12 July 2002

Outdoor sows have feed underfoot

The growing trend towards allowing pigs and poultry

greater access to pasture has encouraged scientists

to look more closely at its dietary value. North-east

correspondent, Wendy Short reports from a joint

meeting held by the British Society of Animal Science

and the Nutrition Society

ABOUT one-quarter of the UK sow population is kept outdoors, rising from just 6% in the 1970s, and they could benefit from eating grass.

In many cases, sows have little available grass to eat, but it can provide half the maintenance diet for dry sows, Sandra Edwards of Newcastle University told delegates at the Leeds University-based meeting.

This can be achieved by strip grazing properly managed pasture and fitting nose rings.

"But nose rings have already been banned in Denmark because they encourage nitrate leaching. And so far our research has found nothing else which is as effective at reducing pasture damage."

For growing pigs, it is a different matter. They have less capacity in their gut, so cannot physically eat enough grass to sustain more than a small percentage of their dietary requirement, said Prof Edwards.

Growth rates would inevitably suffer if outdoor finishing relied more on grazing, although this may be acceptable on some systems, such as for organic production.

"We know little about grass intake in growing pigs at the moment. But a small study has shown that only about 4% of intake comes from grass when young pigs also have access to ad-lib concentrate.

"When concentrates are reduced to 70% of dietary requirements, the young animals will still only take in about 5% grass."

Prof Edwards also reported that research into the amount of exercise taken by outdoor sows has shown that the average animal covers 1-3km/day.

She estimated that this exercise, plus the genotype of outdoor animals and additional energy losses through keeping warm, means they need about 15% more concentrate feed a year than housed sows.