I think this is a bad translation from English, that is now being translated back to English, where the crop was originally translated to corta instead of estomago or any other equivalent.
The crop is the part of the cow's digestive organs that secretes the rennet - for the cud process (food re-chewing). Those stomach liquids, preferably of the calf (hence newborn) are also used for the production of dairy foods such as yellow cheese.