Genetic parameters of objectionable fibers and of their associations with fleece traits in Corriedale sheep1

Abstract

The aim of this research was to assess the variability and genetic relationships among binary traits denoting the presence or absence of objectionable fibers, namely pigmented (BINPPF), medullated (BINPMED), and kemp fibers (BINPK), and of fleece traits (fiber diameter [FD] and clean fleece weight [CFW]) in Corriedale sheep. Additionally, the total response to selection against objectionable fibers and indirect responses when selecting for fleece traits were evaluated. Fiber records from 679 animals and fleece records from 795 animals obtained from 2 experimental flocks (from 2005 to 2007) were used; the pedigree file included a total of 3,792 animals. Heritability and genetic correlations among the traits were estimated with a multivariate animal model under a Bayesian setting. Heritability estimates (posterior SD) for BINPPF, BINPMED, and BINPK were 0.35 (0.08), 0.37 (0.10), and 0.63 (0.09), respectively; for CFW and FD, estimates were 0.42 (0.09) and 0.43 (0.08), respectively. The genetic correlations between CFW and the 3 types of objectionable fibers were very low (i.e., <0.2). Thus selection for CFW is not expected to affect the number of such fibers in any direction. The same occurred for the genetic correlation between BINPK and FD. Genetic correlations between FD and BINPMED and FD and BINPPF were positive and favorable (0.50 and 0.56, respectively). Selecting for lower FD would decrease the numbers of objectionable fibers. The expected correlated responses in BINPPF, BINPMED, and BINPK when selecting for CFW were -0.03 (0.11), 0.03 (0.11), and -0.05 (0.18), respectively; when selecting for FD, the correlated responses were -0.26 (0.11), -0.26 (0.11), and -0.14 (0.16). Overall, this study reports novel information on genetic parameters for the presence of objectionable fibers and their associations with fleece traits in sheep. Our findings suggest that it could be possible to improve FD while at the same time reducing the content of BINPMED and BINPPF in wool; however, improvements in CFW are likely to have no effect on the numbers of objectionable fibers.

Genetic parameters for medullated fiber and its relationship with other productive traits in alpacas

“…These values were 0.225 and 0.237 for, respectively, PM and MFD for Huacaya genetic type, and 0.664 and 0.237 for Suri genetic type, suggesting the PM heritability in Suri genetic type the possible existence of a major gene segregating, maybe the same found for FD reported by Pérez-Cabal et al (2010). These values were similar than others estimated in other species, being 0.37 for PM in sheep (Sánchez et al, 2016), 0.23 in Angora goats (Allain and Roguet, 2006) and 0.29 in Argentinean lamas (Frank et al, 2011). This is promising since under similar heritabilities, such as those for FD and SD, a satisfactory response to selection has been shown in the same population with an important genetic progress (Gutiérrez et al, 2014), especially in Huacaya genetic type for FD.…”

“…Related to prickling is the definition of the objectionable fibers in sheep. These contaminating fibers would gather the kemp, colored fibers and medullated fibers (Sánchez et al, 2016). Thus, quality tests were established in this concern, in which only a maximum of 100 contaminating fibers per kilogram of top were allowed (Hansford, 2003).…”

Variation in Wool Characteristics across the Body in a Herd of Alpacas Kept in Poland

“…In addition to the variation in fiber diameter across the body, the incidence of medullated fibers also varies across the body. These two factors affect the prickliness of the finished product [21][22][23]. Hence, breeding fine-wool alpacas with non-medullated fibers should be the focus of all breeders.…”

Variabilidad fenotípica del porcentaje de fibras meduladas en el vellón de alpaca Huacaya

“…Para fines de selección por PM y otras características de las fibras meduladas, se sugiere que la región del flanco (ijar) es la región más representativa (Aylan-Parker yMcGregor, 2002). como el incremento del porcentaje de fibras meduladas fragmentadas y no meduladas en el vellón de alpacas puede atribuirse a la selección dirigida para reducir el DMF que se practica en Pacomarca(Cervantes et al, 2010) Sánchez et al, 2016;Cruz et al, 2017;Pinares et al, 2018)…”