低蛋白质饲粮中添加尿素对肉兔消化代谢的影响

Low Protein Diet Supplemented with Urea Affects Digestion and Metabolism of Meat Rabbits

本试验旨在研究低蛋白质饲粮中添加尿素对肉兔消化代谢的影响。采用单因子随机区组试验设计,选择90只50日龄体重相近的健康新西兰兔,随机分为3组,1个对照组和2个试验组,每组15个重复,每个重复2只。对照组饲喂粗蛋白质含量为11.11%的基础饲粮,2个试验组分别饲喂在基础饲粮中以糊化淀粉缓释尿素的方式添加1%、2%和3%尿素的试验饲粮。预试期为10 d,正试期为30 d。正试期的第13～18天收集试验兔排出的全部粪便和尿液。结果表明:与对照组相比,1%尿素组试验兔的有机物表观消化率、总能表观消化率及利用率、沉积氮、氮利用率和消化氮利用率显著或极显著升高(P<0.05或P<0.01),而2%尿素组试验兔的消化能、代谢能、沉积氮、氮利用率和消化氮利用率显著或极显著降低(P<0.05或P<0.01)。对照组试验兔盲肠内容物脲酶活性和微生物蛋白浓度显著或极显著低于其余2组(P<0.05或P<0.01),而2%尿素组试验兔盲肠内容物氨氮和尿素氮浓度显著或极显著高于其余2组(P<0.05或P<0.01)。由此得出,低蛋白质饲粮中添加1%尿素可改善肉兔有机物、总能和氮的利用效率,提高盲肠内容物脲酶活性和微生物蛋白浓度;添加2%尿素则会降低肉兔氮的利用效率,提高盲肠内容物脲酶活性及微生物蛋白、氨氮和尿素氮浓度。

The aim of this study was to investigate the effects of urea supplementation in a low protein diet on digestion and metabolism of meat rabbits.A single factor randomized block design was used in the experiment.Ninety New Zealand rabbits at 50 days of age with the similar body weight were randomly allotted into 3 groups with 15 replicates per group and 2 rabbits per replicate.One group was the control group and the rest groups were the experimental groups.The rabbits in the control group were fed a basal diet with 11.11% crude protein,and the rabbits in the 2 experimental groups were fed the basal diets supplemented with 1% and 2% urea by the way of the starea,respectively.The duration of the preliminary experiment was 10 d and the duration of the formal experiment was 30 d.All of the feces and urine that the experimental rabbits excreted were collected from the thirteenth day to the eighteenth day during the formal experiment.The results showed as follows: compared with the control group,the apparent digestibility of organic matter,apparent digestibility and availability of gross energy,deposit nitrogen,nitrogen availability and digested nitrogen availability of rabbits in 1% urea group were significantly increased(P<0.05 or P<0.01),while the digestible energy,metabolizable energy,deposit nitrogen,nitrogen availability and digested nitrogen availability of rabbits in 1% urea group were significantly decreased(P<0.05 or P<0.01).The urease activity and microbia crude protein concentration in cecal digesta of rabbits in the control group were significantly lower than those in the 1% and 2% urea groups(P<0.05 or P<0.01),while the concentrations of ammonia nitrogen and urea nitrogen in cecal digesta of rabbits in 2% urea group were significantly higher than those in the control group and 1% urea group(P<0.05 or P<0.01).In conclusion,low protein diet supplemented with 1% urea can improve the utilization efficiency of organic matter,gross energy and nitrogen,and increase the urease activity and microbia crude protein concentration in cecal digesta of meat rabbits;low protein diet supplemented with 2% urea can decrease the utilization efficiency of nitrogen,and increase the urease activity and the concentrations of microbia crude protein,ammonia nitrogen and urea nitrogen in cecal digesta of meat rabbits.