What do uneven litters cost?

Uneven litters at birth – some nice big piglets, but rather too many small ones – is a problem that’s been with us for years, writes John Gadd. It’s now coming to a bit more prominence with the welcome large litters of 14 or more we see regularly these days due to genetics and better management.

Talking to one of my clients three years ago, he was certain that an uneven litter cost him a lot. With really big litters, he felt that the two smallest in the litter were nearly costing him the profit from the two biggest by the time they reached slaughter weight. But how right was he?

This set me searching for evidence of any work done on the relationship between even and an uneven litter in weight terms. Rather surprisingly I could find very little information on this aspect of uneven litters, if any, and nothing at all on what the difference early on might be in economic terms by slaughter.   

Two-farm trial
With the help of two interested clients, we had a go at finding out. This was a farm trial and not a scientific one, so it must be viewed in this light, but we did consult a rather hesitant statistician in setting it up (he was unable to visit the farms and wanted more replicates). If the end result was to comprise minor differences, this may have been important, but two things have encouraged us to float the findings on the water:
1, The satisfactory difference in the economic benefit surprised us.
2, The groups of even-litter pigs looked so much better at slaughter – fit and with a better ‘bloom’. And that was the opinion of the three of us, all experienced at looking at pigs.

While it was a farm trial, it was done on commercial money-making units under real conditions, and with actual marketing returns at the end of it. We would have liked to measure more litters through to slaughter, it’s true, but production constraints and labour availability constricted us.

Results
We selected and weighed 21 ‘even’ litters and 19 ‘less-even’ litters of about the same size (averaging 12.3 and 12.1 born-alives respectively) and deliberately avoided some of the litters where the differences in weight were considerable.

It is my long-held belief that any early-pig trial should, wherever possible, be carried on to slaughter under identical rearing conditions – as we did here – so that some econometric guideline figures can be mentioned, using whatever assumptions the researcher cares to apply. Sure, they are just guidelines, but useful nevertheless to those of us at the sharp end, as profit comes once the pigs are slaughtered.

The results (see Table 1, below) showed that the average uneven litter liveweight was 8kg less than the even litter liveweight and that the uneven litters ate, on average, 61kg more food.

Expressed in terms of MTF (saleable Meat per Tonne of Feed eaten to finish weight, which automatically takes into account FCR, ADG, mortality and KO%), the even litters put on an extra 181kg per tonne of saleable meat for each tonne of feed consumed than the uneven litters, and that’s extra income.

So, in cash terms, if we take a deadweight price of 170p/kg, the even litters produced an extra return of £307 for each tonne of food fed to slaughter – a 4.7% improvement over the uneven litters.