Vol. 9, Special Issue 4, Part F (2025)

Haematological parameters are important indicators of physiological health, immune function, and disease resistance in poultry. Pesticide affecting mitochondrial function, can induce toxic effects on the haematopoietic system and compromise overall productivity. Tolfenpyrad, a Mitochondrial Electron Transport Inhibitor (METI) pesticide, has been reported to disrupt oxidative balance leading to haematological changes in mammals. Its use is widespread in agriculture, and horticulture. But studies on its toxic effects in chickens have not yet been conducted. The aim of the study was to assess the haematological parameters among hens and roosters. Hens and roosters (18 each) of same hatch and aged 25 weeks were divided into one control and two treatment groups (n=6 in each group). The birds were exposed to 1/20^th LD₅₀ (Male Treatment 1, Female Treatment 1,) and 1/40^th LD₅₀ (Male Treatment 2, Female Treatment 2) doses of Tolfenpyrad over a period of 8 weeks by oral gavage to crops. Total erythrocyte count (TEC), total leukocyte count (TLC), haemoglobin concentration (Hb), packed cell volume (PCV), mean red blood cell volume (MCV), mean haemoglobin quantity and concentration (MCH and MCHC), differential leukocyte count (DLC), and platelet count were estimated at the beginning (0^th week), 4^th week and 8th week of trial. Results indicated effects dependent om the sex of the birds, with roosters showing significant increases in TEC, Hb, and PCV while hens were not affected. Signs of extramedullary haematopoiesis were seen during histopathological evaluation of sections of spleen in roosters exposed to Tolfenpyrad. These findings point to the potential risks of Tolfenpyrad exposure in chickens, and a need for monitoring and controlled use of Tolfenpyrad in areas near poultry farms and in environments frequently visited by birds.