Relationship between Morphometric Measurements and Leptin Levels of Horses Vary Among Breeds

Abstract

Obesity in domestic horse populations is becoming more prevalent, manifesting in increased occurrences of metabolic issues. Currently, obesity in horses is determined by subjective visual assessment, which is not reliably standardized. Circulating leptin levels directly correlate with adipose tissue mass; therefore, leptin levels could potentially be used as an objective measure of obesity in horses. To determine the relationship between body mass, as defined by morphometric measurements, and plasma leptin levels, blood was collected via jugular vein from horses (n=35) from four different breeds with known varying risks of obesity and obesity‐related conditions (Saddlebreds, n = 7, draft/draft crosses, n=7, stock horses, n=11, and Welsh ponies, n=10), in southern Wisconsin and northern Illinois every 60 days for one year. Morphometric measurements included neck circumference, height, and girth. These measurements were used to calculate neck circumference to height ratio (NCHR) and girth to height ratio (G:H). For both NCHR and G:H calculations, a greater value indicates increased obesity. Plasma leptin levels (repeated measures MANOVA, F3,29=5.65, p=0.004), NCHR (repeated measures MANOVA, F3,31=26.64, p<0.0001), and G:H (repeated measures MANOVA, F3,31=23.00, p<0.0001) varied significantly among breeds. In addition, the relationship between leptin levels and NCHR (repeated measures MANOVA, F3,29=6.44, p=0.002) and leptin levels and G:H (repeated measures MANOVA, F3,29= 6.55, p=0.002) varied significantly among breeds. Among these results, post hoc analysis revealed Saddlebreds had the highest leptin levels (pairwise contrast, F1,29=10.51, p=0.003), lowest NCHR (pairwise contrast, F1,31=52.87, p<0.0001), and lowest G:H (pairwise contrast, F1,31=60.93, p<0.0001) compared to all other breeds. This suggests Saddlebreds have a different relationship between obesity and leptin levels compared to other breeds. Saddlebreds are known to have various metabolic issues, such as an increased risk of insulin resistance, even when visual inspection and exercise regimen would suggest normal insulin sensitivity. Therefore, unique relationships between leptin levels and obesity in some horse breeds may be associated with varying risks of obesity‐related conditions.Support or Funding InformationThis work was sponsored by the Biomedical Scholars Program at Beloit College.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.