饲喂不同蛋白质含量代乳粉的犊牛的生长、养分利用及体组成
Growth, nutrient utilization, and body composition of dairy calves fed milk replacers containing different amounts of protein.
作者信息
Blome R M, Drackley J K, McKeith F K, Hutjens M F, McCoy G C
机构信息
Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
出版信息
J Anim Sci. 2003 Jun;81(6):1641-55. doi: 10.2527/2003.8161641x.
Male Holstein calves < 1 wk of age were allowed a 2-wk adaptation period after purchase, and then were blocked by BW and assigned randomly within block to either a baseline slaughter group or one of four experimental groups (n = 8 to 9 per group). Treatments were isocaloric milk replacers (12.5% solids) fed at 12% of BW that contained 16.1, 18.5, 22.9, or 25.8% CP (DM basis) from whey protein sources. After a 6-wk feeding period, all calves were slaughtered and the weights and chemical composition of the viscera-free carcasses (VFC; including head, hide, feet, and tail) were determined. Gain of BW (0.38, 0.45, 0.56, and 0.62 kg/d) and gain:feed ratio (0.51, 0.59, 0.71, and 0.78) increased linearly (P < 0.001) as dietary CP increased; rate of change in body length, wither height, and heart girth also increased linearly (P < or = 0.05). Balance measurements conducted during wk 3 and 4 of the experimental period showed that both absorbed N (16.9, 20.0, 25.8, and 30.6 g/d) and retained N (7.6, 9.0, 13.2, and 15.6 g/d) increased linearly (P < 0.001) as dietary CP increased. Retained N as a percentage of absorbed N increased linearly (P < 0.01) as dietary CP increased (44.3, 44.7, 50.7, and 50.9%), whereas biological value was unaffected (71.1, 68.7, 69.5, and 67.3%; P = 0.26). Digestible energy and ME represented 94.5 and 89.7% of intake energy, respectively, and were not affected by dietary CP content. Plasma urea N concentration increased linearly (2.9, 3.3, 4.6, and 6.0 mg/dL) as dietary CP increased. Contents of water (68.2, 69.1, 70.2, and 70.5%; P < 0.001) and protein (19.6, 20.0, 20.0, and 20.2%; P < 0.10) in VFC increased linearly, whereas contents of fat (7.2, 6.2, 5.5, and 5.2%; P < 0.001) and ash (5.1, 5.2, 4.8, and 4.7%; P < 0.02) decreased linearly as dietary CP increased. Trends in visceral tissue composition were similar to those for VFC. The content of water in VFC tissue gain increased, whereas contents of fat and energy decreased, as dietary CP increased. Final VFC energy and gain of energy in VFC were not affected by dietary CP. At similar initial ME intakes, increasing dietary CP (i.e., increasing protein: energy) linearly increased ADG, gain:feed, N retention, and deposition of lean tissue in VFC, demonstrating that diet composition can markedly affect components of body growth in preruminant dairy calves.
1周龄以下的雄性荷斯坦犊牛在购入后有2周的适应期，然后按体重进行分组，并在组内随机分配到一个基线屠宰组或四个实验组之一（每组n = 8至9头）。处理方式为提供等热量的代乳粉（固形物含量12.5%），按体重的12%投喂，代乳粉含乳清蛋白来源的16.1%、18.5%、22.9%或25.8%的粗蛋白（干物质基础）。经过6周的饲喂期后，所有犊牛均被屠宰，并测定去内脏胴体（VFC；包括头、皮、蹄和尾）的重量和化学成分。随着日粮粗蛋白水平的增加，体重日增重（分别为0.38、0.45、0.56和0.62 kg/d）和增重：饲料比（分别为0.51、0.59、0.71和0.78）呈线性增加（P < 0.001）；体长、鬐甲高和胸围的变化率也呈线性增加（P ≤ 0.05）。在试验期第3周和第4周进行的平衡测定表明，随着日粮粗蛋白水平的增加，吸收氮（分别为16.9、20.0、25.8和30.6 g/d）和留存氮（分别为7.6、9.0、13.2和15.6 g/d）均呈线性增加（P < 0.001）。随着日粮粗蛋白水平的增加，留存氮占吸收氮的百分比呈线性增加（P < 0.01）（分别为44.3%、44.7%、50.7%和50.9%），而生物学价值不受影响（分别为71.1%、68.7%、69.5%和67.3%；P = 0.26）。可消化能量和代谢能分别占摄入能量的94.5%和89.7%，且不受日粮粗蛋白含量的影响。随着日粮粗蛋白水平的增加，血浆尿素氮浓度呈线性增加（分别为2.9、3.3、4.6和6.0 mg/dL）。VFC中的水分含量（分别为68.2%、69.1%、70.2%和70.5%；P < 0.001）和蛋白质含量（分别为19.6%、20.0%、20.0%和20.2%；P < 0.10）呈线性增加，而脂肪含量（分别为7.2%、6.2%、5.5%和5.2%；P < 0.001）和灰分含量（分别为5.1%、5.2%、4.8%和4.7%；P < 0.02）随着日粮粗蛋白水平的增加呈线性下降。内脏组织组成的趋势与VFC相似。随着日粮粗蛋白水平的增加，VFC组织增重中的水分含量增加，而脂肪和能量含量下降。最终VFC能量和VFC中的能量增重不受日粮粗蛋白的影响。在相似的初始代谢能摄入量下，增加日粮粗蛋白（即增加蛋白质：能量）可使ADG、增重：饲料比、氮留存和VFC中瘦肉组织的沉积呈线性增加，表明日粮组成可显著影响反刍前奶牛犊牛的身体生长组成部分。
Zotero 插件