+ Positive Mitzvah
Sanctify the first born male that opens the womb
“Sanctify to me every firstborn, the first issue of every womb amongst the children of Israel, man and beast” Shmos 13:2
It is a mitzvah to sanctify the first kosher animal and say “Behold this is holy”.
As it says “You shall sanctify to the Lord your God” Devarim 15:19
Even if you do not consecrate it, it is inherently sanctified.
In present times the first born should graze until it develops a blemish and then belongs to the Kohen.
Applicable for men and women.