Boars usually start to become fertile at about 8 months of age, although they don’t become fully fertile until about 12 months of age, and don’t develop the full secondary boar characteristics (thick shield over the shoulders and tusks starting to grow longer) until about 18 months of age. Sows can start to mature at a younger age but ideally should not be mated until at least 10 months of age.
When the sow comes in season there is usually swelling of the vulva and a change in behaviour. Testing the sow by putting pressure on her back to see if she will stand for a mating is not always reliable – some Kunekunes will stand still whether they are in season or not. The season lasts for between 8 and 48 hours, and normally occurs every 18 to 22 days until pregnancy occurs.
The gestation (pregnancy) lasts for about 116 days in Kunekunes – ‘3 months, 3 weeks, 3 days’. Transfer the sow to the farrowing paddock or pen at least 1 week before the piglets are due. This is the ideal time to worm the sow pre-farrowing. A few hours before farrowing the sow will often be nesting – collecting vegetable matter to make a farrowing area. Make sure there is plenty of bedding available – sawdust, shavings, straw, hay or fleece wool (ideal in winter as wool can help keep piglets warm and the wool won’t rot easily if it gets wet or dirty). The use of a heat lamp behind a farrowing rail can help improve piglet survival.
Kunekune sows are usually excellent mothers and rarely have trouble giving birth and rarely attack their piglets. Crushing the piglets will sometimes occur, particularly if the sow is overweight or is ‘too placid’ and won’t get up if she hears a piglet squealing. It is a good idea to have a board at the bottom of the doorway for the first 3 days to stop the piglets getting lost, although not too high a board or the sow may have trouble getting over it if her udder is close to the ground. Be careful of piglets drowning in water troughs etc until they get a bit older.
Breeders vary in what age they wean piglets at. The ideal is to wean at 8-10 weeks of age. Once the sow is fighting off the piglets for food, it is a good idea to provide the piglets with food in a separate area that the sow can’t get at. Some breeders leave the piglets on the sow for convenience, and the piglets will usually wean themselves by 4 months of age.
It is usually a good idea to reduce the sow’s food intake once the piglets are weaned or she may become too fat. Sows will usually come in season within 1 week of the piglets being weaned off.
The average litter size is 6 to 8 piglets, although first litters of up to 12 piglets are not unusual. A litter size of only 1 or 2 piglets is rare, as often with a very few piglets the sow is likely to reabsorb or abort the litter and ‘start again’. As a sow gets older, the number of piglets per litter may reduce, but sows can often keep reproducing up to about 8 years of age. Increasing the sow’s food intake for up to 2 weeks before mating can have a flushing effect on the ovaries and can increase the litter size. Sows that have low litter numbers or are poor mothers should be culled, but often litter size is influenced by environmental factors (such as feed or the boar’s fertility) more than the sows genetic makeup.
There are various causes of infertility, and the first step to trying to solve the problem is deciding who is at fault – the boar or the sow. Many experienced breeders have found that a boar’s fertility varies during the year, with fertility reduced both during very hot weather or very cold weather. Also, a short illness can reduce a boar’s fertility for up to 6 – 8 weeks.
Sows can show infertility in several ways – failure to come on heat, irregular or difficult to detect heat cycles, or continued return to service (i.e. failure to conceive after mating). There are several possible causes of sow infertility – hormonal problems, a reproductive tract damaged by infection, or too fat or too thin in body condition.
If a sow has an infertility problem, hormone treatment may sometimes help. In many situations it is a matter of being patient and setting a time limit (i.e. 12 months of trying) before culling.