Effects of subclinical Eimeria tenella infection on Pectoralis major muscle in broiler chickens

The aim of this study was to evaluate changes in the histological characteristics of the pectoralis major (PM) muscle in chickens as well as histological changes in the caecum after a low dose of Eimeria tenella (E. tenella). The chickens were inoculated orally with 5 × 10 2 E. tenella oocysts (Gr1) and 1 × 10 3 E. tenella oocysts (Gr2) at 16 days of age. Six chickens from each group were sacrificed for post mortem examination at 9 days post-infection (pi) and 16 days pi. Chicken growth was not affected by infection. On the 9th day of infection, caecal villus height was significantly greater in the non-infected control group. However, infected chickens from group Gr1 sacrificed seven days later had an even greater caecal villus height than those of the control (p =.001). Both infected groups had higher PM weights at 16 days pi than did the control group (p = .001). The fibre cross-sectional area was smaller in Gr2 at 9 days pi; however, this parameter was larger in these chickens at 16 days pi. The pH value of PM of group Gr2 was significantly higher than that of the control group or group Gr1 at 16 days pi (p = .020).