Abstract
The aim of the present study was to determine the effect of rearing technology (rearing system and dietary supplementation with a mixed herbal extract) on the production results, selected physiological and blood parameters, and welfare of broiler chickens during the summer production cycle. In the CON and HE groups, broiler chickens were kept on litter without access to free range; additionally, in the HE group, birds from 22 to 42 days of rearing received a mixed herbal extract (50% Melissa officinalis L. and 50% Urtica dioica L.) in the amount of 2 ml/l of water to drinkers with water. In the AP group, birds were reared on litter with access to pasture. During the experiment, production performance and body temperature of the birds were monitored. Blood was also taken from birds in each group and the H:L ratio, levels of corticosterone, glucose and thyroid hormones were determined. The application of 2 ml/l of mixed herbal extract to the drinking water did not improve the production results, nor did it affect the physiological indices of the birds studied. The addition of 2 ml/l of mixed herbal extract to the drinking water only resulted in lower corticosterone levels in the blood of the chickens on day 35 of the experiment. The free-range housing system had a negative effect on the slaughter performance of the broiler chickens. However, housing with access to the free range resulted in lower body temperature, lower mortality, as well as lower glucose, corticosterone and a narrower H:L ratio in the blood of the chickens during the period of increasing air temperature. It can therefore be concluded that housing with access to a free range reduces stress levels and thus improves the welfare of broiler chickens during the summer production cycle compared to confined housing. Comparing the rearing technologies used in the study, it was found that the free-range housing system contributed more to improving the comfort of broiler chickens during the summer than dietary supplementation with the tested herbal mixture extract.