Summer-produced lamb has potential consumer health benefits
Take Home Message: Finishing lambs off grass in the summer will increase the nutritionally beneficial content of polyunsaturated fatty acids and conjugated linoleic acid in lamb.
There is seasonal variation in the concentration of a number of fatty acids in lamb produced under a range of commercial production systems. And the higher concentrations of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) and total conjugated linoleic acids (CLA) in summer-produced lamb may have potential benefits for consumer health.
Just two of the findings of a trial, to determine the fatty acid (FA) composition of lamb produced in Northern Ireland and to examine the effects of both season of slaughter and reported finishing diet, which were presented to delegates at this year’s British Society of Animal Science’s annual conference, held at Queen’s University, Belfast.
“The fatty acid (FA) composition of ruminant meat is influenced by many aspects of the production system including the animal finishing diet. Lamb produced from grass-fed animals contains greater concentrations of LC n-3 PUFA than lamb produced from concentrate-fed animals,” said the University of Ulster’s Alison McAfee, who led the trial.
“Since the animal diet is likely to vary over the farming year, it is possible that the season of animal slaughter will also influence quantities of LCn-3 PUFA found in meat and subsequently available for human consumption,” she added, explaining the rationale behind her work.
Samples of lamb longissimus dorsi (LD) muscle were collected fortnightly from a commercial abattoir over a 12-month period. Producers were identified and contacted to obtain information on whether the finishing diet provided in the month prior to slaughter was grass, concentrates, grass supplemented with concentrates or silage supplemented with concentrates. Total lipid was extracted from lean tissue and FA methyl esters were analysed using gas chromatography.
“And we found that the intramuscular fat content of the LD muscle was not significantly affected by season. But lamb finished in summer had significantly higher concentrations of LCn-3 PUFA and total conjugated linoleic acids (CLA) than any other season,” said Dr McAfee.
“There was a significant interaction between season and diet for docosapentaenoic acid in lamb samples from animals reportedly finished on grass in summer. This interaction showed that summer lambs, which were reportedly finished on grass, had higher proportions of this LCn-3PUFA compared to those finished on concentrates alone or concentrates plus forage.”
Dr McAfee concluded that further research was needed to determine the time course of these changes in order to optimise conversion of the C18:3n-3 from grass to LCn-3 PUFA in the lamb muscle.
Presented to the British Society of Animal Science Annual Conference, April 12 to 14, 2010, Queen’s University, Belfast.
McAfee AJ, McSorley EM, Cuskelly GJ, FEaron AM, Moss BW, Beattie JAM, Doyle A, Gordon A, Wallace JMW, Bonham MP and Strain JJ: “Influence of season and finishing diet on the fatty acid composition of lamb longissimus dorsi muscle.”
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