2009 Volume 13 Issue 1 Pages 40-45
The objective of the present study was to determine the factors associated with the occurrence of decreased pigs born alive (PBA) in parity 2 (D-PBA). The sow data used were farrowing records of 51,259 sows farrowed in parity 1 and parity 2 from 2001 to 2005 relating to 104 herds in Japan. D-PBA was defined as the same or fewer numbers of PBA in parity 2 compared to PBA in parity 1. Mixed-effects logistic regression analysis with contrasts was applied to the results of the study. Of the 51,259 sows studied, 49.5% manifested an occurrence of D-PBA. A high occurrence of D-PBA in sows was associated with PBA 13 or more pigs in parity 1, lactation length 17-19 days, weaning-to-conception interval (WCI) 7-12 days and being conceived during summer in parity 1 (P<0.05). Three two-way interactions between PBA in parity 1 x season of conception, WCI x season of conception, and WCI x PBA in parity 1 were found for the occurrences of D-PBA (P<0.05). In sows having PBA≥13 pigs in parity 1, no difference between the four season groups was found for the occurrences of D-PBA (P<0.05). Meanwhile, in PBA<13 pigs in parity 1, sows conceived during summer had higher occurrences of D-PBA than those conceived during the winter and the fall (P<0.05). Among all the groups categorized by season of conception and PBA in parity 1, sows with WCI 7-12 days had the highest occurrence of D-PBA among the WCI groups (P<0.05). No differences were found in the occurrence of D-PBA among the five age groups of sows at first conception. Additionally, a slight difference (0.3-0.5%) in the occurrence of D-PBA was found between the groups categorized by lactation length from 17-19 to ≥26 days (P<0.05). In conclusion, the occurrence of D-PBA was suggested to be related to the large PBA, the WCI 7-12 days and the conception during summer.
