- The Optical Fibre Diameter Analyser 2000 (OFDA2000) model allows coefficient of variation of fibre diameter (CVFD) to be separated into a between fibre diameter variation component and an along fibre diameter variation component. Both traits are heritable (0.4 and 0.20, respectively) but not as heritable as CVFD on a minicored sample (0.67). Only CVFD between fibres is genetically strongly (-0.7) correlated with SS to nearly the same extend as CVFD (-0.65). It is more effective to use CVFD of wool samples as an indirect selection criterion to improve SS. In addition this will also result in a reduction in the propensity of FD to blowout along the staple. Keywords: Genetic parameters, fibre diameter variation, staple strength, micron blowout.
Sources of Variation in Fibre Diameter Attributes of Australian Alpacas and Implications for Fleece Evaluation and Animal SelectionSources of variation in fibre diameter attributes of Australian alpacas and implications for fleece evaluation and animal selection were investigated using data collected in the years 1994–97, from 6 properties in southern Australia. Data were analysed using REML (multiple regression analysis) to determine the effect on mean fibre diameter (MFD) and coefficient of variation of MFD (CV(FD)) of age, origin (property), sex (entire male, female), breed (Huacaya, Suri), liveweight, fibre colour, individual, and interactions of these effects. The mean (n = 100) age (range) was 4.2 years (0.1–11.9), liveweight 72.0 kg (12.0–134 kg), MFD 29.1 μm (17.7–46.6 μm), CV(FD) 24.33% (15.0–36.7%). A number of variables affected MFD and CV(FD). MFD increased to 7.5 years of age, and correlations between MFD at 1.5 and 2 years of age with the MFD at older ages were much higher than correlations at younger ages. Fibre diameter 'blowout' (increase with age) was positively correlated with the actual MFD at ages 2 years and older. There were important effects of farm, and these effects differed with year and shearing age. Suris were coarser than Huacayas with the effect reducing with increased liveweight; there was no effect of sex. Fleeces of light shade were 1 μm finer than dark fleeces. CV(FD) declined rapidly between birth and 2 years of age, reaching a minimum at about 4 years of age and then increasing; however, CV(FD) measurements on young animals were very poor predictors of CV(FD) at older ages, and the response of CV(FD) to age differed with farm and year. Suris had a higher CV(FD) than Huacayas on most properties, and MFD, liveweight, and sex did not affect CV(FD). Fleeces of dark shade had higher CV(FD) than fleeces of light shade in 2 of the years. It is concluded that there are large opportunities to improve the MFD and CV(FD) of alpaca fibre through selection and breeding. The potential benefit is greatest from reducing the MFD and CV(FD) of fibre from older alpacas, through reducing the between-animal variation in MFD and CV(FD). Sampling alpacas at ages
- A total of 140 Peruvian alpacas of two breeds (Huacaya and Suri) were analyzed for 69 microsatellite markers, in order to make a first approximation to the association analysis with the alpaca fiber diameter, which is the main trait related to alpaca fiber quality. A total of 599 alleles were observed across the two breeds, with a global average of 8.68 alleles per locus. Mean gene diversity in the total population was 0.701, meanwhile both breeds exhibited similar values of 0.686 (Suri) and 0.695 (Huacaya). On the other hand, the values from the inbreeding coefficient (FIS) were 0.154 (Suri) and 0.162 (Huacaya) in both breeds, being the genetic differentiation low between these populations (FST=0.022), and with a gene flow (Nm) value of 9.3. The hierarchical AMOVA corroborated that the differentiation between both breeds only explained the 2.5% of genetic variability. The analysis of association between the microsatellite markers panel and fiber diameter trait was done following an innovative methodology, which was focused in two steps. In the first one, animals were sampled according to a selective genotyping strategy, resulting in six microsatellite markers (LCA68, GLM6, LGU50, VOLP59, LCA85 and LCA90) associated with the genotypes carrying the hypothetical major gene. In the second step, the analysis revealed four significant associations of microsatellite loci (LCA68, VOLP59, LCA9O and GLM6). The subsequent DUNCAN test was used to determine the statistical differences among the fiber diameter EBV means, that corresponded to the different alleles. Eleven out from fourteen alleles of the following loci LCA68 (199, 189, 201, 197, 203 and 205), VOLP59 (112 and110) and LCA90 (243, 229 and 227), showed positive effect (decreasing fiber diameter), and only three alleles for the following loci LCA68 (195) and LCA90 (231 and 249), gave a negative effect (increasing fiber diameter).
Fibre Diameter Measured in the Post-Weaning Age Window is Genetically the Same Trait as Yearling Fibre DiameterYearling fibre diameter profiles from the OFDA2000 instrument were used to derive records on mean and coefficient of variation (CV) of fibre diameter at multiple points in the post-weaning age window, from 20 to 90% of staple profile length. Genetic correlations were calculated between these traits and their yearling equivalents. Results showed that from 50% of the staple profile and higher, post-weaning fibre diameter is genetically the same trait as yearling fibre diameter. Although the derivation of CV of fibre diameter was less accurate, genetic correlations with the yearling expression were greater than 0.9 for all except one percentile point. The expected correlation between post-weaning and yearling fleece weight was also derived, and under simple assumptions it is not unreasonable to expect estimates of genetic correlations greater than 0.9.
Genetic Parameters and Relationships Between Fibre and Type Traits in Two Breeds of Peruvian AlpacasFour fibre traits (fibre diameter, FD; coefficient of variation of FD, comfort factor; and standard deviation of FD) were jointly analysed with six subjectively scored type traits (fleece density, crimp, lock structure, head, coverage, and balance) in two breeds of Peruvian Altiplano alpaca (Suri, SU; and Huacayo, HU) to ascertain their genetic relationship. A total of 2405 fibre records and 2194 type scores were available for the HU breed whereas these figures were 709 for fibre records and 650 for type scores for the SU breed. Estimated heritabilities for fibre traits were moderate to high, ranging from 0.565 to 0.699 in the SU breed and from 0.255 to 0.417 in the HU breed. Genetic and permanent environmental correlations between fibre related traits were extremely similar across breeds suggesting that these traits are fairly the same. Heritabilities estimated for the type traits tended to be lower than those estimated for the fibre traits particularly in the SU breed (ranging from 0.173 to 0.272). Fibre and type traits were, in general, genetically poorly correlated except for crimp in the HU breed, which had favourable correlations, from moderate to high, for fibre traits. In Altiplano areas in which fibre performance recording could not be implemented, crimp scoring makes it feasible to carry out mass selection in the Huacayo breed and furthermore include rural communities in national or regional selection programmes.