Fertility, hatchability and malformations in guinea fowl embryos as affected by dietary manganese

1. The effects of feeding diets containing 54 mg, 60 mg, 65 mg or 70 mg manganese/kg to Guinea fowls on fertility, hatchability and the occurrence of malformed embryos were studied. 2. Dietary manganese affected fertility slightly, but significantly affected hatchability and the occurrence of malformed embryos. 3. Hatchability was most significantly depressed at the lowest dietary concentration of manganese, which also caused a highly significant increase in the proportion of malformed embryos. 4. Although increasing manganese to more than 54 mg/kg improved hatchability and reduced embryonic malformations, the increase did not completely eliminate the latter condition.