Factors associated with prolonged weaning-to-mating interval among sows on farms that wean pigs early

OBJECTIVE: To determine factors associated with weaning-to-mating interval among sows on commercial farms that wean pigs early. DESIGN: Cohort study. ANIMALS: 11,861 farrowing sows. PROCEDURE: Production, farrowing, and feed intake records were reviewed for sows on 16 farms for which mean duration of lactation was between 14.9 and 18.9 days. RESULTS: Among sows with high feed intake during lactation (> or = 5.6 kg/d [12.3 lb/d]), lactation duration was not associated with weaning-to-mating interval, but among sows with low feed intake during lactation (< 5.6 kg/d), weaning-to-mating interval increased as lactation duration decreased. Furthermore, among sows with the lowest feed intake during lactation (< 4.2 kg/d [9.2 lb/d]), those that had heavier litter weights at weaning (> 54 kg [119 lb]) had a longer weaning-to-mating interval than did those that had lighter litter weights at weaning. Sows with low feed intake and high litter weight at weaning accounted for 5 to 20% of sows on each farm. In general, weaning-to-mating interval increased as parity decreased, but the change in weaning-to-mating interval associated with a particular change in lactation duration varied with parity. CLINICAL IMPLICATIONS: When feed intake during lactation is maximized (> or = 5.6 kg/d), lactation duration is not significantly associated with weaning-to-mating interval. Producers should consider fostering or partially weaning litters when sows with high litter weights are not consuming sufficient feed.