Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC 29634.
Nurture Research Center, Provimi, Brookville, OH 45309.
J Dairy Sci. 2020 Sep;103(9):8143-8150. doi: 10.3168/jds.2019-17704. Epub 2020 Jul 16.
Many changes occur in the rumen as calves transition from consuming a liquid diet to a completely solid diet. These changes can influence growth and calf health, being greatly affected by preweaning diet as well as the transitional steps used to wean calves. A 2 × 2 factorial design of moderate [MOD; 0.66 kg of dry matter (DM)] or high (HI; up to 1.1 kg of DM) feeding rates of milk replacer (MR) and abrupt (AB; 7-d step-down) or gradual weaning (GR; 21-d step-down) was used to study how preweaning program affects calf performance from 2 to 4 mo of age. Calves (n = 50) were randomly assigned to 1 of the 4 preweaning treatments. For the following 56-d grower portion of the experiment, calves were grouped into 12 pens based on MR program, with 4 to 5 calves per pen. Data were analyzed as a completely randomized design, with repeated measures when applicable, by PROC MIXED in SAS (version 9.4; SAS Institute Inc., Cary, NC). All calves received ad libitum access to water and a textured starter [42% starch and 20% crude protein (CP)] blended with 5% chopped grass hay. Overall, apparent digestibility coefficients (dC) of DM, neutral detergent fiber, and acid detergent fiber were greater for MOD compared with HI, and apparent dC of DM and ADF were greater for GR than for AB. No significant differences were detected between organic matter, CP, fat, starch, or sugar dC based on treatment, and no interactions were observed. However, by d 56 only starch dC differed by treatment. Weaning body weight (BW), hip width (HW), and hip height (HH) were greater for HI compared with MOD calves. Weaning HH was greater for AB than for GR calves. However, final BW, HW, HH, and body condition score, as well as average daily gain, did not differ among treatments. An interaction occurred where feed efficiency (gain/feed) was reduced with GR weaning in MOD, whereas the opposite occurred in the HI group. When feeding calves a moderate level of MR, a several-step gradual weaning is not necessary to ensure growth and development; however, calves should be gradually weaned when offered a high level of MR.
当犊牛从液体饮食过渡到完全固体饮食时，瘤胃会发生许多变化。这些变化会影响生长和犊牛的健康，并且受到预断奶饮食以及断奶过程中使用的过渡步骤的极大影响。采用中（MOD；0.66 千克干物质（DM））或高（HI；高达 1.1 千克 DM）的牛奶替代品（MR）喂养率的 2×2 析因设计和突然（AB；7 天的逐渐减少）或逐渐断奶（GR；21 天的逐渐减少）来研究预断奶计划如何影响 2 至 4 月龄的犊牛性能。犊牛（n=50）被随机分配到 1 个预断奶处理中。在实验的接下来的 56 天生长阶段，根据 MR 计划将犊牛分为 12 个围栏，每个围栏 4 至 5 头犊牛。通过 SAS（版本 9.4；SAS Institute Inc.，Cary，NC）中的 PROC MIXED 进行完全随机设计分析，当适用时进行重复测量。所有犊牛均可自由获得水和质地良好的启动料（42%淀粉和 20%粗蛋白（CP）），并与 5%切碎的草干草混合。总体而言，MOD 的 DM、中性洗涤剂纤维和酸性洗涤剂纤维的表观消化系数（dC）高于 HI，GR 的 DM 和 ADF 的表观 dC 高于 AB。基于处理，没有检测到有机物、CP、脂肪、淀粉或糖 dC 的显著差异，也没有观察到相互作用。然而，到第 56 天，只有淀粉 dC 因处理而异。HI 犊牛的断奶体重（BW）、臀部宽度（HW）和臀部高度（HH）大于 MOD 犊牛。AB 犊牛的断奶 HH 大于 GR 犊牛。然而，处理之间的最终 BW、HW、HH 和身体状况评分以及平均日增重没有差异。在 MOD 中，GR 断奶时的饲料效率（增益/饲料）降低时会发生相互作用，而 HI 组则相反。当给犊牛喂食中等水平的 MR 时，不需要逐步逐渐断奶来确保生长和发育；然而，当提供高水平的 MR 时，应逐渐断奶。
