The Effect of Season on Muscle Growth, Fat Deposition, Travel Patterns, and Hoof Growth of Domestic Young Horses.

Our objective was to determine the influence of season (winter, spring, summer, and fall) on travel patterns, hoof growth, and longissimus dorsi muscle (LM) height and fat thickness between 13th and 14th ribs in 16 horses aged <4 years (eight males and eight females) of Morgan, Quarter Horse, and Moriesian breeds. Real-time ultrasound images of LM height and fat thickness as well as measures of hoof growth were obtained at the end of each season. Global positioning system tracking was conducted for four randomly selected days and one storm day in each season. Data were analyzed using a linear mixed model procedure in SAS. Season influenced fat deposition (P < .01) with the greatest increase in fall (P < .05) but had minimal effect on muscle growth. Hoof growth was greatest in summer and least in winter (P < .01). The average distance traveled was greater in spring and summer than in fall and winter (P < .01). The horses moved for less time and traveled less distance on storm days (P < .05) compared with nonstorm days. Young horses also traveled less on storm days, which indicates that it may be especially important to provide shelter for them. It was concluded that season influenced fat deposition, distance traveled, and hoof growth of domestic young horses. A better understanding of these factors could help equine professionals manage young horses more efficiently to benefit the horses' physical well-being.