As part of the NADIS surveillance system, pig farm health and productivity is recorded and reported anonymously on a monthly basis. One of the broad parameters measured is pigs reared per sow per year and over the last two years there has been a steady improvement in productivity of surveyed herds, such that the average has risen from around 22.5 to 23.5 pigs per sow per year – a 4.5 per cent improvement (graph 1). Strangely, whilst the trend has been upwards over the full two years, there was a sharp decline this Spring (most recent three month average), which requires further investigation.

Easier to explain is the peak seen through the summer of 2008 (3 periods over 24 pigs per sow per year) with a tail off towards the end of the year as the effects of seasonal infertility in summer/autumn work their way through to farrowings.

Over the last 18 months, of course, PCV2 vaccines have been used on some farms and a separation of specific populations reveals an improvement in vaccinated herds (23 to 24 pigs per sow per year) but a more uneven picture in unvaccinated herds (graph 2).

This improvement is broadly consistent with the figures produced from the BPEX PCV2 research programme recently published, both for the large number of subsidised herds and the specific Leeds trial.

See: BPEX studies on PCV2 vaccines

From the NADIS figures it is also a little surprising that breeder/feeder farms achieve the best productivity, compared to breeder/weaner or breeder only farms. A widely held view is that the pure breeder producer, without finishing pigs to distract him, can concentrate on sow productivity and achieve better results. In the sample population this is not the case (graph 3).

There is also a steady increase in output as herd size increases with herds of 300-700 sows being the most productive (graph 4). The larger herds suffer a fall off in output within the surveyed population.

There is a marked difference in productivity between indoor and outdoor herds with the latter under performing the former by around 8 per cent (graph 5). Given that outdoor herds tend to be breeder or breeder/weaner farms, this may underlie the observations in graph 3 above.

Sows on slats outperform those on straw by over 1.5 pigs reared per sow per year in this population, which again may be influenced by the indoor/outdoor effects.

Again, possibly surprisingly, there is very little difference between batch and continuous (weekly) production despite the advantage of the batch producer being able to concentrate staff efforts on serving and farrowing/piglet rearing at different times.

Despite the concentration of outdoor herds in East Anglia, there is no regional difference in productivity reported for the two main pig-keeping areas (graph 6).

Recording and reporting needs to continue to be able to monitor long term trends, particularly given the role of Circovirus vaccination which would be expected to control breeding herd disease where this virus is implicated.