This study aimed to use a range of non-invasive monitoring technologies to investigate the behavioural and physiological responses of individually housed dairy calves to age at change in milk replacer (MR) feeding frequency. Forty-eight Holstein Friesian calves were individually penned and fed MR (625 g/d) as solids in one of three feeding regimes: (i) once-a-day feeding commencing at age 14 d (OAD14), (ii) once-a-day feeding commencing at age 28 d (OAD28) and (iii) twice-a-day feeding (TAD). Several behavioural (automatic activity sensors), physiological (infrared [IR] thermography and heart rate variability [HRV]) and haematological indicators were used to examine calf responses. Reduction in milk feeding frequency at 14 or 28 d of age increased daily concentrate intakes and drinking water consumption throughout the pre-wean period. Calf lying behaviour was unaffected by reduction in milk feeding frequency; however, TAD calves recorded a significant decrease in total daily lying time during the post-wean period compared with OAD28s. There was no effect of treatment on IR eye or rectal temperature throughout the experiment; however, there was an effect of age, with IR temperature decreasing as calf age increased. OAD14 calves tended to have decreased HRV at days 14 and 16, which is suggestive of an increased stress load. The findings suggest that under high levels of animal husbandry and whilst maintaining the same amount of milk powder/d (625 g/d), reduction in milk feeding frequency from twice to once daily at 28 d can occur without significant impact to behavioural, performance and physiological parameters assessed here.

中文翻译：

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单独饲养的奶牛在不同年龄对母乳喂养频率变化的行为和生理反应

本研究旨在使用一系列非侵入性监测技术来调查单独饲养的奶牛在代乳品 (MR) 喂养频率变化时对年龄的行为和生理反应。48 头荷斯坦弗里斯兰小牛被单独圈养并在三种喂养方式之一中以固体形式喂养 MR（625 克/天）：（i）从 14 天开始每天一次喂养（OAD14），（ii）一次-从 28 天开始的一天喂养 (OAD28) 和 (iii) 一天两次喂养 (TAD)。几种行为（自动活动传感器）、生理学（红外 [IR] 热成像和心率变异性 [HRV]）和血液学指标用于检查小腿反应。在 14 或 28 日龄时减少母乳喂养频率会增加断奶前的每日精料摄入量和饮用水消耗量。小牛躺卧行为不受减少喂奶频率的影响；然而，与 OAD28 相比，TAD 犊牛在断奶后的每日总躺卧时间显着减少。在整个实验过程中，治疗对红外线眼睛或直肠温度没有影响；然而，存在年龄的影响，随着犊牛年龄的增加，红外温度会降低。OAD14 犊牛在第 14 天和第 16 天的 HRV 趋于降低，这表明压力负荷增加。研究结果表明，在高水平的畜牧业和保持相同数量的奶粉（625 克/天）的情况下，在 28 天时将喂奶频率从每天两次减少到一次，而不会对行为、性能产生显着影响。和这里评估的生理参数。