![]() AI aims to improve productive and reproductive traits by introducing daughters from superior breeding bulls into their herds (Mathevon et al., 1998 Kattab et al., 2022). In dairy cattle and buffalo, AI is the most effective strategy for genetic improvement. Furthermore, semen quality parameters are considered to be the most essential indications of bull fertility (Kumar et al., 2014 Singh et al., 2017), because low semen quality is a primary cause of female conception failure that has an impact on farm animals’ profitability as the use of bulls with unknown fertility in service, which reduces overall field fertility, is one of the key constraints to maximizing buffalo production (Oliveira et al., 2013). Moreover, a better understanding of these factors may enable the industry to improve artificial insemination (AI) in bull management to improve semen production (Mathevon et al., 1998). ![]() The genetic makeup of bulls and environmental factors such as season (ambient temperature), age of bulls, bull handlers, and the frequency of semen collection all influence semen traits (Stälhammar et al., 1989 Fuerst-Waltl et al., 2006). Nevertheless, male fertility in cattle can be assessed either directly on the semen or indirectly via the females. In several countries, dairy cows’ fertility has been extensively examined in various cattle breeds for breeding purposes, whereas bull fertility has received limited attention (Weigel et al., 2006 Yin et al., 2019). In dairy cattle, fertility is considered one of the most essential economic characteristics (Druet et al., 2009). 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. 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). Repeatability estimates were 0.14, 0.82, 0.79, 0.06, and 0.78 for VOL, MM, LS, AS, and CONC, respectively. Heritability estimates were 0.08, 0.52, 0.51, 0.04, and 0.49 for VOL, MM, LS, AS, and CONC, respectively. YC and ABC exerted significant effects on most semen traits, whereas SC exerted no significant effect on all the investigated semen traits. 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. A total of 7761 normal semen ejaculates were collected from 26 bulls from 2009 to 2019. 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. ![]()
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