What was Gulliver offered as food in Houyhnhnm? What did he actually eat during his stay there?

In part 4, chapter 2, Gulliver is taken to the country of the Houyhnhnms. There, he is offered a root, a piece of donkey meat, hay, and a pile of oats for food. Gulliver finds that he has to refuse every single offering.
He begins to despair that he will never eat normal food again. Eventually, Gulliver sees a cow passing by, and he tries to indicate to the master horse that he wishes to milk the cow. Fortunately, the horse understands Gulliver's underlying message; he then orders a mare-servant to open up a storeroom, where milk is stored in earthen and wooden jars. The servant gives Gulliver a large bowl of milk to drink, and this takes the edge off his hunger.
Later, the master horse has dinner with an old steed. Among other dishes, the horses dine on oats boiled in milk. After the dinner, the master horse voices his concern about Gulliver's seeming lack of appetite. For his part, Gulliver indicates that he will accept the offer of some dry oats. He then takes the oats, heats them, and rubs the husks off them. Then, he grounds the oats, adds water to them, and forms the mixture into flat cakes. He cooks the biscuits on the fire and eats them with warm milk.
Gulliver also divulges that he sometimes hunts small animals and gathers herbs for food. He either boils the herbs or eats them as a salad with the biscuits. Sometimes, Gulliver makes butter and drinks the whey. The only thing he misses is salt, but he soon accustoms himself to the deprivation.