scholarly journals A further examination of the relative efficiency of three methods of selection for genetic gains under less-restricted conditions

1961 ◽  
Vol 2 (1) ◽  
pp. 106-121 ◽  
Author(s):  
S. S. Y. Young
Keyword(s):  
Relative Efficiency ◽  
Selection Index ◽  
Phenotypic Correlation ◽  
Relative Importance ◽  
Selection Intensity ◽  
Genetic Gains ◽  
Equal Importance ◽  
Independent Culling ◽  
Correlated Characters ◽  
Efficiency Of Selection

The relative efficiency of three methods of selection (index, independent culling levels and tandem) is compared in terms of genetic gains in economic units. The comparison covers cases where variances, heritabilities and economic weights are unequal, while the case of two correlated characters is also examined. Various factors may influence the relative efficiency, including selection intensity, the number of traits under selection, the relative importance of those traits (in terms of a factor λ, which is the product of economic weight, heritability and phenotypic standard deviation), and the correlations between them.The conclusions are:(i) In all circumstances the index is never less efficient than independent culling levels, though in some cases it is no more efficient. Independent culling is, in turn, never less, but in some cases no more efficient than tandem selection.(ii) The superiority of the index over other methods increases with an increasing number of traits under selection, but decreases with increasing differences in relative importance, its superiority being at a maximum when the traits are of equal importance. The superiority of the index over independent culling levels decreases with increasing selection intensity, but its superiority over tandem selection is independent of intensity.(iii) The superiority of independent culling over tandem selection increases with increasing selection intensity or an increasing number of traits under selection, but decreases with increasing differences in relative importance.(iv) The relative efficiency of the index over other methods is much affected by the phenotypic correlation between traits when the traits are of equal importance, the relative efficiency of the index being higher when the phenotypic correlation is low or negative. The effect of genetic correlation is only apparent when the traits are of unequal importance and its influence on relative efficiency changes with changes in other parameters.(v) The relative efficiency of selection methods may be changed by their use for special purposes.

scholarly journals Multistage selection for genetic gain by orthogonal transformation.

Genetics ◽  
1991 ◽  
Vol 129 (3) ◽  
pp. 963-974 ◽  
Author(s):  
S Z Xu ◽  
W M Muir
Keyword(s):  
Selection Index ◽  
Orthogonal Transformation ◽  
Cost Savings ◽  
Breeding Value ◽  
Economic Returns ◽  
Selection Scheme ◽  
Genetic Gains ◽  
Independent Culling ◽  
Total Proportion ◽  
Multistage Selection

Abstract An exact transformed culling method for any number of traits or stages of selection with explicit solution for multistage selection is described in this paper. This procedure does not need numerical integration and is suitable for obtaining either desired genetic gains for a variable proportion selected or optimum aggregate breeding value for a fixed total proportion selected. The procedure has similar properties to multistage selection index and, as such, genetic gains from use of the procedure may exceed ordinary independent culling level selection. The relative efficiencies of transformed to conventional independent culling ranged from 87% to over 300%. These results suggest that for most situations one can chose a multistage selection scheme, either conventional or transformed culling, which will have an efficiency close to that of selection index. After considering cost savings associated with multistage selection, there are many situations in which economic returns from use of independent culling, either conventional or transformed, will exceed that of selection index.

scholarly journals Genetic gains under three methods of selection

1962 ◽  
Vol 3 (3) ◽  
pp. 417-423 ◽  
Author(s):  
D. J. Finney
Keyword(s):  
Linear Function ◽  
Genetic Gain ◽  
Index Selection ◽  
Genetic Gains ◽  
Independent Culling

Results obtained by Young for the expectation of genetic gain in an arbitrary linear function of several traits under selection by independent culling levels, under tandem selection, and under index selection have been obtained in slightly more general form and their dependence on basic genetic and phenotypic parameters exhibited. A warning is given about the effects of selection in modifying the distribution of traits; when the distribution has become appreciably non-normal, any calculation of genetic gains from formulae based on normality will tend to overestimation.

scholarly journals Prediction of genetic gains for breeding objective traits and designing selection schemes for Washera and Gumuz indigenous sheep

2021 ◽  
Vol 4 (1) ◽  
pp. 1-13
Author(s):  
Sisay Asmare ◽  
Sisay Asmare ◽  
Kefyalew Alemayehu ◽  
Solomon Abegaz K. ◽  
Aynalem Haile ◽  
...  
Keyword(s):  
Litter Size ◽  
Selection Index ◽  
Genetic Response ◽  
Breeding Scheme ◽  
Selection Scheme ◽  
Genetic Gains ◽  
Washera Sheep ◽  
Indigenous Sheep ◽  
Breeding Objective ◽  
One Year

In Ethiopia,there are 32.85 millions of sheep,more than 99 % of which are indigenous.However,the productivity of local sheep under traditional production system is low with high mortality of sheep.There are two ways of improving performance of sheep and goats,namely improving the enviroment of animals and/or improving there genetic potential.The aim of this study was to predict genetic gains of breedingobjective traits and select the best sheep selection scheme for Gumuz andWashera sheep. Body size(six month weight and yearling weight) and litter size were breeding objective traits identified by own flock animal ranking experiment and personal interview. Deterministic approach of ZPLAN computor program is used for modeling input parametres of Gumuz and Washera sheep and simulating breeding plans using gene flow method and selection index procedures. One-tier cooperative sheep breeding scheme were proposed whereby ram exchange between and within villages is the main means of genetic dissimination. Genetic gains predicted for six month weight of Gumuz and Washera sheep were 0.43 and 0.55 kg,respectively. Genetic gains predicted for yearling weight of Gumuz and Washera sheep were 0.55 and 0.60 kg,respectively. Genetic gains predicted for litter  size of Gumuz and Washera sheep were 0.08 and 0.09 lambs,respectively. The lower rate of inbreeding, the higher monetary genetic gain for aggregate genotype,higher return to investmnet and higher profit/ewe/year were quality measures of breeding program considered to prefer scheme 4 for both Gumuz and Washera sheep.Hence,for both Gumuz and Washera sheep populations a sheep selection scheme designed with 15 % selection proportion and one year ram use for breeding was recommended. Special emphasis need to be given to yearling weight with higher predicted genetic response and higher percentage return to investment.

