Heat Detection in Sows
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The adult sow usually presents heat between 4 to 6 days postweaning, although it can occur between 2 to 7 days postweaning. It lasts a mean of 48 to 72 hours but it is possible to observe heat periods of 32 to 120 hours. It has been found that sows that become in heat sooner after weaning tend to present a longer heat period and on the contrary, sows that show heat later after weaning, tend to present heat during a shorter period of time. The symptoms of heat are inflammation and reddening of vulva, a change in the texture of the vaginal mucus, a more nervous behaviour and mainly, the standing reflex provoked by the presence of the boar or by the back pressure made with hands by the technician who performs heat detection. The standing reflex marks the beginning of the heat period. It is clearly manifested in the presence of a boar that stimulates sows via visual, hearing, tactile and most of all olfactory by means of pheromones (3-a-androstenol and 5-a-androstenona) produced in the submaxillary glands. Sows must be exposed to the boar from 3º day post weaning, preferably in pens, in groups of 6-8 sows per boar, at least one time per day, advisable two times, during a period enough to allow the boar to examine all the sows. In the case of sows housed in boxes, the boar must walk in front of them during a period enough to stimulate all of them. It is very important that the housing of the sows is far from that of boars, in order to avoiding that sows become accustomed to the stimulus, That will lead to difficulties in heat detection. The best choice is to have separated housing or at least to put a distance to avoid visual contact between them. |