4. Breeding

4.1 Heat (oestrus) in the sow:

The female pig (sow) is ready to breed (reaches puberty) at 7-8 months of age and will show signs of being in heat. Some slow growing types and animals which are underfed will be older when they reach puberty.

The sow will come into heat every 3 weeks throughout the year if she is not mated.

The pig should not be used for breeding when she comes into heat for the first time. It is wiser to allow her to grow for another month before using her for breeding. She will then be better able to carry and suckle a good litter of young. Only sows with 14 teats should be used for breeding so that all her litter can feed.

If the pig is not mated she will come into heat every 21 days, providing she has enough feed and water.


4.2 Signs of heat:

The female pig coming into heat is restless and may not eat. The vulva becomes pink and swollen. When the pig is pressed hard with the hands on either side of her back she will stand still, showing she is ready to accept the male.

The sow will be in heat for 8 to 36 hours.

4.3 How to bring the sow into heat:

Healthy, well fed sows can be brought into heat so that breeding can be controlled.

Putting a sow which is in heat in with those which are not in heat will make some of the latter come into heat. A better method is to pen sows next to a boar so that they can see and smell him. The sows will come into heat especially if the boar is old and smelly.

Gilts should weigh at least 80 to 100 kg before breeding. Ovulation rate increases during successive oestrous periods (up to fifth) following puberty. Thus it is advantageous to delay the breeding of gilts until the second or third oestrous. Litter size increases on an average in succeeding pregnancies up to 5th or 6th litter. It is therefore advantageous to cull the sow from a breeding herd after her fifth or sixth litter as the litter size goes down thereafter.

Age to breed gilts 7-8 months

Weight at breeding 100-120 kg

Length of heat period 2-3 days

Best time to breed in 

heat period Gilts First day

Sows         Second day

Number of services per sow 2 services at an interval of 12-14hours

Period of oestrous cycle 18-24 days (Average 21 days)

Occurrence of heat after weaning 2-10 days

**Gestation period 114 days

The average length of oestrous cycle in pigs is 19-21 days

The oestrous symptoms last for three to five days beginning with vulvar swelling and vaginal discharge. In true oestrous there is frequent urination, reduced appetite, mounting and standing for service detected by the erection of ears and immobility when normal pressure is applied to the back. Best time for breeding is during the latter half of the first day or early on the second day of oestrous.

In many cases the gilts and sows continue to exhibit the standing heat on the next day. In these cases the animals should be rebred and the interval in the case of rebreeding should be 12-14 hours. This procedure will ensure a high conception rate in the herd.  Sows may come into heat two to ten days after weaning and may be bred at this time. But better results can be obtained by breeding them in the second post lactational oestrous. The animals which have been bred should be observed for the appearance of subsequent oestrous.

If sows not conceived even after successful mating with a boar in two continuous oestrous cycles it is desirable to cull them from the herd. It is important not to overfeed sows which have been bred. Over fat sows are apt to produce weak pigs and crush more piglets at farrowing. Sows should gain about 35 kg and gilts about 55 kg from breeding to farrowing.

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