Bechorot 41 - Blemishes Not Severe Enough
Certain blemishes of a firstborn male animal are enough to disqualify it from a sacrifice, but are not severe enough to allow to slaughter it outside the Temple. Their owner is left with no alternative but to wait, either until the animal develops a full-fledged blemish, or until the disqualifying condition leaves. These are: white flecks or water in the eye that are not permanent; back gums that were notched but not uprooted; an animal that has a wart or a boil, one that is old, sick, or foul-smelling; an animal which was a passive or active participant in bestiality; one that killed a person, but according to the testimony of only one witness - which prevents it from being a sacrifice but does not allow the court to execute it.
An animal whose genitals are covered with skin so that its gender it unclear, or one with both sets of genitals cannot be slaughtered anywhere, because that is another not-so-severe blemish. Rabbi Ismael considers the second set of genitals a blemish which permits to slaughter the animal. Another opinion considers such an animal a separate species to whom the laws of firstborn don't apply at all.
Art: Richard Ansdell - The Sick Lamb