Texas Equine Veterinary Association

• 13 • Some horses are thin because the caloric density of the diet does not meet their energy demand, which is commonly referred to as underfeeding. Other horses may have an above average metabolism that requires special husbandry to maintain optimal body condition. A hard keeper is a horse with a high metabolism that requires a high-calorie ration to maintain body condition. Caring for a hard keepers can be a challenge, but the goal should always be to maximize energy or calorie intake, and limit energy spent. Rule Out Health Problems Regardless of age, it is important to rule out health problems that prevent a horse from gaining or maintaining weight. Poor condition can be influenced by stress, lack of appetite, equine gastric ulcer disease, dental problems, intestinal parasites, and illness. Dental problems are the most common because of poor conditioning in older horses. Inadequate dentition not only impacts the horse's ability to breakdown feed when eating but also deters the horse from consuming its full ration. Although some metabolic disorders can lead to obesity, others can increase metabolic rate and cause the horse to lose weight. Horses with Pituitary Pars Intermedia Dysfunction have higher levels of circulating cortisol, which increases the breakdown of carbohydrates, protein, and fat. Pituitary Pars Intermedia Dysfunction can affect up to 20% of the older horse population but can be controlled successfully if caught early with medication and proper diet. General Feeding Guidelines A mature horse can consume around 2–2.5% of their body weight in (dry) feed per day. Total daily intake is limited by the capacity of the horse's digestive system. For example, a 500 kg (1,100 lb) horse can consume around 10 kg (22 lbs) of dry hay per day. Hard keepers may need to consume 2.5% or more of their body weight in dry feed per day to meet heightened energy demands. e National Research Council's maintenance digestible energy requirement for a horse with an above average metabolism is 36.3 kilocalories (Kcal) per kg body weight per day or 18.15 Megacalories (Mcal) per day (for the 500 kg horse) in the absence of work, compared to an average metabolism horse of 33.3 kcal/kg body weight and 16.65 Mcal per day (NRC 2007). However, higher calorie requirements have been reported in moderately thin horses, with between 48–53 Kcal/kg body weight (24–26.5 Mcal per day) reported in horses fed to gain body weight (Gill et al., 2017). Targeting calorie dense feeds is important for the hard keeper while working within the maximum gut capacity. A thin horse requires more energy in the diet to build or maintain fat stores and muscle. For horses, the major sources of energy include fiber, starch, and fat. High amounts of fiber can be delivered from good quality forage. e horse's digestive tract is designed to continuously process high fiber roughage and extract valuable nutrients. Selecting a high-quality hay is important because as lignin content decreases, digestibility of the energy derived from the fiber increases. Digestible sources of fiber are cellulose and hemicellulose, whereas lignin is undigestible fiber. Digestibility of the diet is important because there are losses that happen in energy aer a food Feeding the Hard Keeper Jennifer Gill, Ph.D., is an equine nutritionist and lecturer at the University of Rhode Island in Kingston, Rhode Island. She graduated from North Carolina State University with a doctoral degree in animal science and a research focus in obesity, digestible energy intake, and weight management in horses. Dr. Gill has research articles published in the Journal of Equine Veterinary Science and has mentored graduate students in equine. Dr. Gill currently teaches equine and animal science curriculum, advises students in animal science fields, and continues to conduct research in equine husbandry through industry connections. by Jennifer Gill, PhD

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