HEAT DETECTION IN CATTLE AND SIGNS

A cow in heat indicates that she is ready for breeding and that with an effective service she is ready to become pregnant.

Heifers after puberty and non-pregnant cows should come in heat every 3 weeks or 18 to 23 days. So when records are kept of heats detected it is easier to keep an eye on the animal 18 to 23 days later to see if it comes in heat again. If she was inseminated and does not come in heat, it may be assumed that she is pregnant.

Heat detection procedures 

Normal heat lasts about 8 to 12 hours. It is therefore advisable to observe cows at least three times a day for some 10 to 20 minutes for signs of heat.  A bull will never fail to detect a cow in heat, but mostly bulls are kept apart from the cows, so the farmer has to recognize the heat signs. When cows are grazing in a herd recognizing an animal in heat is not difficult, as other cows will mount her. It will be less easy to detect if cows are housed, but if the animals can walk around, they can still mount one another.

Most difficult is when cows are tied in a stable. Then the farmer must be more watchful to detect other signs like restlessness, bellowing and a drop in milk production and check whether the vulva is swollen and red.

Complications in heat detection 

Under conditions with high ambient temperatures, cows often show signs of heat during the cooler hours of the day, especially at night. In hot climates, heat is of a shorter duration, 6 to 8 hours, making detection more difficult. Frequent observations, particularly during early morning and late evening will help. Cows that are not healthy will not come in heat or will not exhibit clear heat signs. The same applies to cows in a poor condition or loosing body weight because of inadequate feeding, high milk production in the period after calving, or disease.

Heat signs are:

  

• The cow becomes restless, bellows and tries to attract attention of other animals.
•  She tries to mount other animals, she sniffs them and invites being mounted and sniffed at. 
• During standing heat, she will allow mounting and will stand still. This is the most reliable indication of heat and the appropriate moment for (natural) service.
• She may have mud on her flanks from having been mounted before. 
• The hair on her back, the pelvic area and the tail head is ruffled and sometimes bare. The lips of the vulva are coloured red and somewhat swollen. 
• Discharge of clear thin mucus from the vulva, which may be attached to the tail. Often, milk production is less than normal and the cow behaves differently. 
• After heat there may be a bit of bloody mucus discharge on the hindquarters and the tail.