Effects of different levels of oocyst inocula of Eimeria acervulina, E. tenella, and E. maxima on plasma constituents, packed cell volume, lesion scores, and performance in chickens.

The effects of different levels of oocyst inocula of Eimeria acervulina, E. tenella, or E. maxima on plasma carotenoids, total plasma lipids, total plasma proteins, packed cell volume (PCV), bird performance, and coccidial lesion scores were determined in male Hubbard chickens. Each test consisted of an uninfected treatment and either four levels (E. tenella and E. maxima) or five levels (E. acervulina) of inocula. Carotenoids and lipids were significantly (P < or = 0.05) depressed by E. acervulina starting at 10(2) oocysts per bird, whereas 10(4) and higher inoculum levels significantly depressed plasma protein. Carotenoids and lipids were significantly depressed by E. tenella beginning at 10(4) oocysts per bird, whereas 10(2) oocysts per bird and greater levels significantly depressed plasma protein. E. maxima significantly depressed carotenoids and lipids beginning at 6.7 x 10(2) oocysts per bird and plasma protein at 6.7 x 10(4) oocysts per bird. PCV was depressed by E. acervulina and E. tenella starting at 10(4) oocysts per bird but was not affected by E. maxima. Weight gain was significantly depressed by E. acervulina beginning at 10(5) oocysts per bird, by E. tenella at 10(4) oocysts per bird, and by E. maxima at 6.7 x 10(4) oocysts per bird. Coefficients of determination (R2) were highest for carotenoids (0.96-0.99), followed by lipids (0.93-0.96), weight gain (0.89-0.91), feed:weight gain ratio (0.89-0.91), and protein and PCV (0.65-0.92). Results demonstrated that plasma carotenoids and lipids were excellent response variables for measuring the effects on broiler chickens of each of the Eimeria spp. tested.