Vet Chat

Louise Blenkhorn Vet Chat

Louise Blenkhorn, BSc(Hons), BVM&S, MRCVS, is an independent pig veterinary consultant and a pig farmers daughter. Louise's private life is just as busy. A mother of two to Emma and Ava. Louise and her husband Neil, run a successful herd of Limousin beef cattle.

Seasonal Infertility

Following a dry hot summer, only recently am I starting to notice the days draw in and the temperatures start to plummet.

Temperature and speed of change of daylight length are two key causes of seasonal infertility. It is worth noting that the cause is not short day lengths per se, but rather the speed of change. This speed of change is most notable during early Autumn as seen in the below graph.

Seasonal infertility is often confounded by weight loss in lactation following lower feed intakes during hot summer months.

Typically, gilts and young sows are most affected. Seasonal infertility manifests as increased returns to service (often regular i.e. 3 weekly returns), anoestrus/ failure to cycle and late abortions. Generally, the sows remain well in themselves and show no other signs of ill health. Of course, infectious diseases should be ruled out so please consult your veterinarian if you are worried.

Photo: Pig333

Pigs are naturally seasonal breeders so in the commercial world, we try to limit the effects of seasonal infertility to allow sows to breed all year round. During these periods the following guidelines are normally advised :-

● Keep lights on a timer for 16 hours a day at 250 lux – this is very bright! ● Ensure good boar contact after weaning and when encouraging cycling. ● Boars should be rotated if possible ● The use of boar spray can also help oestrus expression, esp in gilts ● Offer 0.25kg/head/day more for 6 weeks after service ● Keep huts and yards well bedded to avoid chilling and excessive temp fluctuations ● Try to avoid excessive weight loss in lactation ● Dextrose can be top dressed at 500g/head/day to ‘flush’ sows for 5 days pre-service.

Of course, there are no 100% effective solutions and some farms appear to be more affected than others. There are hormonal medications which can be used in cases of Photo: Pig333 anoestrus and poor cycling however these often have limited success. If you are experiencing seasonal infertility, please consult your veterinarian.