Selection for reproductive traits in white egg stock using independent culling levels

Schmidt, G. S.; Figueiredo, E. A. P. de

doi:10.1590/s1516-635x2005000400006

Cited by 11 publications

(8 citation statements)

References 5 publications

(6 reference statements)

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“…The nonselected line (CCc) was established from the CC line, in accordance with the methodology proposed by Cowe et al (1959), by randomly mating one male from each sire family with an unrelated female from each dam family. The nonselected line was used as a reference population to compare the effects of selection for egg production in the CC line (Schmidt and Figueiredo, 2005). In this study, the seventh generation of the hens was used.…”

Section: Birdsmentioning

confidence: 99%

Egg production curve fitting using nonlinear models for selected and nonselected lines of White Leghorn hens

et al. 2012

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Egg production curves describe the laying patterns of hen populations over time. The objectives of this study were to fit the weekly egg production rate of selected and nonselected lines of a White Leghorn hen population, using nonlinear and segmented polynomial models, and to study how the selection process changed the egg-laying patterns between these 2 lines. Weekly egg production rates over 54 wk of egg production (from 17 to 70 wk of age) were measured from 1,693 and 282 laying hens from one selected and one nonselected (control) genetic line, respectively. Six nonlinear and one segmented polynomial models were gathered from the literature to investigate whether they could be used to fit curves for the weekly egg production rate. The goodness of fit of the models was measured using Akaike's information criterion, mean square error, coefficient of determination, graphical analysis of the fitted curves, and the deviations of the fitted curves. The Logistic, Yang, Segmented Polynomial, and Grossman models presented the best goodness of fit. In this population, there were significant differences between the parameter estimates of the curves fitted for the selected and nonselected lines, thus indicating that the effect of selection changed the shape of the egg production curves. The selection for egg production was efficient in modifying the birds' egg production curve in this population, thus resulting in genetic gain from the 5th to the 54th week of egg laying and improved the peak egg production and the persistence of egg laying.

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Section: Birdsmentioning

confidence: 99%

Egg production curve fitting using nonlinear models for selected and nonselected lines of White Leghorn hens

et al. 2012

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“…Food consumption, which has a positive correlation with body weight, is an important cost in the production of eggs. It is difficult to apply sufficient selection pressure on key traits in egg-laying stock (3). The aim of this study is to increase egg numbers and egg weight and decrease body weight, thus reducing food consumption.…”

Section: Introductionmentioning

confidence: 99%

Developments in the performance of brown egg layer parental stocks for superior hybrid

Göğer¹,

Demi̇rtaş²,

Yurtoğullari³

2014

Turk J Vet Anim Sci

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This study examines the effect of grandparent, parent, and hybrid brown chickens, selected from 3 generations of pure lines, on hybrid egg-laying performance. The study was conducted at the Poultry Research Station of Ankara. In the first stage, 4 grandparent lines were derived from 2 pure line base populations. Grandparent lines included 2 male lines (low body weight and high egg weight) and 2 female lines (low body weight and high egg production). In the second stage, grandparent male and female lines were reciprocally crossed to produce 4 parent lines. In the third stage, male and female parental lines were crossed to produce 4 hybrid lines. The average age at first egg of grandparents, parents, and hybrids was 147.

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“…The upward trend of the inbreeding level in different layer populations in the range from 0.13 to 1.5% per generation has been carefully evaluated in several studies (Gowe et al, 1993;Nordskorg and Cheng, 1998;Savas et al, 1999;Sewalem et al, 1999;Schmidt and Figueiredo, 2005). Results on the effects of inbreeding on the birds' performance in terms of production and reproduction have been estimated by Sewalem et al (1999) by including the inbreeding coefficient of the hen, the embryo, and the mate as a partial linear regression in the statistical model.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of inbreeding in laying hens by applying optimum genetic contribution and gene flow theory

et al. 2010

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Due to consistent increases of inbreeding of on average 0.95% per generation in layer populations, selection tools should consider both genetic gain and genetic relationships in the long term. The optimum genetic contribution theory using official estimated breeding values for egg production was applied for 3 different lines of a layer breeding program to find the optimal allocations of hens and sires. Constraints in different scenarios encompassed restrictions related to additive genetic relationships, the increase of inbreeding, the number of selected sires and hens, and the number of selected offspring per mating. All these constraints enabled higher genetic gain up to 10.9% at the same level of additive genetic relationships or in lower relationships at the same gain when compared with conventional selection schemes ignoring relationships. Increases of inbreeding and genetic gain were associated with the number of selected sires. For the lowest level of the allowed average relationship at 10%, the optimal number of sires was 70 and the estimated breeding value for egg production of the selected group was 127.9. At the highest relationship constraint (16%), the optimal number of sires decreased to 15, and the average genetic value increased to 139.7. Contributions from selected sires and hens were used to develop specific mating plans to minimize inbreeding in the following generation by applying a simulated annealing algorithm. The additional reduction of average additive genetic relationships for matings was up to 44.9%. An innovative deterministic approach to estimate kinship coefficients between and within defined selection groups based on gene flow theory was applied to compare increases of inbreeding from random matings with layer populations undergoing selection. Large differences in rates of inbreeding were found, and they underline the necessity to establish selection tools controlling long-term relationships. Furthermore, it was suggested to use optimum genetic contribution theory for conservation schemes or, for example, the experimental line in our study.

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Selection for reproductive traits in white egg stock using independent culling levels

Cited by 11 publications

References 5 publications

Egg production curve fitting using nonlinear models for selected and nonselected lines of White Leghorn hens

Egg production curve fitting using nonlinear models for selected and nonselected lines of White Leghorn hens

Developments in the performance of brown egg layer parental stocks for superior hybrid

Evaluation of inbreeding in laying hens by applying optimum genetic contribution and gene flow theory

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