Department of Animal Science, Iowa State University, Ames 50011, USA.
J Anim Sci. 2010 Jan;88(1):69-79. doi: 10.2527/jas.2008-1336. Epub 2009 Sep 25.
Design of breeding programs requires knowledge of variance components that exist for traits included in specific breeding goals and the genetic relationships that exist among traits of economic importance. A study was conducted to evaluate direct and correlated genetic responses to selection for intramuscular fat (IMF) and to estimate genetic parameters for economically important traits in Duroc swine. Forty gilts were purchased from US breeders and randomly mated for 2 generations to boars available in regional boar studs to develop a base population of 56 litters. Littermate pairs of gilts from this population were randomly assigned to a select line (SL) or control line (CL) and mated to the same boar to establish genetic ties between lines. In the SL, the top 10 boars and 75 gilts were selected based on IMF EBV obtained from a bivariate animal model that included IMF evaluated on the carcass and IMF predicted via ultrasound. One boar from each sire family and 50 to 60 gilts representing all sire families were randomly selected to maintain the CL. Carcass and ultrasound IMF were both moderately heritable (0.31 and 0.38, respectively). Moderate to high genetic relationships were estimated among carcass backfat and meat quality measures of IMF, Instron tenderness, and objective loin muscle color. Based on estimates obtained in this study, more desirable genetic merit for pH is associated with greater genetic value for loin color, tenderness, and sensory characteristics. Intramuscular fat measures obtained on the carcass and predicted using ultrasound technology were highly correlated (r(g) = 0.86 from a 12-trait analysis; r(g) = 0.90 from a 5-trait analysis). Estimated genetic relationships among IMF measures and other traits evaluated were generally consistent. Intramuscular fat measures were also genetically associated with Instron tenderness and flavor score in a desirable direction. Direct genetic response in IMF measures observed in the SL corresponded to a significant decrease in EBV for carcass loin muscle area (-0.90 cm(2) per generation) and an increase in carcass backfat EBV (0.98 mm per generation). Selection for IMF has led to more desirable EBV for objective tenderness and has had an adverse effect on additive genetic merit for objective loin color.
育种计划的设计需要了解特定育种目标中存在的性状方差分量和经济重要性状之间存在的遗传关系。本研究旨在评估杜洛克猪肌肉内脂肪（IMF）选择的直接和相关遗传反应，并估计经济重要性状的遗传参数。从美国饲养员购买了 40 头母猪，并随机交配 2 代，与地区种猪场的公猪交配，以建立一个由 56 窝组成的基础群体。从该群体中，随机分配同窝母猪对到选择线（SL）或对照线（CL），并与同一头公猪交配，以建立线间遗传联系。在 SL 中，根据包括在 carcass 上评估的 IMF 和通过超声预测的 IMF 的双变量动物模型获得的 IMF EBV，选择前 10 头公猪和 75 头母猪。从每个 sire 家系中选择一头公猪和 50 到 60 头母猪，代表所有 sire 家系，以维持 CL。 carcass 和超声 IMF 的遗传力均适中（分别为 0.31 和 0.38）。 carcass 背膘和 IMF 的肉质测量、Instron 嫩度和客观腰肌肉色之间估计存在中等至高遗传关系。根据本研究中的估计，与瘦肉颜色、嫩度和感官特性相比，pH 值的更理想遗传优势与更高的遗传价值相关。 carcass 上获得的肌肉内脂肪测量值和使用超声技术预测的测量值高度相关（12 个性状分析中 r(g) = 0.86；5 个性状分析中 r(g) = 0.90）。 IMF 测量值与其他评估性状之间的估计遗传关系通常是一致的。肌肉内脂肪测量值还与 Instron 嫩度和风味评分以理想的方向存在遗传关联。在 SL 中观察到的肌肉内脂肪测量值的直接遗传反应对应于 carcass loin muscle area 的 EBV 显著下降（每代-0.90 cm²）和 carcass 背膘 EBV 的增加（每代 0.98 mm）。选择肌肉内脂肪导致了更理想的客观嫩度 EBV，并对客观腰颜色的加性遗传优势产生了不利影响。
