Comparison between the thermal insulation properties of huacayo alpaca and merino sheep fleeces

Abstract

The aim of the study was to evaluate and compare the fleece thermal insulation of Huacaya alpacas and Merino sheep. The study included 13 clinically healthy Huacaya alpacas and 14 Merino sheep. Fleece samples were taken from the trunk (lateral aspects) of each animal to measure coat fibre length and average fibre diameter. The insulating properties of each sample were determined using a calorimetric method. In addition, infrared thermographic images were taken of the trunk (lateral aspects) for both species in an indoor environment. Four regions of interest (ROIs) were determined from each thermographic image (corresponding to the coat sample sites) and the mean temperature within each ROI was calculated. Merino sheep had significantly (P<0.001) longer and thicker fibres than alpacas, but less efficient (by about 20%) insulation at all sample sites. Sheep in similar experimental conditions therefore had significantly higher fleece surface temperature (by 1-2 °C) than Huacaya alpacas. Infrared thermography also provides information about fleece surface temperatures in vivo, which can be used to validate models of heat exchange in homeotherms.