I live in the "pig factory" of Europe - the efficient, intensive and thus, high-cost pig industries of Britain, Ireland, France, Denmark and the Netherlands. Litter size - particularly piglets born alive/litter - does not seem to be much of a headache for European pork producers.
But much of my work lies farther afield from Europe these days, and boy, have they got problems with litter size! In 1999, three of five visits outside Europe involved, "Please try to get it better" requests.
Paradoxically, a recent tour of some big units in the U.S. revealed that Americans don't seem to be worried about total borns of around 10.2 or so. This is about two pigs total born less than what many of my European clients have achieved since 1997 or so.
These U.S. farms considered 21 pigs weaned/sow/year as "realistic," which is really only a euphemism for "the best we seem to be able to do."
Yet on the best Danish, British and Dutch units, which used to achieve 10.9 pigs weaned/litter (11.8 born alive litter size), our production target is now 26 pigs sold/sow year. Hundreds of us are achieving this.
In Table 1, I provide the sort of litter size levels I find across the world.
Inter-Related Causes Litter size is a huge subject. Some idea of the inter-related causes of achieving suitable litter size are summarized in Table 2.
It may be more useful to describe some differences I notice between what we are starting to do in Europe and what current practices elsewhere are, including those in the U.S.
Influences on Number Born * We are zeroing in on heat detection, especially now that artificial insemination (AI) is becoming more widespread. We are starting to test a day sooner than the textbooks advise. This is a pain, I know. But 10% or more of our (24-day weaned) sows are showing heat at two days, not three or later. Picking this up is worth a quarter of a pig overall.
* Providing she's not over-milky and she is "bagging-down" nicely after weaning, we are keeping energy and protein intake up until service is completed, perhaps to 2/3 of final lactation intake rather than a half to 1/3 as is often advised. This has resulted in half a pig more/litter in my experience.
* We are servicing gilts much later now than Americans are. Look at Table 3 for numbers from one of our national demonstration farms. It is fairly typical of the findings of my clients who now service gilts at much heavier weights.
Yes, it costs, but not to the extent of 0.7 to 1.7 more pigs/litter, plus four to five fewer open days. North Americans tend to regard heavier mating as controversial - we don't!
I don't think that it is necessarily only the weight that's involved. Speed of growth could be too fast as well. Later service lets their hormones catch up with the increasing precocity of growth in the modern gilt. That and a longer induction time give better immunity.
Junior Gilts That's another reason why I like the "junior gilt" concept. I can control speed of growth to puberty and not be a hostage to fortune in terms of the multiplier wanting to get the gilts off and sold as quickly as possible.
* Another under-researched area is the sow's stress condition between weaning and service. We moaned when, on welfare grounds, we had to drop stalls in the United Kingdom and change to group yards with bedding.
Now that we have done so, it seems that many poor litter sizes have melted away without help from the likes of me! I do notice, however, that where space was too cramped, we still have litter size troubles on some problem farms, and I'm building up some field evidence for a later article.
Critical space thresholds and good and bad pen shapes, for example, appear to have an impact on litter size and provide for a fascinating area of behavioral research.
Turmoil The sow must be in mental turmoil after weaning! She's had the trauma of farrowing and the pleasure but hard work of rearing a litter. Then the stress of it is suddenly taken away.
Next, she's mixed in with a group of strange sows and then has the excitement of sex. Wowee!
Anything we can do to smooth over this roller-coaster of emotions compressed into one month, especially the negative ones, surely must help return to estrus and conception.