Development of a Climate Stress Index for Dairy Cows Housed Outside

摘要

Climate change models are suggesting an increase in the severity of extreme weather events.Dairy cows are highly susceptible to heat stress due to their high level of metabolic heat production,which is required to meet the high levels of milk output. Current predictive models, such as the temperature humidity index (THI) and the heat load index (HLI) may not adequately describe the effect of hot climatic conditions on dairy cows kept outside.The aims of this study were to (i) determine the effect of climatic factors on milk production (MP), (ii) assess the usefulness of TH1 and HLI in predicting cow responses to heat load (HL),and (iii) from these develop a heat load model that will predict the impact of climatic stress (specifically heat stress) on dairy cows kept outside. Results from the first summer of the study will be presented in this paper.