Selection for clean fleece weight in Merino sheep. II.* Correlated responses to selection

1974 ◽  
Vol 25 (6) ◽  
pp. 973 ◽  
Author(s):  
R Barlow
Keyword(s):  
Genetic Correlations ◽  
Fibre Diameter ◽  
Correlated Responses ◽  
Strong Negative Correlation ◽  
Fibre Density ◽  
Asymmetrical Pattern ◽  
Selection For ◽  
Fleece Weight ◽  
Positive Correlations ◽  
Staple Length

Correlated responses to selection for high and low clean fleece weight (W) in the Peppin Merino (Fleece plus and Fleece minus flocks respectively) are presented together with estimates of realized genetic correlations where appropriate. There were strong positive correlations between W and greasy fleece weight and between W and clean scoured yield, and a strong negative correlation between Wand crimp frequency. There was no consistent association between W and body weight. Selection for W caused little change in wool colour, a slight improvement in wool character, and an improvement in wool handle in the rams, but not in the ewes. There was an increase in face cover score and a decrease in birthcoat score in the Fleece minus flock, but there was no change in either trait in the Fleece plus flock. Possible reasons for these asymmetries are discussed. Most of the response in W in the Fleece plus flock arose through increases in fibre density, fibre diameter and staple length. Staple length was the major component associated with response in W in the Fleece minus flock. Decreases also occurred in fibre density and wrinkle score but there was no change in fibre diameter. Continued response in W in the Fleece minus flock was through staple length and, to a lesser extent, wrinkle score. The response in fibre density in both flocks arose through change in the ratio of secondary to primary fibres. Two-year-old and lifetime reproductive performances are reported for the two selection flocks. The Fleece minus 2-year-old ewes weaned significantly more lambs than their Fleece plus counterparts over the period studied. The lifetime reproductive performance of ewes was similar in both flocks, although there were significantly more multiple births in the Fleece plus flock. An examination of the divergence between the two flocks revealed no significant time trends. The asymmetrical pattern of response in W in these flocks is discussed in the light of the present data. __________________ *Part I, Aust. J. Agric. Res., 25: 643 (1974).

Response to selection in Australian Merino sheep. III. Single character selection for high and low values of wool weight and its components

1970 ◽  
Vol 21 (6) ◽  
pp. 955 ◽  
Author(s):  
HN Turner ◽  
MG Brooker ◽  
CHS Dolling
Keyword(s):  
Body Weight ◽  
Unit Area ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Initial Response ◽  
Skin Area ◽  
Correlated Responses ◽  
Fibre Number ◽  
Selection For ◽  
Staple Length

Direct and correlated responses are reported for 10 traits in eight pairs of lines under selection for high and low values of single characteristics : clean wool weight per head, clean wool weight per unit skin area (measured only in the groups under selection for it), body weight, wrinkle score, fibre number per unit skin area (adjusted for body weight), fibre diameter, staple length, and percentage clean yield. All groups showed overall divergence in the character under selection, though response was not always symmetrical, and in two cases (long staple and low fibre number) there was no continuing response after the initial response to extreme selection of the base parents. In all except one case, whenever previous estimates of genetic correlation were at the level of 0.2 or higher, correlated responses were in the predicted direction, though not always symmetrical in magnitude. The exception was a previously reported negative correlation between fibre number and staple length, which was not exhibited under selection for either character. Where two characters of a pair were under selection, reciprocal responses agreed in sign; magnitude will be examined in a later paper. Wool per unit area was shown to have a greater influence on clean wool weight than that of surface area, with staple length on this occasion being the most important component of wool per unit area. Reasons for an apparent decrease in the relative importance of fibre number are discussed. Three other points of importance in sheep breeding are again emphasized by these results : 1. Crimp in several pairs of groups was a poor indicator of fibre diameter. 2. Increases in clean wool weight were associated with falls in crimp number, even though fibre diameter actually became finer; diameter, not crimp, should therefore be used as a guide to wool quality. 3. The absence of genetic correlations DL and NL indicates that selection can be for high N (fibre number) with high L (staple length) and low D (fibre diameter) -in other words, a desirable fleece -with no impeding genetic correlations.

