Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/1998
Publication Date: N/A
Interpretive Summary: Coccidiosis is a protozoan disease that costs the U.S. poultry industry in excess of $300 million annually. Control of coccidiosis is primarily through the use of anticoccidial drugs. However, with the rise in drug resistance shown by the coccidia, new methods for control are becoming of increased importance. One method is the use of feed additives. In the field, betaine, a product of sugar beets, was shown to alleviate the weight loss, poor feed efficiency, and intestinal pathology in chickens infected with coccidia. The current studies indicated that nutrient uptake and the integrity of the intestinal cells were apparently enhanced by dietary betaine. Absorption of methionine was significantly enhanced in chicks fed a diet containing betaine as compared with absorption in chicks fed a control diet, and, except in studies using a drug-sensitive isolate of coccidia, was not further enhanced by the addition of the anticoccidial drug, salinomycin. In addition, betaine apparently supported the water balance of intestinal cells through osmolytic activities, allowing the cells to remain metabolically active in the face of osmotic stress produced by the coccidia. Collectively, the data indicate that betaine enhances the growth performance of coccidia-infected chicks through direct activity against the parasite and indirectly, by support of the physiology of the chick.
Technical Abstract: The effect of betaine on survival, invasion, and development of 2 species of avian coccidia, Eimeria tenella and E. acervulina, was examined in vivo and in vitro. Betaine had little direct effect on the parasite because incubation of the sporozoites in concentrations of betaine of up to 1.7 M for 45 min failed to inhibit their invasion of cells. Moreover, cultured cells inoculated with E. tenella and maintained in concentrations of betaine of up to 214 mM (the level of toxicity for the cells) supported development as efficiently as control cultures. Conversely, invasion in chickens given feed containing 1.5 to 3 lb/ton of betaine was significantly lower (50 to 90 %) than invasion in birds not given betaine in the feed. Addition of the anticoccidial drug, salinomycin, at 60 ppm, did not further reduce invasion. Except for a slight decrease in development by E. acervulina, neither betaine alone nor betaine plus salinomycin had a marked deffect on development by the avian coccidia. Electron microscopy showed ultrastructural changes in the host cells and parasites in birds fed betaine. The data suggest that inhibition of invasion plus other physiologic properties of betaine contribute to the protection against avian coccidiosis.