General Principles of Feeding Domestic Animals
Question
I would like to know if there are any rules regarding what actions I am allowed to perform on Shabbat in order to feed my domestic animals, and what actions are prohibited?
Answer
Greetings,
There are two main principles:
a. It is permissible to feed only an animal or livestock that you are obligated to sustain, and that have no means of obtaining food from elsewhere. However, bees, for example, even if you do not provide them with nourishment, they can find flowers and nectar on their own [even if they do not find the specific type of food you desire for them]. Therefore, it is prohibited to feed them on Shabbos. Similarly, it is prohibited to feed birds or stray cats and the like on Shabbos.
b. It is permissible to exert effort to feed the animal only if not feeding it would cause it distress. However, to exert effort in preparing food that would be more appetizing to the animal, when the absence of effort would not cause distress but rather deprive the animal of pleasure, is prohibited on Shabbat.
Source
Shulchan Aruch (Orach Chaim, Chapter 324).