You must understand fixed overhead expenses in order to understand absorption costing and variable costing. Fixed overhead consists of expenses that do not change with your level of production. Examples of fixed overhead include rent, insurance, wages for permanent full-time employees, and lease payments on equipment.
Whereas it may be safe to start a horse as early as two years of age, you must reasonably moderate the demands you are about to place on the developing horse. One hour of riding work may be just fine for a fully developed horse, but it is most often unacceptable for a two-year old.
Most foals will begin to lose interest on their own but if a foal continues to want to nurse, and the mare allows it, it is completely understandable for a foal to nurse up to 8 months old. (In the wild, mustang mares will often allow their foal to nurse up to 1 year old, or about 2 weeks before she gives birth to her next foal). In domesticated horses, where people have some control, it is best to not allow a foal to nurse over the age of 8 months due to concerns about the mares health and well being.