The weaning process may cause intense stress for dairy calves, even when low volumes of liquid diet are fed. Management tools that increase the intake of solid feeds, such as gradual weaning, can provide better physiological and metabolic conditions through better ruminal development, leading to better adaptation to ruminant metabolism and aiding in stress mitigation. The objective of this study was to evaluate the effects of 2 weaning protocols and 2 levels of concentrate intake on the performance and physiological and behavioral variables related to stress in dairy calves. Thirty-six newborn male Holstein calves were used in a randomized block design with a 2 × 2 factorial arrangement: 2 weaning strategies, abrupt or gradual, and 2 levels of concentrate intake at 5 wk of age, high (>350 g/d) or low (≤350 g/d). Calves were equally managed until they were 5 wk of age and then grouped according to concentrate intake. Statistical analyzes were performed using the MIXED procedure of SAS software (SAS Institute Inc., Cary, NC), and no significant interaction was observed between studied factors (weaning method and starter intake level); therefore, we considered each factor separately and their interactions with age. The highest dry matter intake and concentration of β-hydroxybutyrate were recorded for animals with a high level of starter intake independent of the weaning method. Structural growth (cm/wk) and average daily gain were superior for calves with high starter intake, but weaning method had no effect. The gradual weaning protocol increased the time eating starter, regardless of the level of concentrate intake. Even animals with low concentrate intake that were weaned abruptly showed levels of cortisol and acid-soluble glycoprotein within normal physiological levels. Apparently, other factors besides the milk supply affect the starter intake level of calves in a conventional feeding program. The adoption of gradual weaning is not effective in improving performance when a calf has low intake 3 wk before weaning is complete, but it reduced vocalization on d 2 postweaning.

中文翻译：

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对于断奶过程开始时摄入量低的初生犊牛而言，逐渐断奶不会改善其性能。

断奶过程可能会给奶牛犊带来很大的压力，即使进食少量的液态饲料也是如此。逐步断奶等增加固体饲料摄入量的管理工具可通过改善瘤胃发育提供更好的生理和代谢条件，从而更好地适应反刍动物的新陈代谢并有助于缓解压力。这项研究的目的是评估2种断奶方案和2种浓缩物摄入水平对与犊牛应激相关的性能，生理和行为变量的影响。将36只新生雄性荷斯坦犊牛用于2×2因数排列的随机区组设计：2种断奶策略（突然或渐进），2周龄5 wk的精矿摄入量高（> 350 g / d）或低（≤350g / d）。对犊牛进行均等管理，直到它们达到5周龄，然后根据精矿摄入量分组。使用SAS软件的MIXED程序（位于北卡罗来纳州卡里的SAS Institute Inc.）进行统计分析，在研究的因素（断奶方法和起动机摄入水平）之间未观察到明显的相互作用。因此，我们分别考虑了每个因素及其与年龄的相互作用。与断奶方法无关，对于高水平的起子摄入量，记录到最高干物质摄入量和β-羟基丁酸酯浓度。初学者摄入量高的犊牛的结构生长（cm / wk）和平均日增重要好，但断奶方法没有效果。逐渐的断奶方案增加了进食初学者的时间，无论浓缩液摄入量如何。甚至断奶的低浓缩饲料摄入量的动物也会突然出现正常生理水平内的皮质醇和酸溶性糖蛋白水平。显然，在常规喂养程序中，除了牛奶供应外，其他因素也会影响犊牛的初学者摄入水平。当小牛断奶前3 wk低采食时，采用逐渐断奶对改善性能没有效果，但会降低断奶后d 2的发声。