Estimation of genetic parameters for semen traits in Egyptian buffalo bulls

Abstract

This study was conducted to characterize semen traits (ejaculate volume (VOL), mass motility (MM), sperm livability (LS), percentage of abnormal sperms (AS), and sperm concentration (CONC)) of Egyptian buffalo bulls and evaluate the importance of some nongenetic factors (year (YC) and season (SC) of semen collection and age of bull genetically and environmentally at collection (ABC)) affecting the investigated traits. A total of 7761 normal semen ejaculates were collected from 26 bulls from 2009 to 2019. Single-trait and bivariate repeatability animal models using Bayesian methods were used to estimate variance components, heritability, repeatability, and genetic correlations among the investigated semen traits. YC and ABC exerted significant effects on most semen traits, whereas SC exerted no significant effect on all the investigated semen traits. Heritability estimates were 0.08, 0.52, 0.51, 0.04, and 0.49 for VOL, MM, LS, AS, and CONC, respectively. Repeatability estimates were 0.14, 0.82, 0.79, 0.06, and 0.78 for VOL, MM, LS, AS, and CONC, respectively. The genetic correlations between MM and each of LS and CONC were highly significant (0.99 ± 0.01 and 0.95 ± 0.14, respectively), and that between LS and CONC was also highly significant (0.92 ± 0.20). The high heritability estimates for MM, LS, and CONC combined with the favorable high significant genetic correlations between these traits indicated that direct selection for MM may be an effective method to enhance semen quality in Egyptian buffalo bulls and consequently improve fertility.

Principal component analysis of phenotypic and breeding value data for semen traits in Egyptian buffalo bulls

“…These results are consistent with Tables 4 and 5 , where MM, LS, and CONC are strongly associated with PC1, and VOL and AS are more closely associated with PC2. These results are consistent with those of Salem et al ( 2023 ), where the results of genetic correlation is highest between the traits abnormality and the same is true for the traits Motility, live and Concentrate. The prior correlation coefficients between the various PC characteristics represented the complex interactions between these seminal traits as well as the genetic basis of the quantitative traits, which were controlled by a number of genes, each of which contributed differently to each trait.…”

“…0.08 ± 0.07 for VOL and 0.04 ± 0.04 for AS) and low genetic correlations between traits (e.g. 0.17 ± 0.74 between VOL and MM and 0.22 ± 0.72 between VOL and LS) as shown in Salem et al ( 2023 ).…”

“…The variance components, genetic parameters and genetic and phenotypic correlations of VOL, MM, LS, AS, and CONC traits were previously presented by Salem et al ( 2023 ) based on a subset of current ILMTC herd data. High and low heritability estimates along with low and high genetic correlations between these traits suggest that direct selection of some traits increases semen quality in Egyptian buffalo bulls which may be an efficient way to improve fertility.…”

“…Moreover, the principle components might comprise traits with low heritability estimates that are rarely used in a direct selection process (Buzanskas et al, 2013 ). Therefore, after estimating the genetic parameters between the studied traits (Salem et al, 2023 ) and finding some results representing high and low genetic relationships between the traits, it was necessary to investigate PCA.…”

A Single-Step Genome-Wide Association Study for Semen Traits of Egyptian Buffalo Bulls

“…The overall mean values for VOL, MM, LS, AS, and CONC exhibited a degree of similarity to those previously reported by Salem et al (2023) [21] based on a subset of the current data from the IMTC herd. The authors reported that the measured values for VOL, MM, LS, AS, and CONC were 3.89 mL, 62.37%, 60.64%, 3.94%, and 0.67 × 10 9 spermatozoa/mL, respectively.…”