There is no zakaah on horses and donkeys of they are not for trade
The animals on which zakaah is due are the an’aam animals, i.e.:
3-Sheep, which includes goats
That applies if they reach the nisaab and are pastured, i.e., if they graze and eat of the plants that grow on the land, and their owner does not spend anything on buying feed for them. See the answer to question no. 93387 and 40156.
As for other animals, no zakaah is due on them unless they are prepared for sale.
Al-Nawawi said in al-Majmoo’ (5/311): The Muslims are unanimously agreed that zakaah is due on camels, cattle and sheep. As for horses, mules, donkeys, etc., no zakaah is due on them. This applies if they are not for trade; if they are for trade then they are subject to zakaah, because of the report narrated by Abu Hurayrah (may Allaah be pleased with him), that the Prophet (S) said: “The Muslim is not obliged to pay zakaah on his slave or his horse.” End quote.
The scholars of the Standing Committee for Issuing Fatwas were asked: Some people spend the wealth that Allaah has spent them on keeping valuable purebred horses the price of which may be thousands of dinars in order to enter races with the aim of winning the prizes offered. My question is: Are these horses and their offspring subject to zakaah, and what is the nisaab and the rate of zakaah that is due?
If the matter is as described, and they buy them to keep them, not to sell them, then no zakaah is due on them, because the Prophet (peace and blessings of Allaah be upon him) said: “A man does not have to pay zakaah on his horse or his slave.” Saheeh – agreed upon. End quote.
Fataawa al-Lajnah al-Daa’imah (9/216).
And Allaah knows best.