Kononoff P J, Defoor P J, Engler M J, Swingle R S, Gleghorn J F, James S T, Marquess F L S
J Anim Sci. 2017 Jan;95(1):194-200. doi: 10.2527/jas.2016.0926.
A total of 2,948 steers (mean initial BW = 568.9 ± 49.4 kg) were used to evaluate the effect of the LEP R25C SNP genotype on feed intake, growth performance, and carcass characteristics over time. Steers were grouped into 5 blocks, each consisting of 10 pens initially, and then at approximately 24 d prior to the assigned slaughter date, cattle in each pen were randomly selected either to remain in the pen they were in (group A) or to be assigned to a new pen (group B). Steers were allocated to 5 blocks and 6 harvest weeks (-3, -2, 0, 2, 3, and 4 wk) relative to the projected end point. Steers were weighed and ultrasound scanned at 60 and 1 d prior to harvest. Leptin genotype affected ( ≤ 0.011) 12th-rib fat and i.m. fat percentage (IMF) for each slaughter group at both 60 and 1 d prior to slaughter, although rib eye area (REA) was not affected ( = 0.773) by leptin genotype 60 d prior to slaughter in any group. Time affected ( < 0.001) live BW as well as 12th-rib fat, REA, and IMF measured 60 and 1 d prior to each slaughter time. Dry matter intake was also higher ( = 0.003) for cattle of the animals homozygous for the T allele (TT) genotype compared to those with the animals homozygous for the C allele (CC) genotype (9.59 vs. 9.29 ± 0.075 kg). The LEP R25C genotype affected key traits related to carcass fatness; specifically, compared to cattle of the CC genotype, cattle of the TT genotype had a higher ( = 0.016) calculated empty body fat (29.1 vs. 28.8 ± 0.133%) and higher ( = 0.020 calculated yield grade (2.62 vs. 2.52 ± 0.035). Additionally, like for live measures, TT cattle tended ( = 0.093) to have a higher 12th-rib fat (13.2 vs. 12.8 ± 0.26 mm). However, the LEP R25C genotype did not affect KPH ( = 0.854) or marbling score ( = 0.240), nor did it affect any USDA quality measure ( ≥ 0.350). The leptin genotype also affected ( = 0.048) HCW, which was highest for steers of the TT genotype (400.9 vs. 403.5 ± 3.41kg). Results indicate that the leptin R25C genotype and time impacted most traits associated with fatness.
总共使用了2948头阉牛（初始平均体重=568.9±49.4千克）来评估LEP R25C单核苷酸多态性（SNP）基因型随时间对采食量、生长性能和胴体特征的影响。阉牛被分为5个区组，每个区组最初由10个围栏组成，然后在指定屠宰日期前约24天时，从每个围栏中随机选择牛只，要么留在原围栏（A组），要么被分配到新围栏（B组）。阉牛被分配到5个区组和相对于预计终点的6个屠宰周（-3、-2、0、2、3和4周）。在屠宰前60天和1天时对阉牛进行称重并进行超声扫描。瘦素基因型在屠宰前60天和1天时对每个屠宰组的第12肋脂肪和肌内脂肪百分比（IMF）有影响（P≤0.011），尽管在任何组中，屠宰前60天时瘦素基因型对肋眼面积（REA）没有影响（P=0.773）。时间对每次屠宰前60天和1天时测量的活体重以及第12肋脂肪、REA和IMF有影响（P<0.001）。与C等位基因纯合子（CC）基因型的动物相比，T等位基因纯合子（TT）基因型的动物干物质摄入量也更高（P=0.003）（9.59对9.29±0.075千克）。LEP R25C基因型影响与胴体脂肪度相关的关键性状；具体而言，与CC基因型的牛相比，TT基因型的牛计算出的空腹体脂肪更高（P=0.016）（29.1对28.8±0.133%），计算出的产肉等级也更高（P=0.020）（2.62对2.52±0.035）。此外，与活体测量一样，TT基因型的牛第12肋脂肪往往更高（P=0.093）（13.2对12.8±0.26毫米）。然而，LEP R25C基因型对肾周脂肪（P=0.854）或大理石花纹评分（P=0.240）没有影响，对任何美国农业部质量指标也没有影响（P≥0.350）。瘦素基因型对热胴体重也有影响（P=0.048），TT基因型的阉牛热胴体重最高（400.9对403.5±3.41千克）。结果表明，瘦素R25C基因型和时间对大多数与脂肪度相关的性状有影响。
