Ultrasonic scanning measurements of the longissimus thoracis et lumborum muscle to predict carcass muscle content in sheep

Nineteen Omani sheep (average 26 kg body weight) were scanned over the 6th rib, 12th rib and the second-last lumbar vertebra, to determine the maximum depth (B), circumference, area of the cross-section and volume of the longissimus thoracis et lumborum (LD) muscle. The volume of the muscle was estimated by multiplying the average area of its cross-section obtained at the three sites by its length. After slaughter, the LD muscle was dissected out, frozen, and its maximum depth, circumference, length, weight and volume were determined. Correlation and regression analyses were carried out to evaluate relationships between scanning and real measurements and between scanning measurements and carcass total muscle content. Generally there were positive correlations (r = 0·43-0·66) between the LD scanning measurements made at the 12th rib and the corresponding measurements made on the dissected muscle. The volume of the LD muscle estimated from scanning was positively correlated (r = 0·59) with its real volume which was correlated with its weight (r = 0·51) and consequently with the total carcass muscle content (r = 0·69). Ultrasonic scanning can be used to predict the circumference and volume of the LD muscle. These may be used for prediction of total carcass muscle content in sheep in addition to traditional measurements of the muscle (the maximum depth B) and area.