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SEMEN CHARACTERISTICS AS INFLUENCED BY SEASONAL AND CLIMATIC VARIATIONS IN NILI-RAVI BUFFALO BREEDING BULLS.

Byline: S. Hameed, S. Masood, H. Zaneb, M. S. Khan, M. Younis, Habib-ur-Rehman, M. Avais and M. U. R. Khan

Abstract

The present study was conducted to determine the effect of seasonal and climatic variations on semen characteristics of Nili-Ravi buffalo breeding bulls in Sahiwal and Bahawalpur districts of Punjab, Pakistan. For this purpose, 14 adult Nili-Ravi buffalo breeding bulls (n=7 from each of Semen Production Unit (SPU) Qadirabad, Sahiwal and SPU Karaniwala, Bahawalpur), were used. Semen samples were collected fortnightly using artificial vagina. On each collection day, 2 ejaculates were collected from each bull. Results demonstrated significantly higher (P0.05). Semen color score was non-significantly different (P>0.05) between the districts with higher score in Sahiwal and it was higher in autumn and spring seasons but with non-significant (P>0.05) seasonal influence.

Semen pH was significantly lower (P<0.05) in Sahiwal than Bahawalpur and significantly lower (P0.05) between the districts with higher score in Sahiwal and it was higher in autumn season but with non-significant influence of seasons. Significantly higher (P<0.05) individual sperm motility in Sahiwal was recorded as compared to Bahawalpur and it was higher in spring and autumn in Sahiwal. Sperm concentration was significantly increased (P<0.05) in Sahiwal than Bahawal pur. Similarly season influence was also significant with significantly higher (P0.05) difference in ejaculatory volume was recorded in all the seasons with maximum volume in spring season followed by dry summer, humid summer, autumn and winter seasons. Similarly, in buffalo bulls of Bahawalpur district the seasonal influence on the ejaculatory volume was also non-significant (P>0.05) and maximum ejaculatory volume was recorded in humid summer followed by autumn, spring, winter and dry summer. On district wise comparison, ejaculatory volume was significantly higher (P0.05) in semen color score was recorded with maximum score in autumn followed in order by spring, dry summer, humid summer and winter. Similarly in Bahawalpur district the non-significant effect of season on semen color score was observed in same pattern as in Sahiwal district. Semen color score was also non-significantly different (P>0.05), when compared between two districts. However it was higher in Sahiwal.

Semen pH: Semen pH of Nili-Ravi buffalo bulls of Sahiwal and Bahawalpur districts was 6.47+-0.03 and 6.67+-0.03, respectively. In Sahiwal district, significantly lower (P<0.05) semen pH was observed in autumn and dry summer than winter, spring and humid summer. In Bahawalpur district, significantly lower (P<0.05) pH was observed in autumn than all other seasons. When semen pH was compared district wise, it was found significantly lower (P0.05) in autumn followed by spring, dry summer, humid summer and winter. In the buffalo bulls of Bahawalpur district highest mass motility score was also observed in autumn followed by dry summer, spring, humid summer and winter and the difference was also non-significant (P>0.05) among all the seasons as in Sahiwal district. When compared between districts, also a non-significant difference (P>0.05) in mass motility score of buffalo bulls was observed with higher score in Sahiwal as compared to Bahawalpur district.

Individual Sperm Motility: Individual sperm motility in buffalo bulls was 66.02+-2.02% and 49.72+-2.02% in Sahiwal and Bahawalpur districts, respectively. Seasonal influence on individual sperm motility was observed non-significant (P>0.05) in Sahiwal district. Lowest individual sperm motility was recorded during winter season and highest was observed during spring season. Buffalo bulls of Bahawalpur district also exhibited non-significant difference (P>0.05) in individual sperm motility in different seasons with maximum individual sperm motility in dry summer followed in order by autumn, spring, humid summer and winter seasons. On district wise comparison, overall individual sperm motility was significantly higher (P<0.05) in buffalo bulls of Sahiwal district than Bahawalpur district.

