MBY 324:1-15 Laws relating to feeding animals on Shabbos (abridged)MBY 324:1-15 [Based heavily upon Kitzur Shulchan Aruch: 87:11-18, “Metsudah” edition, with notes, translated and annotated by Rabbi Avrohom Davis]
11) A person may not measure out barley, using a measuring cup, to feed his animal; rather, he should just estimate the amount needed. (Note: This is a Rabbinic prohibition, because it appears that he intends to sell the barley in the marketplace. Mishna Berura 246:17)
12) A bundle of hay that was not tied with a permanent knot (i.e. double-knotted) may be untied on Shabbos and placed before an animal. You may cut up hard pumpkins near an animal, provided they were picked before Shabbos. If the pumpkins are soft and the animal can eat them as they are, it is forbidden to cut them up. (Footnote #28: This is unnecessary bothersome activity.)
13) You may place your animal upon growing grass so that it can eat, because this does not constitute “work” for her; the fact that she will be uprooting grass - on the contrary - is a pleasure for her. (See MBY siman 305 which discusses the topic of resting one’s animals on Shabbos.) However, upon grass that a non-Jew cut on Shabbos, which is muktzah, it is forbidden to place an animal for grazing (Footnote #29: For there is a Rabbinic concern that you may inadvertently handle the freshly cut grass which is muktzah.) If the animal has nothing else to eat, this is permitted (i.e. placing the animal there, not handling muktzah, which is a more strict Rabbinic law) in order to avoid causing pain to animals. Similarly, if an animal has nothing to drink, you may instruct a non-Jew to bring water for her, from a well that is situated in a ‘karmelis’ (i.e. a semi-public domain, from which carrying is prohibited mid’rabanan.)
14) You may not hang on an animal a bag or vessel from which it will eat, since this is only for the animal’s comfort - so that it will not have to bend its neck - and you are forbidden to exert yourself on Shabbos solely for the comfort of the animal. However, calves and colts, since they have short necks and it is troublesome for them to eat off the ground (i.e. thus this situation is elevated from comfort of the animal to relieving it from pain), it is permitted to hang a feedbag on them in the yard. An animal may not be allowed to go out with a feeding bag into a ‘reshus harabim’ (public domain), because it is classified as a burden. (See MBY 305.)
15) You may not throw grain for the fowl in a damp place, because it is possible that some will remain there and will sprout afterwards. (Footnote #33: This would constitute the melacha of planting. Shulchan Aruch 336:4 permits throwing grain to hens if it is expected that it will be totally consumed in less than three days, i.e. the time needed for the grain to take root.)
16) If you give feed to your animals it is forbidden to first put it into a sieve to remove the chaff and to cleanse it. (Footnote #34: …although this would only constitute a Rabbinic prohibition of “sifting”, since it is not the usual method of removing the chaff.) But if your purpose is not to strain the grain, but simply to carry it, you may take it with a sieve and carry it to the trough.
17) If you give bran to your animals or your fowl, it is forbidden to put water into it, because of the malacha of ‘lush’ (kneading – see above MBY SIman 321). If you put water in on Friday it is forbidden to knead (i.e. mix) it on Shabbos, but you may pour it from one vessel into another in order to mix it.
18) Animals such as cattle, beasts and fowl that are raised in the house (i.e. a domestic setting), whose feeding is your responsibility, may be fed on Shabbos. (Footnote #36: You may also feed another’s animal, provided it has an owner who is responsible to feed it.) But those not raised in the house and whose feeding are not your responsibility, it is forbidden to trouble yourself in order to feed them. [Footnote #37: However, if you know that the animal is hungry you may feed it regardless of ownership, because it is written (Tehillim 145 - “Ashrei”) ‘V’rachamav al kol ma’asav’ (“His compassion is over all of His creatures”)] Even to merely throw feed before them is forbidden. Therefore, it is forbidden to place food before doves (Footnote #38: even if they are yours!) because they can easily fly out and get food in the fields. There is a special exception given to dogs: Even if it has no owner, there is somewhat of a mitzvah to give food to a dog, as this emulates the Creator Himself: The Holy One, blessed be He, showed the dog compassion; for, because of the scarcity of its food, He caused its food to remain undigested in its intestines for three days! Some are accustomed to place wheat before birds on ‘Shabbos Shira’ (the Shabbos when Parsahs Beshalach is read. According to the Midrash, when the conniving Dasan and Aviram put Manna out on Shabbos morning in attempt to demonstrate that Moshe’s words – that no Manna would fall on Shabbos - did not come true, the birds ate it up and spoiled their plot. To “repay” the birds for saving us from this ‘chilul Hashem’ - desecration of Hashem’s Name - we feed them on that week!) However, it is not proper to put the wheat out on Shabbos, because it is not our responsibility to feed them.