Genetic parameters for lamb autopsy traits

2014 ◽  
Vol 54 (6) ◽  
pp. 736 ◽  
Author(s):  
D. J. Brown ◽  
R. M. Jones ◽  
G. N. Hinch
Keyword(s):  
Genetic Correlations ◽  
Selection Criterion ◽  
Research Centre ◽  
Cooperative Research ◽  
Crown Rump Length ◽  
Australian Sheep ◽  
Lamb Survival ◽  
Fleece Weight ◽  
Indicator Traits ◽  
Overall Mortality

Heritabilities and genetic correlations were estimated between individual and composite autopsy traits for lambs autopsied in the Australian Sheep Cooperative Research Centre information nucleus flocks between 2008 and 2011 (n = 3224). Correlations were also estimated between autopsy categories and the production parameters Yearling greasy-fleece weight and Yearling weight, and the potential survival indicator traits: Lamb ease, Thorax circumference and Crown–rump length. All autopsy trait heritability estimates were low (range 0.01–0.04). For all traits, a higher proportion of the variance was partitioned into the maternal permanent environment than the direct effects (range 0.01–0.12), suggesting that selection based on lamb autopsy results would impart little advantage over the lamb survival trait itself in improving lamb survival. Genetic correlations between Lamb ease and all autopsy traits were positive, indicating that birth trauma is related to all causes of lamb deaths and that Lamb ease may be a useful selection criterion in seedstock flocks to reduce overall mortality. There were also positive genetic correlations between Thorax circumference after adjusting for birthweight and two classes of dystocia, as well as a positive correlation between Thorax circumference and incidences of Starvation mismothering, implying that Thorax circumference may be a useful indirect field measurement to reduce death from these causes. Of concern were the antagonistic genetic correlations estimated between Yearling greasy-fleece weight and a composite trait of All Dystocia classes plus Starvation mismothering (0.27 ± 0.15), implying that selection for increased fleece weight could be having a detrimental effect on overall lamb survival.

Genetic parameters for faecal worm egg count at different ages in Australian sheep under natural challenge

2019 ◽  
Vol 59 (7) ◽  
pp. 1201 ◽  
Author(s):  
L. Li ◽  
D. J. Brown ◽  
A. A. Swan ◽  
J. H. J. van der Werf
Keyword(s):  
Genetic Correlations ◽  
Random Regression ◽  
Research Centre ◽  
Steady Increase ◽  
Cooperative Research ◽  
Multiple Trait ◽  
Full Data ◽  
Different Ages ◽  
Australian Sheep ◽  
Univariate Analyses

The data used in the present study consisted of 24535 worm egg count records on sheep observed from 63 to 560 days of age under conditions of the natural challenge of trichostrongylid species. Records were extracted from the Information Nucleus Flock database of the Australia Sheep Cooperative Research Centre program from 2007 to 2011. Records were observed at various ages and subdivided into weaning (W, ~3 months), post-weaning (P, ~4 months), yearling (Y, ~12 months) and hogget (H, ~18 months) age stages and were used to investigate genetic variation at different age stages in univariate analyses and estimate genetic correlations between age stages in multi-trait analyses. The full data were also analysed by random regression models to study how heritability and genetic correlations varied with age. Heritability estimates from univariate analyses were 0.20 ± 0.05, 0.15 ± 0.02, 0.36 ± 0.09, 0.22 ± 0.06 for W, P, Y and H age stages respectively. A similar trend of heritability over ages was found from random regression analyses, which decreased from 0.16 at 90 days to 0.09 at 120 days, following a steady increase to 0.32 at ~410 days, and then decreased afterwards to 0.24 at 520 days. Strong genetic correlations (>0.8) were found between W and P age stages, along with Y and H age stages. Sire by flock interaction effects were significant, and accounted for the reduced estimates of heritability and increased genetic correlations between age stages. The results indicated that a multiple-trait approach is required for genetic evaluation of worm egg count when measurements are at different ages, and the accuracy of evaluations would benefit from recording at least two separate age stages.

