SELECTION FOR FEED EFFICIENCY IN MICE UNDER AD LIBITUM AND RESTRICTED FEEDING TERMINATED BY FIXED TIME OR QUANTITY OF INTAKE

1982 ◽  
Vol 24 (1) ◽  
pp. 117-126 ◽  
Author(s):  
R. J. Parker ◽  
M. A. Bhatti
Keyword(s):  
Weight Gain ◽  
Random Mating ◽  
Genetic Correlations ◽  
Fixed Time ◽  
Feed Consumption ◽  
Mass Selection ◽  
Control Line ◽  
Initial Weight ◽  
Ad Libitum ◽  
Selection For

Mass selection for feed conversion efficiency (FCE) in mice was practiced for six generations in two lines fed ad libitum (AL) and two lines restricted to 80% of ad libitum (R). In one line of each pair of selected lines the test period was terminated after a fixed time (14 days) (TAL and TR) and in the second line of the pair after consumption of a fixed quantity of feed (WAL and WR). A random mating control line (C), also fed ad libitum was maintained throughout the study. Correlated traits measured were initial weight, final weight, weight gain, feed consumption and litter size. A significant response in FCE was found in the TR and WR lines, the regression of response on generation number being −1.36 ± 0.31 and −1.09 ± 0.39 respectively. There was a significant decrease in initial weight on test in the TR and WAL lines and in those lines mature body weight was significantly lower than in the C line when measured in the sixth generation. Heritability of FCE was higher in the restricted lines (0.31 ± 0.12 for TR and 0.37 ± 0.29 for WR) than in the ad libitum lines (0.13 ± 0.20 for TAL and 0.13 ± 0.25 for WAL). Heritability of FCE was 0.17 ± 0.31 in the C line. Phenotypic and genetic correlations between FCE and weight gain were high and negative in all lines. Progeny from each line were tested in each of the other feeding regimes each generation to measure line × feeding regime interaction. This interaction was statistically significant.

Selection for components of efficient lean growth rate in pigs 2. Selection pressure applied and direct responses in a Landrace herd

1994 ◽  
Vol 59 (2) ◽  
pp. 263-269 ◽  
Author(s):  
N. D. Cameron ◽  
M. K. Curran
Keyword(s):  
Growth Rate ◽  
Genetic Correlations ◽  
Correlated Response ◽  
Selection Line ◽  
Control Line ◽  
Direct Response ◽  
Lean Growth ◽  
Ad Libitum ◽  
Selection For ◽  
Ad Libitum Feeding

AbstractResponses to divergent selection for lean growth rate with ad-libitum feeding (LGA), for lean food conversion (LFC) and for daily food intake (DFI) in Landrace pigs were studied. Selection was practised for four generations with a generation interval ofl year. A total of 2642 pigs were performance tested in the high, low and control lines, with an average of 37 boars and 39 gilts performance tested per selection line in each generation. The average within-line inbreeding coefficient at generation four was equal to 0·04. There was one control line for the DFI and LFC selection groups and another control line for the LGA selection group. Animals were performance tested in individual pens with mean starting and finishing weights of 30 kg and 85 kg respectively with ad-libitum feeding. The selection criteria had phenotypic s.d. of 32, 29 and 274 units, for LGA, LFC and DFI, respectively, and results are presented in phenotypic s.d.Cumulative selection differentials (CSD) were 5·1, 4·5 and 5·5 phenotypic s.d. for LGA, LFC and DFI, respectively. Direct responses to selection were 1·4,1·1 and 0·9 (s.e. 0·20) for LGA, LFC and DFI. In each of the three selection groups, the CSD and direct responses to selection were symmetric about the control lines. The correlated response in LFC (1·1, s.e. 0·19) with selection on LGA was equal to the direct response in LFC. In contrast, the direct response in LGA was greater than the correlated response (0·7, s.e. 0·18) with selection on LFC. There was a negative correlated response in DFI (-0·6, s.e. 0·18) with selection on LFC, but the response with selection on LGA was not significant (0·2, s.e. 0·16).Heritabilities for LGA, LFC and DFI ivere 0·25, 0·25 and 0·18 (s.e. 0·03), when estimated by residual maximum likelihood, with common environmental effects of 0·12 (s.e. 0·02). Genetic correlations for LFC with LGA and DFI were respectively positive (0·87, s.e. 0·02) and negative (-0·36, s.e. 0·09), while the genetic correlation between DFI and LGA was not statistically different from zero, 0·13 (s.e. 0·10). Selection on components of efficient lean growth has identified LGA as an effective selection objective for improving both LGA and LFC, without a reduction in DFI.

