In recent years, there has been an increasing interest in using high quantities of milk or milk replacer (MR) in heat-stressed calves to alleviate the negative effects of high environmental temperatures on their performance. However, observations have indicated a decline in growth performance in the weaning and post-weaning period, which might be optimized with increasing total solids (TS) in milk and weaning age. This study aims to optimize the effects of higher quantities of milk on late weaned calves' performance by increasing TS concentration or delivery route in summer conditions. Forty-eight newborn Holstein calves were used in a 2 × 2 factorial arrangement with the factors of pre-weaning total plane of milk (PM) intake (low vs. high) and milk TS content (12% vs. 17%). The treatments were (1) low PM (LPM) intake with 12% TS (TS intake = 45.9 kg), (2) LPM intake with 17% TS (TS intake = 65.1 kg), (3) high PM (HPM) intake with 12% TS (TS intake = 63.7 kg); and (4) HPM intake with 17% TS (TS intake = 90.3 kg). Calves were weaned at d 83, and the study was terminated at d 103 of age. Performance data (every 10 day), skeletal growth (d 80 and 100), ruminal fermentation parameters (d 48 and 91), and behavioral measurements (d 69, 70, 93 and 94) were analyzed as repeated measurements with PROC MIXED of SAS 9.4 (SAS Institute Inc., Cary, NC). Calves receiving HPM consumed less PMR from d 44 to 83 of age, but they had higher ADG from d 24 to 53 of age compared to those fed LPM (PM × age, P < 0.001). In addition, calves receiving milk with 17% TS had lower PMR intake from d 14 to 83 of age, but greater ADG from d 34 to 53 compared to those receiving milk with 12% TS (TS × age, P < 0.001). Calves that received HPM had greater skeletal growth parameters compared to LPM-fed calves, with a similar effect evident for calves fed milk with 17% TS compared with those fed milk with 12% TS. Calves receiving milk with 17% TS had greater fecal scores and diarrhea occurrence than those fed milk with 12% TS in HPM, but not LPM. Increasing PM and milk TS concentration improved growth in summer-exposed calves as demonstrated by increased pre-weaning ADG, pre- and post-weaning BW, and structural growth.

中文翻译：

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不同采奶平面和乳总固体浓度对夏季后期断奶奶牛生长、瘤胃发酵、健康和行为的影响

近年来，人们越来越关注在热应激犊牛中使用大量牛奶或代乳品 (MR)，以减轻高温环境对其性能的负面影响。然而，观察表明断奶和断奶后的生长性能下降，这可能会随着牛奶中总固体 (TS) 和断奶年龄的增加而优化。本研究旨在通过在夏季条件下增加 TS 浓度或输送途径来优化大量牛奶对后期断奶犊牛生产性能的影响。48 头新生荷斯坦小牛以 2 × 2 的因子排列使用，这些因子包括断奶前的总牛奶平面 (PM) 摄入量（低与高）和牛奶 TS 含量（12% 与 17%）。处理是 (1) 低 PM (LPM) 摄入量和 12% TS（TS 摄入量 = 45.9 kg），（2）LPM 摄入量和 17% TS（TS 摄入量 = 65.1 kg），（3）高 PM（HPM）摄入量含 12% TS（TS 摄入量 = 63.7 kg）；(4) 含 17% TS 的 HPM 摄入量（TS 摄入量 = 90.3 kg）。犊牛在第 83 天断奶，并在第 103 天终止研究。性能数据（每 10 天）、骨骼生长（第 80 天和第 100 天）、瘤胃发酵参数（第 48 天和第 91 天）和行为测量（第 69、70、93 和 94 天）作为使用 SAS 的 PROC MIXED 的重复测量进行分析9.4（SAS Institute Inc.，Cary，NC）。接受 HPM 的犊牛从 44 天到 83 天消耗较少的 PMR，但与喂食 LPM 的犊牛相比，它们在 24 天到 53 天期间的 ADG 更高（PM × 年龄，P < 0.001）。此外，接受含 17% TS 牛奶的小牛在 14 至 83 天龄期间的 PMR 摄入量较低，但与接受 12% TS 牛奶的人相比，第 34 天到第 53 天的 ADG 更高（TS × 年龄，P < 0.001）。与 LPM 喂养的小牛相比，接受 HPM 的小牛具有更大的骨骼生长参数，与喂养 12% TS 牛奶的小牛相比，喂养 17% TS 牛奶的小牛具有相似的效果。接受含 17% TS 牛奶的小牛比喂食含 12% TS 牛奶的 HPM 但不是 LPM 的小牛具有更高的粪便评分和腹泻发生率。增加 PM 和牛奶 TS 浓度可以改善夏季暴露的犊牛的生长，这可以通过增加断奶前 ADG、断奶前和断奶后 BW 以及结构性生长来证明。与饲喂 12% TS 牛奶的犊牛相比，饲喂 17% TS 牛奶的犊牛具有相似的效果。接受含 17% TS 牛奶的小牛比喂食含 12% TS 牛奶的 HPM 但不是 LPM 的小牛具有更高的粪便评分和腹泻发生率。增加 PM 和牛奶 TS 浓度可以改善夏季暴露的犊牛的生长，这可以通过增加断奶前 ADG、断奶前和断奶后 BW 以及结构性生长来证明。与饲喂 12% TS 牛奶的犊牛相比，饲喂 17% TS 牛奶的犊牛具有相似的效果。接受含 17% TS 牛奶的小牛比喂食含 12% TS 的 HPM 牛奶的小牛粪便评分和腹泻发生率更高，但 LPM 没有。增加 PM 和牛奶 TS 浓度可以改善夏季暴露的犊牛的生长，这可以通过增加断奶前 ADG、断奶前和断奶后 BW 以及结构性生长来证明。