Selection for ultrafine Merino sheep in New Zealand: heritability, phenotypic and genetic correlations of live weight, fleece weight and wool characteristics in yearlings

2001 ◽  
Vol 72 (2) ◽  
pp. 241-250 ◽  
Author(s):  
T. Wuliji ◽  
K. G. Dodds ◽  
J. T. J. Land ◽  
R. N. Andrews ◽  
P. R. Turner
Keyword(s):  
New Zealand ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Live Weight ◽  
Production Traits ◽  
Genetic And Phenotypic Correlations ◽  
Selection For ◽  
Staple Strength ◽  
Fleece Weight ◽  
Staple Length

AbstractMerino yearling records from 1988 to 1992 birth years in ultrafine wool selection and random control flocks at Tara Hills High Country Station, New Zealand were analysed for live weight, fleece weight and wool characteristics. Estimates of heritability, genetic and phenotypic correlations among traits using REML methods are presented. Heritabilities (h2) of birth, weaning, autumn, spring and summer live weights and greasy and clean fleece weights were estimated as being 0·35, 0·34, 0·44, 0·43, 0·49, 0·24 and 0·28 respectively; while h2 of yield, fibre diameter, coefficient of variation in fibre diameter, staple crimp, staple length, staple strength, position of break, resistance to compression, bulk, CIE Y and CIE Y-Z were estimated to be 0·58, 0·59, 0·60, 0·45, 0·71, 0·13, 0·18, 0·46, 0·38, 0·38 and 0·42 respectively. Genetic correlations were found to be high among the live weights but low to moderate among fleece weight and wool characteristics. Heritability estimates of fibre diameter, fibre diameter variation and staple length were found to be higher in New Zealand fine wool Merinos than most of those reported in the literature. The results indicate that selection for reduced fibre diameter will have little effect on other major production traits such as live weight and fleece weight.

scholarly journals Genetic parameters for wool traits in Finnsheep lambs

2008 ◽  
Vol 16 (2) ◽  
pp. 124 ◽  
Author(s):  
M-L. PUNTILA ◽  
K. MÄKI ◽  
A. NYLANDER
Keyword(s):  
Genetic Correlation ◽  
Variance Components ◽  
Genetic Parameters ◽  
Fibre Diameter ◽  
Live Weight ◽  
Bivariate Analysis ◽  
Component Estimation ◽  
Selection For ◽  
Fleece Weight ◽  
Staple Length

Genetic parameters were estimated for wool characteristics of white and coloured Finnsheep. The data consisted of 5 309 lambs from ordinary production flocks, the Finnsheep nucleus flock and a breeding flock. The variance component estimation was done applying REML analyses. Wool traits included fleece uniformity, density, staple formation, lustre, crimp frequency, fineness grade and staple length. There was a smaller dataset that contained also lamb live weight, greasy fleece weight and additional fleece characteristics including fibre diameter measured with the OFDA method. The variance components for direct and maternal effects were estimated using bivariate analysis for 42-day, 120-day weight and greasy fleece weight. Heritability for visually assessed wool characteristics varied from 0.23 to 0.43 and for measured traits from 0.45 to 0.62. Staple length had a high negative genetic correlation with crimp frequency and fineness grade. Heritability of greasy fleece weight was high (0.55) and that of fibre diameter 0.62. The genetic correlation between crimp frequency and fibre diameter was negative (- 0.56). The results imply that the assessed traits are useful indicators for fleece quality and those of major importance can be introduced into the breeding programme. The results suggest that there is no antagonism in selection for both growth capacity and wool quantity.;

Quantitative genetic studies on wool yellowing in Corriedale sheep. 1. Wool yellowing susceptibility and wool production traits—genetic parameter estimates

