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.