Standard Deviation Of Fiber Diameter Research Articles

Molecular genetics of wool fibre structure in sheep

Abstract Methods for mapping quantitative trait loci (QTL) are actively used in the sheep to identify chromosomal regions contributing to variation in wool traits. Therefore, this paper summarises and integrates QTL studies in the sheep to identify basic information on the genetic architecture of quantitative traits relating to wool’s important traits from viewpoint of the textile industry. The number of traits, number of QTL/associations and number of related chromosomes for categories of “Fibre” and “Fleece” were 6, 78 and 18, and 5, 97 and 23, respectively. QTL list and associated single nucleotide polymorphisms (SNPs) and genes relating to fibre curvature, fibre diameter coefficient of variance, fibre diameter standard deviation, mean fibres diameter, primary fibre diameter and primary fibre diameter coefficient of variance, fleece yield, greasy fleece weight, staple length, staple strength and wool crimp are presented. This information can be helpful in identifying genes or SNPs underlying the QTL and in the application of molecular genetic information in marker-assisted breeding programs. There is complexity in identifying relationships between wool genes. Part of this complexity in the relationships between wool traits is probably related to the pleiotropic phenomenon. In general, some researchers have found markers that have not been confirmed in other published papers. False positives and false negatives in the statistical methods used can be the reason for the differences in the distinguished genes for the desired traits of wool.

Variation in the ovine KRT34 promoter region affects wool traits

The hard α-keratins are the main component of wool fibre and are assembled in a highly organized fashion into the keratin intermediate filaments (KIFs). Variation in the keratins affects wool structure and fibre characteristics, and thus their genes make ideal candidates for the development of gene-markers. A total of 300 sheep were used for the variation study and 460 Merino × Southdown-cross lambs were used subsequently for the association study. The KRT34 promoter region was investigated using PCR-SSCP. Two different banding patterns (named variants A and B) were observed and a total of three SNPs (c.-435C/T, c.-364A/G and c.-323C/T) were identified in three different sheep breeds. Among the different breeds of sheep that were investigated, the overall frequencies of variants A and B were 37.88 % and 62.12 % respectively. The B variant was the most common in White Dorper sheep (94.83 %), when compared to the Merino (50.00 %) and New Zealand Romney (46.67 %) sheep. The two variants were also observed in the Merino × Southdown-cross lambs, where the presence of A appeared to be associated with decreased fibre diameter standard deviation (FDSD) (P = 0.030) and mean staple length (MSL) (P = 0.039). Associations with genotype were detected with mean fibre diameter (MFD) (P = 0.005) and FDSD (P = 0.008). These results suggest that variation in the KRT34 promoter fragment may affect MFD, FDSD and MSL, it could be a potential marker to improve wool quality.

SsGBLUP Method Improves the Accuracy of Breeding Value Prediction in Huacaya Alpaca.

Simple SummaryAlpaca breeding takes place in the most entrenched areas of the Andes, where the conditions to implement genetic improvement programs are very difficult. Likewise, taking phenotypic records is limited in its ability to predict genetic merit accurately. For this reason, genomic information is shown as an alternative that helps to predict the genetic values of fiber traits more precisely. This study showed how genomic information increased precision by 2.623% for the fiber diameter, 6.442% for the standard deviation of the fiber diameter, and 1.471% for the percentage of medullation compared to traditional methods for predicting genetic merit, suggesting that adding genomic data in prediction models could be beneficial for alpaca breeding programs in the future.Improving textile characteristics is the main objective of alpaca breeding. A recently developed SNP chip for alpacas could potentially be used to implement genomic selection and accelerate genetic progress. Therefore, this study aimed to compare the increase in prediction accuracy of three important fiber traits: fiber diameter (FD), standard deviation of fiber diameter (SD), and percentage of medullation (PM) in Huacaya alpacas. The data contains a total pedigree of 12,431 animals, 24,169 records for FD and SD, and 8386 records for PM and 60,624 SNP markers for each of the 431 genotyped animals of the Pacomarca Genetic Center. Prediction accuracy of breeding values was compared between a classical BLUP and a single-step Genomic BLUP (ssGBLUP). Deregressed phenotypes were predicted. The accuracies of the genetic and genomic values were calculated using the correlation between the predicted breeding values and the deregressed values of 100 randomly selected animals from the genotyped ones. Fifty replicates were carried out. Accuracies with ssGBLUP improved by 2.623%, 6.442%, and 1.471% on average for FD, SD, and PM, respectively, compared to the BLUP method. The increase in accuracy was relevant, suggesting that adding genomic data could benefit alpaca breeding programs.

