Comparison of Effects of Cold and Warm Water Intake in Winter on Growth Performance, Thermoregulation, Rumen Fermentation Parameters, and Microflora of Wandong Bulls (Bos taurus)

Efficient farm practices are crucial for livestock health and performance, and cold stress is a major challenge for cattle in winter. This study aimed to preliminarily investigate the effects of cold and warm water intake in winter on the growth performance, thermal stress indicators, serum hormones and metabolites, rumen fermentation parameters, rumen fiber degrading enzyme, and rumen microflora of yellow cattle during winter. Eight Wandong Bulls (Bos taurus) were divided into two groups: group C, which received cold water (6.36 ± 1.99 °C), and group E, which received warm water (32.00 ± 3.12 °C) for 30 d. The results showed that warm water intake significantly increased ADG (p = 0.024) and DMI (p = 0.046) and decreased (p = 0.047) the ratio of feed intake to weight gain. Furthermore, the heat production, respiratory rate, surface temperature, and rectal temperature of cattle did not alter with water temperature, but the heat production value of the bulls increased (29.64 vs. 25.76 MJ/W0.75 h−1) with cold water intake compared to warm water. The concentrations of thyroxine (p = 0.021), serum urea nitrogen (p = 0.025), and glucose (p = 0.011) increased for the bulls drinking cold water compared to those drinking warm water. The concentrations of NH3-N (p = 0.048), total VFA (p = 0.010), acetate (p = 0.009), propionate (p = 0.009), cellulase (p < 0.01), and xylanase (p < 0.05) were lower in group C compared to group E. Total bacterial abundance, as well as specific species including Ruminococcus flavus, Ruminococcus albus, and Prevotella ruminicola, were lower (p < 0.05) in group C compared to group E. In conclusion, drinking warm water during winter enhanced growth performance by influencing energy metabolism, regulating serum hormones and metabolites, and modulating ruminal microflora of bulls compared to cold water intake.