Li Ching-chuan explains that any antibiotics or sulfanilomide in a chicken need seven to 15 days to be metabolized, and so starting from the 25th day of rearing DaChan Greatwall provides farmers with chemical-free feed for their chickens, ensuring that by the 40th day and their slaughter, all chemicals will be gone from the chicken's system.
李清泉指出，雞隻體內的抗生素與磺胺劑，大約 7 到 15 天內就會代謝殆盡，因此從飼養第 25 天起，大成長城提供給養雞場的飼料就是不添加藥劑的「空白料」，以確保在 40 天宰殺前，體內的藥物已經完全代謝乾淨。