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.

scholarly journals The effects of population size and selection intensity in selection for a quantitative character in Drosophila: I. Short-term response to selection

1968 ◽  
Vol 12 (3) ◽  
pp. 237-248 ◽  
Author(s):  
R. Frankham ◽  
L. P. Jones ◽  
J. S. F. Barker
Keyword(s):  
Quantitative Character ◽  
Selection Intensity ◽  
Realized Heritability ◽  
Response To Selection ◽  
Short Term ◽  
Population Sizes ◽  
Selection For ◽  
Selection Intensities ◽  
Number Of Individuals ◽  
Term Response

1. The response to selection for increased number of bristles on one abdominal segment was studied over 12 generations using a factorial design of three population sizes (10, 20 and 40 pairs of parents) and five selection intensities (10, 20, 40, 80% and controls).2. The responses on the average agreed well with those expected from the estimated base population heritability, but individual replicates diverged considerably.3. Larger populations tended to give greater response to selection, due mainly to larger realized heritabilities.4. There was no consistent effect of selection intensity on realized heritability.5. For populations with the same number of individuals scored, less intense selection gave greater realized heritabilities.

scholarly journals EFFECTS OF POPULATION SIZE AND SELECTION INTENSITY ON SHORT-TERM RESPONSE TO SELECTION FOR POSTWEANING GAIN IN MICE

Genetics ◽  
1973 ◽  
Vol 73 (3) ◽  
pp. 513-530
Author(s):  
J P Hanrahan ◽  
E J Eisen ◽  
J E Legates
Keyword(s):  
Population Size ◽  
Selection Response ◽  
Selection Intensity ◽  
Realized Heritability ◽  
Family Selection ◽  
Effective Population ◽  
Population Sizes ◽  
Selection For ◽  
Selection Intensities ◽  
Term Response

ABSTRACT The effects of population size and selection intensity on the mean response was examined after 14 generations of within full-sib family selection for postweaning gain in mice. Population sizes of 1, 2, 4, 8 and 16 pair matings were each evaluated at selection intensities of 100% (control), 50% and 25% in a replicated experiment. Selection response per generation increased as selection intensity increased. Selection response and realized heritability tended to increase with increasing population size. Replicate variability in realized heritability was large at population sizes of 1, 2 and 4 pairs. Genetic drift was implicated as the primary factor causing the reduced response and lowered repeatability at the smaller population sizes. Lines with intended effective population sizes of 62 yielded larger selection responses per unit selection differential than lines with effective population sizes of 30 or less.

COMPARISON OF PREDICTED AND OBSERVED RESPONSES TO SELECTION FOR YIELD IN WHEAT

1971 ◽  
Vol 51 (3) ◽  
pp. 187-192 ◽  
Author(s):  
J. PESEK ◽  
R. J. BAKER
Keyword(s):  
Triticum Aestivum ◽  
Common Wheat ◽  
Triticum Aestivum L ◽  
Standard Errors ◽  
Selection Differential ◽  
Response To Selection ◽  
Simple Method ◽  
Different Populations ◽  
Selection For ◽  
Heritability Estimates

A simple method of calculating standard errors of heritability estimates is presented. The method is then used to conclude that observed response to selection for yield in five different populations of common wheat, Triticum aestivum L., agreed with the response predicted by multiplying estimates of heritability by the selection differential. It is suggested that a comparison of observed and predicted responses is not the best way to test the theory used in predicting response to selection.

scholarly journals Reducing the period of data collection for intake and gain to improve response to selection for feed efficiency in beef cattle

2018 ◽  
Vol 96 (3) ◽  
pp. 854-866 ◽  
Author(s):  
Richard Mark Thallman ◽  
Larry A Kuehn ◽  
Warren M Snelling ◽  
Kelli J Retallick ◽  
Jennifer M Bormann ◽  
...  
Keyword(s):  
Data Collection ◽  
Beef Cattle ◽  
Feed Efficiency ◽  
Response To Selection ◽  
Selection For

scholarly journals Genetic Variation and Selection for Carotene Content in Carrots

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 821E-821
Author(s):  
Philipp Simon
Keyword(s):  
Genetic Variation ◽  
Combining Ability ◽  
General Combining Ability ◽  
Mass Selection ◽  
Realized Heritability ◽  
Response To Selection ◽  
Carotene Content ◽  
Selection For ◽  
Variation And Selection ◽  
Made In

A six-parent diallel which included carrot inbreds with a range of carotene content from 80 to 490 ppm was evaluated over 2 years. General combining ability accounted for most of the variation observed. Phenotypic mass selection was exercised for high carotene content in three carrot populations. Response to selection continued to be high in one population, HCM, after 11 cycles of selection. In contrast, after three generations of selection, little progress was able to be made in a population derived from primarily Nantes-type open-pollinated cultivars. Realized heritability estimates varied from 15% to 49%. Environment contributed significantly to variation in carotene content.