Revealing Novel Power Laws and Quantization in Electrospinning Considering Jet Splitting—Toward Predicting Fiber Diameter and Its Distribution Part II Experimental

Blends of poly‐ϵ‐caprolactone (PCL) with two different molar masses are deliberately varied to change viscosity independent of polymer concentration enabling to separate viscosity and a direct concentration dependence of the fiber diameter in the electrospinning process. Multiple distributions as a result of jet splitting are determined and analyzed. The existence of essentially two modes in fiber diameter frequency distribution, the base mode and the split mode, is revealed, whereas the scaling laws for each mode can be validated according to the latest theory. Finally, the theoretical predicted upper limit of the ratio of standard deviation of fiber diameter and average fiber diameter is validated.

Genetic analysis of reproduction, body weight and mohair production in South African Angora goats

Abstract Genetic parameters for South African Angora goats were estimated from body weight, mohair production and reproduction data collected from birth on ram and ewe kids, as well as on the adult ewes in three herds from 2000 to 2015. Medium heritabilities were estimated for body weight from birth until 12-month of age and adult body weight, while a high heritability was estimated for 16-month body weight. Heritability for fibre diameter and spinning fineness was high, while a low heritability was estimated for standard deviation of fibre diameter along the length of the staple and for staple length. Medium heritabilities were estimated for fleece weight and the remainder of the fibre traits. Low heritabilities were estimated for all reproductive traits. Heritability estimates of lifetime number of kids born and weaned were higher than the heritability estimated on the individual records. Expressing lifetime number of kids weaned per kidding opportunity further increased the heritability. There were favourable significant genetic correlations of total weight of kids weaned (TWW) with adult body weight and fibre diameter, but significant unfavourable genetic correlations of TWW with adult fleece weight. Fleece weight was, however, unfavourably correlated with fibre diameter. Early fleece weights were genetically favourably correlated with all the adult traits, except with adult fibre diameter. The opposite is true for early fibre diameter, which were genetically unfavourably correlated with all the adult traits, except with adult fibre diameter. Early body weights were also genetically favourably correlated with all the adult traits, except with adult fibre diameter. Maiden ewe reproductive performance at the first parity was favourable genetically correlated with lifetime reproductive performance. Different selection strategies are proposed for ram and ewe selection, where ewe selection should focus on improving reproduction, while the fleece traits should be accommodated under ram selection. Selection of young ewes should be based on early body weight and TWW at the first parity. Too much selection pressure on early fleece weight and fibre diameter should be avoided in the selection of young ewes.

Variation in the KRTAP6-3 gene and its association with wool characteristics in Pakistani sheep breeds and breed-crosses.

This study investigated variation in the keratin-associated proteins gene, KRTAP6-3, in 5 Pakistani sheep breeds/crosses using polymerase chain reaction-single strand confirmation polymorphism (PCR-SSCP) analysis. Different banding patterns were revealed, including previously described patterns and a novel pattern (named variant H). The amplified PCR product of the novel banding pattern was directly sequenced, and a synonymous nucleotide variation c.51T>C was revealed. Among the wool traits assessed, a strong correlation (r = 0.929; P < 0.001) was observed between fibre diameter standard deviation (FDSD) and coefficient of variation of fibre diameter (CVFD), between FDSD and medullation (r = 0.720; P < 0.001), between FDSD and medullation standard deviation (MeSD) (r = 0.734; P < 0.001), between MeSD and coefficient of variance of medullation (CVMed), (r = 0.903, P < 0.001), and between CVFD and medullation (r= 0.660), CVFD and MeSD (r = 0.786; P < 0.001), CVFD and CVMed (r = 0.701; P < 0.001) and medullation and MeSD (r = 0.771; P < 0.001). Variant B was found to be associated (P = 0.018) with CVFD; the presence of B being associated with a higher CVFD, than in its absence (41.08 ± 3.98 versus 36.34 ± 3.08). Variant C was associated with CVMed (P = 0.040), where sheep with C had a lower CVMed than sheep where it was absent. Variation in KRTAP6-3 was found to affect fibre diameter related traits of wool.

