The present invention relates generally to the use of cysteamine or a cysteamine-containing composition for (I) increasing the yield and/or quality of eggs produced by fowls, (ii) preferentially promoting growth rate of female fowls over male fowls and/or (iii) preferentially promoting development of breast muscles of fowls over development of muscles other than the breast muscles. The invention also relates to a method and a cysteamine-containing feed of raising fowls, and a method of preparing such feed.
