Intrabreed Mating Pair Selection Methods for Improvement of Nonlinear Merit from Additive Genetic Inheritance: A Review

Allaire, F.R.

doi:10.3168/jds.s0022-0302(93)77568-2

Cited by 3 publications

(2 citation statements)

References 32 publications

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“…In any mate assignment system, some attention to nonlinear economic values of traits (corrective mating) or positive assortative mating to increase variance of net merit could be better than simply minimizing inbreed-ing (Allaire, 1993). The economic value of net merit is nonlinear, with much higher prices for elite animals, but the current research did not include nonlinear economics or positive assortative mating to increase probability of obtaining elite progeny.…”

Section: A a G A A A A A Amentioning

confidence: 97%

Mating programs including genomic relationships and dominance effects

Sun¹,

VanRaden

O’Connell

et al. 2013

Journal of Dairy Science

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Computerized mating programs using genomic information are needed by breed associations, artificial-insemination organizations, and on-farm software providers, but such software is already challenged by the size of the relationship matrix. As of October 2012, over 230,000 Holsteins obtained genomic predictions in North America. Efficient methods of storing, computing, and transferring genomic relationships from a central database to customers via a web query were developed for approximately 165,000 genotyped cows and the subset of 1,518 bulls whose semen was available for purchase at that time. This study, utilizing 3 breeds, investigated differences in sire selection, methods of assigning mates, the use of genomic or pedigree relationships, and the effect of including dominance effects in a mating program. For both Jerseys and Holsteins, selection and mating programs were tested using the top 50 marketed bulls for genomic and traditional lifetime net merit as well as 50 randomly selected bulls. The 500 youngest genotyped cows in the largest herd in each breed were assigned mates of the same breed with limits of 10 cows per bull and 1 bull per cow (only 79 cows and 8 bulls for Brown Swiss). A dominance variance of 4.1 and 3.7% was estimated for Holsteins and Jerseys using 45,187 markers and management group deviation for milk yield. Sire selection was identified as the most important component of improving expected progeny value, followed by managing inbreeding and then inclusion of dominance. The respective percentage gains for milk yield in this study were 64, 27, and 9, for Holsteins and 73, 20, and 7 for Jerseys. The linear programming method of assigning a mate outperformed sequential selection by reducing genomic or pedigree inbreeding by 0.86 to 1.06 and 0.93 to 1.41, respectively. Use of genomic over pedigree relationship information provided a larger decrease in expected progeny inbreeding and thus greater expected progeny value. Based on lifetime net merit, the economic value of using genomic relationships was >$3 million per year for Holsteins when applied to all genotyped females, assuming that each will provide 1 replacement. Previous mating programs required transferring only a pedigree file to customers, but better service is possible by incorporating genomic relationships, more precise mate allocation, and dominance effects. Economic benefits will continue to grow as more females are genotyped.

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Section: A a G A A A A A Amentioning

confidence: 97%

Mating programs including genomic relationships and dominance effects

Sun¹,

VanRaden

O’Connell

et al. 2013

Journal of Dairy Science

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“…Although the selection index is defined under the assumption of random mating, in practice, index selection is applied to non-random mating populations. A common method of mate selection relies on the expected combining ability of a female with a potential mating partner [ 17 ]. The true combining ability between two potential mating partners is the expected total merit of their offspring.…”

Section: Theorymentioning

confidence: 99%

Selection index theory for populations under directional and stabilizing selection

Wellmann

2023

Genet Sel Evol

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Background The purpose of a selection index is that its use to select animals for breeding maximizes the profit of a breed in future generations. The profit of a breed is in general a quantity that predicts the satisfaction of future owners with their breed, and the satisfaction of the consumers with the products that are produced by the breed. Many traits, such as conformation traits and product quality traits have intermediate optima. Traditional selection index theory applies only to directional selection and cannot achieve any further improvement once the trait means have reached their optima. A well-founded theory is needed that extends the established selection index theory to cover directional as well as stabilizing selection as limiting cases, and that can be applied to maximize the profit of a breed in both situations. Results The optimum selection index shifts the trait means towards the optima and, in the case of stabilizing selection, decreases the phenotypic variance, which causes the phenotypes to be closer to the optimum. The optimum index depends not only on the breeding values, but also on the squared breeding values, the allele contents of major quantitative trait loci (QTL), the QTL heterozygosities, the inbreeding coefficient of the animal, and the kinship of the animal with the population. Conclusion The optimum selection index drives the alleles of major QTL to fixation when the trait mean approaches the optimum because decreasing the phenotypic variance shifts the trait values closer to the optimum, which increases the profit of the breed. The index weight on the kinship coefficient balances the increased genetic gain that can be achieved in future generations by outcrossing, and the increased genetic gain that can be achieved under stabilizing selection by reducing the phenotypic variance. In a model with dominance variance, it can also account for the effect of inbreeding depression. The combining ability between potential mating partners, which predicts the total merit of their offspring, could become an important parameter for mate allocation that could be used to further shift the phenotypes towards their optimum values.

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Applying Breeding Objectives to Dairy Cattle Improvement

Dekkers

Gibson

1998

Journal of Dairy Science

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Otherwise well-researched definitions of breeding objectives and selection criteria may never be used in practice if those definitions do not take into account the perceptions and wishes of the breeders for whom they are designed. Finding selection criteria that are widely accepted and implemented is a daunting task that requires considerable time and full interaction between the scientists and the industry. We review various aspects of this process and, in particular, how scientific principles can be used to ensure that the outcome best meets both the perceptions and needs of the users while remaining as close as possible to the technical economic optimum. Alternative methods of presenting and delivering selection indexes, such as index expression, index formulation, focus on response to selection rather than on index weights, construction of component indexes, and the use of direct accounting for costs of constraints rather than rescaling methods can all help in improving acceptance of an index. Development and implementation of selection criteria also involve consideration of the selective mating decisions that form an integral part of selection decisions in the field. The technical basis of factors that foster emphasis on individual mating decisions in the field are discussed in relation to formulation of the breeding goal and selection index and in relation to nonlinear economic and genetic parameters. Strategies that focus on use of a linear index for the selection of sires and dams followed by selective mating of selected parents have the greatest potential for implementation in the industry. We focus on examples taken from the Canadian dairy industry, but principles apply generally.

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Intrabreed Mating Pair Selection Methods for Improvement of Nonlinear Merit from Additive Genetic Inheritance: A Review

Cited by 3 publications

References 32 publications

Mating programs including genomic relationships and dominance effects

Mating programs including genomic relationships and dominance effects

Selection index theory for populations under directional and stabilizing selection

Applying Breeding Objectives to Dairy Cattle Improvement

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