EN
The aim of this study was to predict in vivo fat and muscle contents of lambs from a fat-tailed Barbarine and a thin-tailed Noire de Thibar (NT) breeds. The prediction was performed using body weight (BW), carcass weight (CW) and ultrasonic measurements. Ultrasonic measurements included subcutaneous fat thickness (FTh), longissimus dorsi muscle depth (MTh), muscle area (MAr) and circumference (MCir), taken on live animals and on carcasses using a real time ultrasound machine equipped with a 3.5 MHz linear probe. Dissected carcass muscle and fat tissues were weighted and then estimated by developing regression equations. BW was the most important estimator for carcass components for both types of breeds. For the fat-tailed breed, muscle content was better predicted by FTh and fat by MAr. The last with BW the latter explained 77 % of fat variation. For the thin-tailed breed BW and in vivo ultrasonic measurements explained 90 and 88 % of variation for fat and muscle contents, respectively. Rusing carcass ultrasonic measurements with CW mildly improved accuracy relative to BW and in vivo measurements.