PSVI-17 - Application of stride length to assess leg soundness for growing gilt

Abstract: The durability of sows would be affected by their leg soundness. Problems of leg or lameness is the second reason for culling especially in the first three parities. Observing the leg structure during the growth period of pigs is necessary in selection programs because traits related to leg structure have intermediate to low heritability. However, long-term tracking of changes in feet and leg structure of pigs using quantitative measuring methods has not been conducted. Such measuring methods have not yet been applied on farms so far. Thus, this study aimed to use stride length data from pressure mat to evaluate leg soundness in growing gilts.

A pressure mat system was used in this study to collect stride length (SL) data and ground reaction force (GRF) data of 23 purebred gilts at 4.5, 6.0, and 7.5 months of age. The SL data obtained in each pig was used to calculate the symmetry index with the SL records of the left and right legs for both front and rear. Similarly, the GRF data enabled the calculation of GRF symmetry index of the left and right leg of a pig for both front and rear. The confusion matrix was applied to compute the accuracy, sensitivity, and specificity by comparing visual inspection of gilt culling or the SL symmetry index to the GRF symmetry index as the standard.

The accuracy, sensitivity, and specificity of visual inspection of gilt culling versus GRF symmetry index at 7.5 months of age were 80%, 31%, and 100%, respectively. Meanwhile, the accuracy, sensitivity, and specificity of the SL symmetry index versus GRF symmetry index at 7.5 months of age were 96%, 85%, and 100%, respectively. At 6.0 months of age, such accuracy, sensitivity, and specificity of the SL were 89%, 67%, and 97%, respectively. But, at 4.5 months of age, such accuracy, sensitivity, and specificity of the SL were 87%, 50%, and 97%, respectively.

These findings suggest that visual inspection for leg soundness of gilt has limited capability to identify pigs with an asymmetry gait which might cause current and future leg problems. But the SL symmetric index shows better potential for that purpose that it will be a suitable objective measure to replace visual inspection for leg soundness in pigs.