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 farms that marketed at least 1000 hogs or 35 sows in 1987. A survey was sent 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 the study and used either the Pigtales(TM) or PigCHAMP(TM) software programs. Yearly average litter size in primiparous sows was higher in herds that were small, where the breeding manager was either a hired person or the husband rather than another family member, and where the boars or sows were moved to one another's pens for estrus detection. In multiparous sows factors associated with higher average litter size included small herds, breeding the sow twice rather than three or more times during estrus, and spending more time on estrus detection and breeding sows. The attitude of the producer was measured by asking if they thought breeding sows was a preferred chore, a least preferred chore, or an activity about which they were ambivalent. Although this factor was associated with litter size, it did not have a monotonic relationship as expected. The factors not significantly associated with litter size in the multivariate analyses included: vaccination for Leptospira spp., hand mating sows, and the timing of breeding with respect to the onset of estrus.