Feeding street animals:
One is not obligated to feed his friends pets or street animals from his own food. [This applies even if the animal is endangered and may die. However, in such a case, one would be obligated to place bodily effort to save the animal, if possible, such as to call a shelter, or give it food of Hefker, and the like.] Nevertheless, it is proper to give a stray dog a small morsel of [even] food [that he owns] in order to emulate Hashem’s ways of mercy. One is to then hit the dog with a stick after throwing it the food in order to discourage it from returning back [and becoming a nuisance]. [Likewise, if one chooses, he may feed other animals as well, and it is considered an act of mercy to do so in a case that the animal is endangered. This however only applies if the dog or animal is not a danger to the public, and does not bark or attack people. If, however, the animal is a nuisance, such as it barks or attacks people, or damages property, then it is forbidden to feed the dog or animal. Likewise, in all cases, it is only permitted to feed the stray animal, animal fodder, or leftover foods that people will not eat, or non-Kosher food, however foods that are Kosher and fit for human consumption are not to be given to stray animals.]
One is not Halachically required to feed stray animals from his own food/money, although it is proper to give some food to a dog on a one-time occasion, if the dog is not a danger to the public. In all cases, one is not to feed stray animals foods that are meant to be eaten by humans, and is rather to feed them animal foods, or leftovers that people do not eat.
Why does the Torah not obligate one to feed stray animals?
Various reasons can be attributed for why we do not find an obligation in this matter.
· Most stray animals have their own way of achieving a source of food, and by people feeding them it invites the animals into the neighborhood, and they can become a nuisance for others.
· The Torah does not command a person regarding all matters, and leaves certain areas to the judgment of man to decide. If one desires to be merciful, and feed the harmless stray animals, he certainly has the choice to do so.
 Admur Hilchos Ovrei Derachim 3; Bava Metzia 88b
The reason: As the Torah did not obligate due to Tzaar Baalei Chaim for one to spend his own money to help animals, and he is only obligated to place bodily effort in saving them. [Admur ibid]
 Admur in Kuntrus Achron 3; Vetzaruch Iyun as to why this is not included in the positive command [Mitzvah 611 in Chinuch] to follow the ways of Hashem and just as He is merciful, so too, you should be merciful”
 Admur Hilchos Ovrei Derachim Halacha 4
 Admur ibid; Admur 324/7 “Doing so contains a slight Mitzvah”; M”A 324/7; Shabbos 155b
How Hashem shows mercy to the dogs: Hashem shows mercy to dogs by having the food stay in their abdomen for 72 hours, being that its food is scarce. [Admur ibid and 324/7]
 Admur ibid; Shabbos ibid
 See regarding feeding birds on Shabbos Shira: Tosefes Shabbos 117; Minchas Shabbos; brought in Ketzos Hashulchan 131 footnote 5; Aruch Hashulchan 324/3; Nemukei Orach Chaim 324; Shaar Halacha Uminhag 1/149
 Olas Shabbos 324/19; Tosefes Shabbos 324; Daas Torah 324; M”B 324/31; Kaf Hachaim 324/45; See Maharsha Shabbos 155b; Admur Hilchos Shemiras Haguf Vihanefesh Halacha 3 that it is forbidden to own such a dog; Vetzaruch Iyun why M”A and Admur ibid omitted this ruling of the Olas Shabbos
 See Taanis 20; M”A 171/1; Machatzis Hashekel ibid; M”B 171/11; Ketzos Hashulchan 39/30; Piskeiy Teshuvos 171/8