scholarly journals MASS SELECTION FOR POST-WEANING GROWTH IN SWINE: II. RESPONSE TO SELECTION

1971 ◽  
Vol 51 (2) ◽  
pp. 497-502 ◽  
Author(s):  
G. W. RAHNEFELD
Keyword(s):  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Average Daily Gain ◽  
Mass Selection ◽  
Realized Heritability ◽  
Response To Selection ◽  
Components Of Variance ◽  
Selection For ◽  
Seven Generations ◽  
Daily Gain

Recurrent mass selection for post-weaning average daily gain was practiced for seven generations in a population of Lacombe swine. Response to selection was positive, but the observed response was estimated to be only 0.33 of the predicted. The pooled estimate of additive genetic variance was 0.0013 ± 0.0002. Realized heritability was 0.126 ± 0.029. The pooled estimate of heritability obtained from components of variance and parent-offspring regression was 0.377 ± 0.058. Litter size was positively correlated with average daily gain (0.14 piglet per generation). No significant effects of selection in reducing additive genetic variance were observed.

PREDICTIONS OF THE EFFECTIVENESS OF INTRAPOPULATION SELECTION VERSUS SELECTION FOR SPECIFIC COMBINING ABILITY IN SWINE

1984 ◽  
Vol 64 (4) ◽  
pp. 799-806
Author(s):  
R. M. McKAY ◽  
G. W. RAHNEFELD
Keyword(s):  
Combining Ability ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Effective Means ◽  
Average Daily Gain ◽  
Mass Selection ◽  
Genetic Covariance ◽  
Selection For ◽  
Sib Selection ◽  
Daily Gain

Additive genetic variance estimates for purebred (Lacombe) and crossbred (Lacombe × Yorkshire) populations and the additive genetic covariance between purebred and crossbred progeny were calculated for postweaning average daily gain, total probe fat, total carcass fat, and litter size in swine. These estimates were used to predict the effectiveness of four methods of intrapopulation selection (IP) relative to selection for specific combining ability (SCA) to determine the most effective means of improving crossbred performance. The intrapopulation methods were mass selection based on information from both sexes (BS), mass selection based on information from one sex (OS), full-sib selection (FS), and half-sib selection (HS). The Lacombe population was selected over 12 generations for increased postweaning average daily gain and the Lacombe × Yorkshire population was generated by breeding Lacombe boars with randomly selected gilts from a Yorkshire control population. Selection for combining ability was the most effective means of improving average daily gain except when information was available on both sexes and the relative selection intensity (SCA/IP) was less than 0.60. Mass selection was superior to SCA for improving total probe fat except when information was restricted to one sex and the relative selection intensity was less than 0.47. For total probe fat and total carcass fat, SCA was superior to FS and HS for relative selection intensities less than 0.65 and 0.74, respectively. Selection for combining ability was superior to OS for litter size regardless of the generation interval length. Key words: Intrapopulation selection, selection for combining ability, additive genetic variance, additive genetic covariance, swine

MASS SELECTION FOR POST-WEANING GROWTH IN SWINE. IV. SELECTION RESPONSE AND CONTROL POPULATION STABILITY

1976 ◽  
Vol 56 (4) ◽  
pp. 783-790
Author(s):  
G. W. RAHNEFELD ◽  
I. GARNETT
Keyword(s):  
Additive Genetic Variance ◽  
Average Daily Gain ◽  
Selection Response ◽  
Relative Magnitude ◽  
Control Population ◽  
Mass Selection ◽  
Gene Effects ◽  
Selection For ◽  
And Control ◽  
Daily Gain

Recurrent mass selection for post-weaning average daily gain was practiced for 11 generations in a population of Lacombe swine. Response to selection was assessed from predicted response, 0.241 ± 0.023 kg; observed response, 0.146 ± 0.018 kg; estimated heritability, 0.327 ± 0.031; and realized heritability, 0.198 ± 0.016. Observed response was estimated to be 0.61 of the predicted. Examination of additive genetic variance, selection differentials, drift variance, inbreeding and regression of post-weaning average daily gain on generation time indicated that the pedigreed Yorkshire control population served as an adequate control. Gene effects were not found to be dependent on the sex of the organism as assessed by the genetic correlation between sexes, covariance between half-sib family means and the relative magnitude of parent–offspring-based estimates of heritability.

