Temperature-humidity index and reproductive performance of dairy cattle farms in Lima, Peru

Abstract

Background: Heat stress result in a mild reduction on milk production, while long term heat stress exposure can severely affect the productive and reproductive performance in dairy cattle. Aim: The objective of this study was to quantify the relationship between reproductive performance and temperature-humidity index in dairy cattle farms in Lima, Peru. Methods: Monthly service, conception and pregnancy rates were measured on four dairy farms from four different Lima localities as reproductive performance indicators, along with an index of heat stress, maximum daily temperature humidity index (Max THI), during a three-year period. In order to establish the relationship between the max THI and the reproductive performance indicators, a multiple regression analysis was made which considered the variable farm and year as explicative variables. Results: The regression model showed an adjusted R-squared of 33.5% with an estimated standard error of 5.75% and was highly significant (p<0.001). The regression coefficients for Max THI for the variables pregnancy rate and conception rate were significant (p<0.0001). With every increasing unit of Max THI, a 0.84% drop of the pregnancy rate, and a drop of 1.74% of the conception rate was estimated by the model. The regression coefficient of Max THI for the service rate variable was not significant. Conclusion: It was concluded that the increase of the Max THI significantly affected the reproductive performance of intensive dairy cattle farms in Lima.