If it is just 2 weeks of age, then it is younger as according to statistics, 3 year of Horse is equal to 6 1/2 year of Human baby, & they don't develop enough quality to participate in a competition at that age
Also, normal weight is 100 pounds for a baby horse, so if it is just 18 pounds, then you should increase it's calorie intake, as it is very less than the normal ]
Hope this helps!