Comparison of two methods for longissimus muscle area measurements

The aim of the study was to determine the variance of longissimus muscle area (LMA) measurements associated with the standard use of polar planimeter (REISS Precision 3005, Germany) and ¨Image tool¨ software program. Measurements were conducted on six dorsal samples taken between 7th and 9th rib of the right halfs of beef carcasses. Firstly, LMA was traced on acetate paper and measured using a planimeter. Secondly, the images of longissimus muscles for computer analysis were obtained by scanning (UMAX PowerLook II) dorsal samples in ratio 1:1. LMA size was determined with ¨Image tool¨ software. Triplicate measurements of LMA were performed by six measurers for each sample and method. Variance components for LMA measurement method associated with measurer, sample and measurement replicates were estimated by REML. The proportion of the total variance in LMA measurement beetwen samples was greater with ¨Image tool¨ (99.79%) than with planimeter (96.49%). The proportion of variance between measurers was 0.12% with ¨Image tool¨ and 0.34% with planimeter. The proportion of error variance due to measurement replicates associated with the use of ¨Image tool¨ program was smaller (0.09 %) than with the planimeter (3.17%). The application of ¨Image tool¨ showed greater precision in measuring LMA than standard planimeter method.