Sperm Concentration: The sperm concentration of Nili-Ravi buffalo breeding bulls was 1023.27+-24.36 million/mL and 854.27+-24.36 million/mL in Sahiwal and Bahawalpur districts, respectively. The buffalo bulls of Sahiwal district showed significantly increased (P<0.05) sperm concentration in autumn and spring compared to other seasons. The sperm concentration was the lowest in winter. Buffalo bulls in Bahawalpur district also demonstrated significant influence (P<0.05) of seasons on sperm concentration with significantly higher (P<0.05) sperm concentration in autumn followed in order by spring, dry summer, humid summer and winter. District wise comparison demonstrated significantly higher (P<0.05) sperm concentration in semen of buffalo bulls of Sahiwal district compared to Bahawalpur district.

Table 1. Semen characteristics of Nili-Ravi buffalo bulls in Sahiwal and Bahawalpur districtsa .

###Districts###Overall P

Semen Parameters

###Sahiwal###Bahawalpur###value

Ejaculatory volume (mL)###4.63+-0.10a###2.60+-0.10b###<0.0001

Semen color (score 0-2)###1.06+-0.07a###0.89+-0.07a###0.0856

Semen pH###6.47+-0.03a###6.66+-0.03b###<0.0001

Mass motility (score 0-5)###2.06+-0.08a###1.86+-0.08a###0.07

Individual sperm motility (%)###66.02+-2.02a###49.72b+-2.02b###<0.0001

Sperm concentration (million/mL)###1023.27a+-24.36a###854.27b+-24.36b###<0.0001

Table 2. Semen characteristics of Nili-Ravi buffalo bulls in Sahiwal district during different seasonsa .

###Seasons

Semen###Overall

###Humid

Parameters###Autumn###Winter###Spring###Dry Summer###P value

###Summer

Ejaculatory

###4.55+-0.22a###4.29+-0.22a###4.87+-0.22a###4.84+-0.22a###4.6+-0.22a###0.5211

volume (mL)

Semen color

###1.36+-0.15a###0.75+-0.15a###1.11+-0.15a###1.09+-0.15a###0.96+-0.15a###0.1921

(score 0-2)

Semen pH###6.22+-0.07a###6.71+-0.07b###6.44+-0.07c###6.37+-0.07acd###6.63+-0.07bce###<0.0001

Mass motility

###2.38+-0.17a###1.72+-0.17a###2.13+-0.17a###2.07+-0.17a###1.99+-0.17a###0.2503

(score 0-5)

Individual

Sperm###67.41+-4.51a###61.17+-4.51a###70.21+-4.51a###66.16+-4.51a###65.12+-4.51a###0.692

motility (%)

Sperm

Concentration###1267.16+-54.48a###857.93+-54.48b###1080.67+-54.48ac###1017.54+-54.48cd###893.06+-54.48bde###<0.0001

(million/mL)

Table 3. Semen characteristics of Nili-Ravi buffalo bulls in Bahawalpur district during different seasonsa .

Semen###Seasons###Overall

Parameters###Autumn###Winter###Spring###Dry Summer###Humid Summer###P value

Ejaculatory

###2.67+-0.22a###2.52+-0.22a###2.6+-0.22a###2.34+-0.22a###2.85+-0.22a###0.5211

volume (mL)

Semen color

###1.07+-0.15a###0.74+-0.15a###0.96+-0.15a###0.91+-0.15a###0.75+-0.15a###0.1921

(score 0-2)

Semen pH###6.44+-0.07a###6.79+-0.07b###6.67+-0.07bc###6.68+-0.07bcd###6.73+-0.07bcde###<0.0001

Mass motility

###2.09+-0.17a###1.73+-0.17a###1.84+-0.17a###1.88+-0.17a###1.76+-0.17a###0.2503

(score 0-5)

Individual

Sperm###53.13+-4.51 a###45.00+-4.51a###49.93+-4.51a###54.47+-4.51a###46.07+-4.51a###0.692

motility (%)

Sperm

Concentration###920.38+-54.48a###761.62+-54.48b###884.50+-54.48abc###881.61+-54.48abcd###823.23+-54.48abcde###<0.0001

(million/mL)

DISCUSSION

In present study, ejaculatory volume was 4.63+-0.10mL and 2.60+-0.10mL in buffalo bulls of Sahiwal and Bahawalpur districts, respectively. Similar results were reported by Kiani et al. (2014) and Younis et al. (1998) in adult Nili-Ravi buffalo bulls. On the other hand, Rehman et al. (2012) recorded decreased ejaculatory volume (1.70+-0.09mL) in Kundi buffalo breed. The difference in ejaculatory volume might be due to the effect of breed. In the present study, season did not influence the ejaculatory volume significantly in both districts which is congruent with the findings of Nazir (1988). Contrary to this, Javed et al. (2000) recorded increased semen volume in autumn and vise-versa in humid summer. Likewise, Younis et al. (1998) recorded increased ejaculatory volume in low breeding season than peak breeding season. Increased ambient temperature in Bahawalpur district resulted in decreased ejaculatory volume of buffalo bulls than Sahiwal district.

