Effect of Oregano Essential Oil Supplementation to a Reduced-Protein Diet on Meat Quality, Fatty Acid Composition, and Oxidative Stability of Longissimus Thoracis Muscle in Growing-Finishing Pigs

We investigated the effects of reduced-protein diet supplemented with oregano essential oil (OEO) on the meat quality, fatty acid composition and oxidative stability in longissimus thoracis (LT) muscle of growing-finishing pigs. A total of 36 growing barrows (Large White × Landrace) with an initial body weight (BW) of 29.0 ± 1.00 kg were obtained from a commercial farm in the Hubei province of China. Pigs were randomly allotted to 1 of 3 treatments based on BW in a randomized complete block design with 12 replicates of one pig per replicate. Pigs were penned individually. Three experimental treatments were formulated to consist of: 1) normal protein diet (NPD), 2) reduced-protein diet (RPD), and 3) identical reduced-protein diet supplemented with 250 mg/kg OEO (OEO). The three diets were based on corn-soybean meal-dried distillers grains with soluble (DDGS). The pigs in the NPD group were offered diets which contained 17% and 15.6% crude protein during the growing (days 0–49) and finishing (days 51–98) periods, respectively. The pigs in the RPD group were offered diets which contained 15% and 13.6% crude protein during their growing and finishing periods, respectively. Experimental diets were balanced with four amino acids (L-lysine, L-methionine, L-threonine, and L-tryptophan) to meet the requirements of growing-finishing pigs (NRC, 2012). RPD and OEO increased (P < 0.05) the b*_45min, tenderness, overall acceptance and intramuscular fat (IMF) content of pork compared with NPD. The percentage of n-3 polyunsaturated fatty acid (n-3 PUFA) and the percentage of monounsaturated fatty acid (MUFA) in muscle of pigs fed with OEO supplemented diet were higher (P < 0.05) and lower (P < 0.05) than those in RPD, respectively. OEO improved (P < 0.01) oxidative stability, total antioxidative capacity and catalase but decreased (P < 0.01) drip loss in LT muscle compared with dietary NPD and RPD. In our study, reduced-protein diet supplementation with oregano essential oil enhanced the sensory attributes and anti-oxidative status of pork meat by improving IMF and n-3 PUFA percentage and antioxidative capacity.