Changes in the oxidative status of dual-purpose hens rearing in the free-range system during cold, thermoneutral and hot period

This trial studied the influence of environmental conditions (cold, thermoneutral and hot period) on oxidative status of different genotypes free-range laying hens and the effect of oxidative stress (OS) on their egg productive performance. In the experiment, carried with a two-year replication, were used six dual-purpose chicken genotypes with different origins. For determination of the oxidative status were measured the levels of lipid peroxidation (LPO), total glutathione (tGSH) and the activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPX). The highest egg production for all chicken genotypes was reported during the thermoneutral period. Biochemical parameters LPO and CAT were relatively more sensitive to environmental impact while the remaining (tGSH, SOD, GPX) exhibited a higher degree of stability. The lowest values of LPO for all genotypes were proved during the thermoneutral period. The cold period was most unfavorable – LPO values are elevated for all genotypes. The SOD and GPX values were higher during the cold and the hot periods compared to the thermoneutral. The results of analysis of variance showed that the factor “temperature period” compared to “year” and “genotype” had the most significant influence on all biochemical parameters (P<0.001). Significant phenotypic correlations (P<0.05) were detected among all biochemical parameters, except for correlation between SOD and tGSH. The chicken genotypes showed differences in their susceptibility to OS. Thermal stress (either cold or heat) affected adversely the oxidative status of hens because it induces OS and can play a significant role in determining chicken welfare and egg production.