scholarly journals A SIMULATION STUDY OF TRUNCATION SELECTION FOR A QUANTITATIVE TRAIT OPPOSED BY NATURAL SELECTION

Genetics ◽  
1980 ◽  
Vol 94 (4) ◽  
pp. 989-1000
Author(s):  
Francis Minvielle
Keyword(s):  
Natural Selection ◽  
Artificial Selection ◽  
Random Mating ◽  
Selection Response ◽  
Quantitative Character ◽  
Mass Selection ◽  
Frequency Selection ◽  
Selection Experiments ◽  
Selection For ◽  
Selective Process

ABSTRACT A quantitative character controlled at one locus with two alleles was submitted to artificial (mass) selection and to three modes of opposing natural selection (directional selection, overdominance and underdominance) in a large random-mating population. The selection response and the limits of the selective process were studied by deterministic simulation. The lifetime of the process was generally between 20 and 100 generations and did not appear to depend on the mode of natural selection. However, depending on the values of the parameters (initial gene frequency, selection intensity, ratio of the effect of the gene to the environmental standard deviation, fitness values) the following outcomes of selection were observed: fixation of the allele favored by artificial selection, stable nontrivial equilibrium, unstable equilibrium and loss of the allele favored by artificial selection. Finally, the results of the simulation were compared to the results of selection experiments.

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

Genetic parameters for egg weight v. age curve, and other egg production and egg weight traits, in synthetic lines of chickens

1983 ◽  
Vol 34 (1) ◽  
pp. 85 ◽  
Author(s):  
BH Yoo ◽  
BL Sheldon ◽  
RN Podger
Keyword(s):  
Standard Deviation ◽  
Genetic Correlation ◽  
Egg Production ◽  
Genetic Parameters ◽  
Genetic Correlations ◽  
Egg Mass ◽  
Control Line ◽  
Egg Weight ◽  
Egg Number ◽  
Selection For

An exponential curve, W = P-Qexp(- Rt), where W is egg weight at age t, was fitted to egg weights of individual pullets, and genetic parameters were estimated for P, Q and R, the residual standard deviation and other egg weight and egg production characters. The data consisted of records collected over six generations on more than 4000 pullets in two selection lines and a control line which originated from a synthetic gene pool of White Leghorn x Australorp crosses. The half-sib and offspring-on-parent regression estimates of heritability pooled over the lines were 0.23 and 0.33 for P, 0.14 and 0.20 for Q, and 0.14 and 0.25 for R. Genetic correlations were estimated to be -0.10 between P and Q, -0.46 between P and R, and 0.90 between Q and R. These estimates suggest that the egg weight v. age curve may be modified to increase the proportion of eggs in desirable weight grades and reduce the incidence of oversized eggs later in the production year. The genetic correlation between mean weight of first 10 eggs and egg weight at 62 weeks of age was estimated to be 0.68, further suggesting that early egg weight may be improved partly independently of late egg weight. The heritability estimates of egg mass output were not higher than those of egg number in spite of the highly heritable average egg weight being an important component of egg mass, probably because of the negative genetic correlation (r = -0.49) between egg number and average egg weight. The standard deviation of individual pullet's egg weights was moderately heritable and genetically correlated positively with egg weight characters and negatively with egg production; these estimates were consistent with the responses to selection for reduced egg weight variability observed elsewhere

Responses in gilt post-farrowing traits and pre-weaning piglet growth to divergent selection for components of efficient lean growth rate

1996 ◽  
Vol 1996 ◽  
pp. 17-17
Author(s):  
J. C. Kerr ◽  
N. D. Cameron
Keyword(s):  
Growth Rate ◽  
Food Intake ◽  
Fixed Time ◽  
Divergent Selection ◽  
Large White ◽  
Lean Growth ◽  
Fixed Weight ◽  
Ad Libitum ◽  
Selection For ◽  
Piglet Growth

Responses in sow traits at farrowing and during lactation and in pre-weaning piglet growth rate were determined in a population of Large White pigs, after seven generations of divergent selection for components of efficient lean growth rate. Information on the factors influencing preweaning piglet growth rate is required for a comprehensive evaluation of alternative selection strategies.There were four selection groups: daily food intake (DFI), lean food conversion (LFC), lean growth rate (LGA) on ad-libitum feeding and lean growth rate on scale feeding (LGS). There were 242 gilts in the study, with 20 gilts in the high, low and control lines of each selection group. Pigs in the ad-libitum selection groups were performance tested over a fixed weight range of 30 to 85 kg. Pigs fed on scale feeding were performance tested for a fixed time period of 84 days from 30 kg with food intake equal to 0.75 g/g of daily ad-libitum food intake. Matings were unsupervised and took place in outside paddocks.

scholarly journals EFFECT OF SELECTION ON HERITABILITY AND GENETIC CORRELATION OF TWO QUANTITATIVE TRAITS IN MICE

1974 ◽  
Vol 16 (3) ◽  
pp. 599-609 ◽  
Author(s):  
T. K. Cheung ◽  
R. J. Parker
Keyword(s):  
Body Weight ◽  
Genetic Correlation ◽  
Quantitative Traits ◽  
Random Mating ◽  
Tail Length ◽  
Control Group ◽  
Mass Selection ◽  
Initial Population ◽  
Significant Difference ◽  
Selection For

