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.

scholarly journals Realized Sampling Variances of Estimates of Genetic Parameters and the Difference Between Genetic and Phenotypic Correlations

Genetics ◽  
1996 ◽  
Vol 143 (3) ◽  
pp. 1409-1416 ◽  
Author(s):  
Kenneth R Koots ◽  
John P Gibson
Keyword(s):  
Genetic Correlation ◽  
Genetic Parameters ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Phenotypic Correlation ◽  
Parameter Estimates ◽  
Sampling Variance ◽  
Phenotypic Correlations ◽  
Genetic And Phenotypic Correlations ◽  
Heritability Estimates

Abstract A data set of 1572 heritability estimates and 1015 pairs of genetic and phenotypic correlation estimates, constructed from a survey of published beef cattle genetic parameter estimates, provided a rare opportunity to study realized sampling variances of genetic parameter estimates. The distribution of both heritability estimates and genetic correlation estimates, when plotted against estimated accuracy, was consistent with random error variance being some three times the sampling variance predicted from standard formulae. This result was consistent with the observation that the variance of estimates of heritabilities and genetic correlations between populations were about four times the predicted sampling variance, suggesting few real differences in genetic parameters between populations. Except where there was a strong biological or statistical expectation of a difference, there was little evidence for differences between genetic and phenotypic correlations for most trait combinations or for differences in genetic correlations between populations. These results suggest that, even for controlled populations, estimating genetic parameters specific to a given population is less useful than commonly believed. A serendipitous discovery was that, in the standard formula for theoretical standard error of a genetic correlation estimate, the heritabilities refer to the estimated values and not, as seems generally assumed, the true population values.

scholarly journals Genetic parameter estimates for important traits on the fifth generation in red tilapia in Vietnam

2021 ◽  
Vol 20 (1) ◽  
pp. 49-57
Author(s):  
Sang V. Nguyen
Keyword(s):  
Body Weight ◽  
Survival Rate ◽  
Genetic Parameters ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Parameter Estimates ◽  
Environment Interaction ◽  
Body Colour ◽  
Red Tilapia ◽  
Gxe Interaction

Genetic parameters comprising heritability, genetic correlation and genotype by environment interaction (GxE) for growth survival rate and body colour at harvest were estimated on the 5th selective generation of red tilapia grown in two environments, freshwater and brackishwater ponds. A total of 116 full-half-sib families was produced as well as 4,432 and 3,811 tagged individuals were tested in freshwater and brackishwater ponds, respectively. Genetic parameters were estimated by ASReml 4.1 software. The heritability for body weight and survival rate was high while medium heritability for body colour in freshwater was observed. The heritability for those traits of red tilapia in brackishwater. Together with the figures in earlier publication on previous generations (G1 to G4) in the same selective population, the expected medium to high response acquires if selection is done for each trait. Genetic correlations among harvest body weight, survival rate and body colour are insignificantly different and ranging from -0.25 to 0.37 (P > 0.05). These results implied that selection on one trait do not influence on responses of the other traits. GxE interaction for body weight and body colour between two tested environments is mostly negligible with genetic correlations ranging from 0.63 - 0.80 while it is important for survival trait (rg = -0.17 ± 0.40).

scholarly journals FEASIBILITY OF EARLY Pinus taeda L. SELECTION TO ASSESS GROWTH VARIABLES IN PROGENY TEST

FLORESTA ◽  
2021 ◽  
Vol 51 (4) ◽  
pp. 937
Author(s):  
Paulo César Flôres Júnior ◽  
Vanessa Ishibashi ◽  
Jorge Luis Monteiro de Matos ◽  
Diego Tyszka Martinez ◽  
Antonio Rioyei Higa
Keyword(s):  
Genetic Correlation ◽  
Genetic Parameters ◽  
Block Design ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Critical Factor ◽  
Early Selection ◽  
Parameter Estimates ◽  
Randomized Block Design ◽  
Adult Plants

Forest species breeding programs require a long period-of-time for plants to reach the proper age to enable selecting superior genotypes, which is a critical factor in selection processes. Thus, the aims of the current study are to estimate genetic parameters in juvenile and adult plants (6, 10 and 20 years) in order to investigate genetic correlations between variables at different ages and at certain ages; as well as to determine whether it is possible performing efficient early selection in juvenile plants. The test was implemented in 1997; it comprised 120 progenies and followed a randomized block design, with five repetitions - linear plots comprised 5 plants at 2.5 m x 2.5 m spacing. DBH (cm), H (m) and VOL (m³) of all tested subjects were measured at the age of 6, 10 and 20 years. Variance components, genetic parameters, as well as genetic correlations between variables and between ages were estimated in Selegen REML/BLUP® software. Genetic parameter estimates have shown superiority at 10 years, in comparison to that estimated at 6 and 20 years. Variable ‘DBH’ has shown high genetic correlation to height (H) and volume (VOL), whereas DBH x VOL have shown high genetic correlation (0.98) in 10-year-old plants. With respect to genetic correlation between ages, 10-year-old plants have shown moderate correlation to 6- and 20-year-old plants. Early selection is indicated for 10-year-old plants, in 20-year cycles, since plants at this age have shown higher selection efficiency to predict gains in comparison to adult plants.

