Heat Tolerances of Jersey and Sindhi-Jersey Crossbreds in Louisiana and Maryland

Abstract

Various crosses of Louisiana-raised Jersey and Red Sindhi cows, ranging from purebred Jerseys to 3/4 Sindhi-1/4 Jersey were exposed to a standard hot environment (105cF air temperature, 34 mm Hg vapor pressure) for 6-hour periods in a climatic chamber. Data were analyzed with respect to ages, stages of lactation, and breed groups, and these data were further compared to those gathered on similar groups maintained at Beltsville, Maryland. Young animals (6 to 12 months) of all breed combinations were less heat tolerant than older (15 to 24 months) individuals; also, the degree of heat tolerance at all ages was directly related to the amount of Sindhi blood in the animal. There were indications of seasonal differences in reactions to the standard hot environment , and evidence that the Louisiana herd was more heat tolerant than the Beltsville herd.