Effects of in ovo injection of chrysin, quercetin and ascorbic acid on hatchability, somatic attributes, hepatic oxidative status and early post‐hatch performance of broiler chicks
Antioxidants are substances that protect cells from the oxidative damages caused by unstable molecules known as free radicals. They are necessary for embryo health and survivability, particularly during the last 3 days of incubation (Malheiros, Ferket, & Gonçalves, 2012).
During the time of hatch, broiler chick embryos show an increased susceptibility to oxidative stress probably due to heightened metabolic rate and O2 consumption, as well as high levels of tissue polyunsaturated fatty acids and insufficient natural antioxidant reserves (Malheiros et al., 2012). The embryo uses a variety of enzymatic (i.e., superoxide dismutase, glutathione peroxidase, catalase) and non‐enzymatic (vitamin E, ascorbic acid, carotenoids, reduced glutathione, coenzyme Q, etc.) antioxidants as well as mineral cofactors (Se, Zn, Mn and Fe) to combat the oxidative stress. Among these components, vitamin E, carotenoids and cofactor minerals are driven from the maternal diet, and the others are synthesised in the tissues (Surai & Fisinin, 2012).
Vitamin C or ascorbic acid (ASA) is a physiologically multifunctional compound needed for a variety of processes in the animal body, including collagen synthesis, lipid metabolism, absorption of inorganic iron, immune system function, protection against free radical damages and reduction of oxidised vitamin E to its active form (Bender, 2003). Studies involving the measuring ASA content of hatching eggs have shown that fresh unincubated eggs are devoid of ASA (Rinaldini, 1960; Surai, Noble, & Speake, 1996). Rinaldini (1960) reported that the absolute amount of vitamin C in embryo body increases gradually after incubation, whereas its concentration (microgram per mg of body weight) showed a downward trend with the most marked falls observed in brain and muscle. It has been reported that hatchling somatic characteristics, antioxidant status and post‐hatch performance may be improved by in ovo delivery of exogenous antioxidants, including ascorbic acid (Hajati, Hassanabadi, Golian, NassiriMoghaddam, & Nassiri, 2014; Lee et al., 2014).
The term “flavonoid” refers to a wide range of polyphenols sharing a common skeleton of phenylchroman (Vassallo, 2008). These compounds, the majority of them showing antioxidant properties, are divided into seven major subclasses, including flavonols, flavones, flavanones, flavanols, anthocyanins, isoflavones and proanthocyanidins (Murphy et al., 2003). Several mechanisms have been proposed for antioxidant activity of flavonoids, including direct scavenging of free radicals, nitric oxide and peroxynitrite, inhibition of xanthine oxidase activity and interaction with enzymatic antioxidant systems (Nijveldt et al., 2001). Quercetin, the most abundant (Ebadi, 2007) and biologically active (Vassallo, 2008) flavonoid belonging to flavonols, is found in vegetable foods and fruits. Chrysin, another example of flavonoids belonging to the flavone subclass, is naturally present in many plant extracts, honey, and propolis (Rapta, Misík, Stasko, & Vrábel, 1995; Williams, Harborne, Newman, Greenham, & Eagles, 1997). Both chrysin and quercetin exhibit marked antioxidant properties (Anand, Mohamed Jaabir, Thomas, & Geraldine, 2012; Liu et al., 2014).