Longevity to the second parity requires good attention to sow health in the first

Difficult parturition, infection, and the use of hormones (such as oxytocin) are postulated as causes of sow stress at farrowing. These stressors can reduce the probability of a sow completing a full lactation or farrowing in the next parity. It is the purpose of this study to assess whether sows treated for health issues have a reduced probability of farrowing in the second parity. The presence of such stressors can be inferred from individual medication data. Approximately 2000 records for farrowed primiparous sows were collected from two maternal lines (Primegro Genetics™, Corowa, NSW) between January 2007 and June 2008. Production and medication records for individual sows were available in the study data. The medication events were broken down to the categories of 1) oxytocin, 2) antibiotics 3) analgesics plus anti-inflammatories and 4) other treatment. A binary trait, FAR2, identified whether sows farrowed in parity 2 (0=no; 1 =yes). All factors significantly affecting the incidence of FAR2 were then identified using logistic regression (Proc LOGISTIC, SAS Institute). Information on medication events were added as potential risk factors to previous models developed by Bunter et al. (2008). Significant factors were identified by fitting a full model containing many effects, then eliminating non-significant effects sequentially based on their Wald test statistic to obtain the final model. Factors that contribute to FAR2 and the odds-ratios for binary effects are presented in Table 1. The odds-ratio compares the ratio of incidence for animals with and without the risk factor (where the odds-ratio = 1); a value of<1 indicated a reduced incidence relative to the reference level.