Outdoor sows and bright spring sunshine

All my life among pigs, I’ve been involved with light and how it affects their performance.

It all started way up in Aberdeenshire as an “improver” – their name for what we Sassenachs call a farm student. Later, in my first real job as a stockman, even further north in Banffshire where winter nights were long and the days tended to be dull and light levels low, I had my first of many subsequent battles with owners to try and persuade them to spend more on lighting the pigs – especially our sows, whose conception rate was nothing special at all.

But this piece isn’t about low light levels affect performance, it’s exactly the opposite: how too much bright light can affect seasonal infertility. I picked this up from experts in the mid-West US midway through my career on farms. Seasonal infertility was very much a problem over there in the 1970s, mainly because of its complexity.

It’s what the vets called “multifactorial” – their euphemism for “we have no idea about the real cause”. One of these factors was the effect of really bright spring sunshine on the many sows they had in outdoor runs.

Oddly, this seemed less of a problem in the summer when it was sunburn stress was what they had to watch out for. I met several very good pig specialist vets out there, and as the normal covered accommodation was far too hot for the sows with outside runs, they tended to lie outside. So, we constructed simple tarpaulin shades.

Discussions with the academics working on seasonal infertility, rather than that caused by stress and other theories, came round to the possibility of too much ultraviolet light (not heat) affecting the sow’s hypothalamus gland, impacting returns and her fertility.

Putting up temporary shades over the outside pens earlier in the year in the mid-West seemed to be beneficial. By chance I arrived back here with this information in a March/early April that was exceptionally sunny and warm. Our local veterinary experts thought there was certainly something in it; some transatlantic phone calls were made, and a few farms troubled with seasonal Infertility on Salisbury Plain were persuaded to erect four telegraph poles to which galebreaker sheets were fixed over the top and halfway down one southerly side, leaving a 0.5m gap at the top to prevent too much lateral wind damage.

We sat back and awaited results the following year. There was a definite improvement on three farms and not on another. This was carried on to subsequent seasons, where we learned that getting the sows into the shade could be a problem, but could be assisted by a small amount of bedding into which some nuts were sprinkled.

I don’t see many (or any last year) of these pole-shades up early enough now as I motor round our outdoor areas, but adding this idea to the other measures you can take to combat seasonal Infertility is worth a try in early spring, especially if it’s a problem when the days four to five months earlier have been very bright and the midday sun made the arks too hot.

So, get shades up early – don’t wait for summer heatwaves and the threat of sunburn.

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About The Author

John Gadd, who has spent 60 years' involvement in pig production, has had more than 2,800 articles about pigs published and has written three best-selling pig textbooks. With hands-on experience that includes managing a grow-out herd at 1,800ft in Banffshire, Scotland, and 20 years in the allied industries with Boots' Farm Department, RHM Agriculture and Taymix, he set up his own international pig management consultancy in the mid 1980s and has now visited more than 3,000 pig units in 33 countries as a pig management adviser. (Photo courtesy Bournemouth Daily Echo)