REPRODUCTIVE-PERFORMANCE OF SOWS ENTERING STABLE AND DYNAMIC GROUPS AFTER MATING

Housing sows in large groups is increasing in popularity but some grou p-housing systems may compromise subsequent reproductive performance. An experiment was designed to test this hypothesis using multiparous s ows weaned at 21 +/-2 days. Two treatments were studied: a stable grou p of 12 sows and a dynamic group of 18 sows. Both treatments had simil ar space allowances in the lying area (1.24 m2 per sow). Sows were all ocated to treatment within 1 week of service and remained on treatment until after day 40 of pregnancy. Each stable treatment group remained unchanged, whereas sows were replaced weekly in the dynamic treatment . Sows were fed using a single electronic feeder for each pen. All sow s were treated similarly for the rest of pregnancy. Eighty and 120 sow s from the stable and dynamic treatments respectively completed pregna ncy. Five second parity sows from the dynamic treatment were removed h aving suffered from aggression. The farrowing rate was 0.78 and 0.85 f or stable and dynamic treatment sows respectively. The stable treatmen t sows had larger litters and a higher proportion of litters having 10 or more total piglets born (P < 0.01). The stable treatment showed a significantly heavier (P < 0.05) litter weight for total pigs born (16 .9 v. 14.6 (s.e.d. 0.57) kg per litter). The parities were uneven so t he data must be treated with caution. However, the results indicate th at the present advice, that sows should be housed in stable groups for the first 4 weeks of pregnancy, should remain unchanged.