Research from the University of Minnesota West Central Research and Outreach Center at Morris indicates that Parity 1 sows achieved lower preweaning mortality of piglets in straw-bedded farrowing pens than did mature sows.

Preweaning mortality of piglets normally increases with litter size and sow parity in farrowing pens. The influences of litter size and sow parity are hard to separate because mature sows have larger litter sizes than younger sows.

In conventional farrowing crate systems, when litter size is equalized, Parity 3-5 sows wean larger litters with lower piglet mortality than either younger or older sows.

But the optimal sow parity to achieve low preweaning mortality and larger litter size at weaning in loose farrowing systems is not clear because sows perform and behave differently than sows in farrowing crates.

This study investigated the effect of sow parity on preweaning mortality and growth performance of piglets in a loose farrowing system when crossfostering was used to standardize litter size.

From eight breeding groups, 119 sows were categorized as Parity 1, 2, 3 or 4+ (Parity 4 to 10). Sows farrowed in a straw-bedded, group-farrowing system where eight sows shared a communal area and farrowed in individual pens.

Litter size was equalized to 11-13 piglets by crossfostering within 24 hours after farrowing. Piglets were weighed individually at birth and at weaning (4 weeks of age).

Young sows (Parity 1-3) had larger live born litter sizes than Parity 4+ sows (Table 1). After litter size was equalized, Parity 1 sows tended to wean more piglets (10.8 vs. 9.5/litter) and achieved lower piglet mortality (11% vs. 22%) compared with Parity 3 and 4+ sows.

However, Parity 1 sows farrowed and weaned lighter piglets compared to Parity 3 and 4+ sows (Table 2).

Piglets averaged about 0.5 lb. of weight gain daily, and the effect of sow parity on average daily gain was negligible.

The performance of Parity 1 sows in loose housing systems means that management strategies should focus on facilitating maternal care of mature sows to achieve their genetic potential in these systems.

Researchers: Y.Z. Li, J. E. Anderson and L.J. Johnston, all of the University of Minnesota. For more information, contact Li by phone (320) 589-1711, fax (320) 589-4870 or e-mail