RESPONSE TO SELECTION FOR BODY WEIGHT OR FEED EFFICIENCY IN MICE TESTED ON CORN, RYE AND WHEAT DIETS

1986 ◽  
Vol 66 (2) ◽  
pp. 389-397
Author(s):  
R. I. McKAY ◽  
R. J. PARKER ◽  
W. GUENTER
Keyword(s):  
Body Weight ◽  
Feed Efficiency ◽  
Mass Selection ◽  
Response To Selection ◽  
Initial Weight ◽  
Commercial Diet ◽  
Final Weight ◽  
Dc Line ◽  
Selection For ◽  
Seven Generations

Mass selection for adjusted feed efficiency (AFE, g gain/g feed) and adjusted body weight (ABW, g) of male mice was practiced for seven generations on each of three diets: corn, rye and wheat. The three experimental diets, fed between 21 and 35 d, were isocaloric (approximately 16.5 MJ GE kg−1) and isonitrogenous (CP approximately 13%). A common commerical diet (PC) was fed at all other times. With each diet two control lines, randomly mated, were tested on either the experimental diets (DC) or a commercial diet (PC). Selection was based upon linear adjustment to a common initial weight (10 g) for either final weight (ABW) or feed efficiency (AFE) measured between 21 and 35 d of age. Response was determined as a deviation from the appropriate DC line. All animals were placed in specially designed individual cages during the test period. Half-sib estimates of heritability in the PC line were 0.13(± 0.11) for ABW and 0.19(± 0.10) for AFE. Half-sib estimates pooled across lines and diets were 0.16(± 0.07) for ABW and 0.28(± 0.07) for AFE. Realized heritabilities for ABW were 0.24(± 0.06), 0.06(± 0.07) and 0.14(± 0.06) for the corn, rye and wheat diets, respectively. Response to selection for AFE was poor with the highest heritability obtained on the wheat diet (h2 = 0.13 ± 0.02). Key words: Selection, mice, body weight, feed efficiency, diets

MASS SELECTION FOR POST-WEANING GROWTH IN SWINE. V. CORRELATED RESPONSE OF REPRODUCTIVE TRAITS AND PRE-WEANING GROWTH

1976 ◽  
Vol 56 (4) ◽  
pp. 791-801
Author(s):  
I. GARNETT ◽  
G. W. RAHNEFELD
Keyword(s):  
Birth Weight ◽  
Average Daily Gain ◽  
Reproductive Traits ◽  
Correlated Response ◽  
Mass Selection ◽  
Gestation Length ◽  
Control Line ◽  
Weaning Weight ◽  
Selection For ◽  
Daily Gain

Female reproductive performance and pre-weaning survival and growth were examined in a population of swine over 11 generations of selection for post-weaning average daily gain (ADG). Three separate breeding groups were used: (1) a Lacombe (L) line selected each generation for ADG, (2) a Yorkshire control (Y) line, and (3) a crossbred Lacombe × Yorkshire group (LY) generated each generation from the L and Y lines. Breeding group differences were evident for litter size, perinatal mortality, pre-weaning mortality, gestation length, birth weight, pre-weaning average daily gain (PreADG) and weaning weight. Selection did not affect number born, number born alive, number weaned or birth weight. When the values for the L line were expressed as a deviation from the control, pre-weaning mortality showed an increase. The increase appeared to be due to a decrease in the control rather than an increase in the L line. Gestation length showed a negative response to selection. As in the case of pre-weaning mortality, the response appeared to be a reflection of the instability of the control line. Genetic gains in PreADG of 0.004 kg/day/generation were realized in both the L line and LY group. Correspondingly, responses of 0.18 and 0.19 kg/generation were realized for weaning weight in the L line and LY group.

Measurement of fleece wettability in sheep and its relationship to susceptibility to fleece rot and blowfly strike

1982 ◽  
Vol 33 (1) ◽  
pp. 141 ◽  
Author(s):  
L Pascoe
Keyword(s):  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Genetic Correlations ◽  
Economic Importance ◽  
Correlated Response ◽  
Response To Selection ◽  
Significant Incidence ◽  
The Mean ◽  
Selection For ◽  
The One

Fleece wettability in sheep is a character believed to be related to susceptibility to fleece rot and blowfly strike. The present study was undertaken to investigate that hypothesis and to assess wettability as a possible character for a selection program. Wool samples were taken from two flocks which had been subject to selection for wool quality and resistance to fleece rot and a third flock which was unselected. The wettabilities of about 800 samples were determined. The results were found to be repeatable and the technique was capable of distinguishing between sheep. Some problems of measurement are discussed. In the one flock with a significant incidence of fleece rot, susceptibility to fleece rot was found to be associated with higher wettabilities. The mean wettability and the variance were found to be significantly higher in the unselected flock than in the two selected flocks. The heritability of wettability was estimated in the two selected flocks and was found to be low. It is argued that there is likely to be more additive genetic variance in the unselected flock and that the observed difference in wettability was due to a correlated response to selection for resistance to fleece rot. It is considered that further work on the heritability of wettability and its genetic correlations with other characters of economic importance could be fruitful.

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.

