A low level of sow retention in the herd is a cause for both economic as well as welfare concerns. The results of the study confirmed that a low lactation feed intake, incidence of lameness or health problems, as well as sow-level characteristics such as higher parity and fewer piglets born alive per litter may adversely affect sow longevity. Sows retained with periparturient health problems had reduced longevity and fewer live-born piglets, and fewer such sows had another farrowing. A prospective data analysis indicated that the overall performance of lame sows in terms of the number of pigs born alive during the period of the study was less, compared with that for non-lame sows. Retaining sows with less severe lameness may enable the producer to meet immediate production targets. The findings suggest that sow removal decisions should be judiciously evaluated after farrowing considering the potential long-term losses. Lameness in swine herds should be minimized and if treatment is not an option lame sows should be culled as soon as possible to reduce long-term losses.
The results also confirmed the high prevalence of claw lesions in breeding female pigs and their association with lameness, specifically, white line and side wall lesions. The results indicate the possibility of nutritional intervention in minimizing claw lesions. However, there are other factors associated with claw lesion development in pigs. The quality of the floor as well as different bio-mechanical factors operating in lesion development are important here. The space between slats, roughness of the surface, and edge design are critical in claw lesion development. Those factors have not been addressed in this study. Further studies are required to understand the mechanism of lesion development in relation to the housing and management systems in place. This information is vital in formulating the appropriate intervention strategy to minimize the incidence of lameness and to improve sow longevity and performance. The studies in this thesis included data from single herds and therefore the generalization of the results may be restricted owing to the wide variations in management, housing and in genetic lines of sows.