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 evaluation of production traits between and within flocks of Merino sheep. II. Component traits of the Hogget fleece

1993 ◽  
Vol 44 (7) ◽  
pp. 1523 ◽  
Author(s):  
SI Mortimer ◽  
KD Atkins
Keyword(s):  
Agricultural Research ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Matter Content ◽  
Research Centre ◽  
Production Traits ◽  
Merino Sheep ◽  
Phenotypic Correlations ◽  
Genetic And Phenotypic Correlations ◽  
Fleece Weight

Components of the fleece and wool quality traits were measured or assessed on Merino hogget ewes in an unselected multiple-bloodline flock over a 7-year period at Trangie Agricultural Research Centre, N.S.W. The traits recorded were face cover score (FC), leg cover score (LC), neck fold score (NF), body fold score (BF), wax content (W), suint content (S), vegetable matter content (VM), dust penetration (D), follicle density (N) and follicle ratio (RA). Genetic differences within and between flocks of Merino sheep were examined for the traits, and estimates of heritability and within-flock genetic and phenotypic correlations and between-flock genetic correlations among the traits were obtained. Genetic and phenotypic correlations were also estimated between these traits and the major wool production traits: greasy fleece weight (GFW), clean fleece weight (CFW), fibre diameter (FD), body weight (BWT) and staple length (SL). Significant strain. flock within strain and flock effects were wresent for all traits. The influence of environmental effects (birth-rearing type, age at measurement and age of dam) on the traits was estimated, with the birth-rearing type being significant and the largest effect for most traits. Paternal half-sib heritability estimates were 0.44� 0.06 for FC, 0.35� 0.06 for LC, 0.24�0.05 for NF, 0.23�0.05 for BF, 0.38�0.07 for W, 0.42�0.07 for S, 0.06�0.04 for VM, 0.22�0.06 for D, 0.20� 0.07 for N and 0.21�0.07 for RA. Estimates of within-flock phenotypic and genetic correlations were in broad agreement with available published estimates. The implications of the results for Merino breeding programs are discussed.

Genetic relationships between faecal egg count and production traits in commercial Merino sheep flocks

2004 ◽  
Vol 79 (1) ◽  
pp. 21-32 ◽  
Author(s):  
G. E. Pollott ◽  
J. C. Greeff
Keyword(s):  
Host Resistance ◽  
Genetic Correlations ◽  
Production Traits ◽  
Eye Muscle ◽  
Merino Sheep ◽  
Sire Model ◽  
Faecal Egg Count ◽  
Selection For ◽  
Staple Strength ◽  
Body Production

AbstractIn several countries the gastro-intestinal parasites of sheep show evidence of resistance to the commonly used anthelmintic treatments. The use of animals with genetic resistance to such parasites has been shown to be a viable alternative in a number of resource flocks. However, the genetics of host resistance to parasites in industry flocks and the effects on production traits of using resistant sheep is relatively unknown. This study addresses these questions using data from 55 commercial Merino flocks in Australia. The heritability and genetic correlations were estimated for faecal egg count (FEC), an indicator of host resistance, and eleven fleece and body production traits. The heritability of FEC (0·26 (s.e. 0·018)), using a sire model, was found to be similar to other estimates reported in the literature from resource flocks. The heritabilities of production traits were also consistent with published reports from resource flocks. The genetic correlations between FEC and the 11 production traits, calculated using a sire model, were mostly zero, except for staple strength (-0·17 (s.e. 0·096)), fat depth (-0·26 (s.e. 0·088)) and eye-muscle depth (-0·18 (s.e. 0·091)). Animal model estimates of heritability and the genetic correlations between the traits were largely similar to the sire model estimates. Correlated responses to selection for reduced FEC based on the sire model genetic parameters were calculated to be less than 0·15% of the trait mean per generation for all traits except staple strength, fat depth, muscle depth and live weight. These were expected to increase slightly under selection for reduced FEC. Thus industry-based selection programmes to increase host resistance to parasites should be effective and have no detrimental effect on production characteristics of Merino sheep in Australia. The full benefit of such industry-based schemes could be improved by a better level of recording in the flocks studied.

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.

