Abstract: In the present study, we assessed the effects of two different feeding systems on the activities and mRNA expression levels of enzymes involved in the AMP-activated protein kinase-acetyl-CoA carboxylase-carnitine palmitoyltransferase (AMPK-ACC-CPT1) pathway, fat content and meat quality in the Biceps femoris muscle of 12-month-old Sunit lambs. The enzyme activities were determined by enzyme-linked immunosorbent assay and gene expression was measured by real-time fluorescence quantitative polymerase chain reaction (PCR). The results showed that AMPK concentration and activity, AMPK mRNA expression, CPT1 concentration, brightness (L* value), yellowness (b* value) and shear force in the biceps femoris muscle of grazed lambs were significantly higher than those in stall-fed lambs (P < 0.05), while the opposite was observed for ACC activity, ACC mRNA expression and intramuscular fat content (P < 0.05). Accordingly we concluded that grazing can activate the AMPK-ACC-CPT1 pathway to reduce intramuscular fat deposition, increase L* and b* values and decrease tenderness, consequently affecting lamb meat quality.

Key words: feeding systems, Sunit lamb, AMP-activated protein kinase, fatty acid β oxidation, meat quality