Gemara

Yevamos 11b (Mishnah): If one widow was Kesherah and the other Pesulah, he does Chalitzah with the Pesulah or Yibum with the Kesherah.

Question: What do Kesherah and Pesulah mean?

They cannot mean permitted and forbidden to all (Kohanim). Since she is permitted to the Yavam (a Yisrael), it makes no difference to him!

Answer #1: Rather, they mean permitted and forbidden to the dead brother. He was Machazir Gerushaso, and the Mishnah permits Yibum with the Tzarah!

Rejection (and Answer #2): Really, they mean permitted and forbidden to Kohanim. Even though it makes no difference to the Yavam, Rav Yosef derived from our Mishnah that one should not spill out water that others could use. (Chalitzah to the Kesherah would forbid her to Kohanim.)

Avodah Zarah 30b (Beraisa): A person may not give exposed water to his or another's animal.

Contradiction (Beraisa): He may give it his own animal to drink.

Answer: He may give it to his own cat (the venom will not kill it).

He may not give it to another's cat, lest it weaken the cat. Even though it will return to health, perhaps the owner needs to sell it now, and no one will buy it.

Chulin 7b: R. Pinchas ben Ya'ir was about to accept Rebbi's offer to host him, but he saw white mules in Rebbi's premises. R. Pinchas said that he cannot eat by someone who keeps damagers in his home.

Rebbi offered to sell them, make them Hefker, cut off their hooves, or kill them. R. Pinchas said that these are forbidden due to Lifnei Iver, causing even more damage, pain to animals, and Bal Tashchis, respectively.

88b (Beraisa): If a man in the desert or on a ship has no dirt, he may grind up a gold coin or burn a garment to cover the blood with the fragments or ashes.

Rishonim

Rif and Rosh (Yevamos 15a and 4:29): If one widow was Kesherah and the other Pesulah, he does Chalitzah with the Pesulah or Yibum with the Kesherah. Our Mishnah teaches that one should not spill out water that others could use.

Rif and Rosh (Chulin 29b and 6:10): If one is in the desert or on a ship and has no dirt, he may grind up a gold coin or burn a garment to use for Kisuy.

Rif and Rosh (Avodah Zarah 10b and 2:13 (Hilchos Giluy)): A person may not give exposed water to his or another's animal.

Rambam (Hilchos Yibum 1:10): If some Yevamos were Kesherim to Kehunah and some were Pesulim, if he does Chalitzah he does so with a Pesulah, to avoid disqualifying a Kesherah to Kohanim.

Rambam (Hilchos Melachim 6:10): One transgresses Lo Tashchis not only for trees. It applies also to one who breaks Kelim, tears clothing, destroys buildings, plugs up springs, or destructively wastes food. He is lashed only mid'Rabanan.

Rambam (Hilchos Rotze'ach 11:15): One may not give exposed water to his or another's animal. One may give it to a cat.

Kesef Mishneh: Even though it weakens the cat temporarily, the Rambam permits even to another's cat because nowadays people do not sell cats.

Rambam (Hilchos Shechitah 1:24): One who will slaughter many animals must check the knife after every Shechitah. If he checked only at the end and the knife was found to be Pasul, they are all Safek Neveilos.

Magid Mishneh: The Rambam advises checking after every Shechitah, but one may opt to delay checking until the end. The Rashba calls this improper, lest the knife be found to be Pasul and he transgressed Bal Tashchis.

Poskim

Shulchan Aruch (EH 161:2): If some Yevamos were Kesherim to Kehunah, if he does Chalitzah he does so with a Pesulah, not with a Kesherah.

Beis Yosef (DH Hayu): R. Yerucham says that we warn him to do Chalitzah with a Pesulah. If he transgresses we excommunicate him, or lash him if he was warned for lashes.

Be'er Heitev (2): Keneses ha'Gedolah says that we do not force him. It is merely good counsel.

Shulchan Aruch (YD 28:21): One who does not have dirt to cover the blood should not slaughter.

Rema: Rather, he should wait until he has dirt. If he is in the Midbar or on a boat and the bird is worth less than the garment he would burn for the gold coin he would grind up, Chachamim enacted that he may slaughter and absorb the blood in a garment or shoe and bless. When he reaches a place where there is dirt, he launders the garment or shoe so the blood comes out and covers it without a Berachah. This is the custom.

Rebuttal (Beis Yosef DH Kosav Od): The Mordechai cites Ge'onim who give this Heter for one who prefers his garment or coin to the bird. This is astounding. If it is permitted, this is better than destroying his garment or coin, which entails Bal Tashchis! Also, he cannot bless if he does not cover the blood in dirt!

Defense (Darchei Moshe): If the bird is worth more and he has no alternative, it is not Bal Tashchis. The Gemara (Bava Kama 91b) permits to cut a fruit tree whose wood is valuable for building. One may bless on absorbing the blood, for it is the beginning of Kisuy.

Rebuttal (Taz): The Ge'onim cannot enact to be lenient when the Gemara was stringent!

Shach (29): We may rely on Poskim who bring the Heter, i.e. the Or Zaru'a and Ra'avan.

Question (Gilyon Maharsha): The Magen Avraham (OC 13:8) permits wearing a four-cornered garment without Tzitzis on Shabbos. The Taz (13:5) permits whenever he cannot put Tzitzis on it, even during the week. (If so, one should be allowed to slaughter without covering if it is forbidden due to Bal Tashchis!)

Pischei Teshuvah (10, citing Noda bi'Yehudah 2 YD 10): Hunting for fun is not Tza'ar Ba'alei Chayim, because the animal dies. Any need of man is not Bal Tashchis; he benefits from the skin. Also, it is not done wastefully. Also, Bal Tashchis primarily applies to something that man can benefit from. There is no loss to man if one hunts wild animals. However, it is a lowly Midah of cruelty. Also, one may not endanger oneself; this arouses mention of his sins.

Mishnah Berurah (15:3): One may remove Tzitzis from a garment and attach nicer strings. Some Acharonim say that if the old strings are intact and Kosher to be put on another garment, one should untie them and not cut them. Chachamim taught that one should not spill out water that others could use. The Chayei Adam permits cutting them if he finds it burdensome to untie them. It is not Bal Tashchis because it is not done wastefully.

Shulchan Aruch (YD 116): Nowadays we are not concerned if water was exposed.

Beis Yosef (YD 116:1 DH Mashkim): (When Giluy was a concern) it was Bal Tashchis to give it to a Tamei animal. One could give to cats; since the cat will return to health, it is not Bal Tashchis.