Poor sow longevity in commercial pork production systems can lead to economic inefficiency and animal welfare concerns (Stalder et al., 2004). In the United States, reported annual breeding female replacement rate averages have exceeded 66% in the past several years (PigCHAMP, 2001, 2002, 2003).
Traditional culling studies are based on retrospective farm data as they are relatively easy and economical to obtain. Producers are typically limited to reporting one reason for culling individual sows by their record keeping software. Additionally, these reasons are typically based on external signs or indications and do not incorporate evidence of internal lesions. Frequently, culling is the result of multiple factors. Sow harvest plants offer researchers an opportunity to confirm farm data and further identify factors related to sow culling. However, studies investigating reasons for sow culling in harvest plants are few. Post-mortem examinations of female pig reproductive organs are a potential source of information concerning sow reproductive failure. Foot lesions, body condition, disease, and other problems may also contribute to sow culling from pork operations. Therefore, information from harvest plants can be used as a diagnostic tool to evaluate these problems and further understand sow culling.
The objective of the first portion of this study was to characterize the physical conditions of cull sows from U.S. Midwestern sow harvest plants. Physical and reproductive conditions of cull sows (3,158) from 2 U.S. Midwestern sow harvest plants were assessed. Body conditioning, feet, shoulders, teeth, lungs, and reproductive tracts were evaluated for visible lesions and abnormal conditions on harvested sows. The most common foot lesions observed among harvested cull sows were rear (n = 2,064, 67.5%) and front (n = 1,024, 32.9%) heel lesions. Cracked hooves were found on the front feet of 703 sows (22.6%) and rear feet of 552 (18.1%) sows. Rear digital overgrowth was observed in 644 (21.1%) sows. The most common reproductive lesion observed among harvested cull sows was ovaries that appeared to be acyclic (n = 277, 9.0%). The presence of ovaries that appeared acyclic increased (P < 0.01) as BCS decreased. Cystic ovaries were found in 192 (6.3%) sows. The incidence of cystic ovaries increased (P < 0.01) as BCS increased. Pneumonia was the most frequent systemic lesion observed (n= 298, 9.7%). The presence of pneumonia increased (P < 0.01) as BCS decreased. The most frequently observed shoulder lesion among harvested cull sows was shoulder abrasions (n = 394, 12.5%). The presence of shoulder abrasions increased (P < 0.01) as BCS decreased. The incidence of reproductive lesions detected in the present study was substantially less than the reported percentage of sows culled for reproductive failure from previous studies and from record keeping summaries.
The objective of the second portion of this study was to relate production data from sows producing pigs in a commercial production system in the U.S with physical conditions evaluated at harvest. Production data from sows producing pigs in a commercial production system were associated with physical conditions evaluated at harvest. Sows (923) from 8 farms, all from one large integrated U.S. pork production system, were evaluated at 2 large Midwestern sow harvest facilities. Body condition, feet, shoulders, teeth, respiratory systems, and reproductive tracts were visually evaluated for lesions and abnormal conditions on harvested sows. Physical conditions evaluated at harvest were analyzed by parity, culling code, farm, and production parameters. Farm culling codes were categorized into poor body condition (BC), old age (G), lameness (L), other (O), poor litter performance (P), and reproductive failure (R). R was the most common culling code in parities 1 to 5 (66.1, 58.1, 52.7, 39.4, and 37.7%, respectively). Front/rear heel lesions, front cracked hooves, front/rear digital overgrowth, and rear missing dew claws increased (P < 0.01) as parity increased. Visibly acyclic ovaries decreased (P < 0.05) and visibly cystic ovaries tended to increase (P < 0.10) as parity increased. The likelihood of normal ovaries did not differ (P > 0.05) between culling codes. Sows culled for R had an 86.2% probability of having normal ovaries. The L culling code had a higher (P < 0.05) prevalence of cracked hooves than the other 5 culling codes combined (30.9 vs. 18.7%). Sows culled for L were leaner and had lower body condition than G, P, and R sows. Sows with no shoulder lesions had more (P < 0.05) lifetime pigs born alive (59.97 vs. 57.96) in comparison to sows with shoulder lesions. Sows with severe teeth wear tended to have fewer (P < 0.10) lifetime pigs born alive (58.94 vs. 60.30), pigs born alive in last litter (9.87 vs. 10.31) and had less (P < 0.01) pigs born alive/day/herd life (0.0704 vs. 0.0734) than sows without severe teeth wear. Sows with no front cracked hooves tended (P < 0.10) to have more pigs born alive/day of herd life (0.0725 vs. 0.0703) compared to sows with front cracked hooves. Sows with no rear digital overgrowth had more (P < 0.05) pigs born alive in last litter (10.22 vs. 9.68) and a trend (P < 0.10) for increased pigs born alive/day/herd life (0.0724 vs. 0.0702) than sows with rear digital overgrowth. Regression coefficient estimates for percent lung involvement from pneumonia were positive and tended to be different from zero (P < 0.10) for lifetime pigs born alive (0.06) and pigs born alive/day/herd life (0.00009). Identifying and correcting suboptimal farm specific fertility factors offer the greatest benefit in improving culling for reproductive failure and hence, sow longevity. The presence of physical conditions evaluated at harvest was associated with farm reproductive parameters.
