To determine whether lactation length was associated with reproductive performance or longevity of sows.
Cohort study.
Data collected between 1986 and 1992 for sows in 15 breeding herds in Minnesota and Iowa.
Sows were grouped into 4 genetic line categories according to their sources and 6 parity categories (1, 2, 3, 4, 5 or 6, and > or = 7). Multivariate regression analysis of reproductive performance was conducted, using the general linear model procedure Logistic regression was conducted with a dichotomous response variable for sow longevity (ie, removal from or retention in the herds). Odds ratios were obtained from estimated coefficients of the regression.
Herd, genetic line, parity, year, month, and lactation length were significant in statistical models for litter (eg, number of live pigs/litter) and interval (eg, weaning-to-mating interval) traits. Interactions between lactation length and year, lactation length and genetic line, lactation length and parity, and lactation length and genetic line and parity were also significant. Sows removed from herds had a significantly shorter lactation length than did sows of the same parity that were retained in the herds. Sows that had shorter lactation lengths were at higher risk of being removed from the herds than were those that had longer lactation lengths.
Lactation length is associated with reproductive performance and longevity, but genetic line and parity play a role as well. Thus, attention should be paid to genetic lines and parity of sows in the herd when implementing an early weaning production practice.