RESPONSE TO SELECTION FOR WEIGHT-PER-DAY-OF-AGE IN RAMBOUILLET AND ROMNELET SHEEP

1975 ◽  
Vol 55 (1) ◽  
pp. 1-8 ◽  
Author(s):  
J. A. VESELY ◽  
H. F. PETERS
Keyword(s):  
Genetic Correlations ◽  
Response To Selection ◽  
Correlated Responses ◽  
Weaning Weight ◽  
Two Generations ◽  
Selection For ◽  
Heritability Estimates

Responses to selection for weight-per-day-of-age (WPDA) to about 170 days in Rambouillet and Romnelet sheep over 5 yr, comprising two generations, were measured by two methods. Correlated responses in weaning weight (WW) at about 100 days, and postweaning gain (PWG) for 70 days were also estimated. The estimates of annual genetic increases in WPDA were quite similar in both breeds and from both methods. The improvements of this trait in Rambouillet and Romnelet were estimated as 9.7 and 6.0 g/yr from method 1, and 9.1 and 7.8 g/yr from method II. Estimates of correlated responses in PWG obtained by both methods and in both breeds were close to expected estimates, but correlated responses in WW appeared to be overestimated. Heritability estimates for WPDA using paternal half-sibs were 0.20 for Rambouillet and 0.18 for Romnelet. All genetic correlations among the three traits were positive. Realized heritabilities for WPDA were 0.28 and 0.20 in Rambouillet and Romnelet by method I, and 0.26 in both breeds by method II.

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.

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.

scholarly journals CORRELATED RESPONSES IN WEIGHTS OF IMPROVED INDIGENOUS PIGS - NIGERHYB - IN NIGERIA

2021 ◽  
Vol 22 (2) ◽  
pp. 113-119
Author(s):  
O. A. Adebambo
Keyword(s):  
Weight Gain ◽  
Birth Weight ◽  
Genetic Correlations ◽  
Correlated Responses ◽  
Good Criterion ◽  
Phenotypic Correlations ◽  
Selection For ◽  
Heritability Estimates ◽  
Indigenous Pigs

Data collected on the weight of 1681 offsprings of improved indigenous pigs from 1984 to 1990 were used to obtain heritability estimates; genetic, environmental and phenotypic correlations among weights and gains from birth to mature and yearling weights. The estimates were used to predict expected change from correlated responses from single trait selection. Heritability estimates obtained from paternal half-sib analysis were birth weight 0.90 ±0. 08; gain from birth to weaning 0.14±0.11; 150 days weight 0.49±18; gain from weaning to 150 days 0.49±0.15; weight gain from.150 days to yearling weight 0.41 ± 026 and yearling weight 0.66±. Genetic correlations among all weights and gains were fairly high, ranging from 0.25 to 0.81. Selection for individual pig weight at 56 days appear to be a single good criterion for selection for growth at other ages with coheritabilities of 0.669 for 56 and 150 days weight and 0,856 for 56 days versus yearling weight.

Genetic evaluation of birth and weaning weight of Gudali and two-breed synthetic Wakwa beef cattle populations under selection in Cameroon: genetic and phenotypic parameters

1993 ◽  
Vol 57 (1) ◽  
pp. 73-79 ◽  
Author(s):  
C. L. Tawah ◽  
D. A. Mbah ◽  
J. E. O. Rege ◽  
H. Oumate
Keyword(s):  
Maternal Effects ◽  
Genetic Relationships ◽  
Genetic Correlations ◽  
Individual Performance ◽  
Genetic Progress ◽  
Weaning Weight ◽  
Maximum Likelihood Procedure ◽  
Derivative Free ◽  
Selection For ◽  
Heritability Estimates

AbstractGenetic parameters for birth and 240-day weaning weights in Gudali and Wakwa cattle breeds in a tropical environment in Cameroon were estimated by derivative-free restricted maximum likelihood procedure using singletrait animal models with maternal effects. Performance data covered the period 1971 through 1985. Heritability estimates for direct effects of live weights at birth and weaning were 0·39 (s.e. 0·10) and 0·27 (s.e. 0·09) in Gudali cattle and 0·65 (s.e. 0·15) and 0·29 (s.e. 0·13) in Wakwa cattle, respectively. Corresponding heritability estimates for maternal effects were 0·06 (s.e. 0·06) and 0·20 (s.e. 0·09) in Gudali cattle and 0·22 (s.e. 0·08) and 0·27 (s.e. 0·12) in Wakwa cattle. Estimates of genetic correlations between direct and maternal effects were negative and substantial for birth weight in Gudali (0·86) and Wakwa (-0·93) and for weaning weight in Gudali (-0·68). The estimate for weaning weight in Wakwa (-0·39) was lower. It was evident from the results that selection on individual performance was likely to yield substantial genetic progress in these traits. Although heritability estimates for maternal effects were low, the negative direct-maternal genetic relationships indicated that selection for these traits should not ignore the maternal component.

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

The role of selection in the improvement of Welsh Mountain sheep

1958 ◽  
Vol 9 (6) ◽  
pp. 819 ◽  
Author(s):  
JM Doney
Keyword(s):  
Birth Weight ◽  
Maternal Environment ◽  
Weaning Weight ◽  
Phenotypic Correlations ◽  
Selection For ◽  
Heritability Estimates ◽  
Fleece Weight ◽  
Staple Length

Means and variances of several economic characters in Welsh Mountain sheep are given. The repeatabilities of, and phenotypic correlations between, these characters are generally within the range of similar estimates given for other breeds. Heritabilities, calculated from parent-offspring correlations, were : birth weight 0.39, weaning weight 0.68, 18-month weight 0.59, greasy fleece weight 0.61, and staple length 0.73. These values are in general higher than similarly derived estimates from other breeds. A method of correcting heritability estimates to remove the error due to correlation between maternal environment, and the character as measured in the dam, is described. This reduces the estimate for weaning weight to 0.48, and that for 18-month weight to 0.16, but does not change that for fleece weight. The use of such estimates in predicting the effect of selection is discussed, and it is concluded that accurate selection for the chosen economic characters will result in improvement at the present genetic stage of the breed.

