Pasture feeding impacts on lamb lipid composition and on blood plasma and cardiovascular risk factors in humans

Abstract

This research aimed to improve the nutritional quality of lamb by exploring and advancing current knowledge surrounding the benefits of pasture feeding for ruminants, focusing on increasing levels of omega-3 (n-3 PUFA) in lamb. The impact of diet on n-3 PUFA composition of lamb meat was evaluated using a systematic review and meta-analysis. Results reinforced the benefits of pasture feeding on n-3 PUFA, particularly C18:3 n-3 and more uniquely C20:5 n-3 in muscle. Three studies (one conducted at an experimental research facility and two commercial) assessed the effect of feeding lambs’ pasture or concentrate on fatty acid (FA) composition of muscle (n =166). The FA composition of two muscles, the longissimus dorsi (LD) and quadriceps femoris (QF) was analysed. Pasture feeding increased levels of C18:3 n-3, C20:5 n-3, C22:5 n-3 and C22:6 n-3 compared to concentrate feeding. Total FA was higher in LD than QF, while long chain n-3 PUFA was higher in QF than LD. Lipidomic profiling analysis identified and characterised lipid species using untargeted UHPLC-MS/MS analysis. Nine lipid species were identified as significantly different between grass vs concentrate diets. Lipid species phosphatidylethanolamine (18:1e_18:1) and lyso-phosphatidylcholine (18:2) were identified as possible biomarkers for grass and concentrate treatments, respectively. A human intervention study evaluating the effect of consuming three portions of lamb (from pasture vs concentrate diets) per week for four consecutive weeks among healthy participants (n=34) was conducted. Increased levels of n-3 PUFA (C18:3 n-3, C20:5 n-3, C22:5 n-3) were detected in blood plasma from participants who consumed grass finished lamb, while consuming concentrate finished lamb increased levels of C18:2 n-6 in plasma PL. There were no positive or negative implications on cardiovascular risk factors (BMI, blood pressure and cholesterol). The benefits of pasture compared to concentrate feeding were confirmed, while unique diet dependent lipid species in muscle were discovered. The successful enrichment of human blood after consuming pasture fed lamb highlights the role of meat in delivering n-3 PUFA into the body. Future research exploring maximising n-3 PUFA in pasture fed meat, while establishing benefits to humans through improvement to health, wellbeing and quality of life is needed.

Thesis embargoed until 31 December 2023

Date of Award	Dec 2021
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Nigel Scollan (Supervisor) & Christopher Elliott (Supervisor)