Congruence between selection on breeding values and farmers’ selection criteria in sheep breeding under conventional nucleus breeding schemes

ABSTRACTThe value of cloning in MOET nucleus breeding schemes has to be considered within the constraint of fixed resources. Under this constraint cloning was found to add to genetic progress only when (i) the heritability is low and (ii) it is used at the expense of a reduction in the number of bull families. This course would exacerbate inbreeding and other potential problems with MOET. All other options for using clones lead to a reduction in genetic progress due to a loss of selection intensity that is not made up for by gains in selection accuracy.

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Some optimum age structures and selection methods in open nucleus breeding schemes with overlapping generations

Animal Science ◽

10.1017/s0003356100040861 ◽

1978 ◽

Vol 26 (3) ◽

pp. 267-276 ◽

Cited By ~ 8

Author(s):

I. R. Hopkins

Keyword(s):

Survival Rates ◽

Age Groups ◽

Selection Methods ◽

Selection Procedures ◽

Transfer Rates ◽

Breeding Schemes ◽

Nucleus Breeding ◽

Genetic Responses ◽

Open Nucleus ◽

Age Structures

ABSTRACTDesigns of open nucleus breeding schemes, which comprise a nucleus having the best males and females and a base comprising the remainder, with some base-born individuals used in the nucleus and vice versa, are studied.Steady-state genetic responses, optimum transfer rates between nucleus and base in both sexes, and genetic differences between nucleus and base are estimated for a range of age structures, selection either within or among age groups (selection methods), nucleus sizes, mating ratios, fertility rates and survival rates appropriate to sheep and cattle populations. With optimum transfer rates between layers maximum or near maximum genetic responses are obtained with nucleus sizes varying from 2 to 15% of the population. Optimum transfer rates are fairly stable for nucleus sizes larger than about 5% and where the same selection procedures are used in both layers. However, a small nucleus with more efficient age structures and selection procedures and more accurate selection than in the base is economically desirable, and then almost no base-born females should be selected as nucleus replacements and up to 70% of male replacements for the base should come from the base. Optimum age structures differed markedly between selection methods.Although few ‘rules of thumb’ about optimum age structures and transfer rates are sufficiently robust to be widely recommended in commercial situations, the nucleus breeding system behaves according to a few basic principles that can be used to predict the direction if not the magnitude of effects of changes in structure.

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Designing dairy cattle breeding schemes under genomic selection: a review of international research

Animal Production Science ◽

10.1071/an11098 ◽

2012 ◽

Vol 52 (3) ◽

pp. 107 ◽

Cited By ~ 67

Author(s):

J. E. Pryce ◽

H. D. Daetwyler

Keyword(s):

Dairy Cattle ◽

Genomic Selection ◽

Genetic Gain ◽

Reproductive Technologies ◽

Progeny Testing ◽

Genomic Breeding ◽

Breeding Values ◽

Scheme Design ◽

Dairy Cattle Breeding ◽

Breeding Schemes

High rates of genetic gain can be achieved through (1) accurate predictions of breeding values (2) high intensities of selection and (3) shorter generation intervals. Reliabilities of ~60% are currently achievable using genomic selection in dairy cattle. This breakthrough means that selection of animals can happen at a very early age (i.e. as soon as a DNA sample is available) and has opened opportunities to radically redesign breeding schemes. Most research over the past decade has focussed on the feasibility of genomic selection, especially how to increase the accuracy of genomic breeding values. More recently, how to apply genomic technology to breeding schemes has generated a lot of interest. Some of this research remains the intellectual property of breeding companies, but there are examples in the public domain. Here we review published research into breeding scheme design using genomic selection and evaluate which designs appear to be promising (in terms of rates of genetic gain) and those that may have unfavourable side-effects (i.e. increasing the rate of inbreeding). The schemes range from fairly conservative designs where bulls are screened genomically to reduce numbers entering progeny testing, to schemes where very large numbers of bull calves are screened and used as sires as soon as they reach sexual maturity. More radical schemes that incorporate the use of reproductive technologies (in juveniles) and genomic selection in nucleus herds are also described. The models used are either deterministic and more recently tend to be stochastic, simulating populations of cattle. A key driver of the rate of genetic gain is the generation interval, which could range from being similar to that in conventional testing (~5 years), down to as little as 1.5 years. Generally, the rate of genetic gain is between 12% and 100% more than in conventional progeny testing, while the rate of inbreeding tends to be lower per generation than in progeny testing because Mendelian sampling terms can be estimated more accurately. However, short generation intervals can lead to higher rates of inbreeding per year in genomic breeding programs.

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Mendelian sampling terms as a selective advantage in optimum breeding schemes with restrictions on the rate of inbreeding

Genetics Research ◽

10.1017/s0016672303006566 ◽

2004 ◽

Vol 83 (1) ◽

pp. 55-64 ◽

Cited By ~ 28

Author(s):

S. AVENDAÑO ◽

J. A. WOOLLIAMS ◽

B. VILLANUEVA

Keyword(s):

Genetic Variation ◽

Genetic Gain ◽

Selective Advantage ◽

Breeding Values ◽

Truncation Selection ◽

Joint Management ◽

Breeding Schemes ◽

Estimated Breeding Values ◽

Available Information ◽

Mendelian Sampling

Quadratic indices are a general approach for the joint management of genetic gain and inbreeding in artificial selection programmes. They provide the optimal contributions that selection candidates should have to obtain the maximum gain when the rate of inbreeding is constrained to a predefined value. This study shows that, when using quadratic indices, the selective advantage is a function of the Mendelian sampling terms. That is, at all times, contributions of selected candidates are allocated according to the best available information about their Mendelian sampling terms (i.e. about their superiority over their parental average) and not on their breeding values. By contrast, under standard truncation selection, both estimated breeding values and Mendelian sampling terms play a major role in determining contributions. A measure of the effectiveness of using genetic variation to achieve genetic gain is presented and benchmark values of 0·92 for quadratic optimisation and 0·5 for truncation selection are found for a rate of inbreeding of 0·01 and a heritability of 0·25.

