Inbreeding depression in livestock species: review and meta‐analysis

Abstract

Inbreeding, by virtue of its consequence on traits of interest, is a topic of major interest for geneticists and animal breeders. Based on meta-analysis conducted on 57 studies and seven livestock species considering a wide variety of selected traits, it was estimated that inbreeding depression corresponds to on average a decrease of 0.137 percent of the mean of a trait per 1 percent of inbreeding. The decrease was larger for production traits (reduction of 0.351%) than for other trait categories. For populations raised as purebreds, inbreeding depression may impact the economic income of breeders. There is a need for studies assessing the existence of an inbreeding purge phenomenon as well as the impact of inbreeding on adaptation capacities of livestock species. Promises brought by the development of dense genotyping as well as functional genomics will increase the capacities to improve our understanding and management of the phenomenon.

Inbreeding depression in the Lizard canary breed estimated by pedigree analysis

“…Several studies on livestock species have shown the heterogeneity of inbreeding depression with neutral or negative or positive effects on different traits (Leroy 2014). As reported by Barczak et al (2009), in a given population "bad" and "good" inbreeding effects are mixed.…”

“…Inbreeding depression has been investigated through a large variety of models and hypotheses according to the type of available data (Leroy 2014). Inbreeding depression can be estimated as a linear doi: 10.17221/8664-CJAS regression coefficient between a phenotypic value and inbreeding coefficient computed by genealogical data.…”

“…Inbreeding depression can be estimated as a linear doi: 10.17221/8664-CJAS regression coefficient between a phenotypic value and inbreeding coefficient computed by genealogical data. Therefore, whatever trait or population is taken into account, it is possible to consider a scaled estimation by dividing the regression coefficient by the mean of the phenotypic trait (Flock et al 1991;DeRose and Roff 1999;Gomez-Raya et al 2009) or by the phenotypic standard deviation (Leroy 2014). Another measure of inbreeding depression is the coefficient of inbreeding depression δ (Lande and Schemske 1985), which is calculated as the proportional decrement in the expected fitness of inbred animals compared to the expected fitness of noninbred animals.…”

Genomic dissection of inbreeding depression: a gate to new opportunities

“…However, in livestock populations, regression of individual performance on F PED of each animal is the most frequent procedure applied (Kristensen and Sorensen, 2005;Leroy, 2014). Although widely applied, the methodology has several critical points, some related to the statistical analysis and the other related to the estimation of inbreeding, which should be taken into account when interpreting results.…”

“…In contrast, inbreeding depression is originally defined for the quantitative trait with no sampling variation in the inbreeding level for individuals with the same F PED (for example, all littermates have the equal F PED ) and with the rate of inbreeding at selected loci that is expected to be the same as at neutral loci. Thus, estimation of inbreeding depression based on F PED (Kristensen and Sorensen, 2005;Casellas et al, 2009;Leroy, 2014) was perfectly adapted for the infinitesimal model (Fisher, 1918). Unfortunately, infinitesimal model (modification with dominance) does not correspond well to the inheritance of all traits, particularly traits controlled by a finite number of loci (Curik et al, 2001(Curik et al, , 2002.…”