3,013. Exchanging vs. Redeeming
Hilchos Arachin Vacharamin 7:7
Exchanging an animal (temurah) doesn’t apply to animals that were consecrated for Temple upkeep because the Torah only addresses exchanging animals that were consecrated for use as offerings. Accordingly, if someone had two animals – one secular and an another consecrated for Temple upkeep – and he tried to substitute the secular one for the consecrated one or to exchange them, his words would be ineffective. However, if he says, “This animal is in lieu of that animal” or “The sanctity of this animal is transferred to that animal,” then his words are effective [because he’s redeeming the consecrated animal rather than exchanging it]. The first animal reverts to secular status and its sanctity attaches to the second animal.
Hilchos Arachin Vacharamin 7:8
The preferred method that should be employed is that both animals consecrated for Temple upkeep and those consecrated for the altar that become blemished should only be redeemed for their values. If a person acted inappropriately and redeemed them for less than that, they are nevertheless redeemed. This is true even if one redeemed consecrated property worth 100 dinar (a large value) using something that’s only worth a prutah (a small coin). Such property reverts to secular status and one may derive benefit from it. By rabbinic enactment, the property must be appraised and the one redeeming it must make up the difference between what he paid and its actual value.