Longevity of breeding sows in relation to leg weakness symptoms at six months of age.

The objective of this study was to evaluate the influence of leg weakness symptoms measured early in life (at 6 months of age) on the longevity of the sows, i.e. the age at culling due to locomotory problems in a Danish pig herd. One hundred and eighty-seven gilts at 6 months of age were selected according to different leg weakness symptoms and were followed until culling and judged for leg weakness once in every gestation using a scale from 1 (normal) to 4 (severe changes). Age at culling, and the main and secondary reasons for culling were recorded. The influence of leg weakness symptoms on longevity was evaluated by survival analysis. Though only 12% of the gilts showed a stiff locomotion half of the sows had suffered from this and nearly one third had been distinctly lame at some time in their life. Buck-kneed forelegs, upright pasterns, legs turned out, standing under position and swaying hindquarters were associated with stiff locomotion or lameness, whereas weak pasterns on hind legs and splayed digits on forelegs were associated with brisk movement (freedom from locomotor problems). The following leg weakness symptoms at the gilt stage were found to have significant negative effects on longevity: buck-kneed forelegs, swaying hindquarters, and standing under position on hind legs.