Use heart girth to estimate the weight of finishing pigs

by 5m Editor
21 June 2004, at 12:00am

By Crystal N. Groesbeck, Kansas State University - Many 4-H participants and swine producers may not have access to an accurate scalefor weighing their pigs. Heart girth measurement can be a tool for 4-H members and producers to estimate body weight and track the growth of pigs.

University of Kansas Using heart girth to estimate weight may also help if only a few pigs need to be weighed because it reduces scale setup and teardown time and transportation of the pigs.

Kansas State University swine researchers recently completed a study to develop a regression equation to determine pig weight based on heart girth, and to validate its accuracy. Heart girth and body weight were measured for 100 growing-finishing pigs (50 to 273 lb.) at the K-State Swine Teaching and Research Center. Heart girth was measured in inches using a cloth measuring tape. The tape was placed directly behind the front legs, wrapped snugly around the heart girth and read directly behind the shoulders.

Heart girth was strongly correlated (r2= .98) with body weight, with the regression equation: pig weight = 10.1709 x Heart girth (inches) – 205.7492. The 95 percent confidence interval shows the projected weight to be ± 10 pounds of the actual weight of the pig. The table below contains the estimated pig weight based on its heart girth measurement.

There are a few problems that may occur when measuring heart girth on pigs. Pigs often squirm or raise and lower their heads, which can cause variations in the measurement. A confined pig is easiest to measure with the cloth tape. We suggest taking three separate heart girth measurements and using the average. Misreading the heart girth measurement by 1 inch will result in a 10-pound error in weight. Averaging three measurements should more accurately represent true girth measurement.

The pigs should be on continuous feed and water to insure accurateresults. We have found heart girth measurements to be inaccurate if pigs have recently been transported or held off feed or water for a short period of time. Heart girth measuring can be useful for 4-H members and swine producers for estimating pig weight.

Table 1. Heart girth vs. pig weight
Heart Girth, inches Pig Weight, lb
25 49
26 59
27 69
28 79
29 89
30 99
31 110
32 120
33 130
34 140
35 150
36 160
37 171
38 181
39 191
40 201
41 211
42 221
43 232
44 242
45 252
46 262
47 272
48 282

Source: Kansas State University Cooperative Extension Service - Swine Update Newsletter - Spring 2003