Genomics and Fertility in Stallions

Polymorphisms of four candidate genes and their correlations with growth traits in blue fox (Alopex lagopus)

To improve the accuracy and genetic progress of blue fox breeding, the relationships between genetic polymorphisms and growth and reproductive traits of the blue fox were investigated. MC4R, MC3R, INHA and INHBA were selected as candidate genes for molecular evolution and statistical analyses. Single-factor variance analyses showed that the MC4R (g.267C > T, g.423C > T, and g.731C > A) and MC3R (g.677C > T) genotypes had significant impacts on body weight, chest circumference, abdominal perimeter and body mass index (BMI) (P < 0.05) in blue fox. The MC4R and MC3R combined genotypes had significant effects on the body weight and abdominal circumference. The different genotypes of INHA g.75G > A had significant effects on female fecundity, whereas the different genotypes of INHBA g.404G > T and g.467G > T and the INHA and INHBA combined genotypes had significant effects on male fecundity. The proteins encoded by the open reading frames (ORFs) of different polymorphic loci were predicted and analysed. The aims of this study were to identify genetic markers related to growth and reproduction in the blue fox and to provide an efficient, economical and accurate theoretical approach for auxiliary fox breeding.

Modelling for the inheritance of multiple births and fertility in endangered equids: Determining risk factors and genetic parameters in donkeys (Equus asinus)

Multiple births or twinning in equids are dangerous, undesirable situations that compromise the life of the dam and resulting offspring. However, embryo vitrification and freezing techniques take advantage of individuals whose multiple ovulations allow flushing more fertilised embryos from the oviduct to be collected, increasing the productivity and profitability of reproductive techniques. Embryo preservation is especially important in highly endangered populations such as certain donkey (Equus asinus) breeds; for which conventional reproductive techniques have previously been deemed inefficient. For instance, becoming an effective alternative to artificial insemination with frozen semen to preserve the individuals' genetic material. The objective of this study was to examine the historical foaling records of Andalusian donkeys to estimate prevalence, risk factors, phenotypic and genetic parameters for multiple births, assessing the cumulative foal number born per animal, maximum foal number per birth and multiple birth number per animal. We designed a Bayesian General Animal Mixed Model with single records considering the 'fixed' effects of birth year, birth season, birth month, sex, farm, location, and husbandry system. Age was considered and included as a linear and quadratic covariate. Gibbs sampling reported heritability estimates ranging from 0.18 ± 0.101 to 0.24 ± 0.078. Genetic and phenotypic correlations ranged from 0.496 ± 0.298 to 0.846 ± 0.152 and 0.206 ± 0.063 to 0.607 ± 0.054, respectively. Predicted breeding values obtained enable the potential selection against/for these traits, offering a new perspective for donkey breeding and conservation.

Genome-wide association study for jumping performances in French sport horses

A genome-wide association study was performed to identify single nucleotide polymorphisms (SNPs) associated with jumping performances of warmbloods in France. The 999 horses included in the study for jumping performances were sport horses [mostly Selle Français (68%), Anglo-Arabians (13%) and horses from the other European studbooks]. Horses were genotyped using the Illumina EquineSNP50 BeadChip. Of the 54,602 SNPs available on this chip, 44,424 were retained after quality testing. Phenotypes were obtained by deregressing official breeding values for jumping competitions to use all available information, that is, the performances of each horse as well as those of its relatives. Two models were used to test the effects of the genotypes on deregressed phenotypes: a single-marker mixed model and a haplotype-based mixed model (significant: P < 1E-05; suggestive: P < 1E-04). Both models included a polygenic effect to take into account familial structures. For jumping performances, one suggestive quantitative trait locus (QTL) located on chromosome 1 (BIEC2_31196 and BIEC2_31198) was detected with both models. This QTL explains 0.7% of the phenotypic variance. RYR2, a gene encoding a major calcium channel in cardiac muscle in humans and mice, is located 0.55 Mb from this potential QTL.