Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, Canada.
Agriculture Centre, Alberta Agriculture and Forestry, Lethbridge, Canada.
J Anim Sci. 2020 Apr 1;98(4). doi: 10.1093/jas/skaa104.
Leptin genotypes can be identified as homozygous normal (CC), homozygous mutant (TT), and heterozygous (CT) based on a single-nucleotide polymorphism in exon 2 of the leptin gene, which has been associated with feed intake and fat deposition in cattle. The experiment was designed as 2 × 2 × 2 factorial with three main factors: (1) genotype (CT or TT) and diets fed 2) with or without triticale dried distiller's grains with solubles (DDG), and 3) with either flaxseed (FS) or high-oleate sunflower seed (SS). Evaluations included growth performance, subcutaneous fat deposition, adipocyte cellularity, meat quality, and fatty acid (FA) profile of various depots. Beef steers (n = 40, 459 ± 31 kg) of either CT or TT genotypes were housed in individual pens with ad libitum access to one of the four diets: 75% steam-rolled barley + 10% barley silage with 10% FS or SS (non-DDG diets, NDG) and 46.5% barley + 10% barley silage + 30% DDG, with 8.5% FS or SS, all on a dry matter basis. Growth performance, ultrasound subcutaneous fat thickness, rib eye area (REA), and plasma FA were measured prior to and during the finishing period. At slaughter, samples of subcutaneous fat, perirenal fat, and Longissimus thoracis (LT) muscle were collected for FA analysis and carcass and meat quality were measured. Compared with CT cattle, TT tended to have less (P = 0.06) C18:2-c9,t11 (rumenic acid) in plasma and subcutaneous fat and a greater proportion (P < 0.05) of C18:0 in subcutaneous, perirenal, and LT fat. Cattle with TT genotype also tended (P < 0.1) to have more total saturated and less unsaturated (USFA) and monounsaturated fats (MUFA) and had less (P = 0.04) linoleic acid in LT. Ultrasound fat thickness, REA, and average diameter of adipocytes in subcutaneous fat at 12 wk were not affected (P > 0.39) by genotype. Generally, carcass and meat quality were similar (P > 0.1) among diets, although adding FS tended to increase (P = 0.06) total USFA of subcutaneous fat including omega-3 FA (P < 0.001). For the high-fat diets evaluated, CT cattle would have more potential to produce beef with enhanced health benefits than would TT cattle.
瘦素基因型可以根据瘦素基因外显子 2 中的单核苷酸多态性鉴定为纯合正常 (CC)、纯合突变 (TT) 和杂合 (CT)。该基因与牛的采食量和脂肪沉积有关。该实验设计为 2×2×2 析因设计，有三个主要因素：(1)基因型 (CT 或 TT) 和喂养的饮食；2) 有无黑麦干酒糟及其可溶物 (DDG)；3) 亚麻籽 (FS) 或高油酸葵花籽 (SS)。评估包括生长性能、皮下脂肪沉积、脂肪细胞数量、肉品质和各种部位的脂肪酸 (FA) 谱。选择 CT 或 TT 基因型的肉牛 (n = 40，体重 459 ± 31 kg) 单独饲养，自由采食四种饮食中的一种：75%蒸汽压碎大麦+10%大麦青贮+10% FS 或 SS(非 DDG 饮食，NDG) 和 46.5%大麦+10%大麦青贮+30% DDG+8.5% FS 或 SS，均基于干物质。在育肥期之前和期间测量生长性能、超声皮下脂肪厚度、眼肌面积 (REA) 和血浆 FA。屠宰时，采集皮下脂肪、肾周脂肪和胸最长肌 (LT) 肌肉样品进行 FA 分析，并测量胴体和肉品质。与 CT 牛相比，TT 牛的血浆和皮下脂肪中 C18:2-c9,t11(瘤胃脂肪酸)较少 (P = 0.06)，C18:0 在皮下、肾周和 LT 脂肪中的比例较大 (P < 0.05)。TT 基因型的牛也倾向于 (P < 0.1) 具有更多的总饱和脂肪和较少的不饱和脂肪 (USFA) 和单不饱和脂肪 (MUFA)，并且 LT 中的亚油酸较少 (P = 0.04)。基因型对 12 周时皮下脂肪的超声脂肪厚度、REA 和脂肪细胞的平均直径没有影响 (P > 0.39)。一般来说，日粮之间的胴体和肉品质相似 (P > 0.1)，尽管添加 FS 会增加 (P = 0.06) 包括 ω-3 FA 在内的皮下脂肪总 USFA (P < 0.001)。在所评估的高脂肪日粮中，与 TT 牛相比，CT 牛生产具有增强健康益处的牛肉的潜力更大。
