Q: I have a 3-year-old filly who will be transitioning into an under-saddle training program this spring. I know young, growing horses in work need more protein, but what percentage of protein should she have in her diet? Are there any other nutrients or components of her diet that will need to change as she works more?

A: Young horses like yours have a lot on their plates as they start work while continuing to grow, and they need their nutrition to pull double duty as well. Both growing horses and performance horses have increased requirements for protein, energy, and many vitamins and minerals compared to adult horses at maintenance. At 3 years old much of your horse’s skeletal growth is complete, and she can move from a growth feed to a performance feed (this transition can happen as early as 2 years old). What does this mean for you when shopping for feeds? Here are a few things to remember:

1. Choose a feed designed for the horse you are feeding. In this case it should be labelled for performance horses, not horses at maintenance or seniors requiring forage replacement (due to compromised dentition), for example. This will ensure the right balance of individual nutrients, as well as the right nutrient-to-calorie ratio, doing the work of ration balancing for you.
2. Choose the right calorie density. If the feed is too rich, she will not be able to eat a large quantity and might fall below the minimum feeding rate (check the fine print in the feeding directions). This could create gaps in the nutrients provided to her. There are well-fortified performance feeds at every calorie level, and the right one for your horse depends on her individual metabolism, workload, and how many calories she gets from forage. Some horses might just need a ration balancer, for instance, while others might need a higher-calorie concentrate. You don’t want her hovering right at the bare minimum feeding rate for a product because, again, she is growing and working.
3. Horses need nutrients in certain amounts, not percentages. It’s an oversimplification to say that she should be on a 14% crude protein feed, when 5 pounds of a 14% crude protein feed and 6 pounds of a 12% crude protein feed both provide the same total amount of crude protein. That being said, low protein feeds such as 10% protein feeds are rarely the right fit for a young performance horse and are often designed for mature horses in light to no work.
4. Protein quality matters, not just quantity. A well-formulated 12% protein feed with added amino acids (especially lysine) will do a better job meeting her needs than a poorly fortified 14% protein feed with low-quality protein ingredients such as dried distiller grains.
5. Keep your forage quality in mind. The better (and higher-protein) your hay is, the less work the feed must do, but the poorer the hay, the more important the feed. However, even high-protein forages are not excellent sources of amino acids because the digestibility/availability of that protein is not as great as it is in concentrate feeds with ingredients such as soybean meal.
6. Electrolytes are of greater importance now that she is in work. Make sure to provide salt year -round and consider a good-quality electrolyte during the “sweating season.”
7. Don’t stress about balancing individual nutrients or buying separate vitamins or minerals to supplement unless she has a specific health issue. Again, the best way you can ensure correct nutrition is to choose a well-formulated feed, from a company you trust, that you can feed at the correct rate while maintaining a proper body condition. When in doubt, consult an equine nutritionist.

In summary, ensuring the correct nutrition for a young horse transitioning into training involves selecting a performance feed that meets increased protein, energy, vitamins, and mineral requirements; paying attention to calorie density and quality of ingredients; and not overlooking the importance of electrolytes.

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