Distribution of intramuscular fat content and marbling within the longissimus muscle of pigs

A better knowledge of intramuscular fat (IMF) content distribution would allow the identification of a predictive site on the longissimus muscle to assess the total IMF content. For this purpose, 50 commercial crossbred pigs of both genders were selected live with ultrasound equipment at the 3rd/4th last rib in order to provide backfat differences varying from 10 to 34.7 mm. Left longissimus muscles were deboned and sliced every 2 cm from the posterior (3rd last lumbar vertebra) to the anterior (5th thoracic rib) end. In all, 14 locations on the longissimus muscle were established and labeled as T5-T14 (thoracic region) and L1-L4 (lumbar region). The slices were used for subjective marbling evaluation and for intramuscular fat content (IMF) measurement. The results showed that total IMF content and marbling scores were correlated (r = 0.86) and followed a similar pattern, with highest values being obtained in the middle section of the thoracic region and in the middle-caudal section of the lumbar area. In addition, both IMF content and marbling scores were anatomical location dependant. Gender did not affect IMF content, but influenced marbling score, castrates being more marbled (score: 2.77 vs. 2.35) than females. The IMF content (R-2: 0.94-0.95) and marbling score (R-2: 0.73-0.81) were the best predictors of mean IMF when measured at or near the grading site (3rd/4th last rib).