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The Gemora suggests a kal vachomer that would result in their being a mitzvah of preserving the life of animals. Although one may have a mitzvah to feed his own animals, the Gemora concludes that there is surely no mitzvah to support the animal (when it is no longer profitable), and certainly one is not obligated to support animals that are not his.
The Tosfos HaRosh asks in the name of Rabbeinu Meir: Why would we have thought differently? There should be an obvious challenge to this kal vachomer from the fact that one is not allowed to slaughter people, but may slaughter animals - this obviously shows that there isn’t any mitzvah to preserve the life of animals!?
The Tosfos HaRosh responds to this question by saying that we would have thought that this mitzvah would apply to animals that one is not allowed to slaughter, such as a bechor that is intermingled with an ox that is destined to be stoned (shor haniskal).
Aside from the actual question of the Tosfos HaRosh, the entire thought that one would be obligated to support animals and help them survive seems a little strange. Especially since in the end, the mitzvah of preserving a life only applies to a Jew and not to an idolater!?
The Biur Halachah (330:2) writes that one is obligated to help a ger toshav woman give birth because on a ger toshav, there is a mitzvah to preserve their life. He entertains the possibility that the Jew can even violate a Rabbinic prohibition to help the ger toshav give birth because when there is a mitzvah to preserve a life, the Rabbis did not issue their decrees. Based on this application of the mitzvah to preserve a life, the mitzvah goes beyond tzedakah; it compels one to actually take care of others and help them through physically challenging circumstances.