27 September 1996

Light and temperature crucial for pigs

AN INCREASE in returns among sows during October could be the result of autumn infertility.

"During early autumn the decrease in day length is most marked and shortens by almost five minutes a day," says East Yorkshire vet Mark White. "At the same time temperature differences between day and night are at their greatest. These factors could be the trigger for hormonal changes in the sow which reduce fertility and increase abortions."

Mr White believes that autumn infertility could increase as producers shift to outdoor production systems or straw yard housing where temperature control is less exact.

Indoor pigs may also show an increase in abortions at this time of year as some ventilation systems struggle to provide an even temperature.

"Pigs find it difficult to cope with large variations in temperature and when they get too cold during the coldest part of the night they can abort," he explains.

Younger and thinner sows are at most risk and increasing feed levels by up to 0.5kg a day to sustain condition could help to reduce losses, he says.

For yarded pigs, veterinary lecturer at East Yorkshire-based Bishop Burton College, Annika Wager, advises extending the day length artificially by providing lighting for 16 hours a day.

"The lighting must be bright enough to read a newspaper at pig level. This should fool the pigs into thinking it is still summer," says Ms Wager.

She suggests increasing boar contact with dry sows in the first month of pregnancy. Boars should be in nose-to-nose contact which can also help to sustain pregnancies through the crucial period where eggs are implanting in the wall of the uterus.

"Even with these measures there could be an increase in returns, so buy in and serve extra gilts to cover any increase in drop-outs," she says.n

Autumn infertility could be on the rise for more sows are housed outdoors or in loose straw yards and are exposed to changes in day length and a greater difference in temperatures between day and night.