1998 ◽  
Vol 49 (8) ◽  
pp. 1195 ◽  
Author(s):  
M. V. Benavides ◽  
A. P. Maher ◽  
M. J. Young ◽  
P. R. Beatson ◽  
T. C. Reid
Keyword(s):  
Selection Index ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Parameter Estimates ◽  
Production Traits ◽  
Correlated Responses ◽  
Percentage Yield ◽  
Fleece Weight ◽  
Average Information

The potential for the reduction of wool yellowing susceptibility (YPC) in Corriedale sheep via selection was examined. The heritabilities of YPC and greasy fleece weight (GFW) and clean fleece weight (CFW), yield percentage (Yield), mean fibre diameter (MFD), and subjective greasy wool colour assessment (Visual), and phenotypic and genetic correlations among these traits were estimated from records on 1492 progeny of 53 sires of a Corriedale flock by using restricted maximum likelihood procedures using an average information algorithm. The heritability of YPC was 0·27 ± 0·06. Genetic correlations between YPC and GFW, CFW, Yield, MFD, and Visual were 0·20 ± 0·14, 0·11 ± 0·14, –0·15 ± 0·13, 0·24 ± 0·14, and 0·95 ± 0·06, respectively. Phenotypic correlations were low between these traits and YPC. Visual had a heritability of 0·30 ± 0·06 and medium-high genetic correlations with all traits, except CFW. Heritability estimates of GFW, CFW, Yield, and MFD were 0·55 ± 0·07, 0·52 ± 0·07, 0·51 ± 0·07, and 0·52 ± 0·07, respectively. The expected correlated responses to selection against YPC are likely to cause reductions in CFW and MFD. Correlated responses from the reduction of Visual are predicted to be greater for all production traits than those from the reduction of YPC. Responses in YPC are predicted to be slightly higher when selection is on Visual (–0·21 score/year) than when selection is on YPC itself (–0·19 score/year). A selection index, including CFW, MFD, and YPC as aggregate breeding and breeding objective traits, calculated at I = +3·26CFW – 0·14MFD + 0·03YPC, predicted a YPC increase, worsening the problem.

Heritability estimates of wool follicle traits in sheep skin

1984 ◽  
Vol 39 (3) ◽  
pp. 399-403 ◽  
Author(s):  
M. A. Abouheif ◽  
C. LeRoy Johnson ◽  
M. P. Botkin
Keyword(s):  
Effective Means ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Heritability Estimate ◽  
Histological Techniques ◽  
Sources Of Variation ◽  
Wool Follicle ◽  
Selection For ◽  
Heritability Estimates ◽  
Fleece Weight

ABSTRACTData were collected from 600 newborn lambs, offspring of 354 Western crossbred ewes and 26 rams, to determine heritability estimates as well as phenotypic and genetic correlations between wool follicle variables using histological techniques. Breed of sire and sire within breed were significant sources of variation in total and secondary wool follicle populations and secondary:primary (S:P) ratio. Heritability estimates calculated by regression of offspring on dam were slightly higher than by paternal half-sib correlation or regression of offspring on sire. Expressed as an average of the three methods of calculation, the heritability estimate for S:P ratio was highest (0·69), followed by estimates for secondary, total and primary wool follicles (0·52, 0·46 and 0·36, respectively). These estimates are similar to the heritabilities of fleece weight, staple length and fibre diameter. Selection for increased density, provided an accurate measure is used, is suggested as an effective means for increasing fleece weight within grade.

Direct and maternal genetic (co)variances for hogget liveweight and fleece traits in Western Australian Merino sheep

2002 ◽  
Vol 53 (3) ◽  
pp. 271 ◽  
Author(s):  
S. W. P. Cloete ◽  
J. C. Greeff ◽  
R. P. Lewer
Keyword(s):  
Genetic Correlation ◽  
Coefficient Of Variation ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Phenotypic Variance ◽  
Selection For ◽  
Fleece Weight ◽  
Variance Estimates ◽  
Western Australian ◽  
Australian Merino

