24/7 turnout is best for young growing horses. They need movement to help strengthen their bones and tendons/ligaments. A quality grass hay or timothy hay is great, or a hay mixed with less than 40% alfalfa.
I don't like Omelene or other grain products. Molasses, corn, wheat, and other grain by-products are just not healthy to feed horses. It's like trying to live on power bars and processed cereal... Just not the best choice.
You can make your own "feed" by using hay pellets or beet pulp, flax meal, and a good vitamin supplement. If you're feeding grass hay or other low protein hay, then alfalfa pellets are a good choice. They are high in protein and lysine, one of the main amino acids horses need, plus calcium for bone growth. Feed 1-2 lbs daily, then 2-5 lbs after she reaches 600 lbs. 1/4-1/2 cup of flax meal provides all the fat your baby needs for growth.
Horsetech.com has some great products and can custom blend you something for your growing baby based on the hay you choose. I would have them add amino acids for muscle development. Their flax is high quality human grade, and they don't charge for the custom work, only for the ingredients. Shipping is also free.