Assessment of Physiological Indicators of Heat Stress Management Interventions in Dairy Cows in Oyo State, South West Nigeria

Heat stress in dairy cattle managed under tropical conditions imposes persistent physiological burdens that reduce milk yield, reproductive efficiency, and cow welfare. This study assessed the effectiveness of selected heat stress mitigation interventions by monitoring physiological and biochemical indicators in Friesian-Zebu cows at a commercial dairy farm in Ibadan, Oyo State, South West Nigeria. Sixty cows were assigned to three management groups over an eight-week hot-dry season period: a control group with standard open housing, a group provided with mechanical cooling fans plus overhead sprinklers, and a group receiving additional dietary electrolyte supplementation. Rectal temperature, respiratory rate, serum cortisol, thyroid hormones, and milk yield were recorded weekly. Cows in the fan-sprinkler intervention group exhibited significantly lower rectal temperatures and respiratory rates compared to controls, along with reduced serum cortisol and preserved triiodothyronine concentrations. Milk yield was 14% higher in the intervention groups combined versus control. The electrolyte supplementation group showed further improvements in blood bicarbonate, countering heat-induced respiratory alkalosis. Physiological indicators returned to seasonal-cooler baseline values within three weeks of intervention initiation. These findings validate the practical efficacy of combined physical cooling and dietary electrolyte management in sustaining dairy cow physiological welfare in South West Nigeria. Keywords: heat stress, cooling interventions, serum cortisol, dairy cows, Oyo State.