scholarly journals Within- and across-flock genetic relationships for breech flystrike resistance indicator traits

2010 ◽  
Vol 50 (12) ◽  
pp. 1060 ◽  
Author(s):  
D. J. Brown ◽  
A. A. Swan ◽  
J. S. Gill
Keyword(s):  
Genetic Relationships ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
The Body ◽  
Production Traits ◽  
Sheep Industry ◽  
Selection Strategies ◽  
Australian Sheep ◽  
Fleece Weight ◽  
Indicator Traits

Flystrike is a major cost for the Australian sheep industry. The industry is currently implementing selection strategies for flystrike resistance to reduce the need for breech flystrike prevention. The following indicator traits are used to select for breech flystrike resistance: wool cover, skin wrinkle on the body and breech, scouring (dags) and wool colour. The aims of this study were to estimate genetic correlations between these indicator traits and production traits using the Sheep Genetics database, to distinguish between within- and across-flock genetic relationships, and to quantify responses to selection using indexes that include breech wrinkle as a proxy trait for flystrike resistance. Breech flystrike indicator traits are all heritable; however, there are significant antagonisms between wrinkle score and some production traits, primarily fleece weight and fibre diameter. Thus, simultaneous improvement in both flystrike resistance and production will be most efficient when index selection is used. Our results show that, depending on the level of emphasis placed on breech wrinkle in the index, reductions in breech wrinkle score of 0.4–0.9 units can be achieved over a 10-year period. As across-flock relationships are generally stronger than within-flock relationships, breeders will be able to take advantage of this additional variation, depending on the relative merit of their flocks. Therefore, ram breeders should combine within-flock selection with across-flock selection where possible. Sheep Genetics released early breech wrinkle Australian Sheep Breeding Values in September 2009 to assist Merino breeders in making faster progress towards reducing breech wrinkle by using flock selection.

A review of genetic and non-genetic opportunities for manipulation of marbling

2004 ◽  
Vol 44 (7) ◽  
pp. 687 ◽  
Author(s):  
B. M. Bindon
Keyword(s):  
Vitamin A Deficiency ◽  
Genetic Correlations ◽  
Consumer Preference ◽  
High Energy ◽  
Water Soluble ◽  
Research Centre ◽  
Chemical Extraction ◽  
Eating Quality ◽  
Gene Marker ◽  
Cooperative Research

The biology of marbling is a considerable issue for the Australian beef industry. Measurement of the trait is still a concern: subjective assessment based on the degree of visual fat deposition and its distribution is the 'industry standard' and the basis for payment of marbling grades. Yet this measurement may be subject to operator error and is influenced by chiller temperature. Chemical extraction gives an unequivocal measure of all fat in the muscle (intramuscular fat percentage: IMF%) and has higher heritability and genetic variation than marble score; but does this mirror exactly what the trade regards as 'marbling'?Progeny test results from the Cooperative Research Centre (CRC) for Cattle and Beef Quality breeding projects provide improved understanding of breed and genetic effects on IMF% and marble score. Estimated breeding values (EBVs) for IMF% have been released to the industry for 7 breeds. Heritability estimates confirm that genetic progress will be faster when selection is based on IMF% rather than marble score. Genetic correlations of IMF% with growth, retail beef yield (RBY%), P8 fat, residual feed intake (RFI) and tenderness are now available to underpin selection indices. A favourable allele for marbling (TG5) on chromosome 14 has been identified by CSIRO/MLA as a direct gene marker for the trait. This is now being marketed as GeneSTAR marbling. Other favourable chromosomal regions are under investigation by the CRC.Nutritional manipulation of marbling remains problematic. It is accepted that high-energy grain diets achieve higher marbling than pasture diets. Within grain-based feedlot diets higher marbling is achieved with maize than barley, while barley diets in turn are better than sorghum. Steam flaking produces higher marbling than dry rolled grain and this effect is more marked with sorghum than maize. Beyond these establishments there are many uncertainties: experiments have examined the effects of diets with high protein; low protein; protected lipid; protected protein; added oil with and without calcium; vitamin A deficiency. None of these manipulations gave consistent improvement in marble score or IMF%. Commercial feedlots supplying Japanese B3/B4 markets may have successful dietary manipulations to enhance marbling but because of its proprietary nature the information is not normally available for scientific scrutiny.Japan is the only market for Australian beef where marbling is an important component of the market specification. There can be no doubt that marbling meets a special consumer preference in that niche market. In other markets scientific evidence for a link between marbling and beef tenderness or eating quality has been difficult to define (marbling is a key component of the USA grading scheme for primal cuts but Australia is not a big supplier to that market). In the domestic Meat Standards Australia market there is a trend for marbling to become more important as a consumer issue in 5-star products where higher order sensory attributes of beef come into play. Early meat science investigations concluded that beef flavour elements were water-soluble. This would exclude marbling fat as having a notable influence on flavour.Marbling remains the major determinant of carcass value in Australia's most valuable beef market. Research should continue to assist Australian producers to meet the specifications of that market with increased precision and reduced costs.