(Co)variance estimates for hogget liveweight, greasy fleece weight, clean fleece weight, clean yield, fibre diameter, and the coefficient of variation of fibre diameter were obtained for a Western Australian Merino resource flock. The flock encompassed 16 medium wool bloodlines and data were available for the period 1982–93. Direct additive genetic variances (h2) — expressed as a ratio of the total phenotypic variance within bloodlines — were estimated at 0.52 for hogget liveweight, 0.44 for greasy fleece weight, 0.42 for clean fleece weight, 0.63 for clean yield, 0.71 for fibre diameter, and 0.62 for coefficient of variation of fibre diameter. Maternal genetic variance estimates were significant (P < 0.05) only in hogget liveweight and fibre diameter, but components within bloodlines were low (0.05 for liveweight and 0.02 for fibre diameter). Direct within-bloodline genetic correlations of hogget liveweight as well as greasy and clean fleece weight with fibre diameter were positive (0.17, 0.31, and 0.31, respectively), suggesting that selection for bigger and heavier cutting sheep would generally lead to a broader fibre diameter. Liveweight was unrelated to clean yield and negatively related to coefficient of variation of fibre diameter (–0.17). Greasy fleece weight was negatively related to clean yield (–0.20). The genetic correlation of clean fleece weight with clean yield was positive (0.37). Wool quantity was, in general, positively related to coefficient of variation of fibre diameter, although the estimated genetic correlations were low (0.12 for greasy fleece weight and 0.07 for clean fleece weight). The genetic correlation between fibre diameter and coefficient of variation of fibre diameter was negative, and fairly low (–0.10). These results are discussed with reference to sheep breeding.

Resistance to nematode parasites in Merino sheep: correlation with production traits

1998 ◽  
Vol 49 (8) ◽  
pp. 1201 ◽  
Author(s):  
S. J. Eady ◽  
R. R. Woolaston ◽  
R. W. Ponzoni ◽  
R. P. Lewer ◽  
H. W. Raadsma ◽  
...  
Keyword(s):  
Variance Components ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Correlated Response ◽  
Production Traits ◽  
Merino Sheep ◽  
Nematode Parasites ◽  
Faecal Egg Count ◽  
Selection For ◽  
Fleece Weight

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), and the CSIRO Finewool Flock (Armidale, NSW) and included a total of 328 sire groups. Resistance to nematodes was measured by faecal egg count (FEC). Data were also available for greasy and clean fleece weight (GFW and CFW, respectively), fibre diameter (FD), and body weight (BW) at a range of ages from weaning to 21 months. Variance components were estimated by restricted maximum likelihood, fitting an animal model and estimating covariances in a series of bivariate analyses. Phenotypic correlations between FEC0·33 and production traits were all close to zero ( –0·09–0·02). Genetic correlations between FEC0·33 and production traits were –0·20, –0·18, and –0·26 for weaning weight, 10-month BW, and 16-month BW, respectively; 0·21, –0·06, and 0·21 for 10-month GFW, 16-month GFW, and 21-month GFW; 0·21, –0·05, and 0·07 for 10-month CFW, 16-month CFW, and 21-month CFW; and –0·09, –0·12, and 0·04 for 10-month FD, 16-month FD, and 21-month FD. When estimates were pooled for all fleece traits and all BW traits, the genetic correlations between FEC0·33 and GFW, CFW, FD, and BW were 0·15, 0·10, –0·06, and –0·21, respectively. Using pooled estimates for CFW, FD, and BW, selection for a breeding objective based on production traits alone would lead to an unfavourable correlated response in FEC0·33 of approximately 1% per year.