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Genetic and Economic Evaluation of Nucleus Breeding Schemes for Commercial Artificial Insemination Firms

Journal of Dairy Science ◽

10.3168/jds.s0022-0302(90)78871-6 ◽

1990 ◽

Vol 73 (7) ◽

pp. 1920-1937 ◽

Cited By ~ 10

Author(s):

J.C.M. Dekkers ◽

G.E. Shook

Keyword(s):

Economic Evaluation ◽

Artificial Insemination ◽

Breeding Schemes ◽

Nucleus Breeding

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Bull Selection in MOET Nucleus Breeding Schemes with Limited Testing Capacity

Acta Agriculturae Scandinavica Section A – Animal Science ◽

10.1080/09064700152717218 ◽

2001 ◽

Vol 51 (4) ◽

pp. 235-245

Author(s):

I. Strandén ◽

P. Korpiaho ◽

M. Pakula ◽

E. A. Mäntysaari

Keyword(s):

Breeding Schemes ◽

Nucleus Breeding ◽

Limited Testing

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Genetic progress and inbreeding for alternative nucleus breeding schemes for beef cattle

Animal Science ◽

10.1017/s1357729800013758 ◽

1995 ◽

Vol 61 (2) ◽

pp. 231-239 ◽

Cited By ~ 5

Author(s):

B. Villanueva ◽

G. Simm ◽

J. A. Woolliams

Keyword(s):

Beef Cattle ◽

Mating Strategies ◽

Percentage Increase ◽

Expected Number ◽

Genetic Progress ◽

Multiple Ovulation ◽

Population Sizes ◽

Breeding Schemes ◽

Nucleus Breeding ◽

Selection Intensities

AbstractAlternative closed breeding schemes for beef cattle are analysed using stochastic computer simulation. Multiple ovulation and embryo transfer (MOET) schemes are compared with conventional schemes (schemes without MOET) with an equal expected number of progeny born per year. Schemes are compared for genetic gain and inbreeding obtained after 25 years of selection. The trait considered, evaluated in both sexes, has an initial heritability of 0·35. Different population sizes and numbers of sires selected are evaluated. Current realistic parameters for embryo production are assumed in MOET schemes.After 25 years of selection, and with no control on inbreeding, cumulative genetic gains are about 50% higher in MOET schemes compared with conventional schemes. The benefit from MOET is mostly due to increased selection intensities in females. The rate of inbreeding increases by up to nearly 300% when MOET is used. This maximum percentage increase in inbreeding following the use of MOET can be reduced to about 100% when selection and mating strategies for controlling inbreeding are used. The effect of the number of sires used on the inbreeding obtained is more important than the effect of the size of the herd. In MOET schemes, increasing the number of sires selected by a factor of three, leads to reductions in inbreeding rates of 40%. When schemes of the same size are compared at similar acceptable inbreeding levels, MOET schemes give around 30% higher genetic progress than conventional schemes.

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The importance of family sizes in adult multiple ovulation and embryo transfer (MOET) nucleus breeding schemes in dairy cattle

Animal Science ◽

10.1017/s0003356100005663 ◽

1991 ◽

Vol 52 (1) ◽

pp. 33-47 ◽

Cited By ~ 4

Author(s):

J. Ruane

Keyword(s):

Monte Carlo Simulation ◽

Monte Carlo ◽

Dairy Cattle ◽

Embryo Transfer ◽

Sex Ratios ◽

Survival Rates ◽

Biological Factors ◽

Multiple Ovulation ◽

Breeding Schemes ◽

Nucleus Breeding

ABSTRACTThe importance of family sizes in adult multiple ovulation and embryo transfer (MOET) nucleus schemes with discrete generations of single trait selection was examined using Monte Carlo simulation. Two areas were investigated. Firstly, the number of sons and daughters per dam was varied in schemes using hierarchical mating designs. With four or eight sires and 32 dams selected, increasing the number of sons per dam from one up to four achieved 1 to 8% higher rates of response but at the expense of increased variation in response and 10 to 56% higher rates of inbreeding. With four or eight sires and 16, 32 or 64 dams selected, the number of daughters was set to two, four or eight (with one son per dam in each case). For schemes transferring equal numbers of embryos, responses were lower with two daughters per dam but were fairly similar with four or eight daughters per dam while inbreeding rates increased as fewer sires and dams were selected. Secondly, the effects of variation in family sizes due to biological factors and chance were investigated with eight sires and 32 dams selected and with hierarchical or factorial (two or four sires per dam) mating designs. When all selected cows yielded embryos, changes in family sizes due to differences in sex ratios, in survival rates of embryos to selection and to variation in the number of embryos per donor reduced response by 1 to 4%. However, when 20% or 33% of the superovulated females yielded no embryos, thus requiring the use of genetically inferior replacements, response was reduced by a further 9 to 13%

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