Genetic parameters of wool colour and skin traits in Corriedale sheep

Abstract

Clean wool colour (CWC) is an important wool price determinant and has been related to suint characteristics, i.e. sudoriparous and sebaceous gland secretions, such as suint percentage and suint K content. In this work heritability, phenotypic and genetic correlations among wool colour and skin traits were examined. The genetic estimates were assessed by Restricted Maximum Likelihood (REML) procedures using average information algorithm (AIREML) in a Corriedale flock. The traits analysed were wool colour traits (CWC), yellow predictive colour (YPC), and Visual Score; suint traits such as suint percentage and potassium and sodium concentrations in suint, and physiological traits such as potassium and sodium concentrations in the skin, including plasma and red blood cells. The objectives of this study were to assess phenotypic and genetic correlations between wool colour and skin traits, and to find the suitability of these traits as indirect selection criteria for clean wool colour. Suint traits were highly genetically correlated to YPC. Suint K, but not suint percentage, was found to have a high genetic correlation with CWC. Skin K, Visual Score, YPC and suint K were amongst the best indirect selection criteria for clean wool colour. However, selection using these traits was expected to reduce CWC from 52% to 49% of that estimated under direct selection.

Genetic parameters for subjectively assessed wool and conformation traits in the Tygerhoek Merino flock

“…Literature h 2 a estimates of COL for Merinos ranged from 0.17 to 0.61 (Mullaney et al, 1970;McGuirk & Atkins, 1980;James et al, 1990;Raadsma & Wilkinson, 1990;Lewer et al, 1995;Groenewald et al, 1999;Naidoo et al, 2004) and from 0.27 to 0.34 for dual-purpose breeds (Mullaney et al, 1970;Benavides & Maher, 2003). The h 2 a estimate of 0.33 obtained from the current study falls within the range of these literature values.…”

Improving the whiteness and photostability of wool

“…Heritabilities of 0.42 for greasy colour score and 0.35-0.54 for objectively measured clean wool colour parameters were measured (James et al, 1990a,b). A recent study on New South Wales (NSW) Merinos has confirmed that greasy wool colour is moderately heritable (0.31-0.35) (Brown, 2006) and this is supported by work in New Zealand on Corriedale sheep (Benavides and Maher, 2003).…”

“…Holt et al showed that a single application of a UV absorber to the backs of sheep offered protection against weathering equivalent to 70% of that offered by rugging, and maintained the brightness and yellowness of back wool to within 0.7 and 0.1 units respectively of the mid-flank values (Holt et al, 1994). Wool stored in its greasy state undergoes colour changes that vary with sheep breed (Baxter, 2001). Merino fleece wools deteriorate in yellowness (Y-Z) by ~0.01-0.1 units per month and brightness (Y) values also decrease slightly (see Section 9.2.3 for definitions).…”

Extraction and characterisation of non‐scourable chromophores from discoloured fleece wool

“…The presence of colour that is not extracted from wool during the scouring process detrimentally affects its subsequent processing, in particular dyeing properties, and therefore is a critical determinant of both the quality and value of the wool [1,2]. Environmental conditions are reported to have the greatest overall effect on colour for a wool clip [3,4], with observation of the development of bright staining linked to warm, humid temperatures, when fungal and bacterial organisms thrive in the wool fleece [5]. Intense yellow discoloration of wool, sometimes termed ‘canary yellowing’, can develop on the sheep, particularly on the belly and lower edges of the fleece, as well as during storage and processing [3,6].…”