Across population genetic parameters for wool, growth, and reproduction traits in Australian Merino sheep. 2. Estimates of heritability and variance components

2007 ◽  
Vol 58 (2) ◽  
pp. 177 ◽  
Author(s):  
E. Safari ◽  
N. M. Fogarty ◽  
A. R. Gilmour ◽  
K. D. Atkins ◽  
S. I. Mortimer ◽  
...  
Keyword(s):  
Maternal Effects ◽  
Variance Components ◽  
Genetic Parameters ◽  
Growth Traits ◽  
Fibre Diameter ◽  
Production Traits ◽  
Merino Sheep ◽  
Reproduction Traits ◽  
Fleece Weight ◽  
Australian Merino

Precise estimates of genetic parameters are required for genetic evaluation systems. This study combined data from 7 research resource flocks across Australia to estimate variance components and genetic parameters for production traits in the Australian Merino sheep. The flocks were maintained for several generations and represented contemporary Australian Merino fine, medium, and broad wool bloodlines over the past 30 years. Over 110 000 records were available for analysis for each of the major wool traits, and 50 000 records for reproduction and growth traits with over 2700 sires and 25 000 dams. A linear mixed animal model was used to analyse 6 wool traits comprising clean fleece weight (CFW), greasy fleece weight (GFW), fibre diameter (FD), yield (YLD), coefficient of variation of fibre diameter (CVFD), and standard deviation of fibre diameter (SDFD), 4 growth traits comprising birth weight (BWT), weaning weight (WWT), yearling weight (YWT), and hogget weight (HWT), and 4 reproduction traits comprising fertility (FER), litter size (LS), lambs born per ewe joined (LB/EJ), and lambs weaned per ewe joined (LW/EJ). The range of direct heritability estimates for the wool traits was 0.42 ± 0.01 for CFW to 0.68 ± 0.01 for FD. For growth traits the range was 0.18 ± 0.01 for BWT to 0.38 ± 0.01 for HWT, and for reproduction traits 0.045 ± 0.01 for FER to 0.074 ± 0.01 for LS. Significant maternal effects were found for wool and growth, but not reproduction traits. There was significant covariance between direct and maternal genetic effects for all wool and growth traits except for YWT. The correlations between direct and maternal effects ranged from –0.60 ± 0.02 for GFW to –0.21 ± 0.10 for SDFD in the wool traits and from –0.21 ± 0.03 for WWT to 0.25 ± 0.08 for HWT in the growth traits. Litter effects were significant for all wool and growth traits and only for LS in reproduction traits. The mating sire was fitted in the models for reproduction traits and this variance component accounted for 21, 17, and 8% of the total phenotypic variation for FER, LB/EJ, and LW/EJ, respectively. The implications of additional significant variance components for the estimation of heritability are discussed.

Genetic and phenotypic parameters for reproduction, production and bodyweight traits in Australian fine-wool Merino sheep

2018 ◽  
Vol 58 (2) ◽  
pp. 207 ◽  
Author(s):  
S. Dominik ◽  
A. A. Swan
Keyword(s):  
Genetic Relationships ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Careful Consideration ◽  
Production Traits ◽  
Merino Sheep ◽  
Wool Production ◽  
Phenotypic Correlations ◽  
Reproduction Traits ◽  
Definition Of

The present study estimated phenotypic and genetic relationships between wool production, reproduction and bodyweight traits in Australian fine-wool Merino sheep. The data for the study originated from the CSIRO Fine Wool Project, Armidale, Australia. Data on wool characteristics, measured at ~10 and 22 months of age, bodyweight and several reproduction traits across consecutive lambing opportunities were analysed. The genetic correlations were moderately negative between fibre diameter measured as yearling and adult, and lamb survival (rg = –0.34 ± 0.15 and rg = –0.28 ± 0.14 respectively) and total number of lambs weaned (rg = –0.32 ± 0.21 and rg = –0.40 ± 0.21 respectively). The genetic correlations of yearling and adult greasy and clean fleece weights with number of lambs weaned and fecundity showed moderately to highly negative relationships and a moderately negative correlation with the number of fetuses at pregnancy scanning. Phenotypic correlations between reproduction and wool production traits were estimated to be zero, with the exception of bodyweight showing low to moderate positive phenotypic correlations with total number of lambs born and weaned. Genetic variances were generally low for the reproduction traits and resulted in low heritability estimates (from h2 = 0.03 ± 0.01 to h2 = 0.12 ± 0.13), with the exception of total number of lambs born (h2 = 0.25 ± 0.03). The study indicated that parameter estimation and trait definition of lifetime reproduction records require careful consideration and more work in this area is required.

Continued selection of Romney sheep for resistance or susceptibility to nematode infection: estimates of direct and correlated responses

2000 ◽  
Vol 70 (1) ◽  
pp. 17-27 ◽  
Author(s):  
C. A. Morris ◽  
A. Vlassoff ◽  
S. A. Bisset ◽  
R. L. Baker ◽  
T. G. Watson ◽  
...  
Keyword(s):  
Maximum Likelihood Estimates ◽  
Research Centre ◽  
Control Line ◽  
Production Traits ◽  
Correlated Responses ◽  
Breeding Lines ◽  
Nematode Parasites ◽  
Phenotypic Standard Deviation ◽  
Selection For ◽  
Fleece Weight

