What does Judaism have to say about the treatment of animals?
As far as how Jewish tradition, and the Torah in general speak of God's love for animals, there is a rabbinic concept of tzaar baalei chaim - literally the woe/pain of living things - roughly rendered as concern for cruelty to animals, but runs deeper than that. The principle is that animals experience pain and suffering, and although are not equivalent to human lives, they must still be dealt with caringly and thoughtfully.
One of the most obvious traditions that reflects this is that of kosher slaughtering - that while it is permissible to eat meat, the animal must be slaughtered in a fashion that is as painless as possible - so one swift motion, with a blade that must be inspected and found free of nicks and cuts. One of the less obvious is the prohibition of plowing one's field with two different animals, specifically, an ox and an ass (Deuteronomy 22:10), although the rabbis enlarge the boundaries greatly and generalize the principle to the mixing of any kinds of natural animal products. The reason most commonly understood is that they work at different paces, and either the ox would be slowed down and frustrated by the ass, or more likely, the ass would get hurt by the ox's strength and size.
In addition, the prohibition against working on Shabbat does include one's ox and ass (Exodus 20:10) - although this is different than observing Shabbat as I mentioned in my first paragraph - it is the consequence of being a part of a Jewish household (i.e., if the cow is sold to a person of a different faith, it can be put to work on Shabbat).