过瘤胃γ-氨基丁酸包被材料优化及其对肉牛热应激状态下生产性能的影响

Optimization of Rumen Protected γ-aminobutyric Acid and Its Effect on Production Performance of Beef Cattle under Heat Stress

旨在筛选一种过瘤胃γ-氨基丁酸(RP-GABA)的复合包被材料配方,并探讨在热应激环境下,肉牛生长性能与RP-GABA的剂量关系。设计3种包被配方,以1%,2%,3%丙烯酸树脂Ⅱ为包衣材料制备RP-GABA,人工模拟牛瘤胃及小肠进行过瘤胃保护试验及过小肠释放试验,以评价三种配方的生物利用度;以最高生物利用度的包被方法制备RP-GABA(GABA含量为50%),按每千克体质量为8、16、24、32 mg/d的剂量添加于基础饲粮中。结果表明,瘤胃液处理24 h,保护率分别为49.95%、79.94%、85.35%;肠液处理8 h,释放率分别为88.24%、70.51%、89.55%。配方Ⅲ包被γ-氨基丁酸具有最高的生物利用度,其抗热应激效果表明。与对照组相比,试验组牛日增重均有显著升高(P<0.05),其中以添加量为16 mg/kg的效果最为显著,平均日增重提高28.30%(P<0.05),料重比降低24.62%(P<0.05),但采食量无显著差异(P>0.05)。配方Ⅲ包被γ-氨基丁酸对夏季锦江黄牛抗热应激的效果最为突出,同时锦江黄牛添加纯GABA的剂量为每千克体质量约7.5~10.0 mg/d为宜。

This experiment was conducted to investigate the effects of rumen protected γ-aminobutyric acid（ RP-GABA） on production performance in heat-stressed beef cattle.In vitro,the RP-GABA film-coated with1%,2%,3% polyacrylic resin Ⅱ was evaluated for its stability in rumen and release rate in gut,then 8,16,24,and 32 mg RP-GABA per day per cattle were employed to resist heat stress in Jinjiang Yellow Cattle. Following 24 hours cultivation in the rumen fluid,the protective rates in rumen were 49. 95%,79. 94% and85.35% respectively; the release rates were 88.24%,70.51% and 89.55% respectively after cultivation in the intestinal juice for 8 hours.In view of this,high bioavailability came from 3% polyacrylic resin Ⅱ,so 3% polyacrylic resin Ⅱ was selected to prepare RP-GABA as film-coating.The effects of RP-GABA on production performance showed that： compared to the control group,the daily gain of the test group increased,the most significant increase was found in the 16 mg/kg group,the average daily gain increased by 28.30%（ P〈 0. 05）,the feed weight ratio reduced by 24. 62%（ P〈 0. 05）,but there was no significant difference in feed intake（ P〉0.05）.It is concluded that RP-GABA can improve the production performance of heat-stressed beef cattle,and the optimum dose of pure GABA is 7.5 ~ 10.0 mg/d per kilogram of body weight.