Genetic parameters for bodyweight, wool, and disease resistance and reproduction traits in Merino sheep. 4. Genetic relationships between and within wool traits

2009 ◽  
Vol 49 (4) ◽  
pp. 289 ◽  
Author(s):  
A. E. Huisman ◽  
D. J. Brown
Keyword(s):  
Coefficient Of Variation ◽  
Genetic Relationships ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Selection Decisions ◽  
Different Ages ◽  
Reproduction Traits ◽  
Staple Strength ◽  
Fleece Weight ◽  
Staple Length

The aim of this paper was to describe the genetic relationship among expressions at different ages of seven wool traits: greasy and clean fleece weights, fibre diameter, coefficient of variation of fibre diameter, staple length and strength, and mean fibre curvature. Genetic correlations among measurements at different ages for the same trait were moderate to high, and ranged from ~0.6 for both fleece weights to 0.9 and higher for mean fibre diameter and curvature. Generally, low to moderate genetic correlations (0.3–0.4) were estimated between fleece weights and fibre diameter, clean fleece weight and staple length, and fibre diameter and staple strength. Small positive genetic correlations (0.2) were estimated between greasy and clean fleece weight with fibre diameter coefficient of variation, and between fibre diameter and staple length. Mean fibre curvature had a negative genetic correlation (approximately –0.4) with most other wool traits, the exceptions were staple strength (~0.0) and coefficient of variation of fibre diameter (approximately –0.1). Fibre diameter, staple length and staple strength had negative genetic correlations with coefficient of variation of fibre diameter (–0.15, –0.10, and –0.61, respectively). The results indicate that for most wool traits only one measurement across ages is required to make accurate selection decisions. The relationships between traits are generally moderate to low suggesting that simultaneous genetic improvement is possible.

Wool characteristics of Iraqi Awassi sheep

1965 ◽  
Vol 65 (2) ◽  
pp. 223-225 ◽  
Author(s):  
M. A. Sharafeldin
Keyword(s):  
Negative Correlation ◽  
Fibre Diameter ◽  
Fibre Length ◽  
Significant Negative Correlation ◽  
Awassi Sheep ◽  
Fleece Weight ◽  
Positive Correlations ◽  
The Relationship ◽  
Staple Length

The physical wool characteristics of 268 Iraqi Awassi ewes were studied in 1963, as well as the relationship between some of these traits. The overall average grease fleece weight, clean wool percentage, staple length, fibre length, fibre diameter and degree of crimp were 3·77 lb., 84·85%, 16·47 cm., 17·37 cm., 33·32/t and 4·18 crimps per 2 cm. respectively. These attributes class the Awassi wool as a carpet wool.Age proved to have no significant effect on any ofthe traits examined. Significant positive correlations were found between grease fleece weight and fibre length and between number of crimps and fibre diameter, while a significant negative correlation was found between clean wool percentage and fibre length.

Comparison of three Australian Merino strains for wool and body traits. II. Estimates of between-stud genetic parameters

1970 ◽  
Vol 21 (5) ◽  
pp. 837 ◽  
Author(s):  
N Jackson ◽  
JW James
Keyword(s):  
Genetic Correlations ◽  
Fibre Diameter ◽  
Short Term ◽  
Breeding Values ◽  
Genetic And Phenotypic Correlations ◽  
Selection For ◽  
Fleece Weight ◽  
Subsequent Selection ◽  
Australian Merino

Data from two-tooth rams and ewes representing seven Australian Merino studs were analysed to provide estimates of between-stud genetic variances and between-stud genetic correlations for 20 wool and body traits. The estimates were used to compare two methods of choosing foundation animals for a new stud: selection within one stud or selection within each of several studs. Where only one trait was considered in selection, and provided that accurate estimates of stud mean breeding values were available, selection from a single stud was superior, although there were some differences between traits in the degree of superiority. Where more than one trait was considered the conclusion depended on the relative magnitudes and signs of the between and within-stud genetic and phenotypic correlations. In the particular case of selection for high clean fleece weight and fine fibre diameter, a strong unfavourable between-stud genetic correlation shifted the emphasis more toward selection from several studs, but selection from a single stud was still superior when accurate estimates of stud mean breeding values for clean fleece weight were available. When response to subsequent selection, as well as immediate gain in choice of founders, was considered, the conclusions were reversed. For a single trait, selection from several studs was always superior in the long term (three or more generations), and also in the short term when accurate estimates of stud mean breeding values were not available.

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