Siman 536

One who needs to ride during the moed even for a stroll, and all the more so if it is for the need of the moed, and he did not attempt to go on foot – he may trim the horse's hooves, and repair its legs with iron, and repair the saddle and the bridle, and all the needs of riding. And we do not say: behold, he could have repaired them before the moed, for behold, he did not know if he would need this. Therefore, if he truly knew that he would need this, and intentionally left it for chol hamoed – it is forbidden. Our teacher, the Rema, wrote that it is permitted to ride during the moed even from city to city, even for no purpose. And such is the custom, except that it is forbidden to repair all the needs of riding if he is not riding for a need or for a stroll. Thus far his words. And it is not understood: since this is his desire – behold, it is a stroll for him. And it is possible that a stroll involves preparation, and his going is at ease. (See Magen Avraham who wrote that from Eretz Yisrael to outside the land for a stroll – one should not repair the needs of riding.) And according to this, also regarding traveling in a wagon – the law is also thus regarding the matter of repairing the wagon, that if he knew before the moed – it is forbidden. And if not – it is permitted.

It is permitted to comb a horse in order to beautify it, for this is a pleasure for it. And even if he combed it on the eve of the Yom Tov, nevertheless it requires a new combing. And one may not mate an animal during the Moed, as it is not for the need of the Moed, nor is it a matter of financial loss. But one may let its blood, and one does not withhold any medicine from it, even if there is melacha involved in this, for this is a matter of financial loss. And similarly, one may not set a hen upon eggs to raise chicks. But if she was set before the Moed and fled from them—he may return her, for if he does not return her the eggs will be ruined and it is a matter of financial loss. And this is provided that it is within three days of her fleeing, for after that there is no benefit. And it is not only necessary to say if she already sat upon them for three days, for then the eggs are completely spoiled. Rather, even if she did not sit for three days, for then they are still fit for eating, nevertheless there is a loss in them. Our teacher, the Rema, wrote: But it is forbidden to set another in her place, even if the first one died. Thus far his words. It must be said that he holds that it would not be effective. For if it should enter your mind that it would be effective—why would they forbid it in a matter of financial loss? (And see Beit Yosef, and Magen Avraham subsection 3. And that which appears correct in my humble opinion, I have written.)