Author
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Augustine, Patricia |
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Submitted to: Prince Agri Products Feed Nutrition Conference
Publication Type: Proceedings Publication Acceptance Date: 4/25/1995 Publication Date: N/A Citation: 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, feed additives, such as betaine, a product of sugar beets, have been shown to alleviate the weight loss, poor feed efficiency, and intestinal pathology in chickens infected with coccidia. Data indicated that betaine was not directly toxic to the parasite. However, when it was included in chicken feed, it significantly interfered with the ability of the parasite to infect the intestinal cells of the birds. Addition of the anticoccidial drug, salinomycin, to the diet containing betaine, did not decrease the infectivity over that produced by betaine, alone, but did decrease the subsequent development of one of the species of coccidia. It is unlikely that the inhibition of parasite invasion and development was sufficient to produce the total effect in field studies. Betaine's other physiological activities such as water retention and enhancement of digestability of nu trients, probably also contribute to the protection against coccidiosis that was observed in the field. 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 effect on development by the avian coccidia. The data suggest that inhibition of invasion plus other physiologic properties of betaine contribute to the protection against avian coccidiosis. |