estrus in female animals.
identifying cows in heat has become one of the most critical techniques in modern dairy farming. As well as acute observation by farmers a number of devices are used as aids, e.g. tail paint, several kinds of color-change patches that are glued onto the cow's tailhead, and devices worn by infertile males that mark the cows.
the point at which the female is receptive to the male mating behavior; used as an indication of ovulation and the time for mating to occur.