Models predict the proportion of bone, muscle, and fat in ewe lamb carcasses from in vivo measurements of the 9th to 11th rib section and of the 12th rib

Abstract

The present work aimed at evaluating models that predict the proportion of bone, muscle, and fat in ewe lamb carcasses using in vivo data obtained from the 9th to 11th rib section and from the 12th rib. A study population of 30 wooled ewe lambs, derived from Texel breed crosses, were fed with different concentrate levels (0%, 20%, 40%, 60%, and 80%) and slaughtered at a weight of 37.70 ± 10.23 kg. Carcass fat content (FC%) and muscle content (MC%) were estimated from models using the proportion of muscle and fat in the 9th to 11th rib section or in the 12th rib, with or without additional data regarding subcutaneous fat thickness (SFT mm) or carcass ribeye area (RA cm2). Carcass bone content (BC%) was predicted based on the proportion of bones in the 9th to 11th rib section or in the 12th rib. Modeling with in vivo data included fasting body weight (FBW), withers height (WH), and ultrasound measurements of SFT and RA. The FC% could be estimated from the carcass SFT and fat content in the 12th rib. The MC% was more accurately predicted from the proportion of muscles in the 9th to 11th rib section and from carcass RA. The 9th to 11th rib section provided the most accurate data for the prediction of BC%. To determine FC% and MC% from in vivo inputs, the model must include FBW and WH. In vivo FBW measurements alone allow for the estimation of BC%. We recommend the use of 12th rib composition for the accurate estimation of carcass fat content, and the use of the 9th and 11th rib section for the prediction of carcass muscle and bone content. Models using in vivo data for the prediction of fat, muscle, and bone in ewe lambs should incorporate FBW and WH.