I hear it all over the world: “We pig producers have been stuck at 12% mortality for years – and it’s getting worse, not better!”, writes John Gadd.
Oh dear, that’s two misconceptions in one sentence, but how come?
First, we need to ask: percentage of what?
At the same benchmarking meeting I once heard: “15% mortality to weaning? Dreadful – pull your socks up!” (This chap attends farrowing, gets 12 born alive and rears 10.2 to weaning)
Then: “5% mortality to weaning, take a bow, that man!” (This farm’s born alives were only 10.75, and his 5% mortality also left 10.2 reared.
Potential income-wise, the two units are the same, so beware of percentages!
Certainly it’s better to lose only half a pig than nearly two per litter, but even so, both farms reared the same. This shows how relying on percentage mortality to weaning can be misleading. Pre-weaning deaths must be linked to the born-alive figure. The Absolute Mortality Figure (AMF) – how many pigs died per litter of those born alive – is a much better yardstick.
Second, as litter sizes increase due to genetics and better farrowing skills, so the relative percentage mortality nearly always rises, too. It’s happening now. As more pigs are born alive, more (mostly the “tailenders” and those less privileged) will tend not to make it to weaning. But expressing this as percentage mortality tends to depress stockpeople.
The percentage mortality to weaning, which is still widely quoted today, doesn’t take into account the litter size or the number born alive. But AMF covers both benchmarks by including born alives.
The AMF is expressed as the number of piglets lost over the number born alive. For example, a typical figure might be “AMF 1.2/12”. This would be 10% mortality of those born alive.
An AMF 0.8/8 would also represent 10% mortality, however AMF 0.8/12 would be just 6.67% mortality.
Litter size and pigs reared/sow year are two of the performance figures that are talked about most today. When mortality is expressed in AMF terms, we can see that the problems of low mortality to weaning could be in the born alives, not necessarily those lost subsequently.
This brings to the fore the value of attended farrowing, prostaglandin use and so on, rather than being tempted to criticise the staff on poor post-farrowing rearing skills resulting in the high mortality-to-weaning figure.
With the big litters some are achieving today, using AMF becomes even more important. Losing 0.8 piglets in a litter of 14 born-alives (AMF 0.8/14) at first glance looks high (it will result in two less weaners/sow/ year), but it’s only 5.7% mortality, which is very good.
And even AMF 1.4/14 is still 10% mortality, which those with big litters using the old percentage mortality terminology will think pretty good – even if they end up 3.36 potential weaners/sow/year adrift, and need to look for the reasons why.
AMF makes you look at things afresh, while percentage mortality doesn’t.
> John Gadd, who is celebrating 60 years’ involvement in pig production this year, 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 1,800 ft 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 consultantcy 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)
