Semen evaluation
The coefficient of variability from the ejaculate volume, sperm concentration and individual motility from the semen collections during 2012-2014 are presenting in Table 1. The semen quality of Madura bulls was not quite different than reported earlier in,
Bos indicus (Brito et al., 2002; Ahmad et al., 2011), Bos taurus (Mathevon et al., 1998a; Mathevon et al., 1998b; Fuerst-Waltl et al., 2006; Boujenane and Boussaq, 2013) and crossbred
(Shaha et al., 2008).
The effect of environmental factor
Age of bull
The age of bulls affected all semen variables (P <0.05). Semen volumes were increased with age. On the contrary, sperm concentrations tend to decrease after the age of 54 months while sperm individual motility decreased after age 42 month and remains stable at the age of 54 - 92 months (Table 1). These results on Madura bulls are in accordance with those reported earlier on
Bos taurus (Mathevon et al., 1998a; Fuerst-Waltl et al., 2006; Boujenane and Boussaq, 2013) and
Bos indicus (Brito et al., 2002; Ahmad et al., 2011). However, some reports suggested that the concentration of spermatozoa was not significantly influenced by age
(Mathevon et al., 1998a; Brito et al., 2002; Snoj et al., 2013). The present report on sperm individual motility were also in agreement to those reported previously
(Brito et al., 2002; Boujenane and Boussaq, 2013) but few studies reported that sperm individual motility was not affected by age
(Fuerst-Waltl et al., 2006; Ahmad et al., 2011).
The quality and quantity of bull semen were determined by its testicular size
(Brito et al., 2002; Siddiqui et al., 2008), furthermore, the semen quality was determined by the number of Sertoli cells per testis
(Moura et al., 2011; Rajak et al., 2014). The testicular growth pattern was both linear and quadratic against age and reaching a peak at the age of 40-50 months
(Torres-Junior and Henry, 2005), therefore the quality and quantity of semen would be changed following the bull age. Moreover, a decrease in semen quality would be occur at different ages in different breeds
(Snoj et al., 2013).
Season
The sperm concentration in this study was affected by Season (P<0.001). The sperm concentrations were generally higher during the wet season (October-March), while the maximum sperm concentrations were obtained at the peak to the end of the rainy season (January-March; Table 1). Meanwhile, the pattern effect of season was not clear against the quality of the semen and might result from environmental temperature, photoperiod, air humidity, feed availability and housing
(Mathevon et al., 1998b). Further research also reported that season has no significant effect on the semen quality of both
Bos taurus and
Bos indicus in the tropics
(Brito et al., 2002). However, the present result was closer to the results reported for both
Bos indicus and
Bos taurus in South Asia climatic conditions
(Fiaz et al., 2008; Bhakat et al., 2011; Tiwari et al., 2012; Bhakat et al., 2014).
Semen collection interval
This study suggested that collection interval affected to both the semen volume (P <0.001) and the sperm concentrations (P<0.05). More semen volumes and sperm concentrations were obtained from 4 days interval compared to 3 days interval (Table 1). Some studies reported that better semen volume and sperm concentration would be achieved from the long interval of the semen collections
(Mathevon et al., 1998a; Fuerst-Waltl et al., 2006; Boujenane and Boussaq, 2013). The collection interval had no effect on the individual motility of spermatozoa as shown in this study
(Fuerst-Waltl et al., 2006).
The reasons of this finding were from the daily production of spermatozoa that accumulate in the epididymis. The daily spermatozoa productions in bull were estimated 2 × 10
9, undergo the maturation when entering the cauda epididymis and accommodated in the epididymis as a reservoir if not to be ejaculated
(Franson et al., 2009). The spermatozoa populations in the epididymis reached 55% of the total spermatozoa produced. Moreover, un-ejaculated spermatozoa could be survived for several weeks in the epididymis
(Jones, 1999; Jones, 2004). These conditions can explain the differences in sperm concentration and semen volume associated with semen collection intervals.
Frequency of ejaculation:
The result obtained in this study indicated that all variable tested were affected by the frequency of ejaculations per day (P<0.001). The first ejaculation resulted in better semen volume and sperm concentration compared to second ejaculation (Table 1). These results are in agreement with the results previously reported by
Fuerst-Waltl et al., (2006), Boujenane and Boussaq, (2013) but the best motility obtained on second ejaculation contrary.
The semen volume was derived from the seminal vesicle, epididymis and other sources. However, the epididymis only contributes a half in the second ejaculation
(Seidel and Foote, 1970). Since the ejaculated spermatozoa only derived from the epididymis as a reservoir, by the successive ejaculation the number of the sperm will be reduced; resulted in the decreasing semen volume and sperm concentration respectively
(Jones, 1999).
Repeatability
The repeatability estimates semen volume, sperm concentration and individual motility were 0.376, 0.445 and 0.576 respectively (Table 2). These results were not much different from those reported for
Bos taurus in the temperate zone
(Taylor and Everett, 1985; Mathevon et al., 1998a; Mathevon et al., 1998b; Boujenane and Boussaq, 2013).
Adaptability of the bulls to their environment was the important individual trait on semen production
(Haque et al., 2001). These results indicated that the Madura bull has a good adaptation and reproductive potential in a local environment.
This study showed that the diversity of semen production occurred in Madura bulls due to the influence of genetic factors and environmental factors. The Madura bulls had a moderate high repeatability of the semen volume, sperm concentration and individual motility which were not too different in general with the other cattle breeds reported. This result indicated that Madura bulls as the indigenous breed had a good reproductive potency for the semen productions under the local environment.
