Ultrasonic measurements of the muscle longissimus dorsi depth (PMLD), subcutaneous fat thickness (EGS) between the 12^th‑13^th dorsal vertebra (D12), 1^st‑2^nd (L1) and 3^rd‑4^th (L3) lumbar vertebra and breast bone tissue thickness at 1^st (EGE1), 2^nd (EGE2), 3^rd (EGE3) and 4^th (EGE4) sternebra were taken on 20 kids from Serrana breed. After slaughter the homologous measurements were taken on the carcass with a calliper.
The left side was spitted into eight standardized commercial joints that were grouped in three commercial categories: 1. first: leg, chump and loin; 2. second: ribs, anterior ribs and shoulder and 3. third: breast and neck. Each joint was then dissected into muscle, bone + remainder, subcutaneous fat and inter‑muscular fat.
The ultrasounds allowed EGE measurements with high precision. In respect to the PMLD measurements, the correlation coefficients were around 0.70 and statistically significant (P < 0.05), except for the PMLDL3 measurement that was 0.621 (P > 0.05).
Slaughter live weight was always the first variable admitted in prediction models (by stepwise regression) of the first, second and third category carcass joints weight, accounting for 99.2, 99.1 and 88.8% of the variation, respectively. In addition, this was the only independent variable admitted by the third category joints and whole carcass muscle prediction models, accounting for 98.8 and 98.7% of the variation, respectively.