Trouw Nutrition AgResearch, Guelph, Ontario, Canada N1G 4T2; Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
Trouw Nutrition AgResearch, Guelph, Ontario, Canada N1G 4T2.
J Dairy Sci. 2017 Jul;100(7):5390-5399. doi: 10.3168/jds.2016-12310. Epub 2017 May 17.
The benefits of feeding elevated quantities of milk to dairy calves have been well established. However, there is a reluctance to adopt this method of feeding in commercial dairy production because of concerns around growth, health, and ruminal development during weaning. The objective of this study was to characterize the effect of an abrupt (0 d step-down) or gradual (12 d step-down) feeding scheme when calves are fed an elevated plane of nutrition (offered 1.35 kg of milk replacer/d). For this experiment, a total of 54 calves were randomly assigned to an abrupt or a gradual weaning protocol before weaning at 48 d of life. Calves were housed and sampled in individual pens for the duration of the experiment, and milk, starter, and straw intake were measured on a daily basis. Body weight was measured every 6 d, whereas blood, rumen fluid, and fecal samples were collected on d 36 (pre-step-down), 48 (preweaning), and 54 (postweaning) of the experiment. Although the growth rates of the step-down calves were lower from d 37 to weaning (0.62 ± 0.04 vs. 1.01 ± 0.04 kg/d), the postweaning average daily gain was greater compared with the group that was abruptly weaned (0.83 ± 0.06 vs. 0.22 ± 0.06 kg/d). Total ruminal volatile fatty acid was greater in the step-down group on the day of weaning (d 48; 59.80 ± 2.25 vs. 45.01 ± 2.25 mmol), whereas the fecal starch percentage was lower during postweaning compared with the abruptly weaned calves (d 54; 3.31 ± 0.76 vs. 6.34 ± 0.76%). Analysis of the digestive tract of bull calves on d 55 revealed minimal differences between gross anatomy measurements of gut compartments as well as no morphological differences in rumen papillae development, yet the total mass of rumen when full of contents was larger in the step-down calves (7.83 ± 0.78 vs. 6.02 ± 0.78 kg). Under the conditions of this study, the results showcase the benefits of a step-down feeding strategy from an overall energy balance standpoint, due to increased adaptation of the gastrointestinal tract preweaning.
向奶牛犊牛饲喂较高数量的牛奶的益处已得到充分证实。然而，由于在断奶期间对生长、健康和瘤胃发育的担忧，商业奶牛生产中不愿意采用这种饲养方式。本研究的目的是描述在犊牛饲喂较高营养水平（每天提供 1.35 千克代乳料）时，突然（0 天逐步减少）或逐渐（12 天逐步减少）减少饲喂方案的效果。为此，本实验共将 54 头犊牛随机分配到突然断奶或逐渐断奶方案中，在 48 日龄断奶。犊牛在实验期间单独饲养并在单个围栏中采样，每天测量牛奶、开食料和稻草的摄入量。每隔 6 天测量体重，在实验的第 36 天（逐步减少前）、第 48 天（断奶前）和第 54 天（断奶后）收集血液、瘤胃液和粪便样本。尽管从第 37 天到断奶时逐步减少的犊牛生长速度较慢（0.62 ± 0.04 比 1.01 ± 0.04 kg/d），但与突然断奶的组相比，断奶后平均日增重更大（0.83 ± 0.06 比 0.22 ± 0.06 kg/d）。在断奶日（第 48 天），逐步减少组的总瘤胃挥发性脂肪酸较高（59.80 ± 2.25 比 45.01 ± 2.25 mmol），而与突然断奶的犊牛相比，断奶后粪便淀粉的百分比较低（第 54 天；3.31 ± 0.76 比 6.34 ± 0.76%）。在第 55 天对公牛犊的消化道进行分析发现，肠道各部分的大体解剖测量值和瘤胃乳头发育的形态差异很小，但充满内容物时，逐步减少组的瘤胃总质量更大（7.83 ± 0.78 比 6.02 ± 0.78 kg）。在本研究的条件下，结果从整体能量平衡的角度展示了逐步减少喂养策略的好处，因为在断奶前胃肠道的适应性增强。
