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

- General discussion -
lem, because three weeks after mating their reproduction will already have been impaired.
However, assessment of back fat gain can provide the farm manager with valuable indica-
tions of whether variation in back fat gain, in general, could be a contributing reason for
impaired reproduction in group housed sows. The time necessary for back fat measurements
was not recorded in this farm study. However, the back fat measurements were estimated
to be possible to perform within two or three minutes per sow including finding the
measuring points, shaving and measuring. A recent Danish test trial showed that back fat
measurements with a similar digital ultrasound back fat indicator, in average requested approximately
one minute per sow if the measuring points were marked and the sows were
shaved in advance (Thorup, 2004 pers. comm.). This, in combination with a low price
(DKK 4,800 ~ EUR 650) makes LEAN-MEATER® a potential management tool. However,
the suitability of the equipment has recently been questioned due to a large withinobserver
variation, which makes it inappropriate for use at individual sow-level (Thorup,
pers. comm.). More accurate two-dimensional back fat indicators are available on the market.
As some of these can be used for pregnancy diagnosis too, they will perhaps be potential
management tools in spite of the considerable larger price.
The 14 herds involved in the farm study differed markedly with respect to the reproduction
performance of the approximately 40 sows observed per herd. Return percentage varied
from 0 to 45% with an average of 11% and litter size differed from 13.6 to 15.7 with an
average of 14.8 total born piglets per litter. These figures support the assumption that group
housing of non-lactating sows does not ‘automatically’ lead to poor reproduction performance
and further that it will be possible to improve the reproduction performance in some
commercial herds.
Improving the reproduction performances is, however, not the only challenge that managers
of group housed sows are facing. Group housing was implemented with the aim to improve
the animal welfare in commercial pig production. However, submissive sows eating in less
than 20% of all observations during feeding because they are kept away from the feed,
sows having less than 10 mm back fat at farrowing and sows with more than 150 skin lesions
at the end of the gestation, as found in the present farm study are not equal to animal
welfare. Therefore, efforts should be made to improve not only the reproduction performance
but also the animal welfare in group housed sows.
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