The aim of this study was to assess the meat quality of Pantaneiro lambs finished in confinement and slaughtered at different body weights (15, 20, 25, 30, and 35 kg). Forty-five non-castrated male Pantaneiro lambs were distributed in a completely randomized design, with five treatments and nine replicates. The animals were housed in individual pens and slaughtered when they reached the target weights. For instrumental and centesimal analyses, the Semimembranosus, Longissimus lumborum, Gluteobiceps, and Triceps brachii muscles were used, whereas for fatty acid profile analysis only the Longissimus lumborum muscle was used. The different body weights influenced the final pH of the meat, but this still remained within the recommended values; however, the meat of heavier lambs had increased water-holding capacity (WHC), redness (a*), and fat content, making it the tenderest but least luminous and humid meat. Greater body weight led to a higher saturated fatty acid (SFA) content, reduction of monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA), higher hypercholesterolemic fatty acid content (H), and higher atherogenicity (AI) and thrombogenicity indexes (TI). Therefore, it was concluded that the meat of lambs slaughtered at lower body weight presented better nutritional quality, making it more suitable for human consumption.

Sheep farming length of stay in the feedlot directly influences system profitability, mainly due to the high cost of feed. Thus, the use of predictive models based on body measurements is an important tool to define the optimal slaughter point and the ideal feedlot period. Thus, the aim was to evaluate predictive models of meat cuts and tissue carcasses concerning weight at slaughter (WS), loin eye area (LEA), and subcutaneous fat thickness (SFT) obtained by ultrasound of the lumbar region of lambs. The WS and ultrasound measurements were obtained from a pre-slaughter collection of 45 lambs, divided into five groups, each weighing 15, 20, 25, 30, or 35 kg, with nine replications per group. Three regression models were evaluated: WS, LEA, and SFT (independent variables) and the cuts yield or tissue composition (dependent variable). Increasing WS resulted in greater carcass weight and commercial cuts. Above 15 kg body weight, bone weight showed little or no increase (allometric coefficient = 0.06), whereas muscle and fat tissues increased steadily, with allometric coefficients of 0.25 and 0.12, respectively. The commercial cuts showed a high and significant correlation with WS and LEA. The muscle and bone proportion of the leg had a significant (p < 0.10) correlation with SFT. For the weight of commercial cuts estimates, the inclusion of LEA and/or SFT with WS did not improve the coefficient of determination but made the predictions equivalent to the measured values. There were high determination coefficients when WS was only used to predict muscle, fat, and bone weight, but it was not efficient in predicting the muscle/fat and muscle/bone ratios and the percentage of tissues. The WS was the variable that best explained the weight and tissue content. The inclusion of LEA and/or SFT made little improvement to the predictive models.