Monteiro A C G, Navas D R, Lemos J P C
1 CIISA, Faculdade de Medicina Veterinária, Universidade Técnica de Lisboa, Avenida da Universidade Técnica, Pólo Universitário Alto da Ajuda, 1300-477 Lisboa, Portugal.
2 Unidade de Investigação de Produção Animal, INIAV-Quinta da Fonte Boa, 2005-048 Vale de Santarém, Portugal.
Animal. 2014 Apr;8(4):675-82. doi: 10.1017/S1751731114000196.
Physicochemical characteristics were determined in the longissimus lumborum muscle, after 8 days of ageing of steers (n=12) and bulls (n=12) from Mertolenga breed slaughtered directly from pasture (day 0) or after a finishing period of 50, 100 and 150 days in a feed-lot facility. Bulls and steers presented similar live weight (averaging 388 kg), carcass weight (CW; averaging 213 kg), dressing percentage (averaging 60%), carcass fatness (11.9% CW) and carcass fat thickness (averaging 3.03 mm). Live weight, CW, carcass fatness and fat thickness increased along time-on-feed. Gender only had a negligible effect on meat characteristics, with b and h being the only parameters of colour affected by gender, also presenting a significant interaction gender × time-on-feed. Nevertheless, both the genders presented a high-quality grade concerning tenderness (Warner-Bratzler shear force (WBSF)). L increased until 50 days on feed and decreased afterwards, whereas a and C values increased along time-on-feed. Pigment content was also affected by time-on-feed and showed a gender × time-on-feed interaction. Beef colour became darker and redder along time-on-feed, but still in a colour range highly acceptable by Portuguese consumers. Despite the increase in intramuscular fat and myofibrillar fragmentation index, as well as the decrease in collagen content of steers and bulls along time-on-feed, it did not affect the tenderness/hardness, indicating a small effect of time-on-feed in meat characteristics. Despite only small differences in carcass characteristics and meat-quality parameters that have been noticed along time-on-feed, those differences were only significant after 100 days on feed. Principal component analysis (PCA) was performed. The first PC axis (39.6% of the total variance) included colour variables a, b and C, and carcass fatness, fat thickness, CW and live weight, whereas the second one (12.7% of the total variance) included h, cooking losses and dressing-out. The principal component (PC) analysis confirmed the lack of differences between bulls and steers and indicates a differentiation of the first two periods of feeding (0 and 50 days on feed) from the two latter (100 and 150 days on feed) periods of feeding.
对直接从牧场屠宰（第0天）或在育肥场设施中经过50、100和150天育肥期后的梅托伦加品种阉牛（n = 12）和公牛（n = 12），在其腰大肌中测定了理化特性。公牛和阉牛的活重相似（平均388千克），胴体重（CW；平均213千克），屠宰率（平均60%），胴体脂肪含量（11.9% CW）和胴体脂肪厚度（平均3.03毫米）。随着育肥时间的延长，活重、CW、胴体脂肪含量和脂肪厚度增加。性别对肉的特性影响可忽略不计，b值和h值是仅受性别影响的颜色参数，同时性别×育肥时间也存在显著交互作用。然而，两种性别的肉在嫩度方面（Warner-Bratzler剪切力（WBSF））均具有较高品质等级。L值在育肥50天前升高，之后下降，而a值和C值随育肥时间增加。色素含量也受育肥时间影响，并呈现性别×育肥时间的交互作用。随着育肥时间的延长，牛肉颜色变得更暗更红，但仍处于葡萄牙消费者高度接受的颜色范围内。尽管随着育肥时间的延长，阉牛和公牛的肌内脂肪和肌原纤维破碎指数增加，以及胶原蛋白含量下降，但这并未影响嫩度/硬度，表明育肥时间对肉的特性影响较小。尽管在育肥过程中胴体特性和肉质参数仅发现了微小差异，但这些差异在育肥100天后才显著。进行了主成分分析（PCA）。第一主成分轴（占总方差的39.6%）包括颜色变量a、b和C，以及胴体脂肪含量、脂肪厚度、CW和活重，而第二主成分轴（占总方差的12.7%）包括h值、烹饪损失和屠宰率。主成分（PC）分析证实了公牛和阉牛之间没有差异，并表明前两个育肥期（0天和50天）与后两个育肥期（100天和150天）存在差异。
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