Abstract
The objective of the present study was to compare sow reproductive performance between induced-farrowing (IF) and natural farrowing (NF) sows in ‘Early’ or ‘Late’ farrowing herd groups, based on the proportions of IF records of sows in each herd. Nineteen herds were identified in a pig database to be herds commonly practicing IF, and were used in the present study. The individual records in the 19 herds included 18,792 farrowing records of 9,703 sows during 2008. The 19 herds were categorized into two groups by the proportion of IF records (less than 50%, or 50% or higher) with sow gestation length (GL) 116 days or more:‘Early Farrowing (11 herds)’ and ‘Late Farrowing (8 herds)' herds. Farrowed sows were categorized into two groups:IF or NF sows. Sows in ‘Early Farrowing’ and ‘Late Farrowing’ herds were analyzed separately by parity and GL groups to compare reproductive performance between the IF and NF sows. In the ‘Early Farrowing’ herds, there were no differences in pigs born alive between the IF and NF sows in any parity or GL group. In contrast, in the ‘Late Farrowing’ herds, the IF sows with GL 114 days in parity 6 or higher had 1.5 fewer pigs born alive than the equivalent NF sows (P<0.05). Also, the IF sows with GL 115 days or more in parity 3 or higher had 0.9 or fewer pigs born alive than the equivalent NF sows (P<0.05). There were no differences in pigs born alive between the IF and NF sows in any GL group in the parity 1 or 2 groups. Additionally, there were no differences between the IF and NF sows in either herd groups for adjusted 21-day litter weight, weaning-to-first mating interval or farrowing percentage in any parity or GL group. In order to improve the number of pigs born alive, such sows delayed farrowing should be carefully monitored, and IF should be practiced for these sows with assisted farrowing.