Evaluation of Bonsmara and Belmont Red cattle breeds in South Africa. 2. Genetic parameters for growth and fertility

2006 ◽  
Vol 46 (2) ◽  
pp. 213 ◽  
Author(s):  
N. J. Corbet ◽  
R. K. Shepherd ◽  
H. M. Burrow ◽  
K. C. Prayaga ◽  
J. van der Westhuizen ◽  
...  
Keyword(s):  
South Africa ◽  
Maternal Effects ◽  
Genetic Parameters ◽  
Growth Traits ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Repeated Measurements ◽  
Maternal Influence ◽  
Parameter Estimates ◽  
Fertility Traits

Genetic parameters were estimated for growth and fertility indicator traits in a South African beef cattle population. Measurements on 5601 pedigreed progeny of 96 Bonsmara sires, 18 Belmont Red sires and 20 Bonsmara × Belmont Red cross sires were recorded over 19 years in 4 diverse climatic regions of South Africa. Growth traits were measured on growing stock from birth to 18 months at pasture. Cow weights were measured at calving and weaning. Age at first calving, and repeated measurements of calving day and calving interval were recorded on 1993 breeding females as indicators of reproductive performance. The traits were analysed using univariate and bivariate animal models with maternal effects fitted. Direct heritability of growth traits (0.11–0.42) and female fertility traits (0.02–0.13) suggested that genetic progress could be made by selection for some traits. Genetic correlations between growth and fertility traits were variable (–0.47–0.85) and indicated that multi-trait selection would be the best method of dealing with multidirectional forces on productivity traits. Genetic correlations between direct and maternal effects on liveweight traits were mostly negative indicating that genetic improvement of traits with strong maternal influence, such as weaning weight, would be complicated and supported the use of post-weaning weights with less maternal influence as selection criteria to improve the direct additive component of growth. The genetic parameter estimates provide useful reference values for estimation of breeding values in a proposed combined-breed genetic evaluation program.

scholarly journals Genetic parameter estimates for resistance to Enteric Septicemia of Catfish on Pangasianodon hypophthalmus

2021 ◽  
Vol 20 (1) ◽  
pp. 39-48
Author(s):  
Dung T. P. Tran
Keyword(s):  
First Generation ◽  
Genetic Parameters ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Parameter Estimates ◽  
Pangasianodon Hypophthalmus ◽  
Sib Families ◽  
Striped Catfish ◽  
Selection For ◽  
Enteric Septicemia

Genetic parameters were estimated for resistant traits against Enteric Septicemia of Catfish (ESC) on the first generation of selection on striped catfish. In total, 8,207 and 5,838 individuals from 147 and 130 full-sib families were challenged by Edwardsiella ictaluri causing ESC on fingerlings and tested growth in pond accordingly. Harvest body weight (HW), length (HL) and survival (SURGROW) from grow-out test and ESC resistant traits such as binary alive-dead survival (SUR) and time to dead (TIME) at different truncated points from challenged test of fingerlings were recorded. Heritability for each trait and genetic correlations among these recorded traits were estimated. High heritabilities were found for HW (0.48) and HL (0.47), and mostly from medium to high values were estimated for SURGROW (0.23), SUR (0.13 - 0.40) and TIME (0.25 - 0.39). Genetic correlations among different truncated SUR and TIME traits were almost highly positive (0.57 - 0.99). Genetic correlations among different truncated SUR and TIME traits with HW and SURGROW were low positive (0.10 - 0.40). In summary, selection for ESC resistance would not negatively affect the growth in fingerling stage.

scholarly journals Genetic parameters of reproductive traits in Tunisian Holsteins

2016 ◽  
Vol 59 (2) ◽  
pp. 209-213 ◽  
Author(s):  
Hafedh Ben Zaabza ◽  
Abderrahmen Ben Gara ◽  
Hedi Hammami ◽  
Borni Jemmali ◽  
Mohamed Amine Ferchichi ◽  
...  
Keyword(s):  
Genetic Correlation ◽  
Genetic Parameters ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Reproductive Traits ◽  
Parameter Estimates ◽  
Calving Interval ◽  
Cattle Herds ◽  
Correlation Estimate ◽  
Fertility Traits

