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Environmental Physiology in the Sub-Tropics. I. Effect of Continuous Environmental Stress on Some Hematological Values of Beef Cattle^{1, 2, 3, 4,}

University of Florida, Gainesville 32601

Abstract

Hematological values were determined in 24 beef cattle under two different sets of environmental conditions. Three bulls and three heifers of each of the Hereford and Brahman breeds were used in each treatment. Twelve animals were housed at 11 months of age in a chamber at an ambient temperature of 21 C and with a relative humidity of 65%. Another 12 animals of the same age were housed at 32 C, 95% R.H. All animals remained under these conditions for a period of 1 year. Blood was collected every 28 days and analyzed for erythrocyte number, leukocyte number, hemoglobin, packed cell volume, mean corpuscular hemoglobin and mean corpuscular volume.

Brahman cattle when compared with Hereford cattle had significantly higher values for erythrocyte numbers and packed cell volume. High temperature-high humidity treatment significantly reduced mean corpuscular volume and mean corpuscular hemoglobin. No significant effects due to the temperature treatment were found in erythrocyte numbers, leukocyte numbers, packed cell volume or blood hemoglobin concentration. However, a slight reduction in hemoglobin concentration was found in animals under a temperature and humidity stress. Significant interactions, found in some parameters, indicated the need to consider the sex as well as the breed of the animals when experiments of this nature are carried out with beef cattle of Asiatic and European origin.

¹ This paper is part of a dissertation submitted by the senior author in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

² The financial support of the Rockefeller Foundation is gratefully acknowledged.

³ Technical help and equipment was received from Dr. Henry Wilson, Department of Poultry Science.

⁴ Department of Animal Science, Florida Agricultural Experiment Station Journal Series No. 3663.

⁵ Present address: Instituto Colombiano Agropecuario. Ap. Aereo 58-13 Bogota 1, D. E. Colombia, South America.