The effects of different intensities of single trait directional selection on the heritability and genetic correlation of two quantitative traits in random mating populations of mice were observed during 14 generations. The initial population was divided at random into five groups (A, B, C, D and E). Group A and Group B were under 30% and 60% mass selection for large 6-week body weight, respectively. Group C and Group D were under 30% and 60% mass selection for long 6-week tail length, respectively. Group E acted as control group with no selection applied. In all groups, the parent population consisted of 15 males and 30 females each generation, mated at random.Direct selection had no apparent effect on the heritability of either the trait under selection or the correlated trait over the 14 generations. Heritability of 6-wk tail length was higher than the heritability of 6-wk body weight. Estimates of heritability of 6-wk tail length ranged from 0.15 ± 0.22 to 0.68 ± 0.24, while estimates of heritability of 6-wk body weight ranged from 0.05 ± 0.17 to 0.33 ± 0.09. There was no significant difference among the estimates of genetic correlation between the two traits in the five selection groups. Estimates of realized genetic correlation between 6-wk body weight and 6-wk tail length seemed to indicate that more intense selection led to some decrease in genetic correlation between the two traits.

Selection for fertility in Australian Merino sheep

1963 ◽  
Vol 14 (4) ◽  
pp. 460 ◽  
Author(s):  
SSY Young ◽  
HN Turner ◽  
CHS Dolling
Keyword(s):  
Body Weight ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Likelihood Method ◽  
Mass Selection ◽  
Genetic Progress ◽  
Subsequent Performance ◽  
Fertility Trait ◽  
Selection For ◽  
The Difference

Phenotypic and genetic parameters for fertility in sheep, in terms of number of lambs born and number weaned, have been estimated in a flock of medium Peppin Merinos. Repeatability of fertility traits over all ages is low, but there is an age effect, the record at 3 years of age having a higher value than those at 2 or 4 years. The regression of subsequent performance on a difference of 1 lamb at the initial lambing was higher for the difference between 1 and 2 lambs than between 0 and 1 lamb, which indicated that selection for twins is likely to raise fertility in the current flock more rapidly than selection against barrenness. The estimate of heritability for 2 years of age was negligible for each fertility trait, but the estimates for the 3-year-old record were higher, the value for lambs born being over 0.3. Mass selection for number of lambs born at 3 years of age would thus be expected to lead to appreciable genetic progress, while there would be at least some progress in number of lambs weaned. Phenotypic and genetic correlations were also estimated between fertility at different ages and 10 sheep and wool traits measured at 15–16 months of age. Phenotypically, fertility is positively correlated with body weight and negatively with skin wrinkle score. Genetically, it is suggested from the estimates that fertility is positively correlated with body weight and staple length and negatively correlated with fibre diameter, clean scoured yield, and wrinkle score. No phenotypic or genetic correlation was found between greasy or clean wool weight and either measure of fertility. The application of the findings to breeding for higher fertility is discussed. In an appendix, a maximum likelihood method of estimating heritability for all-or-none traits in half-sib data is presented.

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.

scholarly journals SELECTION FOR HIGH ADULT BODY WEIGHT IN DROSOPHILA POPULATIONS WITH DIFFERENT STRUCTURES

Genetics ◽  
1975 ◽  
Vol 81 (1) ◽  
pp. 163-175
Author(s):  
A J Katz ◽  
S S Y Young
Keyword(s):  
Body Weight ◽  
Random Mating ◽  
Large Mass ◽  
Mass Selection ◽  
Adult Body ◽  
Large Populations ◽  
Subdivided Populations ◽  
Adult Body Weight ◽  
Selection For ◽  
Selection Intensities

ABSTRACT Selection for high adult body weight in Drosophila melanogaster was practiced for 18 generations in three selection lines. These lines were genetically similar and of equal size but different in population structure. One line represented a large mass-selected, random-mating population, while the other two lines simulated large populations that had been subdivided into partial isolates or demes. Mass selection and random mating occurred within each deme. These two subdivided lines were different only in the rate of effective migration among the demes (5% and 10%). Selection intensities of approximately 20% were applied to these populations. A fourth line served as a random mating control. Heritability of adult body weight in the base population was estimated to be 0.58± 0.22. The results indicate that significantly greater responses were achieved in the subdivided lines than in the large mass-selected line, in spite of the fact that larger selection differentials were applied to the latter. No significant differences in response were observed between the two subdivided lines. Wright (1930, 1931) postulated that selection would be most efficient in subdivided populations with limited interdeme migration. The present findings appear to support this theory.

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