Combined modulatory effects of dietary arginine and olive leaf phenolic extract on growth performance and immune functions of broiler chickens, and meat antioxidant potential during frozen storage.

Background: Nowadays, broilers reared in intensive farming become more susceptible to oxidative stress, which impairs their performance and the quality of their products. Arginine (G) is a crucial amino acid for chickens and feeding on arginine beyond the recommended levels has been shown to positively impact the growth performance of broiler chickens and their immunity. Olive leaves phenolic extract (OLE) is a natural source of powerful antioxidants. The current study aimed to investigate the combined efficacy of these functional feed additives (G + OLE) in enhancing broilers' growth performance, immunity, and muscle development, as well as potentiating meat quality and antioxidant capacity during freezing.

Methods: Broilers (n = 250) were randomly assigned into control (without supplementations) and four groups fed control diets plus 1.5 g/kg arginine alone (G) or with three different levels of OLE; 0.25%, 0.5% and 1% (G + OLEǀ, G + OLEǀǀǀ and G + OLEǀǀǀ, respectively).

Results: During whole rearing periods, G + OLE inclusion boosted efficacy on body weight gain, and feed conversion ratio in a dose-dependent manner. The postmortem pH values at 0.5, and 24 h, drip loss, and cooking loss % of meat were considerably minimized in G + OLE-supplied groups, especially at high levels. Even after 4 weeks of frozen storage, G + OLEǀǀǀ, G + OLEǀǀ groups exhibited the most prominent increase in the breast meat scavenging ability for free radicals (2,2-diphenyl-1-picrylhydrazyl, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid, and ferric reducing antioxidant power) with an inverse minimization in lipid peroxidation attributes (malondialdehyde). Total flavonoid, and phenolic contents, total antioxidant capacity, and antioxidant enzymes' activities in the breast meat were significantly improved by increasing the concentrations of dietary G + OLE. Concordantly, upregulation of genes encoding immunity (immunoglobulins A, G and M), antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase, peroxiredoxin-1, heme oxygenase-1, NAD(P)H dehydrogenase quinone 1, xanthine oxidoreductase, and heme oxygenase 1), and muscle development (myogenic determination factor, myogenin and mammalian target of rapamycin), and downregulation of myostatin, were remarkably recognized in G + OLE-supplied groups.

Conclusions: The outcomes of the current study supported the usage of dietary G + OLE as an innovative feed supplement in the broilers industry to improve broilers` production, and meat quality during frozen storage.