39 Using Finishing Pig Body Measurements as a Tool to Estimate Body Weight

Abstract

Abstract Approximately $220 million is lost every year by the pork industry due to sort losses defined as the loss of value associated with marketing pigs that fall outside the premium body weight (BW) range. Current industry standards of by “eye” measuring results in a sort loss greater than 10% in most loads. Stationary imaging systems to predict BW have been developed to help producers better market their pigs at the appropriate BW; however, they can be costly and still require stockpersons to individually mark relevant pigs. Flank to Flank measurements using a cloth tape have been found suitable for predicting breeding sow and boar weights. The objective of the study was to establish a linear equation based on body measurements (body length, heart girth, and flank) to predict BW in finishing pigs. This study used 223 finisher pigs (121 gilts, 102 barrows), divided between 2 replicate groups (28.5 ±0.7 days). Measurements of BW, body length (base of neck to base of tail), heart girth (circumference around the chest), and flank (measurement was taken in front of hind legs from the bottom of one flank to the other sides bottom of the flank) were measured every 7 d beginning at 135 d of age until 163 d of age. Linear regression was used to establish equations for each body measurement alone and in combination and the R2 coefficient was used to compare predictability of equations. An R2 value of 0.76, 0.24, and 0.65 was found for heart girth, body length, and flank length, respectively. The linear equation from the greatest R2 value measurement was BW = 1.95 × (heart girth) - 101.78. The R2 value can be improved by combining multiple points of measurement provided added variable(s) make a significant contribution. The linear equation accounting for all three measurements [BW = (0.17 × length) + (1.49 × heart) + (0.12 × flank) - 122.98] had R2 = 0.78. The combination of body length and heart girth [BW = (1.45 × heart) + (0.87 × flank) - 118.94] resulted in an equation with a similar accuracy (R2 = 0.78) as all 3 measurements combined. Body length marginally improved the R2 value likely because it had a relatively low R2 value alone. The equation combining heart girth and flank explained the greatest proportion of the variation in BW, although there was limited additional value above heart girth alone. Within a commercial finisher barn, measuring heart girth of every pig may not be practical. However, this method could be suitable to train stockpersons for improved visual estimation of pig weight or to gauge overall barn performance based on a random sampling of pigs just prior to marketing.