Schwab C R, Baas T J, Stalder K J, Mabry J W
Department of Animal Science, Iowa State University, Ames 50011, USA.
J Anim Sci. 2007 Jun;85(6):1540-6. doi: 10.2527/jas.2006-343. Epub 2007 Feb 12.
A study was conducted to evaluate differences in performance and in carcass composition and tissue deposition rates between purebred Duroc pigs sired by boars currently available and those sired by boars from the mid-1980s. Two lines were developed by randomly allocating littermate and half-sib pairs of females to matings by current time period (CTP) or old time period (OTP) boars. Pigs from 2 replications were placed on test at a group mean BW of 63.5 kg. Serial ultrasonic measurements of the 10th-rib LM area (LMA), off-midline backfat (BF10), and intramuscular fat percentage (IMF) were collected every 2 wk in the first replication and used to assess deposition rate differences. Off-test ultrasonic LMA, BF10, and IMF measurements from a total of 557 pigs from 23 CTP sires and 232 pigs from 15 OTP sires across 2 replications and at a mean BW of 109 kg were evaluated. All available barrows and randomly selected gilts (n = 277) were sent to a commercial abattoir, and carcass measurements of 10th-rib backfat, last-rib backfat, last lumbar backfat, and LMA were collected. Analysis of serial backfat measurements revealed a linear relationship between back-fat and BW between 73 and 118 kg for pigs from both time periods. Pigs sired by OTP boars deposited more backfat (P < 0.05) at a faster rate than pigs sired by CTP boars over the entire test period. A curvilinear cumulative tissue deposition pattern was revealed for ultrasonically estimated LMA and IMF within both time periods. Significant linear and quadratic regression coefficient differences between lines indicated that pigs sired by CTP boars deposited more LMA and less IMF per kilogram of BW gain than pigs sired by OTP boars. Pigs sired by CTP boars had more LMA and less BF10 (P < 0.05), whereas pigs sired by OTP boars had more IMF (P = 0.04). Carcass evaluation revealed more (P < 0.01) carcass measurements of LMA and less (P < 0.05) carcass measurements of 10th-rib backfat, carcass measurements of last-rib backfat, and carcass measurements of last lumbar backfat for pigs sired by CTP boars. No difference (P > 0.05) between the time periods was found for ADG over the entire test period. Results from this study illustrate that significant progress in carcass composition has been realized within the Duroc breed since the mid-1980s. The long-term selection response in carcass leanness has also resulted in changes in deposition rates of correlated traits such as LMA and IMF.
开展了一项研究，以评估当前可用公猪所产纯种杜洛克猪与20世纪80年代中期公猪所产纯种杜洛克猪在生产性能、胴体组成及组织沉积率方面的差异。通过将同窝和半同胞雌性猪随机分配给当前时期（CTP）或过去时期（OTP）的公猪进行配种，建立了两个品系。来自2次重复试验的猪在平均体重63.5 kg时开始试验。在第一次重复试验中，每隔2周对第10肋处的腰大肌面积（LMA）、离背中线处背膘厚（BF10）和肌内脂肪百分比（IMF）进行连续超声测量，并用于评估沉积率差异。对来自2次重复试验、共557头来自23头CTP公猪的猪以及232头来自15头OTP公猪的猪在平均体重109 kg时的宰前超声LMA、BF10和IMF测量值进行了评估。所有可用的阉公猪和随机挑选的后备母猪（n = 277）被送往一家商业屠宰场，并收集了第10肋背膘厚、最后肋背膘厚、最后腰椎背膘厚和LMA的胴体测量数据。对连续背膘测量值的分析表明，两个时期的猪在体重73至118 kg之间，背膘与体重呈线性关系。在整个试验期内，OTP公猪所产的猪比CTP公猪所产的猪沉积更多背膘（P < 0.05），且沉积速度更快。在两个时期内，超声估计的LMA和IMF均呈现出曲线累积组织沉积模式。品系间显著的线性和二次回归系数差异表明，CTP公猪所产的猪每千克体重增加所沉积的LMA更多，而IMF更少。CTP公猪所产的猪LMA更多，BF10更少（P < 0.05），而OTP公猪所产的猪IMF更多（P = 0.04）。胴体评估显示，CTP公猪所产猪的LMA胴体测量值更多（P < 0.01），而第10肋背膘厚、最后肋背膘厚和最后腰椎背膘厚的胴体测量值更少（P < 0.05）。在整个试验期内，两个时期的平均日增重（ADG）没有差异（P > 0.05）。本研究结果表明，自20世纪80年代中期以来，杜洛克猪在胴体组成方面已取得显著进展。胴体瘦肉率的长期选择反应也导致了诸如LMA和IMF等相关性状沉积率的变化。