Response to selection in Australian Merino sheep. III. Single character selection for high and low values of wool weight and its components

1970 ◽  
Vol 21 (6) ◽  
pp. 955 ◽  
Author(s):  
HN Turner ◽  
MG Brooker ◽  
CHS Dolling
Keyword(s):  
Body Weight ◽  
Unit Area ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Initial Response ◽  
Skin Area ◽  
Correlated Responses ◽  
Fibre Number ◽  
Selection For ◽  
Staple Length

Direct and correlated responses are reported for 10 traits in eight pairs of lines under selection for high and low values of single characteristics : clean wool weight per head, clean wool weight per unit skin area (measured only in the groups under selection for it), body weight, wrinkle score, fibre number per unit skin area (adjusted for body weight), fibre diameter, staple length, and percentage clean yield. All groups showed overall divergence in the character under selection, though response was not always symmetrical, and in two cases (long staple and low fibre number) there was no continuing response after the initial response to extreme selection of the base parents. In all except one case, whenever previous estimates of genetic correlation were at the level of 0.2 or higher, correlated responses were in the predicted direction, though not always symmetrical in magnitude. The exception was a previously reported negative correlation between fibre number and staple length, which was not exhibited under selection for either character. Where two characters of a pair were under selection, reciprocal responses agreed in sign; magnitude will be examined in a later paper. Wool per unit area was shown to have a greater influence on clean wool weight than that of surface area, with staple length on this occasion being the most important component of wool per unit area. Reasons for an apparent decrease in the relative importance of fibre number are discussed. Three other points of importance in sheep breeding are again emphasized by these results : 1. Crimp in several pairs of groups was a poor indicator of fibre diameter. 2. Increases in clean wool weight were associated with falls in crimp number, even though fibre diameter actually became finer; diameter, not crimp, should therefore be used as a guide to wool quality. 3. The absence of genetic correlations DL and NL indicates that selection can be for high N (fibre number) with high L (staple length) and low D (fibre diameter) -in other words, a desirable fleece -with no impeding genetic correlations.

Estimates of genetic parameters for pre-weaning and post-weaning growth traits of Chios lambs

1980 ◽  
Vol 30 (2) ◽  
pp. 271-276 ◽  
Author(s):  
A. P. Mavrogenis ◽  
A. Louca ◽  
O. W. Robison
Keyword(s):  
Body Weight ◽  
Birth Weight ◽  
Genetic Parameters ◽  
Growth Traits ◽  
Genetic Correlations ◽  
Heritability Estimate ◽  
Weaning Weight ◽  
Phenotypic Correlations ◽  
Selection For ◽  
Daily Gain

ABSTRACTData on 792 Chios lambs born during the 1972/73 and 1973/74 lambing seasons were used to estimate genetic and phenotypic parameters for birth weight, weaning weight, age at weaning, pre-weaning daily gain, body weight at 5, 10, 15 and 20 weeks of age, and postweaning daily gain. Body weight at 15 weeks of age had the highest heritability estimate (0·73 ± 0·17) and that of post-weaning daily gain was also high (0·56 ± 0·15). Selection for either weight at 15 weeks or post-weaning daily gain would be expected to yield a greater response than selection for pre-weaning daily gain or weaning weight. Genetic correlations among weights and/or gains were positive (approximately 0·20). Phenotypic correlations among weights and gains were generally higher than genetic correlations. However, the correlation between pre— and post-weaning daily gain was small (0·08). Likewise, post-weaning daily gain had low correlations with all weights before 10 weeks. Age at weaning had moderate negative associations with all weights but a very low positive correlation with post-weaning daily gain.

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.

EFFECT OF SELECTION FOR CARCASS SCORE ON THE GENETIC IMPROVEMENT OF ITS COMPONENTS IN SWINE

1970 ◽  
Vol 50 (3) ◽  
pp. 585-592 ◽  
Author(s):  
M. H. FAHMY ◽  
C. BERNARD
Keyword(s):  
Analysis Of Variance ◽  
Genetic Improvement ◽  
Genetic Correlations ◽  
Feed Utilization ◽  
Backfat Thickness ◽  
Yorkshire Pigs ◽  
Selection For ◽  
Heritability Estimates ◽  
Sole Criterion ◽  
Three Components

Selection for carcass score was practiced for ten generations in two separate lines of Yorkshire pigs. Three components of the score were studied: carcass length, loin eye area, and backfat thickness. In line 2, carcass score was the sole criterion of selection, while in line 3, it was combined with feed utilization into an overall merit. Line 1, selected solely for feed utilization, served as a control. Carcass length and loin eye area increased by approximately 2 and 9%, respectively, in both lines. However, backfat thickness also increased by about 3% in line 2 and 0.4% in line 3. Pooled heritability estimates derived from the analysis of variance and the regression of offspring on mid-parent were 0.64 for carcass length, 0.48 for loin eye area and 0.67 for backfat thickness. Genetic correlations among the components of carcass score, between the components and carcass score and between the components and feed utilization were moderately high and favorable for combined genetic improvement of all traits.

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