Animal Lore has three functions.
The first purpose is that it acts like Anatomy in respect to Healing, so that with 60 Animal Lore and 60 Veterinary you can cure your pet from poisons. However 80/80 in both skills will not allow you to resurrect your pet.
The second purpose for this skill is to enhance Animal Taming in that the pet orneriness check is made by comparing the creatures "tameable at" level to 80% of the masters Tame skill plus 20% of the masters Lore skill.
The third purpose is for checking your pet's status. As time goes on, your pet will require an upkeep of food, it's happiness decays overtime and can only be replenished by feeding it. See below for details.
"Wonderfully Happy" "Extremely Happy" "Very Happy" "Rather Happy" "Happy" "Content" "Content, I suppose" "Unhappy" "Rather Unhappy" "Extremely Unhappy"