Reproduction performances and conditions of group-housed non ...

Paper II
- Summary -
A review of 15 experiments with group housed sows showed that there are indications that
stress and fear might be contributing reasons for the impaired reproduction seen in some
group housed sows. Possible initiators of stress and fear might be mixing of unfamiliar
sows and high stocking rates. Traditional methods for assessing stress and fear are expen-
sive and/or time consuming and therefore difficult to use in large-scale on-farm studies or
as components in a management tool to analyse and improve the reproduction performance
in group housed sows. Therefore, based on existing knowledge, possible indicators of
stress and fear related reproduction problems suitable for use in practice were put forward
in the paper. However, whether these indicators were suitable to express variation in sows
susceptibility for a good reproduction performance under practical conditions was not
known.
Paper III
Experimental studies have indicated that group housing may lead to individual variation in
feed intake, fear and social stress. However, systematic information of between-herd and
within-herd variation in feed intake, fear and social stress in sows group housed under
various conditions is lacking. Most likely, this is to some extent because of a lack of suitable
assessment methods. With the aim to evaluate indicators of feed intake, fear and social
stress and to get insight in the level and variation in these indicators in group housed sows
under various on-farm conditions, a farm study took place including 14 commercial herds
followed in 11 month. The results showed that back fat, skin lesions and behavioural
measurements might be relevant indicators of the condition of the sows regarding feed
intake, stress and fear at herd, batch, and individual sow level in commercial herds with
group housed non-lactating sows. For almost all indicators the variation between herds was
larger than the variation between batches within herds. However, the largest contribution to
the variation came from the variation between the individual sows. The between-sow
variation in back fat at farrowing was significantly higher in herds with group feeding than
in herds with individual feeding. The study indicated that group feeding may lead to overfeeding
of high ranking sows and severe underfeeding of a few low ranking individuals.
The presence of feeding stalls reduced the level of aggressions the first hour after weaning.
Irrespective of layout, sows older than third parity were involved in most aggressions the
first hour after mixing on the day of weaning. However, three weeks after mating and at
farrowing, these sows had the lowest level of skin lesions indicating that any stress experienced
by these old sows was short-lasting. In herds with no escape possibilities, first parity
sows had the highest level of skin lesions three weeks after mating and at farrowing,
whereas in herds with escape possibilities, second and third parity sows had the highest
level. Herds with electronic sow feeding and large dynamic groups had the highest average
level of skin injuries.
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