Differences in fibre diameter profile characteristics in wool staples from Merino sheep and their relationship with staple strength between years, environments, and bloodlines

Abstract

This study examined differences in fibre diameter profiles (FDPs) and midside characteristics of Merino sheep in 2 environments, 4 bloodlines, 3 years, and 44 sire groups. Environment significantly (P < 0.05) influenced all characteristics except one measure of fibre diameter change and staple length. Bloodline also significantly (P < 0.05) influenced all characteristics except staple strength. The maximum fibre diameter, one measure of fibre diameter change, and staple length were significantly different (P < 0.05) between sires. Variation in fibre diameter profile characteristics between bloodlines and sires changed across the environment in which the sheep are maintained. Despite these differences between bloodlines and sires in the FDP, midside mean fibre diameter, fibre diameter variation, and staple length, there were no significant differences between bloodlines in staple strength. The relationships between the FDP and midside characteristics with staple strength were also examined over these bloodlines and environments. Along-staple variation in fibre diameter (r = –0.32 to –0.50), between-fibre fibre diameter variation (r = –0.25 to –0.48), rate of fibre diameter change (r = –0.16 to –0.38), and midside variation in fibre diameter (r = –0.25 to –0.51) were all negatively correlated with staple strength. Maximum fibre diameter (r = 0.08 to 0.18), minimum fibre diameter (r = 0.25 to 0.49), and midside mean fibre diameter (r = 0.09 to 0.35) were positively associated with staple strength. FDP characteristics explained 5–30% more variation in staple strength than could be explained using the standard midside characteristics of mean fibre diameter, fibre diameter variation, and staple length alone. These relationships were also different between environments and bloodlines. The inclusion of the FDP characteristics as explanatory variables provided an alternative interpretation for how absolute fibre diameter and fibre diameter variation combine to explain staple strength. These results suggested that animals and sires might be able to be selected on FDP characteristics to improve staple strength. More detailed genetic studies are required before these selection strategies can be recommended.

Indicators of functional integrity in production animals

“…While finer measurement resolutions (1-2 mm) can be achieved on clean (grease-free) wool staples, providing a temporal resolution of 2-6 days (depending on the wool growth rate), measurements are more readily performed on greasy wool staples at 5 mm increments and are adequate for ranking animals for differences in longitudinal fibrediameter variation (Gloag and Behrendt 2002). Thus far, studies have examined the influence of breed, nutrition, husbandry practices and prevailing seasonal conditions on longitudinal fibre-diameter variation (Adams and Briegel 1998;Brown et al 2002;Gonzalez et al 2020). Fibre-diameter profiles differ among animals within a flock (Brown et al 2002) and may therefore provide an individualised record of the animal's experience over the preceding year, as seen for other production variables described below.…”

“…Thus far, studies have examined the influence of breed, nutrition, husbandry practices and prevailing seasonal conditions on longitudinal fibre-diameter variation (Adams and Briegel 1998;Brown et al 2002;Gonzalez et al 2020). Fibre-diameter profiles differ among animals within a flock (Brown et al 2002) and may therefore provide an individualised record of the animal's experience over the preceding year, as seen for other production variables described below. Analysis of longitudinal fibre-diameter profiles in cattle hair does not appear to have been reported in the literature.…”

Lã: Características e fatores de produção

“…Sacchero et al (2010) ao avaliarem a resposta da idade dos animais em duas linhas genéticas (selecionados para diâmetros de lã superfina e não selecionados), a saber, ovelhas de segunda esquila (jovens), de terceira e quarta esquila (adultas) e de quinta e sexta esquila (velhas), encontram diferenças nas características de diâmetro somente na linha superfina, onde ovelhas velhas apresentaram maiores diâmetros médios, maiores diâmetros máximo e maiores diâmetros mínimos do ponto de diâmetro máximo até a base da mecha. Fato que se atribui pelo fato que animais mais velhos, quando comparados a animais mais jovens em programas de e melhoramento, são menos selecionados, logo assim melhor transparecendo as características adicionadas com o programa (Brown et al, 2002). Sacchero et al (2011) encontraram diminuições do ponto de diâmetro mínimo referente a 0,6 micras quando comparados a ovelhas velhas.…”