ASSOCIATIONS BETWEEN LITTER SIZE AND SPECIFIC HERD LEVEL MANAGEMENT FACTORS IN ONTARIO SWINE

This retrospective study examined associations between herd management techniques and litter size in a target population of Ontario swin far ms that marketed at least 1000 hogs or 35 sows in 1987. A survey was s ent to these producers to determine their use of computerized records and to solicit their cooperation for the study. Thirty-two percent of the respondents (162/501) kept computerized records in 1989. The final study population included 76 producers who agreed to participate in t he study and used either the Pigtales(TM) or PigCHAMP(TM) software pro grams. Yearly average litter size in primiparous sows was higher in he rds that were small, where the breeding manager was either a hired per son or the husband rather than another family member, and where the bo ars or sows were moved to one another's pens for estrus detection. In multiparous sows factors associated with higher average litter size in cluded small herds, breeding the sow twice rather than three or more t imes during estrus, and spending more time on estrus detection and bre eding sows. The attitude of the producer was measured by asking if the y thought breeding sows was a preferred chore, a least preferred chore , or an activity about which they were ambivalent. Although this facto r was associated with litter size, it did not have a monotonic relatio nship as expected. The factors not significantly associated with litte r size in the multivariate analyses included: vaccination for Leptospi ra spp., hand mating sows, and the timing of breeding with respect to the onset of estrus.