28 May 1999

How gilt reduction can lower fertility

LETTING gilt numbers slip may seem tempting in the current economic climate but could reduce herd fertility, especially when seasonal effects come into play.

Serving more gilts can reduce the impact of seasonal infertility. But with fewer gilts on farms this approach is more difficult, according to Signet pig consultant Malcolm Black.

However, there are other ways of overcoming the problem. "Seasonal fertility is associated with hot weather, mainly on outdoor units. In indoor herds it can arise when temperatures exceed 80F and it is important to ensure adequate ventilation.

"Boars are mainly affected, becoming lazy with reduced sperm levels – which could make a case for AI – but sows can also be affected," he says.

Vet Tony Andrews adds that in outdoor herds a few days of temperatures above 21C (70F) can cause infertility.

"This may occur straight away or up to two months later, due to the sperm development cycle. Serving and feeding pigs at cooler times of day and ensuring good access to water helps."

Now is the time to take action, warns Mr Black. "Outdoor herds start to be at risk in June and making sure sows have good wallows and shading available will help reduce returns to service."