The present study was designed to observe the periodicity of oocyst shedding, the ratio of administered oocysts with the oocysts found in the faeces or intestinal contents of infected birds and effect of artificially induced coccidiosis at different ages on weight gain, FCR, OPG count, mortality and lesion scores. For this purpose 84 day-old chicks were purchased from the market and vaccinated against NDV on day 1 and 21 (Mukteswar strain). The birds were divided into 4 groups i.e. A, B, C and D comprising oC 21 birds each. Group A was kept as non-infected control. Virulent Elmeria en at a dose rate of 50,000 sporulated oocysts/bird was given to group B, C and D on day 15, 25 and 35 of age, respectively.
There was no oocyst excretion in faeces of birds in group A. OPG of faeces in group B was higher than in groups C and 1). rFIe OPO of faeces reached the peak on 6th day post-infection in infected groups, but group D again obtained the peak on 17th day postinfection. The highest caecal oocyst counts were observed in group B than C and 1) groups. It was observed that the recovery of the number of oocysts in purified isolates was 58.74%, 50.05% and 26.87% in B, C and D, respectively as compared to OPG counts. It was also noted that the caecal output of oocyst counts was always lower than the total OPG counts per chick during the period of infection in different groups.
Group A showed the highest weight gain (2155 gms) than the infected groups B (1985 grns), C (1930 gms) and D (1978 grns). Feed conversion ratio in groups A, B, C and D was significantly different showing the values as 1.62, 2.26, 1.89 and 1.82, respectively. Group A being uninfected gave the best FCR followed by the birds in groups D and C. While birds in group B gave the poorest values, it was observed that the weight of faeces per chick was almost equal in groups C (163 gms) and D (166.5 gms), but was significantly lower in B (123.5 gms). However, the highest OPG counts occured in group B and the number of oocysts acquired were the best in this group.
The highest mortality was observed in group B (28%) followed by group D (14%) and group C (10%), while no mortality was recorded in group A.