The Mean Staple Length of Wool Fibre Is Associated with Variation in the Ovine Keratin-Associated Protein 21-2 Gene

Wool and hair fibres consist of a variety of proteins, including the keratin-associated proteins (KAPs). In this study, a putative ovine homologue of the human KAP21-2 gene (KRTAP21-2) was identified. It was located on chromosome 1 as a 201-bp open reading frame (ORF) in the ovine genome assembly from a Texel sheep (v.4 NC_019458.2: nt122932727 to 122932927). A polymerase chain reaction- single strand conformation polymorphism (PCR-SSCP) analysis of this ORF, and subsequent DNA sequencing, identified five sequences (named A-E). The putative amino acid sequences that would be produced, shared some identity with each other and with other KAPs, but they were most similar to ovine KAP21-1, and phylogenetically related to human KAP21-2. The location of the ovine KRTAP21-2 sequence was consistent with the location of human KRTAP21-2, and this suggests they represent different variant forms of ovine KRTAP21-2. Variation in this gene was investigated in 389 Merino (sire) × Southdown-cross (ewe) lambs. These were derived from four independent sire-lines. The sequence variation was found to be associated with variation in five wool traits: including mean staple length (MSL), mean fibre diameter (MFD), fibre diameter standard deviation (FDSD), prickle factor (PF), and greasy fleece weight (GFW). The most persistent effect of KRTAP21-2 variation was with variation in MSL; with the MSL of sheep of genotype AC being 12.5% greater than those of genotype CE. A similar effect was observed from individual variant absence/presence models. This suggests that KRTAP21-2 should be further investigated as a possible gene-marker for improving MSL.

Variation in the ovine KAP8-1 gene affects wool fibre uniformity in Chinese Tan sheep

Chinese Tan sheep are known for producing ‘spring-like’ crimped wool fleeces that consist of both fine wool fibres (non-medulated) and heterotypic wool fibres (frequently medulated). The genetic basis of these unique characteristics is poorly understood. Wool fibres are comprised of hard alpha-keratins embedded in keratin-associated proteins (KAPs). Variation in the KAP8-1 gene (KRTAP8-1) was investigated in Chinese Tan sheep, and the effect of variation in the gene on four key wool traits [mean fibre diameter (MFD), fibre diameter standard deviation (FDSD), coefficient of variation of fibre diameter (CVFD) and mean fibre curvature (MFC)] was investigated for both the fine and heterotypic wool fibres. Three previously identified ovine KRTAP8-1 variants (A, D and E) were detected, but two other previously identified variants (B and C) were not present in these Tan sheep. Of the six genotypes (AA, AD, AE, DD, DE and EE) observed, the effect of the genotype on wool traits were analysed for the three (AA, AE and EE) where the genotype frequency was greater than 5%. Genotype was found to have an effect (P = 0.022) on CVFD in the fine wool. These results suggest that variation in KRTAP8-1 affects fibre uniformity in Tan sheep.

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

The alpaca fiber diameter (FD) varies from 18 to 36 μm, being the finer fiber categories highly appreciated. However, the alpaca fiber presents some limitations in the textile industry due to the high incidence of fiber medullation and diameter variability, both reduces the comfort feeling of the garments. Decreasing or even removing medullation could be a possible selection objective in alpaca breeding programs for increasing economic value of the alpaca fiber. Therefore, the present work aimed to estimate genetic parameters regarding medullation traits, as well as the genetic correlations with other economical important traits, to be able to select the appropriate criteria to reduce or remove medullation on alpaca fiber and help to reduce the prickle factor in the garments. The data was collected from 2000 to 2017 and belonged to the Pacomarca experimental farm. There were 3698 medullation records corresponding to 1869 Huacaya and 414 Suri genetic types. The fiber samples were taken from the mid side, and were analyzed in an OFDA 100® device. The traits analyzed were percentage of medullation (PM), medullated fiber diameter (MFD), FD, standard deviation of FD, greasy fleece weight as fiber traits; density, crimp in Huacaya and lock structure in Suri, head conformation, leg coverage as morphological traits; weaning weight and age at first calving as secondary and functional traits. Genetic parameters were estimated via a multitrait restricted maximum likelihood. The heritabilities for PM and MFD were 0.225 and 0.237 in Huacaya genetic type and 0.664 and 0.237 in Suri genetic type, respectively; heritabilities for other traits were moderate for productive and morphological traits, and low to moderate for secondary and functional traits. The genetic correlations PM–FD and MFD–FD were high and favorable in both genetic types, between 0.531 and 0.975; the genetic correlation PM–MFD was 0.121 in Huacaya and 0.427 in Suri. The rest of genetic correlations with other traits were in general moderate and favorable. The repeatabilities were 0.556 and 0.668 for PM, and 0.322 and 0.293 for MFD in Huacaya and Suri genetic types, respectively. As a conclusion, PM was identified to be a good selection criterion, probably combined in an index with FD to reduce prickling factor.

