The importance of accounting for maternal genetic effects in Australian fine-wool Merino breeding

2005 ◽  
Vol 56 (8) ◽  
pp. 789 ◽  
Author(s):  
M. Asadi Fozi ◽  
J. H. J. Van der Werf ◽  
A. A. Swan
Keyword(s):  
Maternal Effects ◽  
Selection Index ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Genetic Effect ◽  
Index Theory ◽  
Genetic Effects ◽  
Overall Response ◽  
Breeding Objective ◽  
Fleece Weight

(Co) variances for greasy fleece weight (GFW), clean fleece weight (CFW), mean fibre diameter (MFD), staple strength (SS), coefficient of variation of fibre diameter (CVFD), birthweight (BW), weaning weight (WW), and yearling weight (YW) were estimated for 5108 Australian Merino sheep from the CSIRO Fine Wool Project, born between 1990 and 1994. Covariances between these traits and number of lambs weaned per ewe joined (NLW) were also estimated. Significant maternal genetic effects were found for GFW, CFW, BW, WW, and YW. Estimates of heritability were biased upwardly when maternal effects were ignored. The maternal heritability estimates for GFW, CFW, BW, WW, and YW were 0.17, 0.15, 0.38, 0.28, and 0.13, respectively. Maternal effects were not important for MFD, CVFD, SS, and NLW. Direct-maternal genetic correlations within each fleece weight and bodyweight trait were estimated to be moderately negative (–0.26 to –0.48). The effect of ignoring maternal genetic effect was explored using selection index theory. Accounting for the maternal effects in both the selection criteria and breeding objective increased the overall response by 14.3%, 4.8%, 2.6%, 1.4%, and 0.0% in 3, 6, 12, 20 and 30% micron premium scenarios, respectively, compared with when the maternal effects were only included in breeding objective. Complete ignorance of the maternal effects led to overestimation in overall response of 2.8–35.7% for different micron premium scenarios in contrast to when the maternal effects were ignored in the selection index weight, but were included in the breeding objective. The results indicate that the maternal genetic effects of fleece weight and bodyweight should be considered in Merino breeding programs.

Sensitivity of breeding objectives to prices and genetic parameters in Australian Corriedale and Polwarth dual-purpose sheep

1993 ◽  
Vol 33 (3) ◽  
pp. 259 ◽  
Author(s):  
NM Fogarty ◽  
AR Gilmour
Keyword(s):  
Feed Intake ◽  
Selection Index ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Dual Purpose ◽  
Wool Production ◽  
Price Differentials ◽  
Breeding Objective ◽  
Feed Costs ◽  
Fleece Weight

A profit equation was developed for Australian Corriedale and Polwarth dual-purpose sheep kept for both wool and lamb production. Ten traits contribute to income and costs and were included in the breeding objective. These encompass wool production, fibre diameter, and feed intake of breeding ewes and hogget ewe replacements; sale weight and carcass fat depth of lambs; and reproductive rate and mature weight of ewes. The relative economic value for each trait in the enterprise was calculated from the profit equation using income and costs for 1 year. Overall gain ($A) and gain in each trait in the breeding objective from selection using an index of hogget greasy fleece weight, hogget fibre diameter, dam's number of lambs weaned, lamb weight, and lamb fat depth are reported. The sensitivity of the genetic changes in each trait in the breeding objective and index coefficients were assessed for a range of prices of products and feed costs. Sensitivity to changes in heritabilities and genetic correlations was also assessed. The incorporation of these maternal traits into LAMBPLAN is discussed. For the standard parameters and prices used, gain in leanness accounted for one-third of overall gain ($/ewe. s.d. of selection). Other traits that contributed to overall gain were fibre diameter (28%), reproduction (18%), and growth (14%). There was a small gain through feed intake (8%), and a very small loss in wool weight. Measures of fatness, growth, and fibre diameter were the important traits in the selection index. Inclusion of hogget greasy fleece weight and dam's number of lambs weaned each added <1% to the efficiency of the selection index. Varying the sale price for lamb and the price differentials for fibre diameter and fat depth had the greatest impact on overall gain. High lamb price increased gains in both reproduction and lamb weight, whereas, high price differentials for fibre diameter and fat mainly increased gains in the particular trait. A large range in prices for wool had very little effect on the individual traits or overall. Changing feed costs had little effect on overall gain, although high feed cost reduced gains from reproduction which were compensated by reduced feed intake. Halving the heritability value for each trait reduced overall gain, largely through reduction in the trait. Varying the genetic correlations of wool production with other traits had little effect. However, when genetic correlations of reproduction with weight, fat, and fibre diameter were varied there were changes in overall gain, largely through reproduction.

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.

