• Birth Sex Ratios in Sheep Over Nine Lambing seasons: Years 7–9 and the Effects of Ageing

    The birth sex ratio of a commercial flock of Suffolk cross sheep, Ovis aries, was studied over nine consecutive lambing seasons. In all data from 2704 lambs were recorded and analysed. The overall (1985–1993) birth sex ratio was 49.96% male lambs. Ewes with single lambs produced significantly more males (53.04%) than ewes with triplets (45.54% male). A significant positive correlation was found between the flock age and the birth sex ratio (1985–1992). As the flock aged the birth sex ratio changed from female biased to male biased, remained male biased for a number of years, and then became female biased again. This pattern is evident first in single, then in twin and later in triplet births. Among like sex twins (males and females) (1985–1993) more males (53.88%) were born in the first half and more females (45.57% males) in the second half of the lambing season. The difference between the two halves is significant. more »
  • The Impact of Fleece Characteristics on Insulation and Heat Exchange, and the Consequential Effect on Vitamin D of Alpacas in Southern Australia

    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 D3synthesis 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. more »
  • Sheep Coats Can Economically Improve the Style of Western Fine Wools

    Wethers from a mixed bloodline flock in western New South Wales were coated for 12 months between August 1998 and August 1999. The coated and a similar number of uncoated control wethers from each of the 11 bloodlines (2 medium, 3 fine and 6 superfine) were grazed together as part of a larger mob. Dye bands were placed in the fleeces of each wether before fitting of the coats and were removed before shearing when a mid-side sample was taken and a number of subjective assessments made of each fleece. The major effect of the sheep coats was to improve the style of the coated wool by about 1 style grade. This was largely the result of the coated fleeces being whiter, with less tip weathering and lower levels of dust and vegetable matter. There was no significant difference between the 2 treatment groups in wool production, fibre diameter, staple strength or resistance to compression. A partial budgeting approach was used to evaluate the economic returns from using sheep coats based on the observed differences in wool quality. Clean prices and wool values per head for the coated and uncoated sheep from each of the 11 bloodlines were calculated using NSW Agriculture's wether trial software and the flock least squares means for each wool trait. The analysis established it would be economically viable to coat all the sheep except the medium-wool sheep. Even allowing for 20% improvement in the price differential for medium wool, coating them was not economically viable. more »
  • Can We Breed Merino Sheep With Softer, Whiter, More Photostable Wool?

    Genetic parameters (heritability, phenotypic and genetic correlations) were estimated for a range of visual and measured wool traits recorded from the 2008 shearing of the initial cohort of Merino progeny born into the Sheep CRC’s Information Nucleus Flock. The aim of this initial analysis was to determine the feasibility of selectively breeding Merino sheep for softer, whiter, more photostable wool and to quantify the likely impact on other wool production and quality traits. The estimates of heritability were high for handle and clean colour (0.86 and 0.70, respectively) and moderate for photostability (0.18), with some evidence of maternal effects for both handle and photostability. The phenotypic correlations between handle and clean colour and between handle and photostability were close to zero, indicating that achieving the ‘triple’ objective of softer, whiter, more photostable wool in the current generation through phenotypic selection alone would be difficult. There was evidence of an antagonistic relationship between handle and photostability (–0.36), such that genetic selection for softer wool will produce less photostable wool that will yellow on exposure to UV irradiation. However genetic selection for whiter wool is complementary to photostability and will result in whiter wool that is less likely to yellow. Genetic selection to improve handle, colour and photostability can be achieved with few detrimental effects on other visual and measured wool traits, particularly if they are included in an appropriate selection index. more »
  • Measuring Fabric Handle to Define Luxury: An Overview of Handle Specification in Next-to-Skin Knitted Fabrics from Merino Wool

    An examination is presented of the relevance of luxury to the wool textile and garment supply chain. This examination leads to a review of the concept and importance of fabric handle as a means of defining important aspects of fabric quality. Examples are given for woven fabrics of the general relationships between subjectively assessed fabric handle attributes such as fabric softness and smoothness and measured low stress, generally high deformation, fabric properties such as fabric bending rigidity and extensibility. A brief overview is presented of the development of a system for predicting a set of subjectively assessed handle attributes for next-to-skin knitted fabrics from measurable fabric properties. Seven handle attributes selected by experienced assessors as being important for defining tactile sensations associated with next-to-skin knitted fabrics were: fabric smoothness, hairiness, softness, tightness, dryness, warmth and weight. Subjective assessments on a 1–10 scale of these seven attributes, plus an assessment of overall handle, were conducted by 12 experienced assessors on 74 next-to-skin knitted fabrics. The precision of the mean assessment of the 12 assessors ranged between 0.8 and 1.1, indicating that there was sufficient consensus on key fabric handle assessments to justify development of a method for predicting them from measurements of the physical properties of fabrics. All fabrics were tested using the PhabrOmeter fabric evaluation system, which records the force exerted during insertion of a fabric into and through an orifice. Geometric parameters were derived to describe the PhabrOmeter force-displacement curve results, and statistical models were developed to predict the average handle assessments of the 12 assessors. The precision of the models in predicting the handle intensities of eight fabric attributes on an independent validation set of 22 fabrics was significantly better than the precision of an individual assessor (confidence limits = 1.4–2.6 and 2.5–3.8, for predicted and assessed ratings, respectively). A case is made that this technology has the potential to assist in the growth of new markets for Merino wool products. more »