INHERITANCE OF WEIGHTS OF LAMBS REARED ARTIFICIALLY OR WITH THEIR DAMS

1983 ◽  
Vol 63 (2) ◽  
pp. 263-268 ◽  
Author(s):  
J. N. B. SHRESTHA ◽  
H. F. PETERS ◽  
D. P. HEANEY
Keyword(s):  
Genetic Correlation ◽  
Direct Selection ◽  
Milk Replacer ◽  
Response To Selection ◽  
Genetic Response ◽  
Artificial Rearing ◽  
Solid Diet ◽  
Selection For ◽  
Heritability Estimates ◽  
Age Estimates

This study involved 250 lambs reared artificially with milk replacer and solid diet from 2 to 70 days and 316 lambs creep-fed solid diet and reared with their dams from birth to 70 days. Thereafter, all lambs were retained on solid diet to 140 days of age. Heritability estimates for weights of lambs reared artificially tended to be larger than the corresponding estimates for lambs reared with their dams (P > 0.05). Phenotypic variances of lambs reared with their dams were larger at birth and at 35 days, whereas lambs reared artificially had larger phenotypic variances at 70 and 140 days of age. Estimates of genetic correlation between half-sib family means of lambs reared artificially with corresponding half-sibs reared with their dams ranged from 0.15 to 0.91, suggesting the absence of sire × rearing system interaction. We conclude that greater genetic response to selection for lamb weights at various ages could be achieved from direct selection among lambs reared artificially compared to those reared with their dams. However, in the absence of artificial rearing, prospective breeding stock reared with their dams should be tested for postweaning performance to permit full expression of transmitted sire differences. Key words: Sheep, lamb rearing, heritability estimates, genetic correlation

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 The genetic analysis of the direct and correlated response to selection for chaetae in Drosophila melanogaster

1973 ◽  
Vol 22 (1) ◽  
pp. 1-7
Author(s):  
W. R. Scowcroft
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Analysis ◽  
Genetic Correlation ◽  
Statistical Approach ◽  
Correlated Response ◽  
Minor Importance ◽  
Response To Selection ◽  
Genetic Changes ◽  
Selection For ◽  
Selection Of

SUMMARYThe direct and correlated response to selection of scutellar microchaetae and scutellar bristles has been analysed by determining the contribution of the three major chromosomes, alone and in combination with each other, to the overall response. The results of the analysis confirm a previous finding, based on a formal statistical approach, that response to selection for microchaetae had highly pleiotropic effects on scutellar bristles. In lines selected, each for high and low microchaetae, genetic changes in the 2nd and 3rd chromosomes are pre-eminent and essentially equal. Inter-chromosomal interactions are of relatively minor importance in interpreting the response to selection for microchaetae but assume greater importance with respect to the correlated character. The results are discussed in terms of the genetic correlation between fitness and the character measured.

scholarly journals Two-way selection for body weight in Tribolium on two levels of nutrition

1967 ◽  
Vol 9 (3) ◽  
pp. 309-330 ◽  
Author(s):  
R. T. Hardin ◽  
A. E. Bell
Keyword(s):  
Genetic Correlation ◽  
Genetic Parameters ◽  
Genetic Parameter ◽  
Minimum Size ◽  
Direct Selection ◽  
Correlated Responses ◽  
Larval Weight ◽  
Large Size ◽  
Selection For ◽  
Selection Differentials

