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

Abstract

Total conjugated fatty acid concentration in milk from 131 lactating Romney ewes at about the fourth week of lactation was measured spectro‐photometrically 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; P < 0.05). 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.