Serotonin and dopamine levels in plasma and tissues of pheasants in comparison to chickens

The growing global demand for meat products requires optimisation of poultry farming practices to ensure efficient production and animal welfare. Neurotransmitters such as serotonin and dopamine are key indicators of physiological and environmental stress in birds. Although the levels of both neurotransmitters in broilers are reported in scientific literature, such information for pheasants (Phasianus colchicus) is scarce. Therefore, the current study aimed to investigate their concentrations in plasma, brain tissue, and jejunum of healthy pheasants (n=6) and broilers (n=6) using LC-MS/MS analysis. The effect of using heparinised versus non-heparinised (conventional method) needles on the levels of the investigated neurotransmitters in thrombocyte-rich plasma was evaluated. Higher plasma concentrations of serotonin (497.83 ng/mL and 103.5 ng/mL) and dopamine (1.30 ng/mL and 0.51 ng/mL) were obtained by the conventional method in broilers compared to pheasants (P<0.05). In broilers, the plasma levels of both neurotransmitters were higher when blood was collected by the conventional method vs using a heparinised needle: 497.83 ng/mL and 39.32 ng/mL for serotonin, and 1.30 ng/mL and 0.553 ng/mL for dopamine, respectively. A similar difference was observed for plasma serotonin in pheasants: 103.5 ng/mL and 29.51 ng/mL. Significantly higher serotonin concentrations were observed in the cerebrum (45.61 ng/mL) and the jejunum (785.91 ng/mL) of broilers than in respective tissues of pheasants – 8.18 ng/mL and 461.36 ng/mL, respectively. Dopamine levels were significantly higher in the jejunum of broilers (131.73 ng/mL) compared to those of pheasants (2.88 ng/mL). These findings highlight the importance of the blood sampling method for obtaining thrombocyte-rich plasma and reveal species-specific differences in serotonin and dopamine levels between the two Galliformes species.