1 Depressed appetite and milk yield. Tailhead has roughened appearance with possible hair loss. This period of receptivity may last from six to 30 hours and occurs every 21 days on the average. However, the interval between two heats may vary normally from 18 to 24 days . Signs of heat Detection of heat calls for acute observation.
Most cows have a pattern of behavior that changes gradually from the beginning to the end of a heat.
A series of signs that may help to identify cows that need to be observed closely are summarized in Table 1. The onset of heat activity follows a distinct pattern, with most activity occurring in the late evening, through the night, and in the early hours of the morning. Other factors influencing the expression of heat Expression and detection of heat may be more or less easy depending on a number of factors. In larger herds, more than one cow may come in heat at the same time. When this occurs, the chance of detecting cows in heat increases dramatically because mounting activities also increase considerably.