Circulating growth hormone and prolactin concentrations in turkeys and chickens infected with Histomonas meleagridis

1. Histomonas meleagridis was inoculated into young chickens and turkeys and the effect of the infection (blackhead) on circulating growth hormone (GH) and prolactin concentrations determined. 2. During the course of the infection in turkeys there was a marked increase in plasma GH concentration which correlated with the severity of the disease, as judged by liver and caecal characteristics. The infection was less severe in chickens and no correlation between plasma GH and the degree of infection was observed. 3. The concentration of plasma prolactin was increased in the chicken, but not in the turkey, during the invasive period of infection.