不同能量水平的饲粮对3～6月龄犊牛生长发育及血清指标的影响

Effects of Diets with Different Energy Levels on Growth and Development and Serum Indexes of Calves Aged from 3 to 6 Months

本试验旨在研究不同能量水平的饲粮对3～6月龄犊牛生长发育及相关血清指标的影响。选取约98日龄中国荷斯坦断奶母犊牛32头，随机分为A、B、C和D4个组，对应饲喂产奶净能分别为6．24、7．04、7．53和7。85MJ／kg的试验饲粮，试验期82d。于犊牛98、120、150和180日龄清晨空腹测定犊牛生长发育指标，并采集血液样品进行分析。结果表明：1）在试验全期（98～180日龄），4组犊牛平均日增重分别为0．64、0．75、0．78和0．84kg／d，组间差异不显著（P〉0．05），但151～180日龄，D组犊牛平均日增重极显著高于A组（P〈0．01）。2）在180日龄，D组犊牛的体斜长较A组显著提高（P〈0．05）；D组犊牛体况评分极显著高于A组（P〈0．01）。3）产奶净能为7．53和7．85MJ／kg的饲粮可显著改善犊牛饲料转化率（P〈0．05）；饲粮不同能量水平对各日龄犊牛乳头长度影响不显著（P〉0．05）。4）在试验全期，高产奶净能饲粮组（C、D组）犊牛血清胆固醇含量显著高于A组（P〈0．05）；血清低密度脂蛋白含量随饲粮产奶净能升高呈升高的趋势（P〈0．10），血清尿素氮含量则出现降低的趋势（P〈0．10）。5）饲喂产奶净能为7．04MJ／kg的饲粮时，犊牛血清雌二醇和瘦素含量最高；饲喂产奶净能为7．85MJ／kg的饲粮时，犊牛血清胰岛素和胰岛素样生长因子一I含量最低。由此得出，饲喂产奶净能为7．53MJ／kg的饲粮既可保持3～6月龄犊牛较高平均日增重（0．78kg／d），又不会影响犊牛健康、体型及乳腺的正常发育。

This experiment was conducted to investigate the effects of diets with different energy levels on growth and development and serum indexes of calves aged from 3 to 6 months. A total of 32 Chinese Holstein calves aged about 98 days were randomly divided into 4 groups （ groups A, B, C and D ）. Each group was subjected to one of the following 4 diets with 6.24, 7.04, 7.53, and 7.85 MJ/kg net energy for lactation for 82 days. Body growth and blood samples were determined at 98, 120, 150 and 180 days of age prior to morn- ing feeding. The results showed as follows： 1 ） during the experimental whole period （98 to 180 days of age）, the average daily gains which were 0.64, 0.75, 0.78, and 0.84 kg/d, respectively, for the 4 groups, did not differ （P 〉0.05）, but during 151 to 180 days of age, the calves of group D had greater average daily gain than those of group A （P 〈0.01）. 2） At 180 days of age, the body length of calves of group D was sig- nificantly higher than that of group A （ P 〈 0.05 ）. The calves of group D had greater body condition score than those of group A （ P 〈 0.01 ）. 3 ） The diets with 7.53 and 7.85 MJ/kg net energy for lactation improved the feed conversion ratio （ P 〈 0.05 ）. Nipple length did not differ among groups （ P 〉 0.05 ）. 4） During the experimental whole period, calves fed high net energy for lactation diets （groups C and D） had higher serum cholesterol content than group A （ P 〈 0.05 ） ; serum low density lipoprotein content tended to increase with the increasing net energy for lactaion （P 〈0.10）, whereas serum urea nitrogen content had the opposite tendency （ P 〈 0.10 ）. 5 ） Calves fed the diet with 7.04 MJ/kg net energy for lactation had the highest serum contents of estradiol and leptin, and those fed the diet with 7.85 MJ/kg net energy for lactation had the lowest serum contents of insulin and insulin-like growth factor- I. The diet with 7.53 MJ/kg net energy for lactation can maintain the average daily gain of calves （0.78 kg/d） with no adverse effects on body dimensions and mam- mary development.