Comparative Estimation of Fiber Diameter of Nanofibrous Membranes by Image Analysis Methods

The manual methods are often used for measurement of fiber diameter of electrospun membranes, however these methods are not suitable for online quality control. Although number of image analysis methods have been reported for automated measurement of fiber diameter, but there is no literature available regarding reliability, accuracy and simplicity of these measurements. In this study, the distance transform methods suggested by Pourdeyhimi and Ziabari, direct tracking method, DiameterJ software and Zhang method were compared for automated measurement of fiber diameter of electrospun nanofibrous membranes. From one way ANOVA, the difference between the results of fiber diameter was found highly significant. The mean and standard deviation of fiber diameter obtained in case of Ziabari method were extremely close to the results of manual method and also to the true values of the simulated image. Therefore, the more accurate estimation of fiber diameter was confirmed in case of Ziabari method.

Variation in the ovine keratin-associated protein 15-1 gene affects wool yield

AbstractKeratin-associated proteins (KAPs) are constituents of wool and hair fibres and are believed to play an important role in determining the characteristics of the fibres. In the current study, a polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) approach was used to screen for variation in the ovine KAP15-1 gene (KRTAP15-1). Four PCR-SSCP banding patterns, representing four different variants (named A to D), were detected. Four single nucleotide polymorphisms were found within the coding region and three of these were non-synonymous. The effect of this genetic variation on wool traits was investigated in 396 Merino × Southdown-cross sheep. Of the three variants found in these sheep (A, B and C), the presence of B was found to be associated with decreased wool yield, while C was associated with increased wool yield and decreased fibre diameter standard deviation. Sheep of genotype AC had a higher wool yield than those of genotype AA or AB.

Structural Characterization and Association of Ovine Dickkopf-1 Gene with Wool Production and Quality Traits in Chinese Merino

Dickkopf-1 (DKK1) is an inhibitor of canonical Wnt signaling pathway and regulates hair follicle morphogenesis and cycling. To investigate the potential involvement of DKK1 in wool production and quality traits, we characterized the genomic structure of ovine DKK1, performed polymorphism detection and association analysis of ovine DKK1 with wool production and quality traits in Chinese Merino. Our results showed that ovine DKK1 consists of four exons and three introns, which encodes a protein of 262 amino acids. The coding sequence of ovine DKK1 and its deduced amino acid sequence were highly conserved in mammals. Eleven single nucleotide polymorphisms (SNPs) were identified within the ovine DKK1 genomic region. Gene-wide association analysis showed that SNP5 was significantly associated with mean fiber diameter (MFD) in the B (selected for long wool fiber and high-quality wool), PW (selected for high reproductive capacity, high clean wool yield and high-quality wool) and U (selected for long wool fiber with good uniformity, high wool yield and lower fiber diameter) strains (p < 4.55 × 10−3 = 0.05/11). Single Nucleotide Polymorphisms wide association analysis showed that SNP8 was significantly associated with MFD in A strain and fleece weight in A (selected for large body size), PM (selected for large body size, high reproductive capacity and high meat yield) and SF (selected for mean fiber diameter less than 18 μm and wool fiber length between 5 and 9 cm) strains (p < 0.05), SNP9 was significantly associated with curvature in B and U strains (p < 0.05) and SNP10 was significantly associated with coefficient of variation of fiber diameter in A, PW and PM strains and standard deviation of fiber diameter in A and PM strains (p < 0.05). The haplotypes derived from these 11 identified SNPs were significantly associated with MFD (p < 0.05). In conclusion, our results suggest that DKK1 may be a major gene controlling wool production and quality traits, also the identified SNPs (SNPs5, 8, 9 and 10) might be used as potential molecular markers for improving sheep wool production and quality in sheep breeding.

