EFFECT OF WEATHER ON MILK-PRODUCTION OF HOLSTEIN-FRIESIAN COWS IN THE HUMID TROPICS

The effect of mean weather variables (temperature, relative humidity, temperature-humidity index (THI) and total rainfall) on milk yield was investigated in three stages of lactation (early, weeks 1-12; middle, weeks 13-25; late, weeks 26-38) of 27 imported Holstein-Friesian cows and 26 Ghana-born pure progeny in first and second lactation. The mean daily milk yields in early, middle and late lactations were, respectively, 18.7 kg, 15.9 kg and 13.4 kg for the imported cows and 10.8 kg, 8.6 kg and 7.0 kg for the Ghana-born animals. Relationships between milk yield and temperature and THI, though significant, were small and inconsistent. In early, middle and late lactations, weather only accounted for 1.6%, 1.3% and 1.4%, respectively of the variation in milk yield for the imported Friesians and 0.8%, 0.7% and 0.5% for the Ghana-born cows.