Effect of heat stress on physiology and production of dairy cow

Abstract

Dairy farming has become very popular in Bangladesh and most of the farmers reared high yielding dairy breed in their farm. Bangladesh is one of the tropical countries in this South-east Asia where heat stress is a matter of great concern as regard to exotic breed and global warming. The objective of this study was to asses the effect of heat stress on physiology and productive performance of dairy cows. A total of 162 dairy cows at different 28 dairy farm under Chattogram district were studied. The physiological parameters mainly rectal temperature, heart rate, urine specific gravity and respiration rate of individual cows were assessed. The frequency of respiration rate was higher than normal however, the value of other parameters was found in normal range. The frequency of some important behavioral sign related to heat stress like panting, drooling of saliva, tongue protrusion and neck extension were measured. The presence of panting, drooling of saliva, tongue protrusion and neck extension were respectively, 19.14%, 31.48%, 4.94%, and 96.91%. The result showed that extension of neck was most prevalent at the studied farms. Milk yield data of farm showed that 96 cows (59.26%) milk yield over 10 liter per day hence 66 cows (40.74%) milk yield below 10 liter per day. Relationship among rumination rate, panting, drooling of saliva along with respiration rate was compared and result was significantly (p<0.05) related. This study was concluded that the effect of heat stress changes in physiological parameters and may also reduce the productive performance of dairy cows. Proper management regarding heat stress should be taken to reduce heat stress that will help both farmers economic condition as well as welfare of dairy cows.