Direct response to selection for post-weaning net feed intake in mice and correlated responses in post-weaning growth, intake, gross digestibility and body composition

2004 ◽  
Vol 44 (5) ◽  
pp. 489 ◽  
Author(s):  
T. E. Hughes ◽  
W. S. Pitchford
Keyword(s):  
Body Composition ◽  
Feed Intake ◽  
Genetic Correlations ◽  
Heritability Estimate ◽  
Response To Selection ◽  
Correlated Responses ◽  
Direct Response ◽  
Selection For ◽  
Seven Generations ◽  
Daily Gain

Seven generations of divergent selection on a phenotypic index of net feed in mice produced a realised heritability estimate of 0.27 ± 0.07. Despite small negative genetic correlations of net feed intake with daily gain and liveweight, correlated responses in these economically important traits were negligible. Still, more efficient animals tended to be fatter during the early post-weaning phase. Gross digestibility was also affected, which may have implications for the overall energy balance of a biological system.

The Equation for Response to Selection and Its Use for Prediction

1997 ◽  
Vol 5 (3) ◽  
pp. 303-346 ◽  
Author(s):  
Heinz Mühlenbein
Keyword(s):  
Genetic Algorithms ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Linkage Equilibrium ◽  
Realized Heritability ◽  
Response To Selection ◽  
Infinite Population ◽  
Livestock Breeding ◽  
Genotype Frequencies ◽  
Tournament Selection

The Breeder Genetic Algorithm (BGA) was designed according to the theories and methods used in the science of livestock breeding. The prediction of a breeding experiment is based on the response to selection (RS) equation. This equation relates the change in a population's fitness to the standard deviation of its fitness, as well as to the parameters selection intensity and realized heritability. In this paper the exact RS equation is derived for proportionate selection given an infinite population in linkage equilibrium. In linkage equilibrium the genotype frequencies are the product of the univariate marginal frequencies. The equation contains Fisher's fundamental theorem of natural selection as an approximation. The theorem shows that the response is approximately equal to the quotient of a quantity called additive genetic variance, VA, and the average fitness. We compare Mendelian two-parent recombination with gene-pool recombination, which belongs to a special class of genetic algorithms that we call univariate marginal distribution (UMD) algorithms. UMD algorithms keep the genotypes in linkage equilibrium. For UMD algorithms, an exact RS equation is proven that can be used for long-term prediction. Empirical and theoretical evidence is provided that indicates that Mendelian two-parent recombination is also mainly exploiting the additive genetic variance. We compute an exact RS equation for binary tournament selection. It shows that the two classical methods for estimating realized heritability—the regression heritability and the heritability in the narrow sense—may give poor estimates. Furthermore, realized heritability for binary tournament selection can be very different from that of proportionate selection. The paper ends with a short survey about methods that extend standard genetic algorithms and UMD algorithms by detecting interacting variables in nonlinear fitness functions and using this information to sample new points.

MASS SELECTION FOR POST-WEANING GROWTH IN SWINE: I. THE VALUE OF A PEDIGREED CONTROL POPULATION

1971 ◽  
Vol 51 (2) ◽  
pp. 481-496 ◽  
Author(s):  
G. W. RAHNEFELD
Keyword(s):  
Additive Genetic Variance ◽  
Breeding Population ◽  
Control Population ◽  
Mass Selection ◽  
Selection For ◽  
Average Size ◽  
Genetic Value ◽  
Seven Generations ◽  
Two Populations ◽  
Made In

A pedigreed control population of Yorkshire swine has been described. The average size of the breeding population was 20 males and 40 females in each of the seven generations. The effective number of parents per generation was estimated at 87.5. There has been little or no evidence of any significant changes in the genetic value of the population over the seven generations as determined by estimates of additive genetic variance, selection differentials, and other related parameters. The performance of the control population was compared with that of a selected population and with crossbreds produced by mating select population males to control population females. Comparisons were made in the same environments. The comparisons of the effects of the selection program on several traits measured in the two populations have been made, based on the absolute trends in these populations over the seven generations and as a deviation from the performance of the control population.

MASS SELECTION FOR POSTWEANING GROWTH IN SWINE. III. CORRELATED RESPONSE IN WEANING WEIGHT AND FEED EFFICIENCY TO RECURRENT SELECTION FOR POSTWEANING AVERAGE DAILY GAIN IN SWINE

1973 ◽  
Vol 53 (2) ◽  
pp. 173-178
Author(s):  
G. W. RAHNEFELD
Keyword(s):  
Genetic Correlation ◽  
Feed Efficiency ◽  
Average Daily Gain ◽  
Direct Selection ◽  
Correlated Response ◽  
Mass Selection ◽  
Total Response ◽  
Weaning Weight ◽  
Selection For ◽  
Daily Gain

Correlated response in weaning weight and feed efficiency were estimated for a genetically variable population of swine selected during nine generations for postweaning average daily gain. Total response in weaning weight to direct selection for gain was 0.03 kg per generation. This was 3.1% of the predicted response. The estimate of genetic correlation between postweaning average daily gain and weaning weight was found high and positive (> 1). Total response in feed efficiency to direct selection for gain was −0.58 kg per generation. This was 10% of the predicted response. The estimate of genetic correlation between postweaning gain and feed efficiency was −0.35.

Sign in / Sign up

Export Citation Format

Share Document