1) He shouldn't use a measuring cup, because it looks to others as if he is measuring out an amount of barley to sell on Shabbat. This type of prohibition is called ''Ma'arit Ha'ayin'' (lit:''visual appearance''), and forbids doing anything that others might interpret as a transgression. 2) On Shabbat, one is allowed to feed an animal that's dependant on humans for its food.

1) Untying a permanent knot on Shabbat - ''Matir'' - is one of the 39 ''Melachot'' (prohibited categories of activity). 2) One should be careful not to cut it into very small pieces, because this would be like ''grinding'' - ''Tochen'' - grinding is defined as taking a whole object, and breaking it down into tiny pieces (See Mishna Berurah 324:14). 3) Any fruit or vegetable which wasn't picked before Shabbat, is considered ''muktzeh'' - ''set apart'' - even if it was picked on Shabbat by a Gentile (it is forbidden for a Jew to pick anything from a tree on Shabbat). 4) Cutting it up would be considered unnecessary bothersome activity - ''Tircha'' - which is prohibited on Shabbat.

1) Although a Jew is forbidden to uproot grass on Shabbat, the Midrash clarifies that forcing an animal to abstain from grazing, is not considered ''rest'' for it but rather ''suffering'' and therefore isn't a prohibited activity for the animal (Mishna Berurah 324:12). 2) Any piece of vegetation that is separated from its source of growth on Shabbat, whether it was cut by hand or fell off naturally, is considered ''muktzeh'' - ''set apart'' - and cannot be moved on Shabbat. 3) There is nothing basically wrong with allowing one's animal to eat grass that is ''muktzeh'' The reason it's prohibited here is out of concern that the owner might pick up the grass to feed the animal by hand. Therefore, it's allowed to lead the animal onto a narrow path such that the only direction it can go is towards the cut grass, because in that case, the owner is not standing close to the ''muktzeh'' item, and there is no concern that he will inadvertently feed the animal by hand (Shulchan Aruch 324:13). 4) Even though it's rabbinically forbidden to tell a Gentile on Shabbat to perform an activity that would be forbidden to a Jew, in this case, the suffering of an animal overrides that prohibition.