Q: How can I prevent nutritional deficiencies without causing developmental issues in a growing foal?

A: Developmental orthopedic disease (DOD) is a common concern in young horses, referring to a group of conditions where skeletal growth occurs abnormally. While nutritional mismanagement can be a factor, proper nutrition can help manage the risk of developmental issues.

Feeding young horses requires careful planning, starting before birth. Ensuring the mare’s optimal nutrition during pregnancy and lactation is essential for fetal development and milk quality. Once born, foals should begin consuming concentrates at around 28 days old; a good rule of thumb is 1 pound of feed per month of age per day. Feeding with progressive and consistent increases will encourage steady growth curves associated with optimal skeletal development. Erratic changes, feeding an improper concentrate, offering it free-choice, or making sudden changes to the amount of concentrate, can result in the unpredictable growth curves that are the hallmarks of DOD development. You can design your feeding program to support rapid versus moderate versus slow growth rates depending on the goals for that foal, but make these decisions with few changes occurring during the early growth period.

It’s a misconception that excess calories or protein alone causes DOD. Instead, imbalances in these and other nutrients have been linked to abnormal growth. Think of calories as the fuel for growth and nutrients (amino acids, vitamins, and minerals) as the structural building blocks. Too much fuel and too few building blocks will create rapid, incorrect growth. Too little fuel and you will be missing out on some genetic potential for growth, which could hinder muscle development. In addition to energy and protein, other nutrients need to be maintained in certain ratios to ensure optimal utilization. Calcium and phosphorus are classic examples of nutrients that should remain balanced to a ratio of no less than 1:1 (2:1 being optimal). Similarly, zinc and copper must be balanced in a ratio of around 4:1 in a complete diet. 

A simple way to stay on track is to:

1. Feed to suitable body condition, which is when ribs are not or just barely seen and easily felt, and
2. Use only feeds appropriate for growth. Look for items designated for mare and foal, growth, or all life stages. This means the nutrients are balanced for young horses, and the balance between calories and nutrients is appropriate. 

The key difference between growth and performance feed is that a performance feed for an adult horse has a higher ratio of calories to nutrients, meant to support working horses but not adding structural growth. Growth feeds are available at all calorie levels, so the exact choice of concentrate will be dictated by the individual’s metabolism and forage intake and quality. Ration-balancing feeds are a good option to provide nutrients if your horse receives sufficient calories from forage alone. A young horse should generally stay on a growth-appropriate program until 2 years old, sometimes longer for particularly late-maturing breeds such as some warmblood or draft breeds.

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