Comparative study on experimental coccidiosis of Ross and Cobb broilers by quantitation of plasma carotenoids

Coccidiosis is one of the important parasitic disease in birds and animal farms which is caused by eimeria species protozoans.it has worldwide spread and infects a lot of bird species especially commercial birds.disease has clinical and sub-clinical form.moreover than direct losses like increasing of mortality,poor growth rate,decrease of carcass  quality and losses of flock uniformity,the costs of producing new anticoccidiosis vaccines and drugs,make numerous charges on poultry industry annually.comparison between two breeds of Cobb and Ross in the face of parasitical challenge by quantitation of plasma carotenoids is aim of this study.in this study 100 one day broiler chickens of two breeds of Ross and Cobb (each breed 50 chicks) divided into four groups of 25 chickens randomly and kept the same conditions.in the 21 th day of breeding.one group of each breed was callenged by 50000 spourulated eimeria oocysts of 4 main species.after challenging ,blood sample were taken from all groups.after separation of plasma from all samples,plasma carotenoids were measured by spectrophotometric method.according to the results,plasma carotenoids of challenge chickens were decreased comparing with control group significantly(p<0.01).in comparison between Cobb and Ross groups,we had a lower level of plasma carotenoids in Ross chickens that this difference was significantly(p<0.01).it seems that chickens of Cobb strain have lower intestinal damages in same condition of coccidial infection in comparison with strain.