scholarly journals Inbreeding Coefficients in Open Nucleus Breeding Schemes with Overlapping Generations

1987 ◽  
Vol 58 (3) ◽  
pp. 236-244
Author(s):  
Kenji TOGASHI ◽  
Kunio YOKOUCHI ◽  
Hisato TAKEDA
Keyword(s):  
Overlapping Generations ◽  
Inbreeding Coefficients ◽  
Breeding Schemes ◽  
Nucleus Breeding ◽  
Open Nucleus

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

1978 ◽  
Vol 26 (3) ◽  
pp. 267-276 ◽  
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.

Effects of reduced variance due to selection in open nucleus breeding systems

1983 ◽  
Vol 34 (1) ◽  
pp. 53 ◽  
Author(s):  
JP Mueller ◽  
JW James
Keyword(s):  
Genetic Variance ◽  
Breeding Systems ◽  
Breeding Programs ◽  
Transfer Rates ◽  
Constant Variance ◽  
High Heritability ◽  
Breeding Schemes ◽  
Nucleus Breeding ◽  
Open Nucleus ◽  
Parameter Theory

In the design of breeding programs the consideration of open nucleus breeding systems may result in a useful alternative. The available theory dealing with these systems assumes constant parameters, but a more exact approach would take into account the possible changes in genetic variance. Numerical evaluation of formulae allowing for loss of genetic variance due to linkage disequilibrium and increase of variance due to mixing groups with different breeding values, suggests that optimum transfer rates, as predicted from the constant parameter theory, are in close agreement with the actual values; however, genetic gain is overestimated by about 20 % in common cattle and sheep nucleus breeding schemes for traits with high heritability, but less for traits with low heritability. The advantage of opening the nucleus is approximated well by constant variance theory.

Three-tier open nucleus breeding schemes

1997 ◽  
Vol 65 (3) ◽  
pp. 321-334
Author(s):  
R. K. Shepherd
Keyword(s):  
Genetic Gain ◽  
Optimum Structure ◽  
Male And Female ◽  
Asymptotic Rate ◽  
Female Migration ◽  
Breeding Schemes ◽  
Nucleus Breeding ◽  
Selection Methodology ◽  
Open Nucleus

AbstractOptimum designs of three-tier open nucleus breeding schemes are evaluated deterministically by maximizing the equilibrium rate of genetic gain for two methods of selection. Methodology is developed for both restricted and unrestricted migration between tiers and incorporates the loss of variance due to selection. A formula is derived for calculating the asymptotic rate of inbreeding. In the extensive livestock industries, proportional improvements in the equilibrium rate of genetic gain of between 0·12 and 0·22 are possible over a closed nucleus if no restrictions are imposed on male and female migration between tiers. The value of the extra tier in an optimized three-tier open nucleus scheme is approximately 0-45 of the maximum proportional improvement of a two-tier open nucleus over a closed nucleus scheme. The optimum structure is to have approximately 1% and 10% of the population in the nucleus and multiplier respectively. With this optimum structure the asymptotic rate of inbreeding will be reduced to one-sixth of that in a closed nucleus. The effects of various factors on the optimum structure, genetic gain and inbreeding are examined. The advantage of a three-tier open nucleus scheme over a closed nucleus scheme can be reduced substantially if thesefactors are operating.

scholarly journals Simulation of Optimal Open Nucleus Breeding Schemes to Improve Growth Traits and Carcass Composition of Lori-Bakhtiari Lambs

2016 ◽  
Vol 7 (13) ◽  
pp. 152-143
Author(s):  
حشمت الله عسکری همت ◽  
عبدالاحد شادپرور ◽  
سید رضا میرایی آشتیانی ◽  
رسول واعظ ترشیزی ◽  
◽  
...  
Keyword(s):  
Growth Traits ◽  
Carcass Composition ◽  
Breeding Schemes ◽  
Nucleus Breeding ◽  
Open Nucleus

scholarly journals Inbreeding Coefficients in Open Nucleus Breeding System for Beef Cattle Population

1989 ◽  
Vol 60 (11) ◽  
pp. 1022-1027
Author(s):  
Toshihiro YAMAGISHI ◽  
Hitoshi JYOUNAI ◽  
Yutaka MIZUMA
Keyword(s):  
Beef Cattle ◽  
Breeding System ◽  
Cattle Population ◽  
Inbreeding Coefficients ◽  
Nucleus Breeding ◽  
Open Nucleus
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