Olive oil contains a variety of antioxidants, including vitamin E. Its consumption protects against oxidative stress, which is involved in many pathological conditions, affecting animals’ development and their general welfare. The present study aimed to investigate the effect of olive paste flour (OPF) on the antioxidant status and performance of broiler chickens raised in field conditions. Total of 18.000 broilers was randomly allocated in equal numbers in two poultry houses. The chickens were grouped according to their diet as follows: Control group: chickens fed commercial poultry feed, and OPF group: chickens fed control dietsin the starter period, but they got a supplement of OPF in grower, and finisher 1 and 2periods, respectively. The birds were raised under identical field conditions (ventilation, vaccination, lighting, etc.). Antioxidant status was assessed by measuring the concentration of vitamin E in plasma, as well as the total antioxidant capacity (TAC) in plasma and muscle tissue. According to the statistical analysis of the results, the addition of OPF to chickens’ diet significantly enhanced plasma α-tocopherol concentration (p≤0.05). TAC did not show any significant differences in chicken plasma nor muscle tissue(p>0.05).Feed intake (FI) was higher in OPF group, while Body weight (BW) was lower. Liveability was similar for the two groups. The feed conversion ratio (FCR) was higher, and the European production efficiency factor (EPEF) was lower in broilers of the OPF group compared to those of the control group.Samples of roasted breast from chickens of both groups were used for organoleptic characteristics evaluation. Results showed that samples of the OPF group smelled more intensely and were more tasteful than those of the control group.However, other organoleptic characteristics did not differ. In conclusion, the results demonstrated that although the addition of OPF to chickens’ diet can cause growth retardation, it can significantly increase the plasma α-tocopherol concentration. Further studies are needed to optimize the concentration of OPF in poultry feed in order to avoid growth retardation or even to promote growth in broiler chicks.

Naturally occurring antibodies (NAbs), which are major components of innate immunity, exist in circulation under healthy conditions without prior antigenic stimulation and are able to recognize both self- and non-self-constituents. The present study aimed at identifying potential immunological differences between commercial fast- and slow-growth broilers (n = 555) raised in conventional and free-range systems, respectively, through the use of the specificity, isotypes and levels of circulating NAbs. The possible beneficial effect of oregano-based dietary supplementation was also evaluated. To this end, serum IgM and IgY NAbs against self- (actin and DNA) and non-self- antigens (trinitrophenol and lipopolysaccharide) were measured by ELISA and further correlated with genotype, season and performance. Significantly higher levels of IgM NAbs against all antigens were found in slow-growth compared to fast-growth broilers. IgM NAb levels were also significantly increased in dietarily supplemented slow-growth broilers versus those consuming standard feed. Moreover, significantly elevated levels of anti-DNA IgY NAbs were found in fast-growth compared to slow-growth broilers, whereas the opposite was observed for anti-LPS IgY NAbs. Multivariate linear regression analysis confirmed multiple interactions between NAb levels, genotype, season and performance. Overall, serum NAbs have proven to be valuable innovative immunotools in the poultry industry, efficiently differentiating fast-growing versus slow-growing broilers, and dietary supplementation of plant extracts can enhance natural immunity.

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