Anti-heat stress lick block supplementation alleviated the detrimental effects of heat stress on dairy cows.

Abstract

INTRODUCTION: Heat stress poses a significant challenge to the development of dairy industry, affecting cows' well-being and overall productivity, leading to substantial economic losses. In this study, the impact of a specifically formulated anti-heat stress lick block supplement on milk production, milk quality, feed intake, rectal temperature, respiratory rate, and rumen fermentation in cows exposed to heat-stress was evaluated. METHODS: Twenty-four healthy Holstein lactating dairy cows were divided into two blocks based on milk yield (low and high), Parity (2-3 parity), and lactation days (114&#x202f;&#xb1;&#x202f;8 d). The cows in each block were randomly assigned to either a control group without lick block supplementation or a treatment group receiving lick block. The trial lasted for 6&#x202f;weeks, including a 2-week adaptation phase followed by 4&#x202f;weeks of feeding treatment. RESULTS: Heat stress levels varied from severe (THI&#x202f;>&#x202f;88) to moderate heat stress (THI&#x202f;>&#x202f;80) in the first 2&#x202f;weeks, gradually decreasing to mild heat stress (THI&#x202f;>&#x202f;72) in the following weeks. With the decrease in heat stress, dry matter intake (DMI) and milk production increased (Week:&#x202f;<&#x202f;0.05), the rectal temperature and respiratory rate of cows decreased (Week:&#x202f;<&#x202f;0.05). Lick block supplementation tended to increase DMI (&#x202f;=&#x202f;0.09), and improved milk yield (&#x202f;<&#x202f;0.05) without affecting (&#x202f;>&#x202f;0.05) milk composition, leading to increased milk yields of fat, protein, and lactose (&#x202f;<&#x202f;0.05). Although the overall rectal temperature of cows in the lick block group did not differ from the control group (&#x202f;>&#x202f;0.05), the respiratory rate of cows in the lick block group significantly decreased (&#x202f;<&#x202f;0.05) in the second and third weeks. Supplementation with the lick block increased (&#x202f;<&#x202f;0.05) rumen pH and decreased (&#x202f;<&#x202f;0.05) NH-N and propionate concentrations in dairy cows, and tended to lower the acetate-to-propionate ratio (&#x202f;=&#x202f;0.07), total VFA concentration (&#x202f;=&#x202f;0.07), and butyrate concentration (&#x202f;=&#x202f;0.09). CONCLUSION: Supplementation of anti-heat stress lick block alleviated the detrimental effects of heat stress on dairy cows within a certain range of temperature and humidity.