scholarly journals Genetic Variability And Selection Response To Heat Tolerance Through Membrane Thermostability In Spring Wheat (Triticum Aestivum L)

1970 ◽  
Vol 23 (2) ◽  
pp. 15-22
Author(s):  
NCD Barma ◽  
MA Islam ◽  
MA Hakim ◽  
DKR Sarker
Keyword(s):  
Genetic Variability ◽  
Heat Tolerance ◽  
Selection Response ◽  
Research Centre ◽  
Direct Selection ◽  
Realized Heritability ◽  
Response To Selection ◽  
Early Generation ◽  
Membrane Thermostability ◽  
Selection For

The present investigation was undertaken to study the genetic variability and selection response of heat tolerance measured through membrane thermostability (MTS) in F2 derived F4 and F5 generations of five wheat crosses: Kanchan × Gourab, Gourab × Fang 60, Kanchan × Pavon 76, Gourab × Pavon76 and Fang 60 × Pavon76. Each cross was consisted of 65, 60, 77, 72 and 64 F4 bulks including two parents. The study was conducted both in the field and laboratory of Wheat Research Centre, Dinajpur during 2002-03 and 2003-04. A completely randomized design for laboratory experiment and randomized complete block design for field experiments was followed with three replications. Acquired thermal tolerance through Membrane Thermo-stability assay was performed in controlled environment as per method described by Ibrahim and Quick (2001). Other morpho-physiological traits were measured from field experiment. The crosses Kanchan × Gourab, Kanchan × Pavon 76 and Fang 60 × Pavon76 showed high genetic variability with high population mean for MTS in F4 bulks. These crosses also exhibited high-observed response to selection, realized heritability and heritability in standard unit indicating expected good gain through early generation selection. Direct response to selection for this trait was significant in these crosses in F5 generation. Direct selection for MTS significantly improved biomass, grain yield, thousand grain weight, grain filling rate and canopy temperature depression in crosses Kanchan × Pavon 76, Gourab × Pavon76 and Fang 60 × Pavon76 with few exceptions. Direct selection of MTS also improved chlorophyll retention at 21 days after anthesis in crosses Gourab × Fang 60 and Gourab × Pavon76. Significant intergeneration correlations (F4 vs. F5) were observed for MTS in all five crosses studied indicating possibility of effective improvement of this trait through selection in early generation.   Key words: Membrane thermostability; selection response; realized heritability; intergeneration correlation.DOI: http://dx.doi.org/10.3329/bjpbg.v23i2.9320 Bangladesh J. Pl. Breed. Genet., 23(2): 15-22, 2010

scholarly journals DIRECT RESPONSE TO SELECTION FOR POSTWEANING GAIN IN THE RAT

Genetics ◽  
1975 ◽  
Vol 80 (1) ◽  
pp. 171-189
Author(s):  
R L Baker ◽  
A B Chapman ◽  
R T Wardell
Keyword(s):  
Relative Magnitude ◽  
Realized Heritability ◽  
Response To Selection ◽  
Direct Response ◽  
Selected Lines ◽  
History Of ◽  
Regression Techniques ◽  
Selection For ◽  
Rats And Mice ◽  
Seven Generations

ABSTRACT The effectiveness of selection for 3–9-week gain was examined in a population of rats with a history of past selection for high 3–9-week gain. Lines were selected for high (U line) and low (D line) 3–9-week gain with two replicates of each line. Two randomly selected lines were also kept, one originating from the same base population as the two selected lines (R line) and the other originating from a population that had been randomly mated for the previous 27 generations (C line). Two replicates of each of these lines were kept. After seven generations of selection, a randomly selected line (relaxed line) was formed from each of the two upward- and each of the two downward-selected lines. Results have been presented for 13 generations of selection. The environmental trend for 3–9-week gain, as indicated by the randomly selected R and C lines, was consistently negative in all four lines. Realized heritabilities calculated by deviating the response to selection from the trend in the R or C lines resulted in non-significantly higher values in the D lines than the U lines. Six generations of relaxation of selection indicated no effect of natural selection in the U lines or the D lines. The relative magnitude of the drift, error and common environmental variances were estimated by the methods given by Hill (1971). The estimates of these parameters then led to calculation of the degree of bias in the sampling variances of the realized heritability estimates. As was predicted by Hill (1971), estimates of the variance of realized heritabilities obtained by using standard regression techniques were less than those obtained using Hill's formulae. The results are discussed in relation to other similar studies with rats and mice.

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