颈静脉灌注不同模式的氨基酸混合物对泌乳奶牛乳蛋白合成的影响

本试验旨在比较颈静脉灌注酪蛋白模式和理想模式的氨基酸混合物对泌乳中期荷斯坦奶牛乳产量、乳成分以及乳腺对氨基酸摄取利用的影响。选择8头泌乳中期泌乳天数:(82±11)d]荷斯坦奶牛作为试验动物,试验采用随机区组设计,将试验牛随机分为2组,分别颈静脉灌注160g/d酪蛋白模式(Casein组)和理想模式的氨基酸混合物(R组)。2个试验组分别以各自灌注前作为空白对照组(C1组为Casein组的空白对照组,C2组为R组的空白对照组)。预试期14d,灌注期5d。试验采用全混合日粮(TMR)饲喂,以玉米、豆粕、棉籽粕、玉米青贮、苜蓿干草和羊草为主要原料,参照NRC(2001)奶牛饲养标准配制。结果表明:灌注酪蛋白模式的氨基酸混合物后,乳蛋白产量和含量较灌注前呈上升趋势(乳蛋白产量上升7.14%,P=0.078;乳蛋白含量上升3.27%,P=0.072);并且,奶牛动脉血浆中异亮氨酸(Ile)、亮氨酸(Leu)、赖氨酸(Lys)和组氨酸(His)的浓度较灌注前有不同程度的上升(Ile的浓度提高31.5%,P=0.097;Leu的浓度提高65.9%,P=0.041;Lys的浓度提高36.9%,P=0.088;His的浓度提高40.1%,P=0.010),而苏氨酸(Thr)、缬氨酸(Val)、蛋氨酸(Met)、苯丙氨酸(Phe)和精氨酸(Arg)的浓度在数值上虽较灌注前高但无显著差异(P0.05)。灌注酪蛋白模式的氨基酸混合物后,奶牛乳腺对天冬氨酸(Asp)和半胱氨酸(Cys)的摄取率显著升高(Asp的摄取率提高95.2%,P=0.031;Cys的摄取率提高49.6%,P=0.031),而奶牛乳腺对甘氨酸(Gly)的摄取率显著降低(降低158.3%,P=0.041)。灌注理想模式的氨基酸混合物后,乳蛋白含量比灌注前有上升趋势(提高5.78%,P=0.064),而乳脂产量显著低于灌注前(降低8.57%,P=0.015);并且,奶牛动脉血浆中Arg的浓度有上升趋势(提高18.0%,P=0.093),而酪氨酸(Tyr)的浓度呈下降趋势(降低47.8%,P=0.074)。灌注理想模式的氨基酸混合物后,奶牛乳腺对谷氨酸(Glu)、Cys和Ile的摄取率显著上升(Glu的摄取率提高118.7%,P=0.015;Cys的摄取率提高77.4%,P=0.032;Ile的摄取率提高46.0%,P=0.012),而奶牛乳腺对Ser的摄取率呈下降趋势(降低56.2%,P=0.052)。灌注氨基酸混合物后,Casein组乳脂产量增量显著高于R组(P=0.012),且Casein组的乳产量增量(P=0.095)和乳糖产量增量(P=0.091)较R组有升高的趋势,而2组间其他指标增量无显著差异(P0.05)。由此得出,在本试验条件下,颈静脉灌注酪蛋白模式和理想模式的氨基酸混合物均可提高泌乳奶牛的乳蛋白含量,而灌注酪蛋白模式氨基酸混合物同时可以促进乳蛋白产量的升高,因此,颈静脉灌注酪蛋白模式氨基酸混合物的效果优于灌注理想模式氨基酸混合物。

Effects of Jugular-Infused Amino Acid Mixture of Different Profiles on Milk Protein Synthesis of Lactating Dairy Cows

This experiment was undertaken to compare the effect of jugular-infused amino acid mixture of casein and ideal profiles on milk yield,milk composition,extraction and utilization of amino acids in mammary gland of mid-lactation Holstein cows.Eight mid-lactation lactation days: (82±11) d] Holstein cows were used for this study.The dairy cows were randomly assigned to 2 groups by a random block design.The 2 groups were randomly distributed as jugular infusions of 160 g amino acid mixture of casein (Casein group) and ideal profiles (R group),and taken themselves before infusion as blank control group (C1 group was the blank control group for Casein group,and C2 group was the blank control group for R group),respectively.The adaptation period lasted for 14 days and the infusion period lasted for 5 days.Total mixed ration (TMR) was adopted and formulated by corn,soybean meal,cottonseed meal,corn silage,alfalfa hay and Chinese wildrye according to Feeding Standard of Dairy Cow for NRC (2001).The results showed that compared with before infusion,the milk protein yield and content had upward trends after jugular-infused amino acid mixture of casein profile (milk protein yield was increased by 7.14%,P=0.078;milk protein content was increased by 3.27%,P=0.072),in addition,the arterious plasma concentrations of isoleucine (Ile),leucine (Leu),lysine (Lys) and histidine (His) were increased in different extent (Ile concentration was increased by 31.5%,P=0.097;Leu concentration was increased by 65.9%,P=0.041;Lys concentration was increased by 36.9%,P=0.088;His concentration was increased by 40.1%,P=0.010),and the arterious plasma concentrations of threonine (Thr),valine (Val),methionine (Met),phenylalanine (Phe) and arginine (Arg) in Casein group were numerically higher than those in C1 group,but the differences were not significant (P>0.05).The extraction rates of aspartic acid (Asp) and cysteine (Cys) by mammary gland for cows of Casein group were significantly higher than those of C1 group (Asp extraction rate was improved by 95.2%,P=0.031;Cys extraction rate was improved by 49.6%,P=0.031),whereas the extraction rate of glycine (Gly) by mammary gland for cows of Casein group was significantly lower than that in C1 group (decreased by 158.3%,P=0.041).Compared with before infusion,infused amino acid mixture of ideal profile tended to increase the milk protein content (increased by 5.78%,P=0.064) and significantly decrease the milk fat yield (decreased by 8.57%,P=0.015),moreover,there were an upward trend of arterious plasma Arg concentration (increased by 18.0%,P=0.093) and a downward trend of arterious plasma Tyr concentration (decreased by 47.8%,P=0.074) after cows were infused amino acid mixture of ideal profile.After cows were infused of amino acid mixture of ideal profile,the extraction rates of glutamic acid (Glu),Cys and Ile by mammary gland were significantly improved (Glu extraction rate was improved by 118.7%,P=0.015;Cys extraction rate was improved by 77.4%,P=0.032;Ile extraction rate was improved by 46.0%,P=0.012),and the extraction rate of Ser was decreased (decreased by 56.2%,P=0.052).However,the milk fat yield increment (P=0.012) of Casein group was significantly higher than that of R group,and the milk yield increment (P=0.095) and lactose yield increment (P=0.091) tended to be higher for cows receiving amino acid mixture of casein profile than for those receiving amino acid mixture of ideal profile,but the other index increments had no significant differences between Casein and R group (P>0.05).Under this experiment condition,the milk protein content of lactating dairy cows can be increased by the jugular infusions of amino acid mixture of casein and ideal profiles,and the milk protein yield has an upward trend when lactating dairy cows are received jugular infusion of amino acid mixture of casein profile.So,the application effect of jugular-infused amino acid mixture of casein profile is superior to the jugular-infused amino acid mixture of ideal profile.