Parameters necessary for predicting direct and correlated responses for large and small 13-day larval weight in T. castaneum on two levels of nutrition were estimated in the base population. Larval weight in the GOOD environment was approximately twice that observed in POOR. Heritabilities (estimated from the ratio of sire component to total phenotype variance) of larval weight on the two rations were similar, 0·21 ± 0·06 and 0·19 ± 0·05 for GOOD and POOR, respectively. Heritabilities based on dam-offspring covariances were similar to these, but those obtained from full-sib covariances were much larger (0·97 ± 0·07 for GOOD and 0·69 ± 0·07 for POOR). This suggested that considerable dominance rather than maternal effects were present. The genetic correlation between growth on GOOD and growth on POOR was estimated as + 0·60 ± 0·21.The selection experiment was replicated four times with each replication extending over eight generations. Good agreement between predicted and observed values for direct selection was observed for large selection in both environments and small selection in POOR. However, response to small selection in GOOD was significantly greater than predicted in all four replications and was associated with increased selection differentials. Realized heritabilities were approximately the same for both directions in GOOD yet asymmetrical responses occurred for all replications due to unequal selection differentials. On the other hand, realized heritabilities were asymmetrical in POOR. Those observed for small selection were more than twice the size of those calculated for large lines. However, the responses in POOR were symmetrical since the selection differentials varied inversely with the realized heritabilities.Because of the asymmetry observed for heritabilities and selection differentials, correlated responses were poorly predicted. The average effective genetic correlation between growth in GOOD and growth in the POOR environment agreed remarkably well with the base estimate, yet asymmetry of the genetic correlation was a consistent phenomenon with values for the large lines being less than the base parameter while small lines were uniformly larger.Asymmetries of the various genetic parameters were not anticipated from base estimates. They were not caused by sampling or chance fluctuations since all four replications were remarkably consistent. Asymmetry for any one genetic parameter (e.g. heritability) was associated with a particular environment or direction of selection while other genetic parameters reacted asymmetrically in populations exposed to a different set of environmental treatments.For maximum performance in a single environment, these results show that selection should be practiced in that environment. With regard to mean performance in GOOD and POOR environments, selection for large size in POOR gave some 25% more gain than selection in GOOD. Selection for small size in either environment was equally effective in obtaining minimum size in both environments.

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

Selection for weaning weight in Merino sheep. 1. Direct response to selection

1965 ◽  
Vol 5 (19) ◽  
pp. 353 ◽  
Author(s):  
WA Pattie
Keyword(s):  
Response To Selection ◽  
Direct Response ◽  
Weaning Weight ◽  
Merino Sheep ◽  
Inbreeding Coefficients ◽  
Selection For ◽  
Heritability Estimates

The heritability of corrected weaning weight has been estimated by dam-offspring and paternal half-sib correlations in a random-bred, medium-wool Peppin Merino flock. All weights were corrected for age and type of birth within each year. The dam-off-spring heritability estimates were 0.28 � 0.10 for ewes and 0.32 � 0.11 for rams. The paternal half-sib estimates were 0.18 � 0.07 for ewes and 0.19 � 0.13 for rams. Responses in flocks selected for high and low weaning weight for four generations (1951 to 1961) were used to calculate realized heritabilities. These were 0.33 � 0.03 and 0.18 � 0.06 for ewes and rams respectively in the high weaning weight flock, and 0.22 � 0.10 and 0.23 � 0.19 for ewes and rams in the low weaning weight flock. The average increases in inbreeding coefficients since selection commenced were 3.97 per cent in the high weaning weight flock, 3.58 per cent in the low weaning weight flock and 0.39 per cent in the randomly selected control flock. The regressions of weaning weight on inbreeding, independent of the effects of selection, ranged from -0.076 to -0.387 with an average of -0.191 lb weaning weight per one per cent inbreeding.

A REPEAT MATING DESIGN IN A SELECTION EXPERIMENT

1980 ◽  
Vol 60 (4) ◽  
pp. 833-841
Author(s):  
R. J. PARKER ◽  
T. K. CHEUNG ◽  
K. M. WITTENBERG ◽  
C. G. HICKMAN
Keyword(s):  
Selection Response ◽  
Mass Selection ◽  
Response To Selection ◽  
Genetic Response ◽  
Mating Design ◽  
Litter Weight ◽  
The Third ◽  
Mating Population ◽  
Selection For ◽  
Selection Intensities

The separation of genetic and environmental trends in a repeat mating design and the effectiveness of such a design in producing genetic response to selection were observed during eight cycles of directional selection for high 12-day litter weight in mice. A random-bred control was used to monitor the repeat mating design in estimating environmental trend. Two mass selection populations (M1 and M2) under different selection intensities were used to assess the success of the repeat mating design in achieving selection response. From the third to the eighth cycle, the estimated genetic gain in 12-day litter weight for the repeat mating population was 0.89 ± 0.25 g per cycle. The selection response from the repeat design was lower than from one mass selection population (M2) but higher than from the other (M1). The environmental trend estimate of −0.79 ± 0.78 g per cycle was in fair agreement with the estimate of −0.88 ± 0.55 g per cycle from the random bred control.

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