Effects of dietary supplementation with an olive mill wastewater phenolic extract on the growth performance, oxidative status, and meat quality traits of finishing pigs

Phenolic compounds from olive mill wastewater (OMWW) have a strong antioxidant capacity, so there is increasing interest in using them in feed for livestock, including pigs. This study tested the effects of dietary supplementation with a polyphenol extract from OMWW for female Landrace × Duroc heavy finishing pigs. There were three groups: the control diet (C group), the control diet supplemented with 74 ppm of OMWW polyphenols (P-LOW group), and the control diet supplemented with 225 ppm of OMWW polyphenols (P-HIGH group). Each experimental group comprised 45 pigs (<i>n</i> = 15 × 3 replicates), for a total of 135 pigs. The effects of the phenolic extract were assessed <i>in vivo</i> (growth performance) and postmortem (backfat thickness; pubertal status; histopathology of the liver, ovary, uterus, fat, and muscle; morphometry of the liver, ovary, and uterus; antioxidant status in the blood, muscle, and liver; effects on the quality and physicochemical characteristics of the raw meat). There were no significant differences between the treatments regarding the growth performance traits, histopathological and morphometric findings, and backfat thickness. However, there was an increase in 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity in the liver of the P-HIGH group, alongside higher serum paraoxonase activity and ferric reducing antioxidant power. Meat quality analysis showed that cooking loss and redness (a*) decreased, while yellowness (b*) increased in the P-LOW and P-HIGH groups, indicating that OMWW polyphenols influenced the structure and water retention capacity of the meat. Additional research is required to better understand the role of dietary OMWW polyphenols in relation to the technological quality and antioxidant state of pork meat.