Abstract：
Dairy cows may suffer thermal stress during the colder seasons especially due to their open-air housing systems. Free water temperature (FWT) and feed temperature (FT) are dependent on ambient temperature (AT) and can be critical for maintaining body and reticulorumen temperature (RT) in cold conditions. The objective of this study was to determine the effects of FWT and FT on RT fluctuations, and of AT on RT and drinking and eating behaviors in late-lactation cows during cold exposure. Data were collected from 16 multiparous lactating cows for four 6-d periods during the autumn and winter seasons. The cows (224 ± 36 days in milk; mean ± SD) had an average milk yield (MY) of 24.8 ± 4.97 kg/d and RT of 38.84 ± 0.163 °C. Daily average AT ranged from 4.38 to 17.25 °C. The effects of the temperature and amount of the ingested water or feed on RT change and recovery time, and the effect of the daily AT on RT, feed and water intake, and drinking, eating, and rumination behaviors were analyzed using the generalized additive mixed model framework. Reticulorumen temperature change and recovery time were affected by FWT (+0.0596 °C/°C and -1.27 min/°C, respectively), but not by FT. The amount of the ingested free water and feed affected RT change (-0.108 °C/kg drink size and -0.150 °C/kg meal size, respectively), and RT recovery time (+2.13 min/kg drink size and + 3.71 min/kg meal size, respectively). Colder AT decreased RT by 0.0151 °C/°C between 9.91 and 17.25 °C AT. Cows increased DM intake (DMI) by 0.365 kg/d per 1 °C drop in AT below 10.63 °C, but with no increase in MY. In fact, MY:DMI decreased by 0.0106/°C as AT dropped from 17.25 to 4.38 °C. Free water intake (FWI) was reduced by 0.0856 FWI:DMI/°C as AT decreased from 17.25 to 8.27 °C. Cold exposure influenced animal behavior with fewer drink and meal bouts (-0.432 and -0.290 bouts/d, respectively), larger drink sizes (+0.100 kg/bout), and shorter rumination time (-5.31 min/d) per 1 °C decrease in AT from 17.25 °C to 8.77, 12.53, 4.38, and 10.32 °C, respectively. In conclusion, exposure to low AT increased feed intake, reduced water intake, and changes in eating, drinking and rumination behaviors of dairy cows in late lactation. Additionally, the consequences of cold exposure on cows may be aggravated by ingestion of feed and free water at temperatures lower than the body, potentially impacting feed efficiency due to the extra energetic cost of thermoregulation.
摘要：
奶牛在较冷的季节可能遭受热应力,特别是由于它们的露天壳体系统。自由水温度（FWT）和进料温度（FT）取决于环境温度（AT），并且对于在寒冷条件下保持身体和网状温度（RT）至关重要。这项研究的目的是确定FWT和FT对RT波动的影响，以及冷暴露期间泌乳后期奶牛在RT上的AT和饮酒和进食行为。在秋季和冬季，从16头多胎泌乳母牛中收集了四个6天的数据。奶牛（牛奶中224±36天；平均值±SD）的平均产奶量（MY）为24.8±4.97kg/d，RT为38.84±0.163°C。每日平均AT范围为4.38至17.25°C。摄入水或饲料的温度和数量对RT变化和恢复时间的影响，以及每日AT对RT的影响，饲料和水的摄入量，喝酒,吃,并利用广义加性混合模型框架分析了沉思行为。FWT(+0.0596°C/°C和-1.27min/°C,分别)，但不是FT。摄入的游离水和饲料的量影响RT变化（-0.108°C/kg饮料大小和-0.150°C/kg膳食大小，分别)，和RT恢复时间(+2.13min/kg饮料大小和+3.71min/kg膳食大小，分别)。较冷的AT在9.91和17.25°CAT之间将RT降低了0.0151°C/°C。奶牛在低于10.63°C的AT中每下降1°C，DM摄入量（dmi）增加0.365kg/d，但没有增加我的。事实上,MY：随着AT从17.25下降到4.38°C，MI下降了0.0106/°C。自由水摄入量(FWI)降低0.0856FWI:DMI/°C,AT从17.25降低至8.27°C。冷暴露影响动物行为，饮酒和进餐次数较少（-0.432和-0.290次/d，分别)，更大的饮料尺寸（+0.100公斤/回合），从17.25°C到8.77、12.53、4.38和10.32°C，每降低1°C时，照明时间（-5.31min/d）更短，分别。总之,暴露于低AT增加饲料摄入量，减少水的摄入量，和饮食的变化，泌乳后期奶牛的饮水和反刍动物行为。此外,在低于身体的温度下摄入饲料和自由水可能会加剧寒冷暴露对奶牛的后果，由于温度调节的额外能量成本，可能会影响饲料效率。
