Interactions between the associations of parity, lactation length, and weaning-to-conception interval with subsequent litter size in swine herds using early weaning

Sixteen farms having an average lactation length between 14.9 and 18.9 days were selected based upon producers' willingness to keep records of product ion and lactation feed intake. Data contained 9162 subsequent litter-size r ecords abstracted from computerized production information-system files and lactation feed-intake records. Two-way interactions between the associatio ns of parity and lactation length, and parity and weaning-to-conception int erval with subsequent litter size were found in the same statistical model. Subsequent litter size did not increase in parities 1 and 2 as lactation l ength increased - but subsequent litter size in sows of parities 3-6 increa sed. In only parity 1, sows with weaning-to-conception interval 6-12 days p roduced 0.5 fewer pigs at subsequent farrowing than those with weaning-to-c onception interval 1-5 days. However, in multiparous sows, no difference in subsequent litter size was found between weaning-to-conception intervals 1 -5 and 6-12 days. (C) 1998 Elsevier Science B.V. All rights reserved.