As pork producers take up the challenge to house gestating sows in groups vs. individual stalls, questions arise about the impact that mixing and grouping will have on farrowing rates and litter sizes.

In a joint Michigan State University/University of Guelph study, 617 newly bred, mixed-parity sows were assigned to individual stalls or grouped 15/pen. Each group of 15 unfamiliar sows was comprised of three sows at each of 2, 7, 14, 21 and 28 days after breeding. Sows were fed 5.5 lb. of standard gestation ration once a day, on the floor. Of the total, the 122 sows housed in individual stalls after breeding served as “controls” (Table 1).

Sows spent five weeks in groups and then were moved to individual stalls until they farrowed.

Neither the impact of grouping, nor the day of gestation they were grouped appeared to affect subsequent litter size. However, farrowing rate tended to be lower for sows mixed at 14 days of gestation.

“Mixing of strange sows into groups can be done without adversely affecting fertility,” researchers noted. “However, the period about the time of first signal for maternal recognition of pregnancy (10-14 days) is more sensitive to the stress of grouping strange sows and therefore should be avoided.”

The National Pork Board and the University of Guelph-Ontario Ministry of Agriculture, Food and Rural Development Animal Research Program funded the study.

Researchers: Glen Cassar, Monica Seguin, Tina Widowski, Abdolvahab Farzan, Adroaldo Zanella, and Robert Friendship, University of Guelph; and Roy Kirkwood, DVM, Michigan State University. Contact Kirkwood by phone, (517) 432-5198 or e-mail: Kirkwood@cvm.msu.edu.

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