An experimental comparison of selection methods

Genome ◽  
1989 ◽  
Vol 32 (5) ◽  
pp. 791-795
Author(s):  
D. C. Winkelman ◽  
I. McMillan ◽  
G. W. Friars ◽  
L. R. McKay
Keyword(s):  
Response Selection ◽  
Experimental Comparison ◽  
Pupal Weight ◽  
Control Line ◽  
Response To Selection ◽  
Selection Methods ◽  
Single Generation ◽  
Sire Family ◽  
Males And Females ◽  
Selection For

Five methods of selection each in five replicates were examined for single-generation response in high and low 21-day pupal weight of Tribolium castaneum. The methods of selection tested were individual (ID), dam family or full (DF), sire family or half-sib (SF), progeny test (PT), and index (IX). A selection intensity, involving as parents the top 25% of the individuals on any specific phenotypic scale, was applied throughout the experiment. Each replicate included a contemporaneous, randomly mated control line. Responses attained with each method were compared with predicted gains and with results observed for other methods. Differences in responses of males and females were also assessed. Response to selection was markedly asymmetrical with greater gains observed in the downward direction. In the lines selected for low pupal weight, males and females were found to respond similarly and actual responses did not differ from those predicted. Ranking of methods by responses obtained for downward selection yielded the order IX > ID > PT > DF > SF. Selection for high pupal weight yielded differences in responses of males and females and the observed responses were significantly less than those predicted in all cases except that of PT-selected females. Observed responses for males were ordered as IX > ID > PT > DF > SF, while those for females were PT > IX > DF > SF > ID. When the data from both sexes were combined, the order of responses was PT > IX > DF > ID > SF.Key words: asymmetrical response, selection, Tribolium, pupal weight.

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.

Selection for prolificacy in pigs

1984 ◽  
Vol 1984 ◽  
pp. 43-43
Author(s):  
E. Avalos ◽  
C. Smith ◽  
M. Bichard
Keyword(s):  
Litter Size ◽  
Selection Index ◽  
Generation Interval ◽  
Sire Family ◽  
Males And Females ◽  
Selection For ◽  
One Year

Pigs can be bred at 6 months of age. By this time it is possible for their dams to have two litter records (at 12 months and 18 months of age) on which selection for litter size can be based. Hence, a generation interval of one year for both males and females can be achieved. Ollivier (1974), has shown that this system maximizes the rates of response. The accuracy with which replacements are chosen can be increased further by including information from other relatives (dam and sire family) in a selection index.

scholarly journals AN EXPERIMENTAL COMPARISON OF INDIVIDUAL, FAMILY AND COMBINATION SELECTION

Genetics ◽  
1974 ◽  
Vol 76 (4) ◽  
pp. 823-836
Author(s):  
S P Wilson
Keyword(s):  
Experimental Comparison ◽  
Pupal Weight ◽  
Individual Selection ◽  
Family Selection ◽  
Effective Population ◽  
Random Drift ◽  
Single Generation ◽  
Individual Family ◽  
Population Sizes ◽  
Combination Selection

ABSTRACT Two selection experiments comparing the relative efficiencies of individual, family, and combination selection were conducted. The expected results for larval weight of Tribolium (h  2 = 0.20) and for pupal weight (h  2 = 0.40) were that combination selection would be a more efficient method than family selection, and that family selection would exceed individual selection. In experiment I, individual selection produced more response (P < 0.05) than did combination or family, which was not in agreement with expectation. There was confounding of inbreeding levels and random drift due to differential effective population sizes in the lines selected by different methods. Experiment II consisted of ten single-generation selection tests. An advantage of this approach is that it eleminates the inherent problems of differential inbreeding levels and differential rates of genetic drift due to unequal population sizes among the methods of selection. There were no statistically significant differences in efficiency among the three methods of selection for both traits. This was contrary to theoretical expectations but does suggest that with traits of 20% h2 or higher, and where feasible, one may be justified in basing selection decisions on the phenotype of the individual only. Other advantages of single generation testing are that it allows more precise testing of selection theory and unbiased standard errors for estimates of realized heritability.

SELECTION INTENSITY AND RESPONSE TO SELECTION FOR YEARLING WEIGHT IN BEEF CATTLE

1973 ◽  
Vol 53 (1) ◽  
pp. 1-12 ◽  
Author(s):  
J. A. NEWMAN ◽  
H. T. FREDEEN ◽  
G. W. RAHNEFELD
Keyword(s):  
Beef Cattle ◽  
Control Line ◽  
Selection Intensity ◽  
Realized Heritability ◽  
Selection Differential ◽  
Response To Selection ◽  
Absolute Increase ◽  
Selection Program ◽  
On Line ◽  
Selection For

