Effects of Seasonal Climatic Changes on Certain Physiological Reactions, Semen Production and Fertility of Dairy Bulls

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Abstract
The physiological reactions, semen characteristics, and fertility of 14 dairy bulls were studied in conjunction with climatic conditions for 53 weeks in a subtropical environment. It was not possible to show statistically significant breed differences in respiration rate, body temp., or fertility of bulls of the Holstein, Guernsey, and Jersey breeds. When the data were grouped according to max. temp. intervals, only respiration rate was found to be consistently related to climatic conditions. Absolute humidity and mean environmental temp. were found to be more highly correlated with respiration rate over the entire temp. range than was max. temp. 6-week moving avgs. of climatic measurements and fertility in artificial breeding use were calculated. On this basis the following coeffs. of correlation between fertility and climatic measurements were obtained max. temp. -0.46; minimum temp. -0.45; vapor pressure -0.55. These correlations are significant at the 1% level.