Physiological Responses of Holstein, Brown Swiss and Red Sindhi Crossbred Bulls Exposed to High Temperatures and Humidities

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Abstract
Studies were conducted to determine the effect of short period exposure to cycled hot climatic conditions on physiological response and semen characteristics of different breeds of dairy bulls and also to determine whether there are differences in responses between purebred and Red Sindhi crossbred bulls. Two bulls each of Holstein Friesian, Brown Swiss, and the respective Red Sindhi crossbreds of these breeds were used. The bulls were exposed daily during a period of 7 days for 8 hours to a maximum temperature of 104° F. and 30 mm. Hg. vapor pressure. The minimum conditions were 82° F. and 22 mm. Hg. vapor pressure. The crossbred bulls showed lower rectal temperatures than the purebreds under both minimum and maximum thermal conditions, but their respiration rates were lower only under minimum conditions. The flank and scrotal skin temperatures were lower only under maximum conditions. The efficiency of the heat regulatory mechanism of the scrotal and body skin was demonstrated by the maintenance of lower scrotal and flank skin temperatures than those of the body and air under heat stress. High temperatures and humidities had deleterious effects on semen quality as evidenced by lowered initial motility, concentration, and total numbers of spermatozoa and increase in spermatozoan abnormalities. These adverse effects were more marked in purebred than in crossbred bulls. Recovery of semen quality occurred to some extent in all bulls during the 9 weeks after heat stress, but was more rapid and more nearly complete in the Red Sindhi crossbred than in the Holstein and Brown Swiss Bulls. Copyright © 1963. American Society of Animal Science . Copyright 1963 by American Society of Animal Science

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