New Zealand Journal of Agricultural Research abstracts
Conjugated linoleic acid concentration (CLA) in the m. longissimus
thoracis of the offspring of Romney ewes screened for high and low CLA
in their milkfat
T. W. Knight*
M. H. Tavendale
A. F. Death
AgResearch Grasslands
Private Bag 11 008
Palmerston North, New Zealand
M. Agnew
AgResearch Ruakura
Private Bag 3123
Hamilton, New Zealand
*Email: terry.knight@agresearch.co.nz
Abstract Total conjugated fatty acid concentration in
milk from 131 lactating Romney ewes at about the fourth week of lactation
was measured spectrophotometrically to identify 20 ewes with high and 20 ewes
with low concentrations of conjugated linoleic acid (CLA) in the total fatty
acid (TFA) of their milk. The persistence of these differences in CLA concentration
was measured in milk from this and a subsequent lactation. The CLA concentration
was also measured in plasma collected from these ewes 6 months after their
lambs were weaned and in the m. longissimus thoracis(LT) of the offspring
from these ewes. Allocation of ewes to the High CLA and Low CLA groups were
confirmed by measuring the CLA concentration in the milkfat using gas liquid
chromatography (GLC) (r = 0.73; P< 0.001). High CLA ewes
had higher (P < 0.001) concentrations of CLA than Low CLA ewes
in milkfat collected in the fourth week (2.55 versus 1.49 ± 0.07 g
100 g-1 TFA) and eighth week (2.18 versus 1.66 ± 0.09 g
100 g-1 TFA) of lactation, during the subsequent lactation (1.36
versus 0.90 ± 0.08 g 100 g-1 TFA), and in plasma collected
6 months after weaning (0.41 versus 0.34 ± 0.02 g 100 g-1
TFA; Differences between the groups in trans-vaccenic acid (TVA) concentrations
were consistent with the differences in CLA concentrations in milk and plasma.
Lambs slaughtered at 28 weeks of age (12 weeks post-weaning) from High CLA
ewes had a 37% higher (P < 0.05) CLA concentration in the TFA extracted
from the LT than lambs from Low CLA ewes (0.82 versus 0.60 ± 0.06 g
100 g-1 TFA). Single-born lambs from the High and Low CLA groups
had a 35% higher (P < 0.01) CLA concentration in the LT than twin-born
lambs from these groups (0.81 versus 0.60 ± 0.06 g 100 g-1
TFA), suggesting that differences in CLA concentration in the meat were due
to differences in the ingestion of CLA in milk. It is concluded that a higher
concentration of CLA in the milkfat of ewes resulted in a higher concentration
of CLA in the meat from their lambs and that the ranking of ewes for concentration
of CLA in milkfat persisted for at least two lactations.
Keywords ewes’ milk; lamb; conjugated linoleic acid;
animal variation
A03069; Received 5 December 2003; accepted 27 May 2004; Online publication
date 17 August 2004
New Zealand Journal of Agricultural Research, 2004, Vol. 47: 287-297
0028-8233/04/4703-0287 © The Royal Society of New Zealand 2004
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