Collar based activity sensors are in common use as a means of detecting oestrus to optimise farm fertility and hence productivity. More recently, the same acceleration-derived signals have been processed to detect the time spent ruminating and eating which gives an insight about animal welfare. Herdsman+ has utilised the self-same platform and through artificial intelligence has enhanced the value of the system to provide a quantifiable measure of the time duration that an animal shows signs of heat stress. Heat stress has a significant impact on both animal welfare and productivity and an unbiased measure of level of stress on an individual basis informs welfare based intervention decisions.