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It is generally assumed that stress around oestrus and during early pregnancy reduces reproductive performance of pigs. In our experiment, late prepuberal gilts (age at arrival 225
±
6 days) were housed in groups of four. Stress treatment consisted of once weekly regrouping and twice weekly feed competition of the 28 Stress gilts during 6 consecutive weeks, starting 13 days after arrival. Control gilts (
n
=
28) were not treated.
During the 0.5–1.5
h after regroupings, Stress animals fought consistently more than the Control animals; up to 13 of the Stress animals fought for at most 60% of the time compared to one Control animal fighting for at most 3.3% of the time. The day before first regrouping, gilts had on average 4.0
±
0.9 skin scratches. By week 6, this number had reduced to 2.1
±
1.0 in Control, but remained 4.0
±
1.3 in Stress gilts (
P
<
0.05). In the afternoon after regroupings, skin scratches increased up to 6.3
±
1.6 in the Stress gilts. Saliva cortisol in the afternoon before regrouping did not differ between weeks 1, 3 and 6, nor did it differ between Stress and Control. In Stress gilts, saliva cortisol was increased in the afternoon of first regrouping, in Batch 2 only (from 1.8
±
0.4 to 4.1
±
0.9
ng/ml;
P
<
0.05).
Animals showing a second oestrus within 5 weeks after arrival were inseminated. Duration of second oestrus of these animals was 2.48
±
0.66 days in the Stress gilts (
n
=
24) and 2.21
±
0.58 days in the Control gilts (
n
=
22;
P
>
0.10). At Day 35 after insemination, pregnancy rate was 100% in both groups. Ovulation rate and number of total and vital fetuses was similar (
P
>
0.10). The Stress treatment during a 6-week period around insemination consistently resulted in fighting but did not result in long term effects on cortisol levels and did not impair reproductive performance.