Apple J K, Maxwell C V, Kutz B R, Rakes L K, Sawyer J T, Johnson Z B, Armstrong T A, Carr S N, Matzat P D
Department of Animal Science, University of Arkansas, Fayetteville 72701, USA.
J Anim Sci. 2008 Oct;86(10):2711-22. doi: 10.2527/jas.2007-0327. Epub 2008 May 23.
Crossbred pigs (n = 216) were used to test the interactive effect, if any, of ractopamine (RAC) and dietary fat source on the performance of finishing pigs, pork carcass characteristics, and quality of LM chops during 5 d of simulated retail display (2.6 degrees C and 1,600 lx warm-white fluorescent lighting). Pigs were blocked by BW and allotted randomly to pens (6 pigs/pen), and, after receiving a common diet devoid of RAC for 2 wk, pens within blocks were assigned randomly to 1 of 4 diets in a 2 x 2 factorial arrangement, with 5% fat [beef tallow (BT) vs. soybean oil (SBO)] and RAC (0 vs. 10 mg/kg). Diets were formulated to contain 3.1 g of lysine/Mcal of ME and 3.48 Mcal/kg of ME. Across the entire 35-d trial, pigs fed RAC had greater (P < 0.01) ADG and G:F, but RAC did not affect (P = 0.09) ADFI; however, performance was not affected (P >or= 0.07) by dietary fat source. Carcass weight, LM depth, and lean muscle yield were increased (P < 0.01), whereas fat depth was decreased (P = 0.01), in carcasses from RAC-fed pigs; however, carcass composition measures were similar (P >or= 0.27) between fat sources. Feeding 10 mg/kg of RAC reduced (P <or= 0.04) the proportions of SFA and MUFA and increased (P < 0.01) the proportion of PUFA and the iodine value, in pork backfat. Conversely, backfat from carcasses of BT-fed pigs had greater (P < 0.01) percentages of SFA and MUFA, and lower (P < 0.01) percentages of PUFA, than backfat from SBO-fed pigs. Moreover, the PUFA:SFA and iodine value were considerably reduced (P < 0.01) by including BT in swine finishing diets. The LM from pigs fed RAC had greater pH values (P = 0.03) and received greater (P <or= 0.01) American and Japanese color scores during retail display. The LM from RAC-fed pigs had lower (P <or= 0.02) L*, a*, and b* values, whereas the LM of SBO-fed pigs received greater (P < 0.01) subjective color scores and b* values, as well as lower L* values, than the LM of BT-fed pigs. Across the 5-d display period, oxidative rancidity was not affected by dietary RAC (P = 0.58) or fat source (P = 0.47). Neither RAC nor fat source altered LM cooking losses and shear force values. Feeding 10 mg/kg of RAC will improve rate and efficiency of gain, carcass composition, and LM quality. And, even though fatty acid composition of backfat samples was altered by dietary fat source, performance and carcass composition, as well as quality during 5 d of retail display, were similar when pigs were fed diets formulated with BT or SBO.
选用216头杂交猪来测试莱克多巴胺（RAC）与日粮脂肪来源对育肥猪生产性能、猪胴体特性以及猪里脊肉排（LM）在5天模拟零售展示期（2.6℃和1600勒克斯暖白色荧光照明）的品质的交互作用（若存在）。猪只按体重进行分栏，随机分配至栏舍（每栏6头猪），在接受不含RAC的普通日粮2周后，栏舍内的猪只再按2×2析因设计随机分配至4种日粮中的1种，日粮含5%脂肪（牛油（BT）与大豆油（SBO））以及RAC（0与10毫克/千克）。日粮配方为每兆卡代谢能含3.1克赖氨酸以及代谢能为3.48兆卡/千克。在整个35天的试验期内，饲喂RAC的猪平均日增重（ADG）和料重比（G:F）更高（P<0.01），但RAC对采食量（ADFI）无影响（P = 0.09）；然而，日粮脂肪来源对生产性能无影响（P≥0.07）。饲喂RAC的猪的胴体重、LM厚度和瘦肉产量增加（P<0.01），而脂肪厚度降低（P = 0.01）；然而，不同脂肪来源间的胴体组成指标相似（P≥0.27）。饲喂10毫克/千克RAC可降低（P≤0.04）猪背膘中饱和脂肪酸（SFA）和单不饱和脂肪酸（MUFA）的比例，并增加（P<0.01）多不饱和脂肪酸（PUFA）的比例和碘值。相反，饲喂BT的猪的胴体背膘中SFA和MUFA的百分比更高（P<0.01），PUFA的百分比更低（P<0.01），相比于饲喂SBO的猪的背膘。此外，在猪育肥日粮中添加BT可显著降低（P<0.01）PUFA:SFA和碘值。饲喂RAC的猪的LM在零售展示期间pH值更高（P = 0.03），且美国和日本颜色评分更高（P≤0.01）。饲喂RAC的猪的LM的亮度值（L*）、红度值（a*）和黄度值（b*）更低（P≤0.02），而饲喂SBO的猪的LM相比于饲喂BT的猪的LM，主观颜色评分和b值更高（P<0.01），L值更低。在5天的展示期内，氧化酸败不受日粮RAC（P = 0.58）或脂肪来源（P = 0.47）的影响。RAC和脂肪来源均未改变LM的烹饪损失和剪切力值。饲喂10毫克/千克RAC可提高生长速度和效率、改善胴体组成以及LM品质。并且，尽管日粮脂肪来源改变了背膘样本的脂肪酸组成，但当猪饲喂含BT或SBO的日粮时，其生产性能、胴体组成以及5天零售展示期的品质相似。
