Effects of Group Housing after Weaning on Sow Welfare and Sexual Behaviour28 January 2015
An Australian-Danish study has found that sows housed in groups at weaning and re-grouped after insemination experienced higher stress than sows housed in individual stalls at weaning and mixed in groups after insemination, leading to less successful mating within five days of weaning for the group-housed sows.
A project comparing the effects of grouping sows after weaning or within two days after insemination on sexual behaviour, aggression, injuries, stress, and mating success was conducted by J-L. Rault of the University of Melbourne with others at Rivalea Australia and from Denmark at the University of Copenhagen and the Pig Research Centre of the Danish Agriculture and Food Council.
In their paper in Journal of Animal Science, they explain that, at weaning (day 0), 360 sows were housed in groups of 10 sows at 4.4 square metres per sow either group weaned (GpW) or in individual stalls (stall weaned; StW), with 18 groups per treatment.
Six days after weaning (day 6), seveninseminated GpW sows were moved to pens at 2.1 square metres per sow and keeping acquainted sows, and simultaneously, groups of seven inseminated StW sows were mixed at 2.1 square metres per sow.
Group-weaned sows showed greater variation in the onset of oestrus (P=0.02) but not in the length of oestrus compared to StW sows (P=0.21), with seven per cent fewer GpW sows inseminated within five days of weaning (P=0.05).
Group-weaned sows showed lower sexual receptivity scores, showing less spontaneous standing during boar exposure and partly compensating by a greater response to the back-pressure test (both P<0.01).
The GpW treatment also showed greater variability in sows inseminated twice within six days of weaning, with three out of 18 pens having only five mated sows out of 10.
Mixing after weaning resulted in higher levels of stress than mixing after insemination, with GpW sows having higher plasma cortisol concentration than StW sows on day 1 (P<0.001) but no treatment differences on day 7 in cortisol concentration or aggression at feeding (P=0.48).
Group-weaned sows experienced greater weight loss during the first week post-weaning (P=0.05).
Anogenital sniffing in GpW sows was frequently observed from days 2 to 5 but mounting and flank nosing increased on days 4 and 5.
Frequency of sexual behaviour initiated by GpW sows tended to correlate with weight loss (P=0.08), and sexual behaviour received correlated positively with cortisol concentration on day 1 (P=0.005).
In conclusion, Rault and co-authors noted that sows housed in groups at weaning and regrouped after insemination experienced higher stress than sows housed in individual stalls at weaning and mixed in groups after insemination.
This, they observed, resulted in lower mating success within five days of weaning, which in turn increased between-week variability. The lower sexual receptivity in sows grouped at weaning may be due to suppressed oestrus-related behaviour, with ovulation occurring, or delayed ovulation beyond day 6.
The researchers added that further research is needed to identify underlying mechanisms to reduce variability, manage aggression and sexual behaviour, and optimise oestrus detection in group-housed weaning systems.
Rault J-L., R.S. Morrison, C.F. Hansen, L.U. Hansen and P. H. Hemsworth. 2014. Effects of group housing after weaning on sow welfare and sexual behavior. Journal of Animal Science. 92:5683-5692.
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