Opportunities for genetic improvement of lamb survival

2010 ◽  
Vol 50 (12) ◽  
pp. 1017 ◽  
Author(s):  
F. D. Brien ◽  
M. L. Hebart ◽  
D. H. Smith ◽  
J. E. Hocking Edwards ◽  
J. C. Greeff ◽  
...  
Keyword(s):  
Rectal Temperature ◽  
Selection Index ◽  
Genetic Correlations ◽  
Direct Selection ◽  
Reproduction Rate ◽  
Crown Rump Length ◽  
Selection For ◽  
Lamb Survival ◽  
Net Reproduction ◽  
Birth Time

Data on lamb survival and associated traits involving records from 15 192 lambs, 6308 dams and 284 sires from the Sheep CRC’s Information Nucleus were studied. Lamb survival to 3 days of age and to weaning was 85 and 80%, respectively, and heritability (±s.e.) was 0.014 ± 0.010 and 0.010 ± 0.010, respectively. Of the 14 traits recorded at birth, time taken for the lamb to bleat, rectal temperature and crown–rump length had the highest genetic correlations with lamb survival to weaning (–0.43 ± 0.32, 0.56 ± 0.33 and –0.38 ± 0.36, respectively). Under selection for a multi-trait objective including net reproduction rate (but not lamb survival), survival was predicted to decline genetically by 0.25 lambs weaned per 100 lambs born.year, although this was reversed to a gain of 0.20 lambs weaned per 100 lambs born.year by including the trait in the breeding objective and using 50 half-sib and 50 progeny records per selection candidate. Accuracy of selection for lamb survival was improved to 0.735 with a selection index of lamb survival to weaning, lamb ease, birth coat score, time taken to bleat, rectal temperature and crown–rump length, with the addition of 50 half-sibs and 50 progeny records per candidate. Our results suggest that unless actively incorporated into breeding objectives, lamb survival may genetically decline; however, gains are possible with direct selection using half-sib and progeny records. The addition of indirect selection criteria for lamb survival can further improve accuracy, up to 93.4%, but requires further investigation.

Preliminary estimates of genetic parameters for carcass and meat quality traits in Australian sheep

2010 ◽  
Vol 50 (12) ◽  
pp. 1135 ◽  
Author(s):  
S. I. Mortimer ◽  
J. H. J. van der Werf ◽  
R. H. Jacob ◽  
D. W. Pethick ◽  
K. L. Pearce ◽  
...  
Keyword(s):  
Meat Quality ◽  
Nutritional Value ◽  
Genetic Correlations ◽  
Research Centre ◽  
Quality Traits ◽  
Live Animal ◽  
Sheep Industry ◽  
Meat Quality Traits ◽  
Australian Sheep ◽  
Meat Colour

