Various factors can require special attention to nutrition in a horse. Factors like age, stage of development, gestation or lactation in a mare, old age and the level of physical activity in the horse will require more nutrients then hay alone can provide. Use of grains, protein supplements, vitamin/mineral supplements or preferably, complete mixed rations will be required to meet the increased nutritional demands of these horses. In mature, inactive horses, it is not uncommon to have significant variation in how well they maintain their body condition on hay diets and the "poor doers" may have to be supplemented and the "easy doers" may have to be restricted. Various health conditions can also require special attention to diet. Consultation with your veterinarian or equine nutritionist is advised to establish the appropriate diets for any specific case.