Mir P S, Mir Z, Kubert P S, Gaskins C T, Martin E L, Dodson M V, Calles J A Elias, Johnson K A, Busboom J R, Wood A J, Pittenger G J, Reeves J J
Agriculture and Agri-Food Canada Research Centre, P.O. Box 3000, Lethbridge, AB, T1J 4B1.
J Anim Sci. 2002 Nov;80(11):2996-3004. doi: 10.2527/2002.80112996x.
The effect of breed and diet on insulin response to glucose challenge and its relation to intramuscular fat deposition was determined in 36 steers with 12 each of greater than 87% Wagyu (referred to as Wagyu), Wagyu x Limousin, and Limousin breeds. Weaned steers were blocked by weight into heavy, medium, and light calves and placed in six pens with two pens per weight type and with two steers of each breed per pen. Three pens with steers from each weightclass were fed backgrounding and finishing diets for 259 d, while the other three pens were fed the same diets where 6% of the barley grain was replaced with sunflower oil. Prior to initiation of the finishing phase of the study the intravenous glucose tolerance test (VGTIT) was conducted in all steers. Once steers were judged as carrying adequate 12th-rib fat, based on weight and days on feed, they were harvested and graded and samples of the longissimus muscle were procured for determination of fat content and fatty acid composition. Dietary oil improved (P = 0.011; 0.06) ADG and feed conversion efficiency of steers during the latter part of backgrounding and only ADG during early part ofthe finishing period. Generally percent kidney, pelvic, and heart fat was the only adiposity assessment increased (P = 0.003) by dietary oil. The IVGTT results indicated that insulin response to intravenous glucose was lower in Limousin steers than in Wagyu steers. Dietary oil decreased (P = 0.052) fasting plasma insulin concentration in Wagyu steers compared with Limousin steers. The correlation coefficients among the IVGTT measures and intramuscular fat content or marbling score were less than 0.4, and only a negative trend existed between fasting insulin and USDA marbling scores. However, the carcasses of the Wagyu steers graded US Choice, and 66% of the Wagyu carcasses graded US Prime, which were substantially better than the quality grades obtained for the carcasses from the other breed types. Dietary oil did not affect muscle fat content but increased (P = 0.01) conjugated linoleic acid (CLA) concentrations by 339%. Results indicated that IVGTT measures were not appropriate indices of marbling potential in cattle and that dietary oil can enhance CLA content of beef.
在36头阉牛中测定了品种和日粮对葡萄糖激发试验中胰岛素反应的影响及其与肌内脂肪沉积的关系，其中每种品种各12头，分别为大于87%的和牛（称为和牛）、和牛×利木赞牛以及利木赞牛。断奶阉牛按体重分为重、中、轻三组，放入六个围栏中，每个体重类型两个围栏，每个围栏中每种品种各两头阉牛。每个体重组的三头阉牛喂食育肥前期和后期日粮259天，而另外三个围栏中的阉牛喂食相同日粮，但用向日葵油替代6%的大麦谷物。在研究育肥阶段开始前，对所有阉牛进行静脉葡萄糖耐量试验（VGTIT）。一旦根据体重和采食天数判断阉牛第12肋骨处脂肪含量充足，就对其进行屠宰、分级，并采集背最长肌样本以测定脂肪含量和脂肪酸组成。日粮添加油提高了（P = 0.011；0.06）阉牛在育肥前期后期的平均日增重（ADG）和饲料转化效率，在育肥期前期仅提高了ADG。一般来说，日粮添加油仅使肾脏、盆腔和心脏脂肪百分比这一肥胖评估指标增加（P = 0.003）。静脉葡萄糖耐量试验结果表明，利木赞阉牛对静脉注射葡萄糖的胰岛素反应低于和牛阉牛。与利木赞阉牛相比，日粮添加油降低了（P = 0.052）和牛阉牛的空腹血浆胰岛素浓度。静脉葡萄糖耐量试验指标与肌内脂肪含量或大理石花纹评分之间的相关系数小于0.4，空腹胰岛素与美国农业部大理石花纹评分之间仅存在负相关趋势。然而，和牛阉牛的胴体等级为美国特选级，66%的和牛胴体等级为美国极佳级，明显优于其他品种类型的胴体质量等级。日粮添加油不影响肌肉脂肪含量，但使共轭亚油酸（CLA）浓度增加了339%（P = 0.01）。结果表明，静脉葡萄糖耐量试验指标不是牛大理石花纹潜力的合适指标，日粮添加油可提高牛肉中CLA的含量。
