Use this URL to cite or link to this record in EThOS:
Title: Quantitative genetic studies on growth and reproductive traits in broiler chickens
Author: Koerhuis, Alphonsus Nicolaas Maria
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1996
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Please try the link below.
Access from Institution:
This thesis considers three major quantitative genetic topics characteristic of growth and reproductive traits in broiler breeding, i.e. (1) the estimation of maternal effects in juvenile body weight (JBWT), (2) selection for food conversion into growth defined as a ratio (FCR), and (3) non-normality and curvilinearity of heritability of egg production distributions and the genetic relationships of those reproductive traits with juvenile growth. Restricted maximum likelihood (REML) methods based on the individual animal model were utilised in the estimation of variance components to make optimum use of the data and take account of selection. Estimates of the maternal additive genetic variation were small relative to the direct additive genetic variation of JBWT for two broiler populations investigated. The negative estimates of the direct-maternal genetic correlation (rAM) were unexpected and prompted the investigation of more appropriate and detailed statistical models taking account of direct-maternal environmental covariation, estimated either as the covariance between the environmental maternal and the environmental residual effects or as a maternal phenotypic effect through regression on the mother's phenotype. Whilst the goodness-of-fit of these alternative models was superior, the estimates of rAM were not much affected. The choice of the fixed effect structure was shown to be paramount in the estimation of maternal effects. Thus far, maternal effects were lumped together into a single component. Next, the results were described of an experiment conducted to identify individual pathways related to the egg causing maternal variation in JBWT and to establish their effect on offspring-parental regressions. Antagonistic maternal pathways of egg weight at the start and at the 18th day of incubation were observed. Their effects largely offset each other and hence biased the offspring-dam regression only slightly. A high loss in egg weight during incubation, indicative of poor egg shell quality, was identified as the likely cause for the negative estimates of rAM.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available