不同牧草来源日粮对奶牛瘤胃发酵和微生物蛋白合成的影响

Effects of different forage sources on rumen fermentation characteristic and microbial protein synthesis

试验旨在研究不同牧草来源日粮对奶牛瘤胃发酵和微生物蛋白合成的影响。选用8头体重为(632±12)kg泌乳中期奶牛(135±16 DIM),随机分为4组,采用4×4重复拉丁方设计,共4期,每期21 d,其中14 d适应期,7 d采样期。四组日粮均以玉米青贮为基础,粗饲料分别由苜蓿草、燕麦草、羊草和稻草组成,日粮等能等氮且中性洗涤纤维(NDF)和非纤维性碳水化合物(NFC)含量相同。结果显示:(1)四组日粮中奶牛干物质采食量(DMI)差异不显著(P>0.05),瘤胃液p H、NH3-N、总挥发性脂肪酸(TVFA)和支链挥发性脂肪酸浓度均无显著差异(P>0.05),稻草组乙酸含量偏低,丙酸含量偏高,但与其他三组并无显著差异(P>0.05)。(2)稻草组奶牛每日尿排泄量有增加的趋势(P=0.08),牧草来源对每日尿酸排泄量无显著影响(P=0.87),但稻草组中尿囊素显著低于苜蓿草、燕麦草和羊草组(P=0.01),造成总嘌呤衍生物(PD)含量显著降低(P=0.01),稻草组微生物蛋白(MCP)产量比苜蓿草组降低124 g/d。综上可知,在日粮NDF和NFC含量相同的条件下,不同牧草来源日粮对奶牛瘤胃发酵无显著影响,且苜蓿草、燕麦草和稻草组微生物蛋白合成无显著差异。

A total of 8 Holstein dairy cows with average weight （632±12）kg and middle lactation [（135±16）DIM] were selected,and a replicated 4×4 latin square design was used to evaluate the effects of forage sources on rumen fermentation characteristics and microbial protein （MCP） synthesis.Alfalfa hay （AH）,oat hay （OH）,leymus chinensis （LC） and rice straw （RS） were primary sources of fiber,diets were isonitrogenous and isocaloric,and based on corn silages,total mixed ra-tions with equivalent neutral detergent fiber （NDF） and nonfiber carbohydrate （NFC）.The results showed that： （1）The dry matter intake （DMI）,the concentrations of pH,ammonia nitrogen,TVFA and branched volatile fatty acids were not affected by the source of dietary forages （P 〉 0.05）.The acetate content of rice straw was much lower, and the content of propionate was much higher than other groups.（2）The urine excretion of cows had the trend of increasing in rice straw group（P =0.08）, the source of dietary forages had no effect on uric acid excretion,but allantoin output of rice straw was lower than alfalfa hay,oat hay and leymus chinensis（P =0.01）,so the total purine derivatives （PD）excretion significantly decreased.Microbial protein of rice straw lower than alfalfa hay by 124 g/d.According to the resul ts,the cows were fed with AH, OH, LC, and RS with equivalent NDF and NFC contents had no unfavourable effect on ruminal fermentation and MCP synthesis.