Abstract. Multi-trait Bayesian procedure was used to estimate genetic parameters for reproductive traits in Tunisian Holstein cows. A total of 31 348 lactations of the calving years 2005 to 2012 were analyzed. Fertility traits were the calving interval (CI), days open (DO), days to first insemination (DFI), days from first insemination to conception (FIC), and number of inseminations per conception (NI). Posterior means of heritabilities of CI, DO, DFI, FIC, and NI were 0.047, 0.03, 0.025, 0.024, and 0.069, respectively. Posterior means of repeatabilities of the same respective traits were 0.106, 0.094, 0.051, 0.036, and 0.17. Genetic correlations among female fertility traits were also computed. Calving interval and DO had the highest genetic correlation estimate (0.85) because they have overlapping genetic meanings. The lowest genetic correlation estimate (−0.25) was found between DFI and NI. Genetic parameter estimates are low and are even lower than those reported in most literature, implying that more focus should be put upon improving the management of reproduction in dairy cattle herds in Tunisia.

scholarly journals  Reduction of traits for genetic evaluation of linear described traits in the Old Kladruber horse

2012 ◽  
Vol 57 (No. 4) ◽  
pp. 160-170 ◽  
Author(s):  
L. Vostrý ◽  
J. Přibyl ◽  
P. Šimeček
Keyword(s):  
Genetic Similarity ◽  
Genetic Parameters ◽  
Selection Index ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Principal Component ◽  
Parameter Estimates ◽  
Selection Indexes ◽  
Measure Of Uncertainty ◽  
Selection Of

The estimated genetic parameters were used for selection of important conformation traits and reduction in the number of the described characteristics. For reduction in the number of described traits from the original 36 to 24, the traits were selected according to: measure of genetic similarity (cluster analysis), measure of uncertainty multidimensional quantity, value of the variance of aggregate genotype, value of the variance of selection index and correlation of trait to the first principal component of the genetic matrix. Reduction in the number of the described traits was based on the value of heritability coefficient and genetic correlations matrix. The reliabilities of selection indexes were estimated between 0.41 and 0.53. Among the three multivariate analysis methods evaluated in this study, the variance of selection index had the highest reliabilities of selection indexes. The estimation of selection index variance which omitted traits with low heritability coefficient and high genetic correlation was the most suitable for the traits selection. This procedure would enable the breeders to reduce field costs (e.g. time, labour) required for obtaining the genetic parameter estimates necessary for a specific breeding programme.  

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.

Genetic parameter estimates for feeding pattern and production traits in pigs

1997 ◽  
Vol 1997 ◽  
pp. 31-31
Author(s):  
A.D. Hall ◽  
W.G. Hill ◽  
P.R. Bampton ◽  
A.J. Webb
Keyword(s):  
Feed Intake ◽  
Genetic Parameters ◽  
Genetic Parameter ◽  
Feeding Pattern ◽  
Parameter Estimates ◽  
Group Housing ◽  
Production Traits ◽  
Production Environment ◽  
Feeding Patterns ◽  
Potential Benefits

Until recently, to enable accurate recording of feed intake, pigs were kept in individual pens. The advent of electronic feeders has allowed accurate records of feed intake and feeding patterns in group housing which is more similar to that found in the production environment. The objectives of this study were to estimate genetic parameters for these feeding pattern traits and their correlations with production traits to show potential benefits in selection.

Genetic parameter estimations and genomic insights for teat and udder structure in young and mature Canadian Angus cows

2021 ◽  
Author(s):  
K Devani ◽  
J J Crowley ◽  
G Plastow ◽  
K Orsel ◽  
T S Valente
Keyword(s):  
Animal Model ◽  
Genetic Correlation ◽  
Genetic Parameters ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Age Groups ◽  
Morbidity And Mortality ◽  
Parameter Estimations ◽  
Angus Cattle ◽  
Genetic Evaluations

Abstract Poor teat and udder structure, frequently associated with older cows, impact cow production and health, as well as calf morbidity and mortality. However, producer culling, for reasons including age, production, feed availability, and beef markets, creates a bias in teat and udder scores assessed and submitted to the Canadian Angus Association for genetic evaluations towards improved mammary structure. In addition, due to the infancy of the reporting program, repeated scores are rare. Prior to adoption of genetic evaluations for teat and udder scores in Canadian Angus cattle, it is imperative to verify that teat and udder scores from young cows are the same trait as teat and udder scores estimated on mature cows. Genetic parameters for teat and udder scores from all cows (n=4,192), and then from young cows (parity 1 and 2) and from mature cows (parity ≥ 4) were estimated using a single trait animal model. Genetic correlations for the traits between the two cow age groups were estimated using a two-trait animal model. Estimates of heritability (PSD) were 0.32 (0.07) and 0.45 (0.07) for young teat and udder score, and 0.27 (0.07) and 0.31 (0.07) for mature teat and udder score, respectively. Genetic correlation (PSD) between the young and mature traits was 0.87 (0.13) for teat score and 0.40 (0.17) for udder score. GWAS were used to further explore the genetic and biological commonalities and differences between the two groups. Although there were no genes in common for the two udder scores, 12 genes overlapped for teat score in the two cow age groups. Interestingly, there were also 23 genes in common between teat and udder scores in mature cows. Based on these findings, it is recommended that producers collect teat and udder score on their cow herd annually.

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