Kosher foods are those that conform to the regulations of the Jewish Halakhic law framework, kosher meaning fit or allowed to be eaten only by the Halakhic community. A list of some kosher foods are found in the book of Leviticus 11:1-47. There are also certain kosher rules found there. Reasons for food not being kosher include the presence of ingredients derived from nonkosher animals or from kosher animals that were not slaughtered in the ritually proper manner, a mixture of meat and milk, wine, or grape juice (or their derivatives) produced without supervision, the use of produce from Israel that has not been tithed, or the use of non-kosher cooking utensils and machinery.
Every law of Kashruth, according to all Jewish Rabbinic authorities of the ages in a rare agreement, makes the assertion that the laws can be broken when any life is at stake. Among the dozens of sources for the laws of "Pikuach Nefesh" (the Jewish term for saving any life) is the multiple discussions in the Talmud, for instance B. Yoma 83a (translated from the original Judeo-Aramaic) "We have agreed in the case of saving a soul he may be given [by a doctor in this case] to eat even unclean things, until his eyes are lightened from death". All laws in Judaism can be temporarily broken, to save a life (excluding 3: Idolatry, Murder and Sexual Immorality) the exceptions, where you must be willing to die, are learned by the Talmudic Rabbis from various locations in the Torah (see Daniel Chapter 1 for instance) .
Any Torah observant Jew must see animals "as good", as God does in Genesis 1:21-24.