Identification of the Ovine Keratin-Associated Protein 26-1 Gene and Its Association with Variation in Wool Traits.

Keratin-associated proteins (KAPs) are structural components of wool and hair fibres, and are believed to play a role in defining the physico-mechanical properties of the wool fibre. In this study, the putative ovine homologue of the human KAP26-1 gene (KRTAP26-1) was sequenced and four variants (named A–D) were identified. The sequences shared some identity with each other and with other KRTAPs, but they had the greatest similarity with the human KRTAP26-1 sequence. This suggests they represent different variants of ovine KRTAP26-1. The association of these KRTAP26-1 variants with wool traits was investigated in the 383 Merino-Southdown cross sheep. The presence of B was associated (p < 0.05) with an increase in mean fibre diameter (MFD), mean fibre curvature, and prickle factor (PF). The presence of C was found to be associated (p < 0.05) with an increase in wool yield (Yield) and mean staple length (MSL), and a decrease in MFD, fibre diameter standard deviation (FDSD), and PF. The results suggest that sheep with C have, on average, higher wool quality. These results may be useful in the future development of breeding programs based on decreasing wool MFD and FDSD, or on increasing wool MSL.

Polymorphism of KRT83 and its association with selected wool traits in Merino-cross lambs

Keratins are structural proteins in the cortex of wool fibres. It is thought that variation in the keratin genes (KRTs) affects wool structure and characteristics. Polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) analysis was used to investigate three regions of ovine KRT83. These regions were a portion of the promoter, the exon 2 region (including part of intron 1) and a region encompassing exon 3-4 (including all of exon 3, intron 3, exon 4 and part of intron 4). Initially, in 300 New Zealand Romney, Merino and White Dorper sheep obtained from 26 farms, one, two and four PCR-SSCP banding patterns were observed for these regions respectively. The exon 2 region contained two single nucleotide polymorphisms (SNPs) and the exon 3-4 region contained five SNPs. Investigation of the effect of the variation in the exon 3-4 region on variation in some wool traits were subsequently undertaken in 489 Merino×Southdown-cross sheep from seven sire-lines. The four variants identified in the original 300 sheep (designated A-D) and a new variant (E containing a new SNP) were observed with a frequency of 64.6%, 15.4%, 6.6%, 10.1% and 3.3%, respectively. General linear mixed-effects models (GLMMs) were used to investigate associations between the presence or absence of the variants and the wool traits, with a second set of models testing associations between common genotypes and those traits. The presence of A was associated with a decrease in fibre diameter standard deviation (FDSD) and coefficient of variation of fibre diameter (CVFD). The presence of C was associated with an increase in mean fibre diameter (MFD), mean fibre curvature (MFC) and prickle factor (PF), and a decrease in wool yield (Yield) [clean fleece weight (CFW)/greasy fleece weight (GFW)×100%]. A trend for association between the presence of C and increased FDSD was also detected. The presence of D was associated with an increase in MFD and PF, and a decrease in Yield. The presence of E was associated with a decrease in CVFD. Genotype AD had a higher GFW and a lower Yield than AA, and AC and AD tended to have increased MFD compared to AA and AB. These results suggest that ovine KRT83 might be a useful candidate gene for improving wool traits.

Variation in the Ovine KAP6-3 Gene (KRTAP6-3) Is Associated with Variation in Mean Fibre Diameter-Associated Wool Traits.

Polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) analysis was used to investigate variation in the ovine KAP6-3 gene (KRTAP6-3) in 383 Merino × Southdown-cross lambs from four sire-lines, and to determine whether this variation affects wool traits. Five PCR-SSCP banding patterns, representing five different nucleotide sequences, were detected, including four previously identified (named A, B, C, and F) variants and one newly identified (named G) variant. A new non-synonymous single nucleotide polymorphism (SNP) and a 45-bp deletion were detected in variant G. Of the three common genotypes (AA, AB, and AG) identified in these sheep, wool from sheep that were AG, on average, had a lower mean fibre diameter (MFD), fibre diameter standard deviation (FDSD), and prickle factor (PF) than wool from AA sheep, whereas wool from AB sheep, on average, had a higher MFD, FDSD, and PF than wool from AA sheep. This suggests that variation in ovine KRTAP6-3 affect MFD, FDSD, and PF, and that this gene may have potential for use as a gene-maker for improving fibre diameter-associated wool traits.

A Quantitative Study on Simultaneous Effects of Governing Parameters in Electrospinning of Nanofibers using Modified Neural Network using Genetic Algorithm

In this article, modified neural networks using genetic algorithms were employed to investigate the simultaneous effects of four of the most important parameters, namely; solution concentration (C); spinning distance (d); applied voltage (V); and volume flow rate (Q) on mean fiber diameter (MFD), as well as standard deviation of fiber diameter (StdFD) in electrospinning of polyvinyl alcohol (PVA) nanofibers. Genetic algorithm optimized neural networks (GANN) were used for modeling the electrospinning process. The results indicate better experimental conditions and more predictive ability of GANNs. Therefore, the approach of using genetic algorithms to optimize neural networks for modeling the electrospinning process has been successful. RSM could be employed when statistical analysis, quantitative study of the effects of the parameters and visualization of the response surfaces are of interest, whereas in the case of modeling the process and predicting new conditions, GANN is a more powerful tool and presents more desirable results.

Characterization and Multi-Response Morphological Optimization for Preparation of Defect-Free Electrospun Nanofibers Using the Taguchi Method

The study presents a method on producing defect-free polyvinyl alcohol-gelatin (PVAG) nanofibers by considering multiple morphological characteristics of the produced nanofibers using the Taguchi method. Aside from minimizing the average fiber diameter, the method was also used to produce consistent, monodispersed PVAG nanofibers without the usual defects of beading and splattering. The experiments are performed considering the effect of polymer composition (PVAG ratio and solvent ratio of water, formic acid, and acetic acid H2O:FA:HAc) and process factors (tip-to-collector distance TCD and solution flow rate) on fiber morphology. Fiber morphology is measured in terms of 4 responses: average fiber diameter, standard deviation of fiber diameter, occurrence of beading, and occurrence of splattering. Results show that maximum overall desirability for electrospinning PVAG nanofibers at smallest average diameter and deviation (26.10 ± 9.88 nm) with chance of moderate beading and zero splattering is predicted at PVAG mass ratio of 6.5:3.5, H2O:FA:HAc solvent volume ratio of 4:4:2, TCD of 12.5 cm, and flow rate of 1 ml h-1. Results of confirmatory run agree with the predicted factor levels at maximum desirability, with average fiber diameter and standard deviation measured to be 26.95 ± 6.39 nm. PVAG nanofibers of the confirmatory run are also both bead-and splatter-free. Results suggest the application of Taguchi method can offer a robust and rapid approach in deriving the conditions for production of new and high-quality PVAG nanofibers for tissue engineering scaffolds.

Genetic parameters estimation for preweaning traits and their relationship with reproductive, productive and morphological traits in alpaca