Using performance from progeny born in 2007 and 2008 generated by the Information Nucleus program of the Cooperative Research Centre for Sheep Industry Innovation, preliminary estimates of heritability were obtained for a range of novel carcass and meat attributes of lamb relevant to consumers, including carcass characteristics, meat quality and nutritional value of lamb. Phenotypic and genetic correlations of live animal traits with carcass composition and meat quality traits were also estimated. The data were from progeny located at eight sites, sired by 183 rams from Merino, maternal and terminal meat breeds and were representative of the Merino, Border Leicester × Merino, Terminal × Merino and Terminal × Border Leicester-Merino production types of the Australian sheep industry. Data were available from 7176 lambs for weaning weight, 6771 lambs for ultrasound scanning and 4110 lambs for slaughter traits. For the novel meat quality traits, generally moderate to high heritability estimates were obtained for meat quality measures of shear force (0.27 aged 1 day, 0.38 aged 5 days), intramuscular fat (0.39), retail meat colour (range of 0.09 to 0.44) and myoglobin content (0.22). The nutritional value traits of omega-3 fatty acids and iron and zinc contents tended to have low to moderate heritabilities (0.11–0.37), although these were based on fewer records. Fresh meat colour traits were of low to moderate heritability (0.06–0.21) whereas measures of meat pH were of low heritability (~0.10). For the carcass traits, estimates of heritability were moderate to high for the various measures of carcass fat (0.18–0.50), muscle weight (0.22–0.35), meat yield (0.24–0.35), carcass muscle dimensions (0.25–0.34) and bone weight (0.27). Results indicate that for most lamb carcass and meat quality traits there is sufficient genetic variation for selection to alter successfully these characteristics. Additionally, most genetic correlations of live animal assessments of bodyweight, muscle and subcutaneous fat with the carcass and meat quality traits were favourable. Appropriate definition of breeding objectives and design of selection indexes should be able to account for the small unfavourable relationships that exist and achieve the desired outcomes from breeding programs.

Inclusion of skin follicle traits in selection indices in breeding programs improves genetic gain in Australian fine-wool Merinos

2007 ◽  
Vol 58 (9) ◽  
pp. 921 ◽  
Author(s):  
M. Asadi Fozi ◽  
J. H. J. Van der Werf ◽  
A. A. Swan
Keyword(s):  
Body Weight ◽  
Coefficient Of Variation ◽  
Genetic Parameters ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Selection Criterion ◽  
Breeding Programs ◽  
Breeding Objectives ◽  
Staple Strength ◽  
Fleece Weight

Genetic parameters for skin follicle traits, wool traits, body weight, and number of lambs weaned per ewe joined were estimated for 5108 10-month-old Australian fine-wool Merinos born between 1990 and 1996. These animals were descended from 261 sires and 2508 dams. The skin follicle number index that is based on skin surface area, and primary, secondary, or total follicle density were introduced as possible early-age selection criteria estimated at 6 months of age. Heritability estimates for total, secondary, and primary follicle number index were 0.45 ± 0.04, 0.46 ± 0.04, and 0.38 ± 0.04, respectively. The genetic correlations of total follicle number index with clean fleece weight, mean fibre diameter, staple strength, coefficient of variation of fibre diameter, body weight, and number of lambs weaned were 0.16, –0.67, 0.00, 0.03, 0.22, and 0.22, respectively. Responses to selection on indices including and excluding follicle traits were calculated based on the genetic parameters estimated, and with annual responses calculated using an optimised age structure. On average, 10% greater response was predicted when total follicle number index was used as an additional selection criterion in different micron premium scenarios. In comparison, skin follicle density had a smaller effect on genetic improvement. The extra response was ~1%. Similar index responses were obtained when total follicle number index was used as a replacement selection criterion for clean fleece weight, mean fibre diameter, and coefficient of variation of fibre diameter for breeding objectives with low emphasis on fibre diameter. In objectives with high emphasis on fibre diameter, unfavourable correlated responses in staple strength and CV of fibre diameter limited the effectiveness of using total follicle number index as a selection criterion. Although the use of total follicle number index as an additional selection criterion can be favourable for some breeding objectives, measuring this trait is currently cost prohibitive to inclusion in Merino breeding programs.

