Curvilinear Trends in Direct and Some Correlated Responses to Nineteen Generations of Selection for Part Record Rate of Egg Production in a Randombred Line of Chickens

Ibe, S. N.; Rutledge, J. J.; McGibbon, W. H.

doi:10.3382/ps.0610821

Cited by 4 publications

(2 citation statements)

References 17 publications

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“…Hence the observed decline in rate of response for egg production in later periods may be attributed to decline in additive genetic variance ( Figure 2) rather than other factors. Whereas Yamada et al (1958) found the exhaustion of additive genetic variance as the main reason for cessation of response in their study, Ibe et al (1982) reported that large inbreeding effects were found to in uence the response to selection. Gowe and Fairfull (1985), though they did not nd a signi cant response to selection for egg production to 273 d in the last 10 generations, did not observe any signi cant decline in heritability/genetic variance of the trait.…”

Section: Discussionmentioning

confidence: 90%

Factors affecting direct and correlated responses in a White Leghorn population under long term selection for egg number

Sharma

Johari²,

Kataria³

et al. 1998

British Poultry Science

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1. Data on 13,773 pullets, the progeny of 30 to 50 sires and about 135 to 220 dams per generation of a strain of White Leghorn under long-term selection for part period egg production over 16 generations, were examined. 2. Realised genetic gain per generation was highly significant for egg production (2.55 eggs), egg weight (-0.51 g), age at sexual maturity (-2.30 d) and 40 week body weight (-11.73 g). 3. The significant genetic response of 4.46 to 4.72 eggs per generation was realised in the first 8 generations only, which was accompanied by a marked decline in egg weight (-1.67 and -0.79 g per generation) and in age at sexual maturity (-4.63 and -6.39 d per generation). The 20 and 40 week body weights showed significant improvement in the last 4 generations. 4. Realised heritabilities were much lower in the last 8 than in the first 8 generation. 5. The additive genetic variance for most traits, except 20 week body weight and genetic covariances of egg production with egg weight and age at sexual maturity, declined significantly. 6. Natural selection did not seem to play any major role. No appreciable change in fitness traits was observed in the selected line. 7. The time trends were non-significant for all the traits in the control line, indicating its stability over generations.

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Section: Discussionmentioning

confidence: 90%

Factors affecting direct and correlated responses in a White Leghorn population under long term selection for egg number

Sharma

Johari²,

Kataria³

et al. 1998

British Poultry Science

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“…Selection for increased egg production in laying hens is generally based on cumulative part records (up to about 40 weeks of age) (SAADEH et al 1968;CRAIG et al 1969;KINNEY et al 1970;POGGENPOEL and ERASMUS 1978;GARWOOD and LOWE 1979;GARWOOD et al 1980;AYYAGARI et al 1980;IBE et al 1982;GOWE and FAIRFULL 1985;POGGENPOEL et al 1996). In general, the results indicated that selection for increased egg production based on part records led to increased rate of lay in the part record and to a positively correlated response in the full record.…”

Section: Introductionmentioning

confidence: 97%

Genetic and phenotypic parameters for monthly egg production in White Leghorn hens

