Do not redeem the firstborn of a kosher animal.
“The firstborn ox …. you shall not redeem” Bemidbar 18:17
At this time when the Temple does not exist it is permissible to sell it and the buyer must treat it with the holiness of the firstborn animal.
The firstborn that has a disfiguring defect can be sold whether it is alive or ritually slaughtered, provided it is not sold in the meat market.
This applies for man and women.