Influence of various factors on farrowing rate on farms using early weaning.

A database containing 12,110 farrowing records from 16 commercial farms was abstracted from the PigCHAMP production information system. The farms were selected based on the willingness of producers to keep records and average weaning age. The ADFI records of 10,846 of these lactating sows were also obtained. Sows weaned at < or = 7 and > 28 d after farrowing were excluded. Farrowing rate excluding sows culled for nonreproductive reasons after mating from the denominator was 85.5%. Parity, farrowing season, and the lactation length x ADFI interaction were associated with farrowing rate (P < .05) using a categorical additive linear model in the CATMOD procedure in SAS (1988). Parity 1 sows had a lower farrowing rate than parities 2 and > or = 6 (P < .05). The summer and spring groups had the lowest and second-lowest farrowing rates among the four seasons (P < .05). In the high ADFI (> or = 5.7 kg) group, no differences in farrowing rate were observed between lactation length groups. In the low (< or = 4.2 kg) and medium (4.2 to 5.6 kg) ADFI groups, farrowing rate varied depending on lactation length. In conclusion, our results suggest that optimizing ADFI (> or = 5.7 kg) alleviates the negative effects of lactation length on farrowing rate.