Reproductive performance of hens fed field beans and potential relationships to vicine metabolism

Field beans (faba beans, broad beans, horse beans, ackerbohnen, Vicia faba L.) depress weight of eggs when fed to laying hens. Vicine isolated from field beans has been shown to depress egg weight and hatchability when fed in large amounts. The present study was undertaken to determine the effect of using three varieties of field beans, varying in tannin and total vicines content, at 20% in breeder diets on reproductive performance of hens and associated vicine transfer from the diet to the egg. Data on egg production, feed consumption, egg weight, body weight, egg quality, hatchability, and hen blood chemistry were obtained. Direct spectrophotometric and high pressure liquid chromatographic (HPLC) analyses of field beans, egg albumen, and egg yolk were conducted. Performance of the hens was excellent on all production characteristics except that there was a nonsignificant reduction in egg weight, a significant reduction in egg shell thickness for hens fed all three types of field beans, and a highly significant reduction in hatchability of eggs from hens fed one but not the other two sources of field beans. The hatchability effect was not correlated with vicine or tannin content of the field beans and only traces of vicine were transferred to the egg by the hen from the diet. Although larger amounts of vicine depressed hatchability when injected into fertile eggs, the trace amounts found in eggs from feeding field beans did not account for the reduction in hatchability observed in this study. It is possible that the hydrolysis product of vicine, divicine or the analogous product from convicine, isouramil, or both, may be involved in toxicity, because these substances are known to be the cause of a hemolytic anemia in some humans that suffer from favism due to consumption of field beans.