Relationship between ultrasound measurements of body fat reserves and body condition score in female donkeys

Several methods have been developed to monitor body fat reserves of farm animals and body condition scoring (BCS) is generally assumed to be the most practical. Objective methods, such as real time ultrasonography (RTU), are accepted methods for measuring fat reserves in several farm species but there is no published information about the use of RTU to monitor body fat reserves in donkeys. The aim of the present study was to determine the relationship between RTU measurements and BCS in female donkeys (jennies) (n = 16) with a BCS of 3-7 on a 9 point scale.Ultrasound images were captured using an Aloka 500-V scanner equipped with a 7.5 MHz probe and subcutaneous fat (SF, range: 1.0-14.0 mm) and thoracic wall tissue (TD, range: 5.6-21.4 mm) depths measurements were determined. A significant correlation was found between BCS and all RTU measurements (0.65 < r < 0.86; P < 0.01). Linear regression models described the relationships between RTU measurements and BCS and between log transformed RTU measurements and log transformed BCS. All equations with variables transformed into a logarithmic scale gave better coefficients of determination (0.42 < r2 < 0.75) and an increase of 7-23% in this coefficient. The study suggested that RTU depth measurements have a logarithmic relationship with BCS and that RTU combined with image analysis permits accurate fat and tissue depths measurements to monitor fat reserves in jennies.