2,596. An Invalid Shechita v'Es B'no

Hilchos Shechita 12:3

The prohibition against slaughtering an animal and its young only applies to shechita, as per Leviticus 22:28, “Do not slaughter…,” from which we see that the prohibition is to slaughter both of them. If someone decapitated the first animal, or if he botched the first slaughter and made the animal a neveila, it is permitted to slaughter the second. Similarly, if someone slaughtered the first and decapitated the second or made it a neveila, he is not liable to lashes.

Hilchos Shechita 12:4

If a person with congenital deafness, someone lacking full intellectual faculties, or a minor slaughtered the first animal unsupervised, it is permitted to slaughter the second animal because the first slaughter was not halachically valid.