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

- General discussion -
GENERAL DISCUSSION
The specific aims of this thesis were 1) to identify important causes for impaired reproduction
performance in group housed sows and 2) to define and evaluate indicators suitable for
use in decision-making to improve the reproduction performance of commercial herds with
group housed sows.
Based upon a review study, the hypotheses put forward were: 1) individual variation in energy
intake as well as fear and social stress might be important causes for impaired reproduction
performance in group housed non-lactating sows, and 2) back fat, skin lesions and
behavioural measurements might be indicators of these characteristics, suitable to express
variation in sows’ reproduction performance under practical conditions.
The results of the detailed farm study, including 14 commercial herds, supported that group
housing may lead to individual variation in feed intake severe enough to impair pregnancy
rate and perhaps also litter size (Paper IV). The 14 herds were chosen to represent different
layouts and management routines to ensure that any relation found could be transferred to a
broad spectrum of herds. For the 554 sows followed, a significantly (P=0.02), positive correlation
between back fat gain and chance of pregnancy was found and further a tendency
(P=0.08) to a positive correlation between back fat gain and litter size. The modelled relations
indicate that a sow with a negative back fat gain of 0.5 mm per week has 5 percentage
points lower chance of pregnancy after first mating and 0.6 fewer born piglets per litter
compared to a sow with a positive back fat gain of 0.5 mm per week. In addition, it was
found that sows eating less than 20% of all observations three weeks after mating had a
significantly (P