Physiological responses of chicken gut tissue to coccidial infection: comparative effects of Eimeria acervulina and Eimeria mitis on mucosal mass, carotenoid content, and brush border enzyme activity.

Broiler chicks, 3 to 4 wk of age, were inoculated with either Eimeria acervulina or E. mitis, and mucosal dry weights, brush border enzyme activities, and carotenoid contents as well as plasma carotenoid levels were measured at 3, 5, and 7 days postinoculation (PI). At 5 and 7 days PI mucosal dry weights, brush border enzyme activities, and carotenoid contents were significantly decreased at primary sites of infection (duodenum, E. acervulina; lower small intestine, E. mitis). In contrast, at sites remote from infection, mucosal dry weights and brush border enzyme activities were significantly increased above control values. However, mucosal carotenoid contents were significantly decreased. Between 5 and 7 days PI mucosal renewal as signalled by increases in dry weight was accompanied by increases in brush border enzyme activities. However, mucosal carotenoid contents were further decreased. High correlations were found between plasma carotenoid levels and total mucosal carotenoids in control and coccidia-infected chicks, but not in 48-h-starved chicks. Infection with coccidia increased this correlation, and the increase with E. acervulina infection was significant. These data indicate that hyperplastic and renewing mucosal tissue is defective in absorbing carotenoids, and further, that there is no direct relationship between mucosal carotenoid content and brush border enzyme activities. Apparently carotenoids are not mobilized from body depots during the first week of coccidial infections as they are during 48-h starvation.