Dietary supplementation of grape seed proanthocyanidins improves growth performance, carcass traits, and meat quality in growing-finishing pigs

Grape seed proanthocyanidin (GSP) is a type of plant polyphenol with a wide variety of biological activities, such as antioxidant properties. This study investigated the effects of GSP supplementation on growth performance and meat quality in growing-finishing pigs. A total of 180 pigs (with an initial average body weight of 30.37 ± 0.66 kg) were randomly assigned to five treatments: a control diet or a control diet supplemented with GSP at 15, 30, 60, and 120 mg/kg. Each treatment group comprised six replicate pens (6 pigs per pen). Results showed that GSP supplementation linearly increased the average daily gain (<i>P</i> = 0.048) and quadratically decreased the feed intake to gain ratio (<i>P</i> = 0.049) with the lowest values at 30 and 60 mg/kg GSP. Serum concentrations of immunoglobulins (Ig) (IgA, IgG, IgM), total antioxidative capacity, catalase, and total superoxide dismutase were elevated with the peak levels at 30 mg/kg GSP (<i>P</i> < 0.05). Serum glutathione peroxidase increased and malondialdehyde decreased quadratically (<i>P</i> < 0.05), with peak and trough levels at 120 and 60 mg/kg GSP, respectively. The GSP also improved dressing percentage and muscle redness (a∗_{45 min}) with optimal levels at 30 and 60 mg/kg (<i>P</i> < 0.05). Additionally, GSP supplementation quadratically reduced the muscle yellowness (b∗_{24 h}) and shear force (<i>P</i> < 0.05), with the lowest values at 120 mg/kg. The expression level of myosin heavy chain I in muscle was quadratically increased with maximum expression at 30 and 60 mg/kg (<i>P</i> = 0.015). Furthermore, the expression levels of fatty acid synthase, phosphoenolpyruvate carboxykinase (<i>PEPCK</i>), and glucokinase in the muscle were decreased quadratically (<i>P</i> < 0.05) with the lowest values at 120 mg/kg. Additionally, GSP supplementation at 60 mg/kg upregulated the expression of hepatic hormone-sensitive triglyceride lipase and <i>PEPCK</i> (<i>P</i> < 0.05). These results suggest that GSP enhances carcass characteristics and meat quality in growing-finishing pigs, potentially through improved antioxidative capacity, modified muscle fiber type distribution, and altered glucose-lipid metabolism in muscle and liver.