Yearlings
By the time they are a year old, rate of growth has slowed to only about 60% to 75% of what it was as a weanling. As a result, even though weight has almost doubled from the weaning weight, calorie requirements go up only about 30%. Don't make the mistake of thinking the yearling needs twice as much grain because he's now twice as big. That as sumption is where all the fat yearlings come from! The yearling's hindgut is also fully developed at this point, which means he can very efficiently ferment hay and pasture. He still needs a diet that is higher in protein and minerals than an adult horse much bigger than he is, but not quite as concentrated as the weanling.
The simplest way to make the transition from weanling diet to yearling diet is simply to keep your level of grain or mineral/protein supplement feeding exactly the same from the age of 6 months through the yearling year, and meet the growing horse's calorie requirements otherwise from increased hay. It's really that simple.
Making It Work for You
Let's see how you would actually go about all this in real life! The first step is to find out what you need to supplement (if anything) to bring your hay or pasture into balance. Your state university can help you with this, or you might want to hire a professional. What you will end up with is a supplement that is designed to meet adult horse needs, which you will feed depending on the amount of hay fed or in a set amount per adult size horse on pasture.
Once you have that critical hay/pasture portion of the diet balanced, it's very easy to take advantage of a wide variety of products on the market for horses. Table III is a comparison of three different products-an adult type horse feed, a growth formula horse feed, and a concentrated protein/mineral supplement. The high protein and mineral supplements are usually pelleted and fed just like a feed, but in smaller amounts so there's less chance of forcing rapid growth or excessive weight gain.
If you choose to go with a growth formula, weigh your youngster at 6 months of age, feed grain according to the body weight recommendations at that time, and continue this rate of feeding after he becomes a yearling. Meet increased calorie needs by feeding more hay, with the minerals to match it. If the horse gets too heavy on that amount of grain, you can substitute the protein/mineral supplement (these are pelleted) instead and cut back on calories without sacrificing protein and minerals. If you have adult horses as well, you can actually turn your regular adult horse feed into a growth formula by adding as little as 3¼ ounces of the protein and mineral supplement to each pound of your regular grain, then feed this combination at the same feeding level as recommended for the growth feed.
