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Eighty-seven Manchego sucking lambs raised exclusively on maternal milk were slaughtered. The carcasses were weighed immediately after dressing and classified according to hot carcass weight (HCW): low HCW (<5.5 kg), medium HCW (5.5 to 6.5 kg) and high HCW (≥ 6.5 kg). The effects of this classification system on carcass and meat quality were studied. Carcass conformation improved as carcass weight increased; carcasses became more compact. Carcass fatness increased (P < 0.001) as carcasses became heavier. With regard to the joints, leg (P < 0.001) and shoulder (P < 0.05) proportions decreased as carcass weight increased, whereas loin-rib (P < 0.001) and flank (P < 0.001) proportions increased. The proportion of fat in the leg clearly increased in the heavier carcasses (P < 0.001), while that of bone decreased (P < 0.001) and that of muscle was not affected. pH at 24 h in the m. longissimus dorsi and m. semitendinosus decreased as carcass weight increased. The only meat colour parameter affected by carcass weight was the yellowness index; lighter-weight carcasses displayed lower index (P < 0.05). Cooking losses were unaffected as carcass weight increased, whereas with regard to tenderness, the shear force value tended to be higher in the low carcass weight group. No differences between carcass weight groups were found in the sensory analysis. Fatty acid composition did not show any significant effect due to carcass weight except in stearic fatty acid (C18:0); C18:0 proportion decreased (P < 0.01) as carcasses became heavier. Carcass weight affected carcass quality (all carcass quality parameters studied were higher in the heavier carcasses), whereas meat quality varied little as a result the small variation between carcass weights in sucking lambs.

The effects of sex and weight on instrumental meat quality characteristics of Rubia de El Molar autochthonous ovine breed were studied. Four weight groups (10, 15, 20 and 25 kg, each of the groups with seven males and seven females) were assessed. A decrease of longissimus thoracis muscle (LT) lightness from 43.39 for 10 kg lambs to 38.84 for 25 kg group was observed. LT redness and yellowness indices and chromaticity values increased as weight increased. The percentage of juice expelled increased from 11.52 (10 kg) to 17.15 (15 kg). The percentage of intramuscular fat in biceps femoris (BF) and supraespinatus (SE) muscles increased as weight increased. Warner–Bratzler shear force (WBSF) in raw meat and hardness in cooked meat increased as liveweight increased. However, a decrease in the amount of soluble collagen in quadriceps femoris (QF), biceps femoris (BF) and infraespinatus (IE) muscles was observed as weight increased. Sex effect was only observed for intramuscular fat content in QF and BF muscles (2.4% in males and 2.9 in females) and WBSF in raw meat (26.12 N for males and 21.25 N for females). Weight had a greater effect than sex on Rubia de El Molar meat quality characteristics.

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