The aim of this study was to estimate the genetic parameters for preweaning traits and their relationship with reproductive, productive and morphological traits in alpacas. The data were collected from 2001 to 2015 in the Pacomarca experimental farm. The data set contained data from 4330 females and 3788 males corresponding to 6396 and 1722 animals for Huacaya and Suri variants, respectively. The number of records for Huacaya and Suri variants were 5494 and 1461 for birth weight (BW), 5429 and 1431 for birth withers height (BH), 3320 and 896 for both weaning weight (WW) and average daily gain (DG) from birth to weaning, 3317 and 896 for weaning withers height (WH), and 5514 and 1474 for survival to weaning. The reproductive traits analyzed were age at first calving and calving interval. The fiber traits were fiber diameter (FD), standard deviation of FD (SD), comfort factor and coefficient of variation of FD and the morphological traits studied were density, crimp in Huacaya and lock structure in Suri, head, coverage and balance. Regarding preweaning traits, model of analysis included additive, maternal and residual random effects for all traits, with sex, coat color, number of calving, month–year and contemporary group as systematic effects, and age at weaning as linear covariate for WW and WH. The most relevant direct heritabilities for Huacaya and Suri were 0.50 and 0.34 for WW, 0.36 and 0.66 for WH, 0.45 and 0.20 for DG, respectively. Maternal heritabilities were 0.25 and 0.38 for BW, 0.18 and 0.32 for BH, 0.29 and 0.39 for WW, 0.19 and 0.26 for WH, 0.27 and 0.36 for DG, respectively. Direct genetic correlations within preweaning traits were high and favorable and lower between direct and maternal genetic effects. The genetic correlations of preweaning traits with fiber traits were moderate and unfavorable. With morphological traits they were high and positive for Suri but not for Huacaya and favorable for direct genetic effect but unfavorable for maternal genetic effect with reproductive traits. If the selection objective was meat production, the selection would have to be based on the direct genetic effect for WW but not on the maternal genetic effect that has been shown to have less relevance. Other weaning traits such as WH or DG would be indirectly selected.

An ovine quantitative trait locus affecting fibre opacity in wool

This experiment was originally structured as a genome-wide screen for quantitative trait loci (QTL) affecting resistance or susceptibility to facial eczema disease (FE), a liver mycotoxicosis. Two Finnish Landrace (F) rams were crossed to three Texel (T) ewes to produce three cross-breed (designated F×T) rams. The F×T rams were then outcrossed to 210–230 Coopworth ewes each to generate three half-sib families, and 200 progeny per sire family were used in the FE QTL experiment. In a FE-phenotyping trial, the 600 five-month old lambs were orally challenged with a fixed dose rate of sporidesmin (FE mycotoxin) to determine their disease status. About 217 informative microsatellite markers, which were evenly spaced throughout the 26 ovine autosomes, were analysed in the FE study. Genotyping for the FE experiment was conducted in two stages: a primary and a secondary screen. In the initial primary screen, 46 most FE-resistant and 46 most FE-susceptible progeny of each sire family were selectively genotyped with the markers and analysed. Resulting chromosomes carrying suggestive and significant FE QTL were then followed up in a secondary screen when all progeny were genotyped for final analysis; there were seven chromosomes that underwent secondary screening, viz. OAR1, OAR2, OAR6, OAR13, OAR18, OAR19 and OAR20. During the FE-phenotyping trial period, mid-side wool samples were collected from the unshorn lambs for fibre measurement; the wool traits measured included yield, staple length (StapLen), crimp frequency, fibre curvature (FCurv), fibre opacity (FOpac), fibre diameter mean (FDMean) and fibre diameter standard deviation (FDsd). In a linkage analysis of wool traits, using the Haley–Knott regression method with the available “FE-generated” genotypes, a highly significant QTL for fibre opacity was detected on OAR20.

A 57-bp deletion in the ovine KAP6-1 gene affects wool fibre diameter.

High glycine-tyrosine keratin-associated proteins (HGT-KAPs) are predominantly present in the orthocortex of wool fibres. They vary in abundance in different wools and have been implicated in regulating wool fibre properties, but little is known about the functional roles of these proteins in the fibre matrix. In this study, we used polymerase chain reaction--single-strand conformational polymorphism (PCR-SSCP) analysis to screen for variation in a gene encoding the ovine HGT-KAP6-1 protein. We identified three gene variants (A, B and C). Variants A and B were similar to each other, with only three nucleotide differences occurring downstream of the coding sequence. However, variant C had a 57-bp deletion that would notionally result in a loss of 19 amino acids in the protein. The presence of C was found to be associated with an increase in mean fibre diameter (MFD), fibre diameter standard deviation (FDSD), coefficient of variation of fibre diameter (CVFD) and prickle factor (percentage of fibres over 30 microns; PF). Sheep of genotype BC produced wool of greater MFD, FDSD and PF than sheep of genotypes AA, AB and BB. The CVFD was greater in the BC sheep than the AB sheep. The results suggest that variation in ovine KRTAP6-1 affects wool fibre diameter-associated traits and that the 57-bp deletion in this gene would lead to coarser wool with greater FDSD, CVFD and PF.