Dimensional Measurements and Visual Appraisal As Predictors of Liveweight of Finishing Pigs

The objective of the study was to determine the accuracy of dimensional measurements and visual appraisal as predictors of BW in finishing pigs. One day prior to marketing, 169 group-housed pigs (n=4 or 5 pigs per pen) were individually weighed and three dimensional measurements were recorded, including flank-to-flank distance measured with a measuring tape (FF) and heart girth circumference measured with a measuring tape (TAPE) and a 3/8” polyethylene tube (TUBE). A panel composed of ten individuals with either less than (n=5) or greater than (n=5) one year of swine experience were briefly trained before visually estimating BW on group housed pigs. Finally, the length of time for a trained individual to perform FF, TAPE, and TUBE on finishing pigs in group pens was recorded. The accuracy of visual appraisal and dimensional measurements were defined as the correlation between predicted and actual BW. Regressions for visual and dimensional predictions were generated using PROC REG and time data were analyzed using PROC MIXED in SAS. Fixed effects of models included experience level (Visual Panel), tool (Timing) with pen, panelist (Visual) and person (Timing) as random effects. There were no differences (P>0.10) in accuracy of prediction between experience level of panelists. Visually predicted BW was moderately correlated (R²=0.42) with actual BW. As the standard deviation of BW within pen increased (3.3 to 12.2 kg) the accuracy of visual prediction decreased (R²=0.64 to R²=0.02). Heart girth measured with TAPE was highly correlated with BW (R²=0.66) with the following regression equation: BW= - 86.73618*TAPE+1.9249. Similarly, TUBE was highly correlated with BW (R²=0.61) with the following regression equation: BW= - 88.9183*TUBE+1.91752. However, FF was moderately correlated with BW (R²=0.38) with the following regression equation: BW= - 29.97947+FF*1.75463. There were no differences in the time needed for a trained individual to estimate FF or TUBE (11.5 vs. 14.2 s; P>0.05), yet TAPE required greater time to measure compared to either FF or TUBE (18.7 s; P<0.05). Results suggest the that high accuracy and low labor requirements of TUBE indicate this is a valid tool for commercial producers to predict the liveweight of finishing pigs prior to marketing.