Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2000
Publication Date: N/A
Interpretive Summary: Coccidiosis causes significant economic losses in the poultry industry by reducing weight gains and feed efficiency. The conventional treatment for coccidiosis involves the use of chemicals applied as feed additives. However, drug resistance has become widespread reducing the efficacy of chemotherapy. Recently the use of attenuated live the vaccines coupled with hchemotherapy has been effective in reducing losses due to coccidia. It is clear that effective control in the future will be by a combination of chemotherapy and vaccine tailored to the particular needs of the producer. In order to effectively implement these strategies producers will need new methods to evaluate the impact of coccidiosis on poultry growth. The current research address this issue by determining the mechanisms associated with muscle loss during coccidia infection in broiler chickens. A method was developed to measure an amino acid in muscle plasma and excreta of coccidia infected chickens that was indicative of breast muscle breakdown. These results indicated muscle breakdown was correlated with intensity and duration of infection. This method may form the basis for assessing impact of coccidiosis during poultry production.
Technical Abstract: To assess muscle breakdown during avian coccidiosis, the level of the non- metabolizable amino acid 3-methylhistidine (3MH) was determined in muscle, plasma and excreta from chickens infected with Eimeria acervulina. The changes in 3MH levels during infection were assessed at 1-29 days post inoculation (DPI) in animals given 5 x 105 oocysts per bird. The effect of levels of parasitism were evaluated at 8 DPI in birds receiving 5 x 103, 5 x 104, 5 x 105 or 1 x 106 oocysts each. The 3MH levels of plasma, muscle and excreta samples were determined by high pressure liquid chromatography after derivatization with fluorescamine. Weight gains, breast muscle weight, eviscerated weight, plasma carotenoid levels, dry weight of muscle and gross lesion scores were also determined. Infected birds had significantly elevated plasma and muscle 3MH at 4 and 8 DPI following a single dose of E. acervulina. The increase in 3MH levels had an inverse relationship with the time course of weight gain and plasma carotenoid levels. Plasma and muscle 3MH levels returned to control values by 15 DPI and remained unchanged from control values through remainder of experiment (29 DPI). Breast weight was decreased in infected birds but the ratio of breast weight to eviscerated body weight was unchanged. Excretion of 3MH decreased relative to controls at 4 and 8 DPI and returned to control levels on 15 DPI. The plasma and muscle levels of 3MH were related to severity of infection, however levels of excreted 3MH were not. The results suggest that muscle breakdown, as assessed by plasma and muscle levels of 3MH, increases during the acute stage of E. acervulina infection.