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Factors Concerned in the Comparative Heat Tolerance of Jersey, Holstein and Red Sindhi-Holstein (F₁) Cattle

Louisiana Agricultural Experiment Station, Baton Rouge^{1, 2,}

Abstract

Two studies were conducted during which lactating and non-lactating Jersey, Holstein, and Red Sindhi-Holstein (F₁) cattle were compared under varying conditions of thermal stress. The total heat production and heat production per unit of surface area of non-lactating Red Sindhi-Holstein crossbreds were shown to be lower than those of Jerseys and Holsteins. The principal difference in heat balance between lactating Red Sindhi-Holsteins and the European breeds was in heat production rather than heat loss. The difference in heat production appeared to be associated with basal heat production rather than with that due to milk production. The increment of heat associated with each pound of FCM produced was estimated to be 10, 13 and 10 Kilo Calories per hour for Jerseys, Holsteins and Red Sindhi-Holstein crossbreds, respectively.

Exposure to elevated temperatures and humidities resulted in initial increases in heat production apparently due to elevated body temperatures and respiratory activity among the Jersey and Holstein cows.

¹ This research was conducted in cooperation with the Dairy Husbandry Research Branch, ARS, as a portion of RMS-3 Southern Regional Cooperative Dairy Cattle Breeding Project.

² The authors wish to express their appreciation to Dr. M. W. Schein and Mr. C. E. Hyde of the Livestock Research Farm, U.S.D.A., Jeanerette, Louisiana, for assistance in construction of respiratory volume equipment.