N-羟甲基蛋氨酸钙水平对泌乳期奶牛血清含氮物和游离氨基酸的影响

为研究N-羟甲基蛋氨酸钙（N-hydroxymethyl methionine calcium，N-HMM-Ca）对荷斯坦奶牛血清含氮物和游离氨基酸的影响，试验选用胎次、产奶量和泌乳天数相近的30头健康荷斯坦奶牛，随机分为5组。对照组饲喂基础日粮，试验组分别在基础日粮中添加0.15%、0.30%、0.75%和1.50% N-HMM-Ca，预试期14 d，正试期42 d。结果显示：①日粮中补充N-HMM-Ca对奶牛血清中总蛋白、白蛋白、球蛋白含量无显著影响（P>0.05）。第14天，1.5%组血清肌酐浓度显著低于对照组（P<0.05）；第42天，1.5%组尿素氮浓度显著低于对照组（P<0.05），而0.75%组尿酸浓度极显著高于其他组（P<0.01）。②第14天，0.15%组血清中谷氨酸、丝氨酸、精氨酸、亮氨酸、异亮氨酸、赖氨酸及总游离氨基酸浓度最高，与对照组相比差异显著或极显著（P<0.05；P<0.01）；试验第42天，0.15%组血清中精氨酸、胱氨酸及总游离氨基酸浓度最高。0.30%组血清中谷氨酸、丝氨酸、酪氨酸、蛋氨酸、缬氨酸、赖氨酸浓度最高，与对照组相比差异显著或极显著（P<0.05；P<0.01）。综上所述，在基础日粮中添加0.15%、0.30% N-HMM-Ca对泌乳期奶牛血清含氮物含量无显著影响（P>0.05），且添加0.15% N-HMM-Ca能够显著提高泌乳期奶牛血清游离氨基酸含量，综合考虑，N-HMM-Ca的添加量以0.15%为宜。

Effects of N-hydroxymethyl Methionine Calcium Supplementation Levels on Serum Nitrogenous Compounds and Free Amino Acids of Lactating Dairy Cows

To study the effects of N-hydroxymethyl methionine calcium (N-HMM-Ca) supplementation levels on serum nitrogenous compounds and free amino acids of lactating dairy cows. 30 lactating Holstein dairy cows with similar parities,milk yield and days in milk were randomly assigned into 5 groups. The control group was fed with basal diet,test groups were fed with basal diet supplemented with 0.15%,0.30%,0.75% and 1.50% N-HMM-Ca,respectively. The experiment was lasted for 56 d,including 14 d of adaptation period and 42 d of experimental period. The results showed as follows:①Comparing with control group,the total protein,albumin and globulin in experimental groups were not significantly affected (P>0.05).On the 14th day,serum creatinine concentration in 1.5% level group was significantly lower than control group (P<0.05);On the 42th day,urea nitrogen concentration in 1.5% level group was significantly lower than control group (P<0.05),while the concentration of uric acid in 0.75% level group was extremely significantly higher than that in other groups (P<0.01).②On the 14th day,the concentration of serum Glu,Ser,Arg,Leu,Ile,Lys and total free amino acids in 0.15% level group was highest,which were significantly or extremely significantly higher than control group (P<0.05;P<0.01).On the 42th day,serum Arg,Cys and the total free amino acids in 0.15% level group were the highest. And serum Glu,Ser,Tyr,Met,Val and Lys in 0.30% level group were highest,which were significantly or extremely significantly higher than the control group (P<0.05;P<0.01). In summary, adding 0.15% or 0.30% N-HMM-Ca on diet of lactating dairy had no significant effect on serum nitrogen content (P>0.05),but adding 0.15% N-HMM-Ca could increase the concentration of serum free amino acids. Considering all the facts,the recommended amount of N-HMM-Ca on diet of lactating dairy cows was 0.15%.