New Revised Standard Version
A firstling of animals, however, which as a firstling belongs to the LORD, cannot be consecrated by anyone; whether ox or sheep, it is the LORD’s.

Contemporary English Version
All first-born animals of your flocks and herds are already mine, and so you cannot promise any of them to me.

New American Bible
Note that a firstborn animal, which as such already belongs to the LORD, may not be dedicated. Whether an ox or a sheep, it is the LORD’s.

Douay-Rheims Bible
The firstborn, which belong to the Lord, no man may sanctify and vow: whether it be bullock, or sheep, they are the Lord's.

The firstborn, which belong to the Lord, no man may sanctify and vow: whether it be bullock, or sheep, they are the Lord's.

the firstling [heb] first born, etc.

which

Exodus 13:2,12,13 Sanctify unto me every firstborn that openeth the womb among the children of Israel, as well of men as of beasts: for they are all mine. . . .

Exodus 22:30 Thou shalt do the same with the firstborn of thy oxen also and sheep: seven days let it be with its dam: the eighth day thou shalt give it to me.

Numbers 18:17 But the firstling of a cow, and of a sheep and of a goat thou shalt not cause to be redeemed, because they are sanctified to the Lord. Their blood only thou shalt pour upon the altar, and their fat thou shalt burn for a most sweet odour to the Lord.

Deuteronomy 15:19 Of the firstlings, that come of thy herds and thy sheep, thou shalt sanctify to the Lord thy God whatsoever is of the male sex. Thou shalt not work with the firstling of a bullock, and thou shalt not shear the firstlings of thy sheep.