AnimalsChickens - each chicken requires 2oz of water a day and /25 lbs of feed a day. They can live in a cage no smaller than 2x its own size. Each chicken can produce one egg a day. The addition of a rooster will allow for breeding additional chickens for eggs when the hens get too old.
According to some quick online research, hens produce the most mmount of eggs in the first 1-3 years of their lives and then slowly lay fewer and fewer. For the purposes of Garnet having hens for the purpose of producing eggs for food, after a chicken turns three she will have that chicken lay a fertile egg with the roosters help and repeat this process until a healthy female chick hatches and turns into a pullet. At that point she will likely take the older chicken to town to be butchered for 65% of its weight into meat.
While she could still get eggs out of an older hen, the ability to have consistent lays and fresh meat every few years is incentive to keep the chickens young, healthy and fat. If a Hen goes into their third year and is still laying consistent eggs, she may keep it until it starts to lay less than one a day. Also, as her gear grows, ie the addition of a cart, or eventually a wagon, she may choose to keep more hens and get more eggs. Also, chickens usually begin laying at 6months but prefer to start laying in the spring and will often wait until spring if they mature in the middle of winter. (So try to plan the fertilizing of eggs to not be 6 months prior to winter if avoidable.)
http://www.mypetchicken.com/backyard-chickens/chicken-help/At-what-age-do-hens-start-laying-eggs-H41.aspx -- most info above found via this link.
Additional Horses - The additional horse, or horses would be primarily used for pulling the cart, or the wagon to alow for more stuff to be transported as she moves with the Tent City of Endrykas. Preferribly the breeds would be colorsplash (for drafting purposes) or a hearty mixed breed who could easily pull the cart or wagon. (Maybe 1 for a cart and 2 for a wagon?) The cart would be purchased first then gifted, or sold so she could acquire a wagon. (I would also be interested in breeding Garnet's Strider and having her slowly collect Striders to pull her things, at least until they bond and move on to their new homes.)
Rabbits - After talking to Prophet I believe that breeding rabbits might be too difficult at least until she has a Pavilion and maybe some friends to help her out. The ability to breed rabbits for a constant supply of meat and pelts would be nice, but it might be easier to just hunt and trap for rabbits until she raises her Animal Husbandry skill with her chickens.