The impact of fleece characteristics on insulation and heat exchange, and the consequential effect on vitamin D of alpacas in southern Australia

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Abstract

Alpacas are a fleeced mammal, originating from the high altitudes of the Andes in South America, and imported into southern Australia as part of a niche alpaca-fibre industry. The climatic conditions in Australia where alpacas are raised are much hotter, but with lower (and seasonal) ultraviolet (UV) radiation levels, than what alpacas were adapted to in the Andes. Although the industry breeding objectives are to achieve higher quality and quantity of fleece, the knowledge on how these parameters are affecting animal health and welfare in Australia is limited. In particular, it is unknown if the insulation of the fleece would protect alpacas from radiant heat (and heat stress) during an Australian summer. Additionally, it is unknown if certain 'desirable' fleece types (combinations of fleece characteristics) affect the potential of alpacas to sweat, and/or to block out UV radiation penetration to the skin for the synthesis of vitamin D. The purpose of the research in this thesis is to investigate the influence of the fleece characteristics on insulation from radiant heat, and its consequential effect on potential heat stress and vitamin D synthesis of alpacas in southern Australia.

First, the potential for heat loss via sweating was tested by quantifying the density of total, primary, and secondary follicles and sweat gland ducts in the skin of Huacaya alpacas varying in fibre thickness. Second, to measure the impact of the fleece characteristics (diameter, density, length and colour) on the insulation and radiant heat load, I tested alpaca fleeces (half with light colouring and half with dark) which had a range of fibre diameters and densities and were cut to three different fleece lengths. Fibre diameter and fibre/follicle density were correlated in all circumstances. Third, because of the insulating effects of the fleece, the effect of fleece structure has on the level of vitamin D3 was tested for two groups of alpacas, selected for their fibre quality (fine and dense or thick and sparse fibre), in both winter and summer, and also pre- and post-shearing in spring. Lastly, I investigated the importance of fleece distribution, particularly around the face, and measured the effect of face-wool cover and fleece colour (light vs dark) on vitamin D production during winter when the UV intensity was low.

It is indicative from these results that the fleece is an efficient barrier against solar and UV radiation and should help to prevent heat stress on alpacas if managed correctly, but may hinder vitamin D synthesis. With increased primary follicle density and sweat gland duct density parallel to total follicle density, sweating potential is not limited. While fleece structure had little impact on the insulation, radiant heat load, or vitamin D3 synthesis, fleece length was an important factor, with reduced fleece length being favourable for vitamin D3 synthesis but a longer fleece more favourable for insulation from radiant heat. Additionally, alpacas with more face-wool, or those that are dark-coloured, are at higher risk of vitamin D deficiency in winter than alpacas with lighter-coloured fleeces or less face-wool, and therefore these animals need to be managed during winter by additional supplementation or clipping around the face to expose a larger area to UV radiation. It has been demonstrated that longer fleece will reduce the radiant heat load in summer but shorter fleece is beneficial for vitamin D3 synthesis when levels are low at the end of winter. While vitamin D deficiency remains as an issue for the alpaca fibre industry, overall, breeding selection towards higher quality and quantity of fleece should not be detrimental to the health of alpacas in Australia.
Original languageEnglish
QualificationDoctor of Philosophy
StateUnpublished - 2015


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