Joke on me. I heard my dairyman uncle say it seveeral times,
and thought he was saying "beaslings". The colostrum from cows is quite yellow, with extra fat, apparently. I never tasted it. Since it has important antibodies, the calf needs it. I don't remember how many days it lasts, before
the new milk can be sold. Site I found implies that it is three days.
I'll be doubledipped in dogie dung. Colostrum is now peddled as a marvelous health aid. Search for "dairy cows colostrum". One thing about human colostrum, it has strong laxative effect, which helps clear infant intestinal tract of solids baby swallows in utero.