响。选取体重(197.07±11.11)kg和体况相近的荷斯坦奶公牛90头,随机分为3组,每组30头,各组间平均体重差异不显著(P>0.05)。试验分3个体重阶段(200~300 kg、300~400 kg、400~500 kg)进行。在每个体重阶段,Ⅰ组、Ⅱ组和Ⅲ组分别饲喂低、中和高蛋白质水平饲粮。在同一体重阶段各组饲粮能量水平相同,精粗比均为90∶10。试验期193 d。结果显示:1)试验各组各体重阶段及全期平均日增重(ADG)、干物质采食量(DMI)、可消化干物质采食量(DDMI)、DDMI/ADG和DMI/ADG均差异不显著(P>0.05)。2)200~300 kg体重阶段,Ⅰ组中性洗涤纤维(NDF)的表观消化率显著高于Ⅲ组(P<0.05);300~400 kg体重阶段,Ⅲ组粗蛋白质(CP)的表观消化率比Ⅰ组提高了4.27%(P<0.05),Ⅰ组的NDF表观消化率比Ⅱ、Ⅲ组分别提高了16.06%和10.42%(P<0.05)。3)200~300kg体重阶段,Ⅲ组CP消化量极显著高于Ⅰ组(P<0.01);300~400kg体重阶段,各组间CP消化量差异极显著(P<0.01),Ⅰ组NDF消化量显著高于Ⅱ、Ⅲ组(P<0.05);400~500kg体重阶段及全期,各组间CP消化量差异极显著(P<0.01)。4)各体重阶段,血清生长激素(GH)含量随饲粮蛋白质水平的升高有所增加,但各组间差异不显著(P>0.05);200~300 kg体重阶段,Ⅲ组血清甲状腺素(T4)含量显著高于Ⅰ组(P<0.05);300~400 kg体重阶段,Ⅲ组血清葡萄糖(GLU)含量显著高于Ⅰ组(P<0.05),Ⅱ、Ⅲ组血清谷草转氨酶(AST)活性比Ⅰ组分别提高了8.63%和10.98%(P<0.05)。综合分析各项指标得出,在本试验条件下,6~12月龄不同体重阶段奶公牛的饲粮蛋白质水平建议值(干物质基础)如下:200~300kg体重阶段,饲粮蛋白质水平为15.00%;300~400kg体重阶段,饲粮蛋白质水平为15.00%;400~500kg体重阶段,饲粮蛋白质水平为14.00%。

The purpose of this experiment was to study effects of high concentrate diets with different protein levels on fattening performance,nutrient apparent digestibility and serum biochemical indices of Holstein bulls.Ninety Holstein bulls with the body weight of(197.07±11.11)kg and similar body condition were randomly divided into three groups with 30 calves in each group,and there was no significant difference in average body weight among three groups(P>0.05).The trial was carried out in three body weight stages(200 to 300 kg,300 to 400 kg and 400 to 500 kg).Each test stage included groupsⅠ,ⅡandⅢ,whose were fed low,medium and high protein level diets,respectively.In the same stage of body weight,the energy level of diets in three groups was the same,and the ratio of concentrate to roughage was 90∶10.The whole trial period lasted for 193 d.The results showed as follows:1)the average daily gain(ADG),dry matter intake(DMI),digestible dry matter intake(DDMI),DMI/ADG and DDMI/ADG in each body weight stage and whole period of the experiment were not significantly different(P>0.05).2)In the stage of 200 to 300 kg body weight,the apparent digestibility of neutral detergent fiber(NDF)in groupⅠwas significantly higher than that in groupⅢ(P<0.05);in the stage of 300 to 400 kg body weight,the apparent digestibility of crude protein(CP)in groupⅢwas 4.27%higher than that in groupⅠ(P<0.05),and the apparent digestibility of NDF in group I was 16.06%and 10.42%higher than that in groupsⅡandⅢ(P<0.05),respectively.3)In the stage of 200 to 300 kg body weight,the CP digestion of groupⅢwas extremely significantly higher than that of groupⅠ(P<0.01);in the stage of 300 to 400 kg body weight,there was an extremely significant difference in CP digestion among groups(P<0.01),and the NDF digestion in groupⅠwas significantly higher than that in groupsⅡandⅢ(P<0.05);the digestion of CP in the stage of 400 to 500 kg body weight and whole period was extremely significantly different among groups(P<0.01).4)The content of serum growth hormone(GH)in each body weight stage was increased with the increase of dietary protein level,but there was no significant difference among groups(P>0.05).In the stage of 200 to 300 kg body weight,serum thyroxine(T 4)content in groupⅢwas significantly higher than that in groupⅠ(P<0.05).In the stage of 300 to 400 kg body weight,the content of serum glucose(GLU)in groupⅢwas significantly higher than that in groupⅠ(P<0.05),and the serum aspartate aminotransferase(AST)activity in groupsⅡandⅢwas 8.63%and 10.98%higher than that in groupⅠ(P<0.05),respectively.Comprehensive analysis of various indicators,under the conditions of this experiment,the recommended values of dietary protein levels(dry matter basis)for 6 to 12 months old Holstein bulls in different body weight stages as follows:in the stage of 200 to 300 kg body weight,the appropriate protein level is 15.00%;in the stage of 300 to 400 kg body weight,the appropriate protein level is 15.00%;in the stage of 400 to 500 kg body weight,the appropriate protein level is 14.00%.