Q: A comment on flavonoïds, even if they are absorbed at low level some of them play an indirect role in inducing at gene level endogenous antioxidant systems.
Reinforcing the anti-oxidant defenses of the gut definitely improve its resistance to aggressive factors such as dietary ones (induced by mycotoxins for instance) or induced by microorganisms (bacteria, virus). Polyphenols and flavonoids may bring antioxidant benefits reinforcing the host response to xenobiotics.
Q: Is there a significant difference on the meat between chicken fed with Organic selenium and another fed with mineral selenium?
We assume that you mean organoleptic properties: improving the antioxidant status of the meat often is "indirectly" perceived by consumers influencing their choice. The conservation of the meat is also improved reducing the changes in color, texture,.. during storage or processing. Drip losses are clearly reduced when birds receive an organic selenium source compared to a mineral one.
Q: Oxidative impaires male fertility .. What about female ?
Indeed, the spermatozoids are clearly affected by oxidation. But ovocytes and particularly their membrane is also rich in polyunsaturated fats and prone to oxidation. Most parameters linked to egg production such as the export of vitellogenin by the hepatocyte toward the ovary is conditioned by membrane phospholipids. Preserving them from oxidation will help to enhance fertility. Hatchability is also clearly affected by oxidative stress situations and can be restored by using the right antioxidant solution.
Q: You said free radicals are used as weapons against bacteria, play a role of messenger: what about (too) high antioxidant intake?
Indeed, you're right. Free radicals are normal elements in the metabolism that help our body to get rid of xenobiotics. Antioxidant have to be balanced and an excess of one will not compensate for a deficiency of another and might event counteract the benefits of their nature. Proposing a balanced of efficient antioxidant solutions is thus key to improve animal performance under challenging conditions.
Q: Is oxidative stress affecting fertility ?
yes indeed, hot conditions and ageing are good examples of oxidative stress that affect fertility. An optimal balance of antioxidants has long been shown to improve fertility in a wide range of animal species including human.
Q: Is oxidized fat in the diet a source of oxidative stress?
Yes, oxidized fat can induce some toxicity depending the level and thus increase oxidative stress to the animal. It has long been worked at, but nowadays it is sometimes difficult to link the actual used index (iodine, …) to the decreased performance. However, lipid peroxydes have clearly a negative effect on sensitive molecules to oxidation. Antioxidant systems can help to alleviate those negative effects, particularly the selenoprotein Glutathione peroxidase 2 have been demonstrated to detoxify different lipid peroxides.