Effect of crossbreeding on components of Hogget wool production

1992 ◽  
Vol 43 (6) ◽  
pp. 1417 ◽  
Author(s):  
WS Pitchford
Keyword(s):  
Maternal Effects ◽  
Fibre Diameter ◽  
Nutrient Supply ◽  
Genetic Effects ◽  
Wool Production ◽  
Nutrient Demand ◽  
Fleece Weight ◽  
Meat Sheep

Australia's prime lamb industry is based on systematic three way crossbreeding. This paper examines various genetic effects on wool production, important determinants of profitability of the meat-sheep enterprise. Data from three purebred (Merino, Corriedale and Dorset Horn), six F1 and the six three-way cross lines were analysed. Direct genetic effects were important for all traits analysed. Maternal effects were generally not important. Individual heterosis was large for clean fleece weight (13%) and hogget weight (10%) and important also for fibre diameter (2%). Maternal heterosis averaged 3% for clean fleece weight, -2% for fibre diameter, and 1% for hogget weight (5% rams; -3% ewes). These results support the hypothesis that the action of individual heterosis through increased nutrient demand results in increased mature weights. Also, the effect of maternal heterosis is to increase nutrient supply resulting in increased rates of maturation.

Effects of inbreeding on four families of Peppin Merinos

1957 ◽  
Vol 8 (3) ◽  
pp. 299 ◽  
Author(s):  
JM Doney
Keyword(s):  
Fibre Diameter ◽  
Genetic Effect ◽  
Direct Consequence ◽  
Specific Gene ◽  
Single Strain ◽  
Merino Sheep ◽  
Fibre Number ◽  
Per Se ◽  
Fleece Weight ◽  
Australian Merino

The influence of inbreeding on several fleece and body characters in a strain of Australian Merino sheep is reported. The four families from which data were taken were derived from a single strain of Peppin Merinos. Inbreeding without selection has been carried on since the foundation of the families between 1939 and 1944. Inbreeding is responsible for a reduction in body size, fertility, greasy and clean fleece weight, and wrinkle score, but has relatively little influence on the fleece components (yield, staple length, fibre diameter, and density of fibre population). It follows that the reduction in fleece weight is a direct consequence of a decrease in total fibre number. Since the reduction in fibre number is likely to be a correlated effect of low pre-natal and early post-natal growth rates, it is suggested that the inbreeding has had no genetic effect on the several independent systems involved in adult wool production but has affected only those associated with fitness and vigour. The depression due to inbreeding therefore may not be caused by specific gene fixation but by increased homozygosity per se.

Genetic parameters for calving difficulty using complex genetic models in five beef breeds in Australia

2016 ◽  
Vol 56 (5) ◽  
pp. 927 ◽  
Author(s):  
M. G. Jeyaruban ◽  
D. J. Johnston ◽  
B. Tier ◽  
H.-U. Graser
Keyword(s):  
Genetic Parameters ◽  
Linear Models ◽  
Random Effect ◽  
Genetic Correlations ◽  
Genetic Effect ◽  
Genetic Effects ◽  
Gestation Length ◽  
Calving Ease ◽  
Direct Genetic Effect ◽  
Calving Difficulty

Data on Angus (ANG), Charolais (CHA), Hereford (HER), Limousin (LIM) and Simmental (SIM) cattle were used to estimate genetic parameters for calving difficulty (CD), birthweight (BWT) and gestation length (GL) using threshold-linear models and to examine the effect of inclusion of random effect of sire × herd interaction (SxH) in the models. For models without SxH, estimated heritabilities for direct genetic effect of CD were 0.24 (±0.02), 0.22 (±0.04), 0.31 (±0.02), 0.22 (±0.04) and 0.17 (±0.01) for ANG, CHA, HER, LIM and SIM, respectively, whereas maternal heritabilities ranged from 0.13 to 0.20. Estimated heritabilities for direct genetic effect of BWT were 0.38 (±0.01), 0.37 (±0.03), 0.46 (±0.01), 0.35 (±0.02) and 0.36 (±0.01) for ANG, CHR, HER, LIM and SIM, respectively, whereas maternal heritabilities ranged from 0.08 to 0.11. Estimated heritabilities for direct genetic effect of GL were 0.59 (±0.02), 0.42 (±0.04), 0.50 (±0.03), 0.45 (±0.04) and 0.42 (±0.03) for ANG, CHR, HER, LIM and SIM, respectively, whereas maternal heritabilities ranged from 0.03 to 0.09. Genetic correlations between direct genetic effects of CD with BWT were highly positive and with GL were moderately positive for all five breeds. Estimated genetic correlations between direct genetic effects and maternal genetic effects (rdm) ranged across the five breeds from –0.40 (±0.05) to –0.16 (±0.02), –0.41 (±0.03) to –0.27 (±0.08) and –0.47 (±0.10) to –0.06 (±0.12) for BWT, GL and CD, respectively. Fitting SxH interaction as additional random effect significantly increased the log-likelihood for analyses of BWT, GL and CD of all breeds, except for GL of CHA. The estimated heritabilities were less than or equal to the estimates obtained with models omitting SxH. The rdm increased (i.e. became less negative) for BWT, GL and CD of all five breeds. However, the increase for GL was not substantially high in comparison to the increase observed for BWT and CD. Genetic parameters obtained for BWT, GL and CD, by fitting SxH as an additional random effect, are more appropriate to use in the genetic evaluation of calving ease in BREEDPLAN.