Ten years of selection for yearling weight in two replicate herds of beef Shorthorns has resulted in genetic increases of 4.8 ± 3.1 and 4.1 ± 3.0 kg/yr in males and 3.3 ± 2.7 and 2.3 ± 1.5 kg/yr in females. These increases were measured as deviations from an unselected control line mean and comprise about 40–45% of the absolute increase in yearling weight that took place during the selection program. The accumulation of selection differential was irregular at first but, in the last 6 yr of the program, advanced regularly at rates of 12.1 ± 0.7 and 11.2 ± 0.9 kg/yr for males and 9.1 ± 0.3 and 7.6 ± 0.4 kg/yr for females. Estimates of realized heritability derived from the two herds were.49 ±.12 and.51 ±.16 for males and.50 ±.11 and.29 ±.08 for females. A separate evaluation, based on line crosses within one herd, tended to confirm the heritability estimates.

COMPARISON OF FOUR METHODS OF SELECTION FOR RESISTANCE TO LEPTOSPHAERULINA BRIOSIANA IN ALFALFA

1979 ◽  
Vol 21 (2) ◽  
pp. 179-186 ◽  
Author(s):  
R. R. Hill Jr. ◽  
K. T. Leath
Keyword(s):  
Selection Method ◽  
The Other ◽  
Correlated Response ◽  
Response To Selection ◽  
Selection Methods ◽  
Family Selection ◽  
Colletotrichum Trifolii ◽  
Family Types ◽  
Medicago Sativa L ◽  
Selection For

Three cycles of selection for resistance to Leptosphaerulina briosiana (Poll.) Graham &Luttrell were conducted in two alfalfa (Medicago sativa, L.) germplasm pools, MSA and MSB. Each germplasm pool was used to compare four methods of selection: phenotypic recurrent, half-sib family, full-sib family, and alternating generations of selfed family and half-sib family. Response to selection for resistance to L. briosiana was greater in MSA than in MSB. Differences between selection methods were not significant. Selection for resistance to L. briosiana generally increased resistance to Stemphylium botryosum Wallr., but the magnitude of the correlated response varied with germplasm pool and selection method. The initial selfed families in both germplasm pools were significantly less resistant to Colletotrichum trifolii Bain than the other family types. Resistance to C. trifolii increased with selfed family selection for resistance to L. briosiana in MSA but not in MSB.

The direct and maternal components of the response to divergent selection for yearling growth rate in angus cattle

1990 ◽  
Vol 51 (3) ◽  
pp. 505-513 ◽  
Author(s):  
R. M. Herd
Keyword(s):  
Growth Rate ◽  
Average Daily Gain ◽  
Divergent Selection ◽  
Daily Weight Gain ◽  
Control Line ◽  
Response To Selection ◽  
Direct Component ◽  
Angus Cattle ◽  
High Line ◽  
Selection For

ABSTRACTA crossmothering experiment was conducted to measure the direct and the maternal components of the response to divergent selection for yearling growth rate in beef cattle. The animals were from three closed lines of Angus cattle. Two lines had been selected since 1974 for either high (high-line) or low (low-line) average daily gain from birth to yearling, and the third line was maintained as a randomly bred control-line. A total of 221 female calves born between 1984 and 1987 was used in the crossmothering experiment, and an additional 113 cows bearing calves in 1988 were used to obtain more records of milk production.On average, high-line calves born in 1984-87 were 45 kg heavier at weaning (200 days of age) than low-line calves and 65 kg heavier at yearling age, corresponding to a proportional divergence in daily weight gain of 0·29 and 0·32 respectively. The direct component of the response to selection was 0·82 (s.e. 0-05) of the divergence in body weight at weaning and 0·89 (s.e. 0·05) at yearling age. The maternal component was 0·18 (s.e. 0·06) and 0·11 (s.e. 0·04) for weaning and yearling weight respectively. Over the years 1984-88, high-line dams produced 1·15 times the milk of low-line dams and only 1·03 times that of control-line dams. There were small differences in the composition of milk sampled in 1984 which resulted in the milk of high-line dams having a higher content of metabolizable energy (ME) than that of control-line dams. The ME in the milk consumed by the calves from the three selection lines was sufficient to fuel similar proportions of their pre-weaning growth and indicated that the expression of the maternal component of the selection response may be via small differences in the quantity and quality of the milk produced by the dams. Expression of the direct component appeared to be at least partially via differences in appetite of the calves. These results, together with results for sheep, mice and rats, show that the direct component of the response to selection for growth is much larger than the maternal component.

Correlated response to selection for litter size in pigs: II. Carcass, meat, and fat quality traits

2002 ◽  
Vol 80 (10) ◽  
pp. 2566 ◽  
Author(s):  
J. Estany ◽  
D. Villalba ◽  
M. Tor ◽  
D. Cubiló ◽  
J. L. Noguera
Keyword(s):  
Litter Size ◽  
Correlated Response ◽  
Quality Traits ◽  
Response To Selection ◽  
Fat Quality ◽  
Selection For
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