Abstract：
The study investigated the effects of dietary protein level and the inclusion of hydroponic barley sprouts (HB) on lactation performance, blood biochemistry and N use efficiency in mid-lactation dairy cows. Treatments were arranged in a 2 × 2 factorial design with 2 crude protein (CP) levels [16.8% and 15.5% of dry matter (DM)], with HB (4.8% of DM, replacing 4.3% of alfalfa hay and 0.5% of distillers dried grains with solubles (DDGS)) or without HB. Forty-eight multiparous Holstein dairy cows (146 ± 15 d in milk, 40 ± 5 kg/d of milk) were randomly allocated to 1 of 4 diets: high protein diet (16.8% CP, HP), HP with HB (HP+HB), low protein diet (15.5% CP, LP), or LP with HB (LP+HB). An interaction between CP × HB on dry matter intake (DMI) was detected, with DMI being unaffected by HB inclusion in cows fed the high CP diets, but was lower in cows fed HB when the low CP diet was fed. A CP × HB interaction was also observed on milk and milk protein yield, which was higher in cows fed HB with HP, but not LP. Inclusion of HB also tended to reduce milk fat content, and feeding HP resulted in a higher milk protein and milk urea N content, but lower milk lactose content. Feed efficiency was increased by feeding HP or HB diets, whereas N efficiency was higher for cows fed LP or HB diets. There was an interaction on the apparent total-tract digestibility of DM and CP, which was higher when HB was fed along with HP, but reduced when fed with LP, whereas the digestibility of ADF was increased by feeding low protein diets. In conclusion, feeding a low protein diet had no adverse effect on cow performance, while feeding HB improved milk and milk component yield, and N efficiency when fed with a high CP diet, but compromised cow performance with a low CP diet.
摘要：
研究了日粮蛋白质水平和水培大麦芽（HB）对泌乳性能的影响，泌乳中期奶牛的血液生化和氮素利用效率。处理以2×2阶乘设计排列，具有2个粗蛋白（CP）水平[干物质（DM）的16.8％和15.5％]，有HB（占DM的4.8%，用可溶物（DDGS）代替4.3％的苜蓿干草和0.5％的干酒糟）或不含HB。48头多胎荷斯坦奶牛(146±15d，40±5kg/d的牛奶）随机分配到4种饮食中的1种：高蛋白饮食（16.8％CP，HP),带HB的HP（HP+HB），低蛋白饮食（15.5%CP，LP),或带HB的LP(LP+HB)。检测到CP×HB对干物质摄入量（MDI）的相互作用，在饲喂高CP日粮的奶牛中，MDI不受HB含量的影响，但在饲喂低CP日粮时，饲喂HB的奶牛较低。乳和乳蛋白产量也观察到CP×HB相互作用，在用HP喂养HB的奶牛中，不是LP。包含HB也倾向于降低乳脂含量，饲喂HP导致较高的乳蛋白和乳尿素N含量，但牛奶乳糖含量较低。饲喂HP或HB日粮提高了饲料效率，而饲喂LP或HB日粮的奶牛的氮效率更高。DM和CP的表观总道消化率存在相互作用，当HB与HP一起喂食时，但是当喂食LP时减少了，而饲喂低蛋白饮食可增加ADF的消化率。总之,饲喂低蛋白饮食对奶牛的生产性能没有不利影响，在饲喂HB提高牛奶和牛奶成分产量的同时，和高CP饮食时的氮效率，但低CP饮食会损害奶牛的性能。
