V. Berthelot et al., Softness and fatty acid composition of subcutaneous adipose tissue, and methylmalonic acid concentrations in the plasma of intensively reared lambs, SMALL RUMIN, 41(1), 2001, pp. 29-38
The aim of the present work was to study the relationships between lamb gro
wth performance, soft adipose tissue and fatty acid composition of subcutan
eous adipose tissue of intensively reared lambs, and to determine if the oc
currence of soft fat, and of odd numbered (Odd FA) and methyl-branched-chai
n fatty acids in subcutaneous adipose tissue was related to plasma concentr
ations of methylmalonic acid (MMA), For this purpose, a sensitive gas chrom
atography assay to measure low plasma concentrations of MMA was developed a
nd validated. In all, 49 male lambs were reared from 23.6 to 41.0 kg. They
were fed ad libitum with hay and pelleted concentrates containing either ce
reals (80%, C) or sugar beet pulp (70%, BP). Plasma concentrations of MMA w
ere measured 12 days before slaughter. Softness score and fatty acid compos
itions 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 low
er 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 lo
w (2.02 +/- 1.98 mu mol/l). No clear relationships between MMA concentratio
ns 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 metaboli
se MMA was exceeded. (C) 2001 Elsevier Science B.V. All rights reserved.