Authors : G. Maria Nassuna-Musoke , J.D. Kabasa and M. John King
Abstract: In order to know whether heat stress associated with the warm tropical environment in Central Uganda has a direct effect on the physiology of imported temperate Friesian cows, physiological responses of 81 Friesian animals grouped into Zero Grazed (ZG), n = 28 and Open Grazed (OG), n = 53 cows to heat stress were measured. The responses examined included Hair Coat Temperature (HCT), Breathing Rate (BR) and Rectal Temperature (RT). Cow responses were measured repeatedly every 7-9 days during 4 seasons, between 1200 and 1700 h, simultaneously with spot measurement of microclimatic parameters, i.e. ambient Temperature (TA), Relative Humidity (RH), Solar Radiation (SR), Wind Speed (WS) and black globe Temperature (TBG). Statistical analyses of physiological responses were done using the SAS 6.12 statistical package and included FREQ procedure, TTEST and GLM. Results indicated that animals responded to changes in the microclimate and temperature, relative humidity and solar radiation were directly causing heat stress to a proportion of cows at the smallholder farms. These climatic parameters had stronger effects on animal responses in OG than ZG cows accounting for up to 24 and 36% of variation in physiological the parameters, respectively. Wind movements were important in reducing hyperthermia in both systems.
G. Maria Nassuna-Musoke , J.D. Kabasa and M. John King , 2007. Response of Friesian Cows to Microclimate on Small Farms in Warm Tropical Climates . Journal of Animal and Veterinary Advances, 6: 899-906.