The welfare of gestating sows in conventional stalls and large groups on deep litter

Abstract

Confinement of breeding sows and gilts is a controversial welfare issue in livestock production and there is worldwide interest in finding alternative housing systems for gestating pigs. This study measured aspects of the welfare of gestating sows housed in either large groups on deep litter (Hoops) or conventional stalls (Stalls). Six hundred and forty sows were studied, with 40 recently mated sows weekly entering each treatment over an 8-week period; groups of 85 were formed using 40 experimental and 45 non-experimental animals. Sows in Hoops had a higher ( P < 0.001) number of scratches, a higher ( P < 0.01) return rate to oestrus after mating (13.20% versus 7.35%) and there was a trend ( P = 0.06) for higher salivary cortisol concentrations in week 1 of gestation (6.29 nM versus 4.03 nM). Sows in Stalls had a higher incidence of lameness at weeks 9 and 15 of gestation (13.8% versus 0.8% at week 15) ( P < 0.01). There were changes in some leucocyte sub-populations in the Stalls treatment late in gestation: the percentage of neutrophils was higher (46% versus 41% of WBC), the number and percentage of lymphocytes was lower (4.59 × 10 6 c/mL versus 5.16 × 10 6 c/mL and 41.6% versus 46.5% of WBC) and consequently there was a higher neutrophil:lymphocyte ratio (1.22 versus 0.94) ( P < 0.05). There was a trend ( P = 0.06) for a lower reproductive failure in the Stalls treatment (14.5% versus 27.3%); farrowing rate was higher (76.8% versus 66%), and while sows in Stalls weaned fewer piglets per litter (8.31 versus 8.97), the average weaning weight of these piglets was higher (8.69 kg versus 8.01 kg) ( P < 0.01). The combination of these reproductive parameters resulted in sows in the Stall treatment weaning the equivalent of 39 more piglets per 100 mated sows. The results suggest that sows in large groups on deep litter faced greater welfare challenges in the early stages of gestation based on the findings of increased scratches, a higher rate of return to oestrous and a trend for higher cortisol concentrations early in gestation, all possibly a consequence of aggression. In contrast sows in stalls faced greater welfare challenges later in gestation based on a higher incidence of lameness and an increased neutrophil:lymphocyte ratio perhaps as a consequence of increased stress. In conclusion, these data suggest that in both housing systems the welfare advantages and disadvantages change overtime.