The effect of mixed herb extract on selected stress parameters in broiler chickens of three genetic lines

The aim of the study was to determine the effect of adding a mixture of anti-stress herbs to drinking water on stress hormone levels and the heterophil to lymphocyte ratio in the blood of intensively reared broiler chickens of three genetic lines. The experiment was performed with ‘Ross 308’, ‘Cobb 500’ and ‘Hubbard Flex’ broiler chickens, which were divided into three experimental groups. Birds were maintained on litter for 42 days at a stocking density less than 33 kg/m2. All the groups were provided with the same environmental and feeding conditions. In each group from 21 to 35 days of rearing, water drinkers were supplemented for 5 h/day (08:00–13:00 hours) with an alcoholic extract from mixed herbs (30% chamomile, 10% oregano, 10% yarrow, 10% knotgrass, 10% valerian, 20% inflorescence of large-leaved lime) at 2 ml/l water. At 21, 28, 35 and 42 days of rearing, blood was collected from 10 birds per group to determine corticosterone, noradrenaline and adrenaline levels. The heterophil to lymphocyte ratio (H:L) was also calculated. On day 42 of the study, 500 broiler chickens were characterised by the lowest noradrenaline concentration and a lower H:L ratio compared to ‘Ross 308’ and ‘Hubbard Flex’ (p ≤ 0.05) and ‘Ross 308’ chickens (p ≤ 0.01), respectively. It was concluded from the study that the herb extract had the most favourable effect on relieving the body’s physiological response to stress, and thus on improving welfare in ‘Cobb 500’ compared to ‘Ross 308’ and ‘Hubbard Flex’ broilers. It can therefore be considered that active substances in herbs have varying effects on the body of broiler chickens of different origin.