Effect of feed restriction on muscle fibre characteristics and meat quality traits in pigs
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The aim of this study was to evaluate the effect of feed restriction on muscle fibre composition and meat quality traits in pigs. Forty crossbred pigs (Pietrain × Large WhiteSire) × (Landrace × Large WhiteDam) were divided into two feeding groups: ad libitum (AL) and restricted (R1). The effects of feed restriction on muscle fibre characteristics of the musculus longissimus lumborum et thoracis (MLLT) and meat quality traits were evaluated. Muscle fibres were stained and classified as fibre types I, IIA, and IIB. For each muscle fibre type, the fibre density, fibre cross-section area (CSA), and fibre proportion were determined. Fibres IIB were divided into small- (diameter < 46 μm), medium- (diameter 46–86 μm) and large-sized (diameter > 86 μm) fibres. The AL group had significantly lower (P < 0.05) percentage area of IIB fibres and lower (P < 0.01) CSA of IIB fibres than did the R1 group. The R1 group had significantly greater content of large-sized IIB fibres and smaller content of medium-sized IIB fibres than did the AL group (P < 0.05). The group fed ad libitum had greater backfat thickness and smaller lean meat content and tended to have better meat quality traits compared to the restricted group. The results of this study show that strong feed restriction had a negative effect on muscle fibre composition, especially on the amount of large-sized fibres IIB, which are associated with poor meat quality.