Why does the Torah see fit to insert "Lo Yevaker ... "?
Rashi: Because with regard to other Korbanos, one should pick the best of one's flock, 1 the Torah needs to teach us that this does not apply to Ma'aser Behemah, and that, should the tenth animal turn out to be a Ba'al-Mum, one is not permitted to swap it for a Behemah without a Mum. 2
What do we learn from "Lo Yiga'el"?
Moshav Zekenim (30) #1: If Ma'aser Behemah got a Mum, it is not redeemed like a Shelamim. The money does not get Kedushah (even so, the owner eats it like Chulin).
Moshav Zekenim (30) #2: It may not be sold. We learn from Cherem, about which it says "Lo Yimacher v'Lo Yiga'el" (verse 28).
Moshav Zekenim #3: Even if it got a Mum and he redeemed it, it is not Chulin to shear or work it. We learn from Bechor, about which it says "Lo Sifdeh." All other Kodshim that became blemished are eaten only after Pidyon.