Experimental comparison of restricted selection index and restricted independent culling levels in Tribolium castaneum

Genome ◽  
1987 ◽  
Vol 29 (1) ◽  
pp. 91-96 ◽  
Author(s):  
J. L. Campo ◽  
B. Villanueva
Keyword(s):  
Tribolium Castaneum ◽  
Selection Index ◽  
Egg Laying ◽  
Experimental Comparison ◽  
Pupal Weight ◽  
Selection Methods ◽  
Adult Weight ◽  
Antagonistic Selection ◽  
Independent Culling ◽  
Restricted Selection

A selection index (I) method was compared with independent culling levels (N), with a restriction in the selection program, using two replicated single generation experiments in Tribolium castaneum, which are considered forms of antagonistic selection. The first experiment was designed to increase adult weight without changing pupal weight, while the second experiment was intended to improve egg laying without changing adult weight. In both experiments the genetic correlation between the traits involved were positive but were higher in experiment 1 than in experiment 2. The proportion of selection was 10%. In experiment 1, the effect of restriction was as expected in both lines since the changes in pupal weight were not significant. Adult weight change was positive for the I line and negative for the N line, showing that the index was a superior method to improve adult weight. In experiment 2, the effect of restriction was also as expected in both lines and changes in adult weight were not significant. Egg laying changed positively in both lines. Therefore, both selection methods were similar in this experiment, even though egg laying change was higher in the I than the N line. Key words: restricted index, restricted culling levels, antagonistic selection, Tribolium.

scholarly journals Selection index based on the relative importance of traits and possibilities in breeding popcorn

2016 ◽  
Vol 15 (2) ◽  
Author(s):  
R.A. Vieira ◽  
R. Rocha ◽  
C.A. Scapim ◽  
A.T. Amaral Júnior ◽  
M. Vivas
Keyword(s):  
Selection Index ◽  
Relative Importance

scholarly journals Interaction of selection and recombination in the fixation of negative-epistatic genes

1996 ◽  
Vol 67 (3) ◽  
pp. 257-269 ◽  
Author(s):  
Yannis Michalakis ◽  
Montgomery Slatkin
Keyword(s):  
Double Mutant ◽  
Static Model ◽  
The Other ◽  
Relative Importance ◽  
Selection Intensity ◽  
Recombination Rates ◽  
Epistatic Interactions ◽  
Evolutionary Transitions ◽  
Negative Epistasis ◽  
Probability Of Fixation

SummaryWe investigated the interaction of recombination and selection on the process of fixation of two linked loci with epistatic interactions in fitness. We consider both the probability of fixation of newly arising mutants (the static model) and the time to fixation under continued mutation (the dynamic model). Our results show that the fixation of a new advantageous combination is facilitated by higher fitness of the advantageous genotype and by weaker selection against the intermediate deleterious genotypes. Fixation occurs more rapidly when the recombination rates are small, except when selection against intermediate genotypes is weak and selection in favour of the double mutant is very strong. In these cases fixation is more rapid when the recombinant rate is large. Mutations of strong effects, deleterious when alone but beneficial when coupled, are fixed more easily than mutations of intermediate effects, at least for large recombination rates. Among the possible pathways the process of fixation might follow, independent substitutions lead to the fixation of the double mutant only when selection is weak. The relative importance of the other pathways depends on the interaction between recombination and selection. The coupled-gamete pathway (i.e. when the population waits until the double mutant appears and then drives it to fixation) is more important as selection intensity increases and the recombination rate is reduced. For all recombination rates, asymmetries in fitness of the intermediate genotypes increase the rate at which fixations occur. Finally, throughout the fixation process, the population will be monomorphic at least at one of the two loci for most of the time, which implies that there would be little opportunity to detect the presence of negative epistasis even if it were important for occasional evolutionary transitions.

Optimum linear indices for non-linear profit functions

1993 ◽  
Vol 56 (1) ◽  
pp. 43-50 ◽  
Author(s):  
H. Pasternak ◽  
J. I. Weller
Keyword(s):  
Selection Index ◽  
Selection Intensity ◽  
Production Traits ◽  
Milk Production Traits ◽  
Optimum Selection ◽  
Non Linear ◽  
Linear Index ◽  
Standard Linear ◽  
Profit Functions ◽  
Selection Intensities

AbstractAn iterative method is presented, based on the method of Moav and Hill (1966) to derive the optimum linear selection index for any number of traits with linear or non-linear profit functions. For non-linear profit functions the index weights will be functions of the trait means prior to selection and the selection intensity. Using the equations developed, the optimum selection index for three dairy cattle milk production traits was computed. Convergence was obtained after three to four iterations, and was robust to the starting values used for iteration. The ratio of expected genetic gains were only marginally different for selection intensities of 1 and 4 standard deviation units. Differences were greater for the index coefficients. All alternative indices tested gave lower gains in profit than the optimum index. For linear profit functions this index reduces to the standard linear index, and for two uncorrelated traits this index reduces to the index of Moav and Hill (1966).

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