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.

Designing complex research projects to estimate genetic parameters plus treatment and other effects - optimising the experimental design

2008 ◽  
Vol 48 (8) ◽  
pp. 1110 ◽  
Author(s):  
D. L. Robinson
Keyword(s):  
Experimental Design ◽  
Genetic Parameters ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Research Centre ◽  
Parameter Estimates ◽  
Cooperative Research ◽  
Number Of Factors ◽  
Integrated Research ◽  
One Year

There is an increasing trend towards integrated research, in which several individuals or institutions pool their expertise and make use of common resources, collaborating towards a common set of scientific goals. Integrated research enables a larger number of factors to be investigated, and the most influential or important ones identified, providing information on how the different factors interact or fit together. Good experimental design is, however, required to ensure the aims can be achieved and resources spent wisely. Issues involved in the experimental design of the Australian Beef Cattle Cooperative Research Centre for Meat Quality are discussed. Theoretical results and simulation studies were used to determine optimal numbers of progeny per sire for estimating genetic parameters. For heritabilities of 0.2 and 0.5, the optima are respectively 21 and 9 progeny with recorded measurements. The curves surrounding the optima are quite flat, so aiming for 10–15 progeny with measurements per trait should provide reasonable accuracy in many situations. Estimates of heritabilities, genetic correlations and phenotypic variances have lower sampling correlations than genetic variances and covariances, suggesting that when results are pooled over different breeds or trials, it is better to pool estimates of heritabilities and genetic correlations than (co)variances. Using sires in more than one year increases the robustness of estimated sire effects and increases the accuracy of genetic parameter estimates for hard-to-measure traits (e.g. feed efficiency) that are not recorded on all animals. Unless sires can be chosen as a true random sample of the population, arrangements of link sires (and other effects such as treatments) should be chosen to provide accurate estimates when all terms in the model are fitted as fixed.

Design and role of an information nucleus in sheep breeding programs

2010 ◽  
Vol 50 (12) ◽  
pp. 998 ◽  
Author(s):  
J. H. J. van der Werf ◽  
B. P. Kinghorn ◽  
R. G. Banks
Keyword(s):  
Large Scale ◽  
Research Centre ◽  
Cooperative Research ◽  
Breeding Programs ◽  
Sheep Breeding ◽  
Genome Association ◽  
Current Design ◽  
Australian Sheep ◽  
Whole Genome Association ◽  
Design Factors

The Australian sheep Cooperative Research Centre has initiated an information nucleus with the aim to estimate genetic parameters for new traits, to undertake a large-scale whole-genome association study and to enhance the breeding values of breeding animals in commercial studs. This paper presents the rationale behind the current design factors to meet the main objectives. It then discusses the potential design of an information nucleus if it were a sustainable part of commercial sheep-breeding programs in the long term. Advantages of such an information nucleus are summarised and quantified where possible.

A strategy for achieving innovation through Sheep Cooperative Research Centre research and development

2010 ◽  
Vol 50 (12) ◽  
pp. 1145 ◽  
Author(s):  
Graham Truscott ◽  
Philip Thomas
Keyword(s):  
Product Development ◽  
New Product Development ◽  
Product Development Process ◽  
Research Centre ◽  
Cooperative Research ◽  
Sheep Industry ◽  
Development Framework ◽  
Sheep Meat ◽  
Adoption Research ◽  
Australian Sheep

The Sheep Cooperative Research Centre’s role to facilitate the transformation of the Australian sheep industry is complicated by the extensive nature of the industry across some 31 000 small to medium farming enterprises, linking to both sheep meat and wool supply chains. Close integration of the market with research and adoption through a product development focus is enabling a staged product development process while providing the management flexibility needed for development of each product type within target markets. This paper presents the basis of the New Product Development Framework and the adoption strategies used across the Sheep Cooperative Research Centre programs to accelerate utilisation of products developed out of research. These strategies include: communication; training coordination; network engagement and use of key influencers; supply chain engagement and the use of specific adoption research tools.

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