AbstractDivergent breeding lines of Romney sheep, selected as lambs for consistently high or low faecal worm egg count (FEC) following natural multi-species challenge by nematode parasites, were established in New Zealand at Wallaceville Animal Research Centre in 1979 and at Rotomahana Station in 1985. In 1988 the Rotomahana lines, including an unselected control line maintained under the same management conditions, were transferred to Tokanui Station where they remained for 4 years. In 1993 elite high and low FEC animals from Tokanui, along with the controls, were transferred to Wallaceville, where merged lines have since been managed together. Selection responses from the lines at Rotomahana and Tokanui, and from a further 5 years of divergent selection in the merged lines, are reported here. For the two most recent lamb crops (1996 and 1997 birth years), log-transformed FECs of the high and low lines were 1·27 and -1·46 phenotypic standard deviation units from the control. After back-transformation to the original scale, where the FEC for control line lambs averaged 1255 eggs per g, the means for the high and low lines were 3Ό5 and 0·27 times the control mean. Animal-model restricted maximum likelihood estimates of her it ability and repeatability for single-record FEC (following separate infections) were 0·28 (s.e. 0·02) and 0·42 (s.e. 0Ό1), respectively. Correlated responses in production traits include significantly decreased post-weaning weight gain and increased dags (breech soiling) in lambs, and decreased fleece weight in yearlings and ewes in the low FEC line, compared with those in the high line. However the low FEC line had proportionally 0·11 more lambs weaned per ewe mated than the high FEC line (F < 0·01). It is concluded firstly that selection for high or low FEC in Romney s has achieved an 11-fold difference between the divergent lines. Secondly, it will generally be necessary in a commercial environment to apply index selection for a combination of increased productivity, decreased FEC and possibly decreased dags, when potential candidates are recorded under conditions of nematode challenge.

Selection for economic characters in Australian Merino sheep. V. Further estimates of phenotypic and genetic parameters.

1955 ◽  
Vol 6 (1) ◽  
pp. 77 ◽  
Author(s):  
FHW Morley
Keyword(s):  
Genetic Correlations ◽  
Minor Importance ◽  
Agricultural Experiment Station ◽  
Genetic Progress ◽  
Sheep Population ◽  
Merino Sheep ◽  
Agricultural Experiment ◽  
Selection For ◽  
Fleece Weight ◽  
Genetic Homeostasis

Estimates of heritability, genetic correlations, phenotypic correlations, and other parameters among eight characteristics were obtained from Merino sheep at Trangie Agricultural Experiment Station. One set of estimates was obtained by parent-offspring regressions from data obtained between 1943 and 1952. Another set was obtained by half-sib analyses from data from sheep with first adult shearings in 1953. Estimates of heritability were: greasy fleece weight, 0.40 ± 0.06; yield (per cent.), 0.39 ± 0.07; clean fleece weight, 0.47 ± 0.07; staple length, 0.56 � 0.07; crimps per inch, 0.47 ± 0.11; folds, 0.50 ± 0.07; body weight, 0.36 ± 0.08; birthcoat, 0.80 ± 0.10. The most important genetic correlation limiting genetic improvement in clean fleece weight is that between this trait and crimps per inch. Because of this the rate of improvement in fleece weight could be reduced by about 30 per cent. whenever crimps per inch is also selected. Other genetic correlations indicate antagonisms between characteristics, but these antagonisms appear to be of minor importance except that between clean fleece weight and crimps per inch. This sheep population does not appear to have reached a state of genetic homeostasis, a t least with respect to the characteristics studied. However, the findings emphasize the necessity for careful evaluation of the economic importance of different traits, and for accurate measurement, if maximum genetic progress is to be achieved.

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.

Will genetics offer a permanent solution to breech strike?

2010 ◽  
Vol 50 (12) ◽  
pp. 1053 ◽  
Author(s):  
J. S. Richards ◽  
K. D. Atkins
Keyword(s):  
Low Cost ◽  
Management Strategies ◽  
Fibre Diameter ◽  
Production Traits ◽  
Predisposing Factor ◽  
Breeding Programs ◽  
Negative Effect ◽  
Selection For ◽  
Fleece Weight

There are several options for managing flystrike other than mulesing. Breeding for plainer animals that do not require mulesing is an attractive, permanent long-term solution. Breech wrinkle is the key predisposing factor for breech and tail strike. Little effort has been made to reduce wrinkle score in sheep because mulesing was so successful and because there is a perception that reducing wrinkle score will reduce fleece weight. Fleece weight will be reduced if single-trait selection for wrinkle is applied, but if breech wrinkle is included in an index, the negative effect of wrinkle on other production traits can be minimised using the same method as that used to accommodate the negative correlation between fibre diameter and fleece weight. Breeding programs for reduced breech wrinkle should be used in combination with short-term tactical management strategies, especially during the initial stages of the breeding program. The need for tactical management will decrease as the program progresses. This approach can be applied using information that can be recorded easily and at low cost.

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