There is a famous picture of Rav Eliahu Lopian feeding the yeshiva’s cat. He explained that if it did its job and got rid of the mice it would have nothing to eat otherwise.
Apparently dog ownership was common among our ancestors as the Torah tells us to give them the meat of treif animals. The Maharal says (חידושי אגדות הוריות יג ע”א ד”ב האוכל) that the dog is a בעל נפש and is called a כלב because he is כולו לב. The Ben Ish Hai in Bnei Yehoyada praises his loyalty. Chazal also praise his characteristic of gratitude.