Ultrasonographic Measurement of Muscle and Subcutaneous Fat Thickness for the Objective Assessment of the Nutritional Status of Alpacas

The aim of this study was to evaluate the ultrasonographic measurement of the subcutaneous fat and muscle layers at two different body locations as an objective tool with which to determine the nutritional status of alpacas. The results of ultrasonographic measurement were related to body weight, determined by scale, and body condition score (BCS), determined by a scoring system. Differences between gender (female/male) and different reproductive statuses (castrated/intact males, pregnant, and early or non-pregnant females) were evaluated. In total, 160 alpacas were examined. Ultrasonography was performed first at the lumbar region, positioning a linear probe (8 MHz) between the second and third lumbar vertebrae perpendicular to the spinal column, and in the gluteal region, measuring the distance between skin, the subcutaneous fat layer, and the muscle layer. The results showed that the gender and pregnancy status of females had a significant influence on the ultrasonographic measurements at both localizations. Significant associations were found between body weight and the BCS. The BCS and ultrasonographic-measured soft-tissue thicknesses at both localizations were significantly associated for males and early or non-pregnant females. According to these results, ultrasonography can be recommended as an objective method with which to determine the nutritional status of alpacas.