A comparison of the topmaking performance of wool from sheep selected by index and visual methods

1999 ◽  
Vol 39 (8) ◽  
pp. 941 ◽  
Author(s):  
A. L. Vizard ◽  
K. A. Hansford
Keyword(s):  
Body Weight ◽  
Coefficient Of Variation ◽  
Selection Index ◽  
Fibre Diameter ◽  
Visual Assessment ◽  
Index Selection ◽  
Visual Methods ◽  
Merino Sheep ◽  
Fleece Weight ◽  
Index Value

Summary. The topmaking performance of fleeces from sheep that were ranked high or low on index selection using objective measurement was compared with that of sheep from the same flock that were ranked high or low on visual assessment. A flock of 451 15-month-old fine-wool Merino sheep were classed by 2 experienced fine-wool sheep classers into 3 grades: best, average and culls. Forty-four sheep were assessed as ‘best’ and 77 sheep were graded as ‘culls’ by both classers. These sheep were defined as the ‘best visual’ and ‘worst visual’ sheep, respectively. Measurements of clean fleece weight, mean fibre diameter, coefficient of variation of fibre diameter and body weight were used in a selection index to rank all sheep in the flock. The selection index was designed to rapidly reduce mean fibre diameter and slowly increase clean fleece weight, whilst maintaining staple strength and body weight. The 44 sheep with the highest index value were defined as ‘best index’ sheep and the group of 77 sheep with the lowest index or obvious physical faults were defined as the ‘worst index’ sheep. Twenty-five fleeces were randomly selected from each of the ‘best’ and ‘worst visual’, ‘best’ and ‘worst index’ sheep for individual processing through to top. The fleeces from the ‘best index’ sheep produced greater quantities of tops that were significantly finer, longer, of lower curvature and produced less noil than all other groups. In contrast to the large difference in quality between tops from the ‘best’ and ‘worst index’ sheep, there was little difference in quality between tops from the ‘best’ and ‘worst visual’ sheep. This indicates that the traditional wool producer views of wool quality are unrelated to processing performance. It was concluded that Merino sheep selected by index selection using direct measurement of fleece weight, mean fibre diameter and coefficient of variation of diameter as selection criteria produced greater quantities of wool of superior processing performance to that from sheep selected using visual assessment.

Quantitative genetic studies on wool yellowing in Corriedale sheep. II. Clean wool colour and wool production traits: genetic parameter estimates and economic returns

2000 ◽  
Vol 51 (2) ◽  
pp. 191
Author(s):  
M. V. Benavides ◽  
A. P. Maher
Keyword(s):  
Selection Criteria ◽  
Selection Index ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Economic Losses ◽  
Direct Selection ◽  
Parameter Estimates ◽  
Selection Indices ◽  
Visual Colour

The potential for improvement of clean wool colour (CWC) in Corriedale sheep via selection was examined. The heritability, and phenotypic and genetic correlations, of CWC, brightness (Y), greasy (GFW) and clean (CFW) fleece weights , yield percentage (Yield), mean fibre diameter (MFD), and visual colour score were estimated from 440 progeny of 19 sires of a Corriedale flock using restricted maximum likelihood (REML) procedures with average information algorithm (AIREML). The heritability of CWC was estimated at 0.27±0.13. Clean wool colour showed strong positive genetic correlations with CFW and MFD. Visual colour score and CWC were also positively genetically correlated. As expected, direct selection criteria against MFD, CWC, or visual colour score would reduce CWC; however, direct selection against MFD would improve clean wool colour with negligible reductions on CFW, thus resulting in small economic gains. Several selection indices were calculated having either CFW, MFD, and CWC or CFW and MFD as selection criteria. The b-values of an unrestricted index were estimated at I1 = + 1.15 CFW + 0.13 MFD + 0.43 CWC, with positive correlated responses for all 3 breeding objective traits (CFW, MFD, and CWC). A second index, where CFW was restricted to nil genetic change, was estimated at: I2 = + 0.14 CFW − 0.02 MFD + 0.01 CWC. This index was expected to cause a negligible genetic gain for CWC (−0.04 Y–Z units/head.year). To avoid economic losses with the reduction on CFW, a third selection index was calculated where CWC was restricted to nil change. The index was estimated at I3 = +0.61 CFW − 0.07 MFD + 0.02 CWC with expected increases in CFW and decreases in MFD. Selection indices with (a) CFW and MFD (I4) and (b) CFW, MFD, and visual colour score (I5) as selection criteria would increase CFW, MFD, and CWC at the same rates observed in I1.

