Feeling the heat: a retrospective investigation of thermal load impacts on calf loss

Abstract

Northern Australia’s beef industry annually experiences high heat loads and variable pasture conditions, yet their impact on reproductive wastage remains relatively unquantified. This study analysed retrospective herd data (26,903 cow-production years; 17 herds) to identify predictors of foetal and calf loss (FCL) in northern Australia, integrating climatic, pasture, and animal-level variables. Multilevel logistic regression revealed animal class, lactation status, relative pasture utilisation rate, body condition score and calving period as major factors. Counterintuitively, monthly heat stress indices (CCI) showed no direct association (p=0.59), potentially masked by monthly averaging or its effect moderated by other factors contained in the model. These results further underscore the importance of grazing and nutritional management in mitigating reproductive losses in northern beef cattle herds.