Date of Completion

Spring 5-1-2015

Thesis Advisor(s)

Dr. Sarah Reed

Honors Major

Animal Science


Muscle mass and strength are important for all horses, but particularly aged horses and horses participating in intense activity, to maintain and improve their ability to perform. The correlation between muscle mass and age, breed, and sex holds implications for use in management in the horse industry, including monitoring changes with age and potential therapeutic treatments and designing specialized training programs based on breed characteristics and sex. The use of ultrasonography for determining muscle characteristics, including area, width, and height, and subcutaneous fat depth provides an inexpensive, noninvasive technique for obtaining these measurements. We hypothesized that muscle area would decrease and subcutaneous fat would increase in adult animals with increasing age, that "easy-keepers" would have greater fat depth than other breeds, and that males would have more muscle than females. Horses from the University of Connecticut herd, ranging in age from 6 months to 21 years, of both sexes and five different breeds, were used to measure longissimus dorsi (LD) muscle area, width, and height, and subcutaneous fat depth. Data was analyzed using the MIXED procedure in SAS. Age, sex, and breed significantly affected LD area and both age and sex had a significant effect on LD height. The area of the LD was greatest in horses 11-15 yr of age (P < 0.02) and greater in males than females (P = 0.0003). Only age had a significant effect on LD width and fat depth (LD width, P = 0.0320; fat depth, P = 0.0046). Determining LD muscle characteristics across various ages, breeds, and sexes provides information that may prove useful in the maintenance of muscle mass in aging horses and offers an explanation for the unique abilities of the sexes and of different breeds.