Doesn't anyone ask concerning an animal for offering, that requires confinement, starvation, and deprivation of water, how there isn't a more humane remedy?
1) We pasken that to cause suffering to animals is a Torah prohibition (see Shulchan Aruch Choshen Mishpat 272:9 in Rema and SM'A #15).
2) In addition one learns from Tosfos Sanhedrin (top 80a) that the suffering caused to an animal by starving to death is worse than if it would have been killed by one blow.
3) However the problem here is that there is a Torah prohibition of making a blemish in holy animals (see Rambam Hilchot Isurei Mizbeach 1:7). Therefore doing a positive action to deface an animal that was set aside as an offering is considered worse than the passive action of leaving it to starve to death (see Gemara Avoda Zara top 13b). It follows that whilst starving an animal to death is generally speaking a Torah prohibiton, nevertheless in this extreme case this is preferable to actively defacing the korban.
I'm not understanding, but the Gemara we're discussing is one I'd never seen.
An animal that is put to pasture, until a blemish should arise, due to its age, is also dispensed with by passive inaction. Isn't this the remedy for other animals that had been sanctified, and not sacrificed?
Shouldn't it fulfill both the necessity for humane treatment of the animal, and respect for it's sanctification, as it does in other cases?
Sometimes, where the animal could still be offered as a sacrifice, it is not possible to put it out to pasture because the owners might be tempted to bring it as a sacrifice (see Gemara Yoma 66a and Rashi DH Hach).