The aim of the present work was to study the relationships between lamb growth performance, soft adipose tissue and fatty acid composition of subcutaneous adipose tissue of intensively reared lambs, and to determine if the occurrence of soft fat, and of odd numbered (Odd FA) and methyl-branched-chain fatty acids in subcutaneous adipose tissue was related to plasma concentrations of methylmalonic acid (MMA). For this purpose, a sensitive gas chromatography assay to measure low plasma concentrations of MMA was developed and validated. In all, 49 male lambs were reared from 23.6 to 41.0kg. They were fed ad libitum with hay and pelleted concentrates containing either cereals (80%, C) or sugar beet pulp (70%, BP). Plasma concentrations of MMA were measured 12 days before slaughter. Softness score and fatty acid compositions of caudal adipose tissue were determined after slaughter. At the end of the trial, 75% of the carcasses had soft adipose tissue. The occurrence of soft fat appears to be related to high metabolisable energy intake per kg body weight. Soft fat was characterised by a higher water content, a lower proportion of saturated even-numbered fatty acids and higher proportions of Odd FA and methyl-branched-chain fatty acids in caudal adipose tissue, compared to firm fat. Despite high proportions of Odd FA and branched-chain fatty acids in caudal adipose tissue, plasma concentrations of MMA were low (2.02+/-1.98&mgr;mol/l). No clear relationships between MMA concentrations and soft fat or the proportions of branched-chain fatty acids other than the Iso and Anteiso acids was observed. It was concluded that the present study does not support the hypothesis that the liver's capacity to metabolise MMA was exceeded.

中文翻译：

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皮下脂肪组织的柔软度和脂肪酸组成，以及集中饲养羔羊血浆中甲基丙二酸的浓度

本工作的目的是研究集中饲养羔羊皮下脂肪组织的羔羊生长性能、软脂肪组织和脂肪酸组成之间的关系，并确定是否出现软脂肪和奇数（Odd FA）皮下脂肪组织中的甲基支链脂肪酸与甲基丙二酸 (MMA) 的血浆浓度有关。为此，开发并验证了一种灵敏的气相色谱法来测量 MMA 的低血浆浓度。总共饲养了 49 只公羊羔，体重从 23.6 公斤到 41.0 公斤。他们随意喂食干草和含有谷物（80%，C）或甜菜浆（70%，BP）的浓缩颗粒。在屠宰前 12 天测量 MMA 的血浆浓度。屠宰后测定尾部脂肪组织的柔软度评分和脂肪酸组成。在试验结束时，75% 的尸体具有软脂肪组织。软脂肪的出现似乎与每公斤体重摄入高代谢能有关。与硬脂肪相比，软脂肪的特点是水分含量更高，饱和偶数脂肪酸的比例更低，尾端脂肪组织中奇数脂肪酸和甲基支链脂肪酸的比例更高。尽管尾部脂肪组织中奇数 FA 和支链脂肪酸的比例很高，但 MMA 的血浆浓度很低 (2.02+/-1.98&mgr;mol/l)。没有观察到 MMA 浓度与软脂肪或支链脂肪酸的比例之间的明确关系，而不是异和反异酸。