The effect of modified roofing on the milk yield and reproductive performance of heat-stressed dairy cows under hot-humid conditions.

The objective was to measure the effects of cooling techniques (shade cloth vs. normal roof) on performance and physiology of 16 Friesian crossbred cows (87.5% Holstein Friesian × 12.5% Brahman) located at Sakol Nakhon Livestock Research and Testing Station, Department of Livestock Development, Ministry of Agriculture and Cooperatives (Sakol Nakhon, Thailand). They were divided randomly into two groups of eight. The two groups were used to evaluate the effects of modified roofing (normal roof fitted with woven polypropylene shade cloth) on the subjects' milk yield and reproductive performance under hot humid conditions. Results indicated that the modified roofing offered a more efficient way to minimize heat stress than the normal roof. The difference was sufficient to enable the cows to have a significantly lower mean rectal temperature and respiration rate (38.56 °C, 61.97 breaths/min) than that of the cows housed under normal roofing (39.86 °C; 85.16 breaths/min). The cows housed under modified roofing produced more milk (P < 0.05) but did not differ significantly in reproductive performance from the cows housed under normal roofing.