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

Abstract

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.

Implementation of genetic evaluation and mating designs for the endangered local pig breed ‘Bunte Bentheimer’

“…) and poultry (König et al . ). However, Figure also illustrates marginal genetic progress when changing constraints in the ‘upper level’: when increasing the constraint at relationship from 0.23 to 0.235, average EBV increased by 1.9 points.…”

“…The decision depends on the ultimate goal: increasing genetic gain while keeping inbreeding at an acceptable level or reducing inbreeding by keeping constant genetic progress (König et al . ).…”

Inbreeding depression of sperm traits in the zebra finch Taeniopygia guttata

“…Under certain circumstances, inbreeding depression can be strong enough to drive populations to extinction (Saccheri et al 1998;Frankham 2005). Hence, knowledge of the extent to which traits are susceptible to inbreeding depression has wide implications for evolutionary (Charlesworth and Charlesworth 1987;Lynch and Walsh 1998) and conservation biology (Crnokrak and Roff 1999;Bijlsma et al 2000;Leberg and Firmin 2008;Knief et al 2015) and agricultural sciences (Sewalem et al 1999;K€ onig et al 2010;Makina et al 2014).…”

Genetic diversity in an indigenous horse breed - implications for mating strategies and the control of future inbreeding

“…For several breeding populations in various species, the use of OC‐selection was theoretically investigated and empirically proven (e.g. König et al. 2010)to be conceptually beneficial.…”