Determination of the effects of aflatoxin B₁ given in ovo on the proximal tibial growth plate of broiler chickens: histological, histometric and immunohistochemical findings

Detrimental effects of aflatoxin B₁ (AFB₁) on the embryonic development of broiler tibia and its proximal growth plate were determined by means of histological, histometric and immunohistochemical methods. For this, 420 fertile eggs from parent stocks of Ross 308 broiler chickens were divided into five groups according to the proposed treatment: a control untreated group, a group injected with 30% ethanol and three further groups to be injected with 5_, 15 or 40 ng AFB₁. The eggs were injected into the air space prior to incubation. Five eggs from each group were opened at 9, 11, 13, 17, 19 and 21 days of incubation and tibial tissue samples were removed, dissected of muscle and connective tissues, and processed by means of routine histological techniques. The cell proliferation rate of the epiphyseal growth plate cells was determined by immunohistochemical assay of proliferating cell nuclear antigen (PCNA) expression. The results showed that both proliferative and hypertrophic zones narrowed significantly (P<0.05), when compared with the controls, in all of the AFB₁-treated groups whereas the transitional zone thickened, especially in the group given 40 ng AFB₁ group. The PCNA positivity indices of 15 and 40 ng AFB₁-treated groups were significantly higher (P<0.05) on days 11, 13, 17, 19 and 21 of incubation. It was concluded that in ovo-administered AFB₁ adversely affected embryonic development of the tibial growth plate, and that affected hatched broilers might also be more susceptible to skeletal disorders during growth.