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Light (I): Seasonal infertility

This is the first of 4 pieces on light by pig farm advisor, John Gadd. In this article Gadd looks at the correct levels of light for sows; before, at and after breeding times.

I first cut my teeth 45 years ago on the problem of light levels for breeding sows. Adequate light levels are very poorly understood, even today.

I usually follow up a visit with a quick phone call or note to ask whether things have improved, as you can learn so much from such advisory checks. What doesn’t work is as important as what does. Fortunately, with regard to advice on the correct levels of light with which to provide sows before, at and after breeding times in particular, the positive responses have been plentiful, 1 comment even finding its way into the pig press:

“Gadd called at our farm to investigate our returns problem. He wasn’t in the operation 1 minute before he told us what we should be doing in our mating area, and it has helped us no end. He told us to light up our mating area using a timing clock and good lights so that it was as bright as daylight, but better... Since we did that we rarely get a return. He showed us how to measure light quickly and very cheaply and said that establishing a good period of darkness in the 24 hours could be just as important as the correct level of light during the day. The funny thing is that it has cost us so little, about $ 200 to $ 300.” (Niel Managh. Australian Pork Journal).

I mention this comment, not for self-aggrandisement, but because it summarises what I will advise in this and the following articles on light.

Too much or too little light?

In my experience, it has nearly always been insufficient light at and around breeding influencing subsequent reproductive performance, and again in the farrowing house, where lighting is bright but still not bright enough, as this has a carryover effect on rebreeding. Sure, things are better now with these more modern buildings, but there are areas in the world where the breeding facilities are still woefully short of light; Eastern European countries especially where I find it very easy to obtain greater numbers born, shorter weaning-to-successful conception times resulting in fewer empty days/sow/year.

Autumn seasonal infertility and light

This is about too much light for sows and gilts, now increasingly being kept outdoors, or as in North America, under cover with access to outside pens. I was over there several years ago when they were plagued with the autumnal variety with its peak in September (northern hemisphere) especially abortions and disappointing ‘no-shows’, and talked to several of their excellent pig specialist vets about it. The consensus was that too much bright light from early spring sunshine was affecting the light-receptor gland and disturbing the normal hormone re-breeding pattern. Drawing tarp shades over the outside runs on such days was tried and got results.

Late winter seasonal infertility

To combat the ‘feral factor’, where even the modern sow has throwbacks to the past hidden in her genes (triggered by reducing daylight) to prevent her conceiving in autumn and have to raise a family in inclement winter weather, these outside runs were lit to at least 60 lux as soon as the reduced daylight commenced from July onwards.

I arrived back in the UK (where 35% of our breeding herds are outdoors) in a bright, clear spring and discussed the American results with our local vets. Some transatlantic phone calls were made, and on three farms with an autumn breeding problem, shaded areas were erected from four telegraph poles with Gale-breaker sheets fixed to the top and sunward side, and a little straw bedding and nuts provided underneath.

Result – a distinct improvement on two farms and not on the other. Moral 1 – for sows outside in spring, get shades up early and don’t wait for summer sunburn. Moral 2 – by means of extra light as daylight reduces, ‘fool’ the sow’s pineal gland into thinking that winter is not on its way, but keep her warm too. This time, 15 farms responded positively.

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