Pig units traditionally experience production losses of up to 10% over summer.
But the seasonal dip can be countered by adopting measures to reduce heat stress, says Neville Kingston of the East Yorkshire-based Garth veterinary partnership.
Mr Kingston told delegates at a BPEX-organised meeting that services between May and October produced an average 5-10% fewer piglets.
Sow mortality also rose sharply.
The decline in litter size was partially because sows tended to eat less in warmer weather, said Mr Kingston.
“Units should switch to three-times-daily feeding and use fans to keep animals cool, with the aim of a 7kg a sow daily feed intake from farrowing to weaning.”
Boar infertility, shorter heat periods and disease challenge were also responsible for the production decline, he added.
“More than 50% of blood samples sent for fertility testing come in during August and September.
The pig’s natural breeding cycle is November-April, so units have to work harder outside that period to maintain production standards.
“Sows tend to have below-average condition scores through summer and wallowing to keep cool can lead to animals contracting leptospirosis.”
Spending more time on heat observation and service were two ways producers can lift performance, said Mr Kingston.
“It costs about 2 to pay for 12 minutes’ worth of labour to make sure each service is carried out correctly.
That will result in a minimum of one extra piglet per litter – which could contribute at least 30 a sow served to margin over feed.”
Rigorous culling and fostering would also improve results, he said.
“When a sow has two consecutive litters that do not match up to average gilt performance, then she should be considered for culling.
Sows with multiple returns and low milk yields should also be sold.
“Some of my clients have reported that putting 12 or more piglets on to gilts is effective at developing their back teats, which can dry up in later parities.”
The check in performance in the growing herd over summer could be explained by the fact that litter sizes in earlier months were larger, leading to lower birth and weaning weights, Mr Kingston explained.
Respiratory disease could also be brought on by excess panting in hot weather.
“A 10% reduction in liveweight gains in summer will reduce output by £4 a pig.
Lowering stocking rates is beneficial, but not always practical. Instead, increase airflow in housing, keep slurry pits empty and clean out straw pens regularly to reduce heat stress.
“Pigs will also be kept cooler when plastic horticultural bubble wrap is stapled to the roof for insulation and outside surfaces are sprayed with water periodically.”
Mr Kingston pointed to the lack of accurate records relating to pig industry performance figures.
“We need up-to-date records to work from. Much of the available data amalgamates records from indoor and outdoor herds.
I would like to see more invest-ment in recording processes.”
Richard Evans, of the Bishopton Vet Group, said the best age to serve gilts was 230-240 days.
“Too many units are serving gilts early and the practice is not cost-effective.
It will lead to poor reproductive performance in subsequent parities.
“Gilts need time to mature and build up sufficient muscle body size and fat layer.
Serving before the recommended age forces gilts to redirect reserves needed for their own development towards producing and feeding their litter.”