Pedigree analysis and inbreeding effects over morphological traits in Campolina horse population

Abstract

Genetic improvement, without control of inbreeding, can go to loss of genetic variability, reducing the potential for genetic gains in the domestic populations. The aim of this study was to analyze the population structure and the inbreeding depression in Campolina horses. Phenotype information from 43 465 individuals was analyzed, data provided by the Campolina Breeders Association. A pedigree file containing 107 951 horses was used to connected the phenotyped individuals. The inbreeding coefficient was performed by use of the diagonal of the relationship matrix and the genealogical parameters were computed using proper softwares. The effective population size was estimated based on the rate of inbreeding and census information, and the stratification of the population was verified by the average relationship coefficient between animals born in different regions of Brazil. The effects of inbreeding on morphological traits were made by the use of inbreeding coefficient as a covariate in the model of random regression. The inbreeding coefficient increased from 1990 on, impacting effective population size and, consequently, shrinking genetic variability. The paternal inbreeding was greater than maternal, which may be attributed to the preference for inbred animals in reproduction. The average genetic relationship coefficient of animals born in different states was lower than individuals born within the same state. The increase in the inbreeding coefficient was negatively associated with all studied traits, showing the importance to avoid genetic losses in the long term. Although results do not indicate a severe narrowing of the population until the present date, the average relationship coefficient shows signs of increase, which could cause a drastic reduction in genetic variability if inbred mating is not successfully controlled in the Campolina horse population.

Genetic parameters estimation in an Italian horse native breed to support the conversion from agricultural uses to riding purposes

“…In this study, we reported the presence of significant inbreeding effect in height at withers only, whilst all remaining traits were not affected by inbreeding. This finding agrees with previous studies where inbreeding mainly impacted morphological features rather than complex traits (Bussiman et al, 2018;Curik et al, 2003;Gómez, Valera, Molina, Gutiérrez, & Goyache, 2009;Klemetsdal, 1998;Vicente et al, 2014).…”

Genetic Structure Analysis of the Pura Raza Español Horse Population through Partial Inbreeding Coefficient Estimation

“…The f e /f a ratio found in this study was 1.74, which indicates a decrease in genetic variability caused by an unequal founder contribution, i.e., some breeding animals become popular and produce more progeny than others. This has also been seen in other horse breeds, such as the Campolina horse population [35] with an f e /f a ratio of 1.51, the Spanish Arab Horse [25] with a ratio of 2.03% or in the Old Kladruber horse with a ratio of 5.40 [26].…”

Genetic analysis of morphological and functional traits in Campolina horses using Bayesian multi-trait model

“…Approximately 45% of all pedigreed animals presented some level of inbreeding. The mean inbreeding coefficient was 5.64% for the inbreds and 2.45% when considering the complete population (a more detailed description of this population can be found in Bussiman et al, 2018).…”