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).

Genetic studies on growth, reproduction and wool productiontraits in Harnali sheep

2016 ◽  
Author(s):  
SPACE Lalit ◽  
Z. S. Malik ◽  
D. S. Dalal ◽  
C. S. Patil ◽  
S. P. Dahiya
Keyword(s):  
Body Weight ◽  
Growth Traits ◽  
Additive Genetic Variance ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Reproductive Traits ◽  
Phenotypic Correlation ◽  
Reproduction Traits ◽  
Heritability Estimates ◽  
Fleece Weight

Data on growth, reproduction and wool traits of 1603 Harnali sheep maintained at Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar over a period of 22 years (1992-2013) were utilized for genetic analysis. The overall least squares mean for birth weight (BW), weaning weight (WW), six month body weight (SMW), age at first lambing (AFL), weight at lambing (WL), average lambing interval (ALI), greasy fleece weight (GFW), staple length (SL) and Fibre diameter (FD) were estimated as 3.35±0.02 kg, 12.41±0.08 kg, 16.30±0.12 kg, 707.05±2.07 days, 26.91±0.10 kg and 402.85±2.40 days, 1.62±0.02 kg, 5.65±0.03 cm and 25.85±0.07 μ, respectively. The effect of year of birth, sex of lamb and dam's weight at lambing were significant for all growth traits. The effect of year of birth and dam's weight at lambing were significant for all reproduction traits and GFW. No definite trend was observed over the years for body weights and reproductive traits. The effect of sex was significant for early growth traits. The heritability estimates were moderate for all the growth traits with high genetic correlations of BW and WW with SMW. Reproduction traits had lower estimates of heritability which indicated presence of lower additive genetic variance for these traits. Heritability estimates for studied wool traits were moderate to high. Positive genetic and phenotypic correlation of BW and WW with six month body weight and grease fleece weight indicated that selection for six month body weight would increase body weight and grease fleece weight.

scholarly journals Genetic and nongenetic factors influencing ewe prolificacy and lamb body weight in a closed Romanov flock

2020 ◽  
Vol 98 (9) ◽  
Author(s):  
Thomas W Murphy ◽  
John W Keele ◽  
Brad A Freking
Keyword(s):  
Body Weight ◽  
Maternal Effects ◽  
Effective Means ◽  
Genetic Correlations ◽  
Genetic Effect ◽  
The United States ◽  
Additive Genetic Effect ◽  
Parameter Estimates ◽  
Phenotypic Variance ◽  
Inbreeding Coefficients

Abstract The U.S. Meat Animal Research Center was the first entity in the United States to import the Romanov breed and it has been maintained as a closed flock for over 30 yr. Incorporating this super-prolific breed into crossbred and composite populations has resulted in large improvements in ewe productivity. However, few have quantified factors contributing to genetic and nongenetic variation in ewe reproduction and lamb growth within purebred Romanov populations, which were the objectives of this study. The pedigree contained a total of 8,683 lambs born to 218 and 1,600 unique sires and dams, respectively. Number of lambs born on a per ewe exposed (NLBE) and lambing (NLBL) basis were analyzed in univariate repeatability animal models. As expected, the proportion of phenotypic variance (σP2) in litter size attributable to additive genetic (0.06 to 0.08) and permanent environmental (0.05 to 0.07) effects of the ewe was low. The service sire permanent environmental effect contributed to a small but significant amount of σP2 in NLBE (0.03) but not NLBL. However, the service sire additive genetic effect did not influence σP2 in NLBE or NLBL. Lamb body weight was recorded at birth (BWB) and upon weaning from either milk replacer (~30 d; BWW-N) or their dam (~60 d; BWW-D) and were analyzed in a three-trait model with random additive direct and maternal effects. Estimated direct heritabilities were low for all body weight (BW) traits (0.07 to 0.10). Maternal heritability was moderate for BWB (0.34) but low for weaning BW (0.11 to 0.18). This was the first to report direct and maternal genetic correlations between BW of nursery- and dam-reared lambs, and both were estimated to be moderate (0.43 to 0.47). Additionally, the direct and maternal effects of BWB were more strongly correlated with BWW-N (0.74 to 0.82) than BWW-D (0.17 to 0.33). Despite inbreeding coefficients having increased at a rate of 0.33% per birth year (1986 to 2019) in this flock, they were not consistently associated with reductions in ewe or lamb performance. Parameter estimates generally agreed with those from less-prolific breeds, and results indicate that selection can be an effective means of improving subcomponents of ewe productivity.

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