Risk of recurrence of repeat breeding in sows with a repeat breeding in the first parity.

Abstract

Risk of recurrence of repeat breeding in sows with a repeat breeding in the 1st parity was investigated in 241 sow herds (1985-1990). The association between repeat breeding in the 1st and subsequent parities was examined using data on 9,120 sows. Each sow contributed only one pair of observations to the total data set. Occurrence of repeat breeding in the 1st and higher parities was presented in terms of recurrent risk rates (rRR), adjusted for different strata of herds. Sows with a repeat breeding in the 1st parity did not have a significantly higher risk rate for recurrence of a repeat breeding in the 2nd parity (rRR = 1.12, 95% confidence interval .97-1.29) and in the 3rd parity (rRR = 1.10, 95% confidence interval .86-1.41) compared to sows without a repeat breeding in the 1st parity. Sows with a repeat breeding in the 1st parity had a slightly higher risk rate for recurrence of a repeat breeding in the 4th or higher parity (rRR = 1.07, 95% confidence interval 1.03-1.10), compared to sows without a repeat breeding in the 1st parity. However, this risk is, in a biological sense, very small.