Anang

Mielenz

Schüler

2000

J Animal Breeding Genetics

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This article reports genetic and phenotypic parameters of monthly egg production and the influence of Box-Cox transformation on the parameters from a population of White Leghorns, selected for feed efficiency. A total of 6450 daughters of 180 sires and 1335 dams were analysed by restricted maximum likelihood (REML) using a multivariate animal model. The traits considered were monthly egg productions, cumulative production of the first 5 months (S5), cumulative production of first 10 months (S10), and survivor egg production in the first cycle (S12). Two sets of data were analysed: the original data and with the Box-Cox method transformed data. The results indicated that there were no great differences in the estimates between untransformed and transformed data. The estimates of heritability for monthly egg production were high for the first period, decreased to reach the lowest during peak production, and increased to the end of lay. The estimates of heritability for cumulative records were generally higher than monthly records. Genetic and phenotypic correlations among monthly egg production totals were generally high for contiguous periods and then decreased as the interval between months increased. The highest genetic correlation between monthly records and S5 was for the second month of production, whereas the correlations between monthly production totals and S10 and S12 reached their peak at the sixth and eighth months of production, respectively. Zusammenfassung Genetische und phä notypische Parameter fü r die monatliche Legeleistung der Rasse Weißes LeghornDas Ziel der Untersuchung bestand in der Schätzung genetischer und phänotypischer Parameter fü r die monatliche Legeleistung bei Legehennen. Insgesamt 6450 Hennen der Rasse Weißes Leghorn, selektiert auf Futterverzehr, welche von 180 Vätern und 1335 Mü ttern abstammen, wurden mit einem Tiermodell unter Verwendung der REML-Methode analysiert. In die Auswertung gingen folgende Merkmale ein: monatliche Legeleistungen, akkumulierte Legeleistungen vom ersten bis fü nften Monat (S5), vom ersten bis zehnten Monat (S10), und eine Gesamtleistung (S12) im ersten Zyklus der Legephase. Zwei Datensätze wurden analysiert: die Originaldaten und die mit der Box-Cox-Methode transformierten Daten. Die Ergebnisse zeigten nur geringfü gige Differenzen zwischen den Schätzungen mit untransformierten und transformierten Daten. Die Heritabilität war im ersten Monat hoch, verringerte sich bis zum dritten Monat und stieg zum Ende der Eiproduktion wieder an. Die Heritabilitäten der kumulativen Leistungen waren hö her als die der monatlichen Leistungen. Die genetischen und phänotypischen Korrelationen zwischen benachbarten monatlichen Legeleistungen waren generell hoch. Die hö chsten genetischen Korrelationen zwischen den monatlichen und den kumulativen Legeleistungen S5, S10 bzw. S12 ergaben sich im zweiten, im siebenten bzw. im achten Monat. U.S.

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Monthly model for genetic evaluation of laying hens 1. Fixed regression

Anang

Mielenz²,

Schüler³

2001

British Poultry Science

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1. This paper addresses the possibility of using a monthly model for the genetic evaluation of laying hens, based on the definition of a test day model with fixed regression as used in dairy cattle, in which monthly records were treated as repeated measurements of the same trait. 2. Production records of 6450 hens, daughters of 180 sires and 1335 dams were analysed using an animal model with restricted maximum likelihood (REML). The traits considered were individual monthly egg production and cumulative egg production in 11 months. Four different models were fitted to various combinations of monthly and cumulative records. The covariates were derived from the regression of Ali and Schaeffer (1987). 3. Spearman rank correlations were computed to compare breeding values from different models. Two types of correlations were computed: between individual breeding values and between sire breeding values based on subsets of full-sib records. 4. The results indicated that a monthly model with nested covariates produced higher heritability and permanent environmental variance than the models with non-nested or without covariates. The estimates of heritability obtained from monthly model were lower than the estimates from the cumulative model. The monthly model resulted in higher correlations of sire breeding values between two subsets of full-sib records than those from cumulative models. 5. In conclusion, the monthly model with nested covariates appears to be better than the model with non-nested covariates or without covariate. Although the heritability estimates obtained from the monthly model were lower, the monthly model with nested covariates could be better than the cumulative model for genetic evaluation of laying hens in the 1st cycle of laying period when using either full or part records. The use of information from odd months of production could be of interest for the evaluation of full records.

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Curvilinear Trends in Direct and Some Correlated Responses to Nineteen Generations of Selection for Part Record Rate of Egg Production in a Randombred Line of Chickens

Cited by 4 publications

References 17 publications

Factors affecting direct and correlated responses in a White Leghorn population under long term selection for egg number

Factors affecting direct and correlated responses in a White Leghorn population under long term selection for egg number

Genetic and phenotypic parameters for monthly egg production in White Leghorn hens

Monthly model for genetic evaluation of laying hens 1. Fixed regression

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