The Torah makes clear that not only humans but the animals in their care must rest on Shabbat. None-the-less, their needs must be taken care of. Not only must animals be fed, but their stalls must be maintained – even on Shabbat. The Mishanah on this page states:
ONE MAY SWEEP OUT [THE MANGER] FOR A STALL OX, AND MOVE [THE REMNANTS] ASIDE FOR THE SAKE OF A GRAZING ANIMAL.
THIS IS R. DOSA'S VIEW, BUT THE SAGES FORBID IT.
ONE MAY TAKE [FODDER] FROM ONE ANIMAL AND PLACE IT BEFORE ANOTHER ANIMAL ON THE SABBATH.
One [Baraitha] taught: One may take [fodder] from before an animal that is fastidious and place [it] before an animal that is not fastidious; while another taught: One may take [fodder] from before an animal that is not fastidious and place [it] before an animal that is fastidious.
Abaye observed: Both [Baraithas hold] that one may take from an ass [to put] before an ox, but not from an ox [and place it] before an ass.