In present study, semen color was also considered a parameter of semen quality. Our results demonstrated that semen color was creamy (score 1.06+-0.07) and milky (score 0.89+-0.07) in Sahiwal and Bahawalpur districts, respectively. The semen color is indicative of semen thickness together with pigment color and also an important indicator of sperm concentration. These findings are congruent with the results of previous studies (Nazir, 1988; Javed et al., 2000) in Nili-Ravi buffalo bulls. Likewise, Kiani et al. (2014) recorded milky white to creamy white semen color in buffalo bulls aged between 6 to 8 years. Similar results were observed in Swamp buffalo (Koonjaenak et al., 2007). Although our results indicated that season had non-significant impact on semen color score in buffalo bulls of Sahiwal district, but exhibited better semen color score in autumn than other seasons. Similarly season did not show significant impact on semen color of buffalo bulls in Bahawalpur district.

Nili-Ravi buffalo bulls demonstrated better semen color score in autumn compared to other seasons (Javed et al., 2000). Koonjaenak et al. (2007) documented non-significant effect of season on semen color score similar to results of this study in both the districts. Better semen color score observed in buffalo bulls in Sahiwal district than Bahawalpur district is indicative of favorable ambient conditions for enhanced spermatogenesis in Sahiwal district. In present study, semen pH of buffalo bulls of Sahiwal and Bahawalpur districts was 6.47+-0.03 and 6.67+-0.03, respectively. Likewise, Javed et al., (2000) documented semen pH 6.45+-0.04 in Nili-Ravi buffalo bulls while semen pH was observed as 5.81+-0.06 in Kundhi buffalo bulls and 6.16+-0.07 in Nili-Ravi buffalo bulls by Rehman et al. (2012) and Younis et al. (1998) respectively. Semen pH of Kundi buffalo breeding bulls aged 6 to 8 years was 6.71+-0.035 (Kiani et al., 2014).

In present study, season had significant impact on semen pH in buffalo bulls in both districts. Semen pH was decreased in autumn compared to the other seasons in both the districts while increased semen pH was determined in winter season. These findings are in close agreement with the findings of Javed et al. (2000) and Younis et al. (1998) who reported low semen pH in autumn and an increase in semen pH in winter season. According to Bhakat et al. (2015) different seasons like hot dry-summer, hot humid-rainy and cold humid-winter also significantly influenced the semen pH in buffalo breeding bulls. Contrary to this, seasons did not influence semen pH in Swamp buffalo breeding bulls (Koonjaenak et al., 2007). Increased semen pH in Bahawalpur district than Sahiwal district in our study may be attributed to inferior semen quality in Bahawalpur, because semen pH is negatively correlated (r= -0.39) with sperm concentration (Younis, 1996).

Moreover, dense and thick semen samples have low pH than thin samples (Shalash, 1972). In present study, mass motility score was 2.06+-0.03 and 1.86+-0.03 in buffalo bulls in Sahiwal and Bahawalpur district, respectively. Mass motility (score 2.18 +-0.11) documented in adult Nili-Ravi buffalo breeding bulls previously at Sahiwal district (Younis et al., 1998) is comparable with the result of present study in Sahiwal district. An increased mass motility was noted in adult Nili-Ravi buffalo breeding bulls (Javed et al., 2000).

Similarly, increased mass motility is reported in Kundhi and Murrah buffalo breeding bulls (Kiani et al., 2014; Bhakat et al., 2015). In present study, although non-significant impact of seasons on mass motility was observed, but it was increased in autumn and decreased in winter season in buffalo bulls in Sahiwal district. Similar pattern of mass motility was observed in Bahawalpur district with non-significant differences among the seasons. These findings in both the district are supported by previous findings in adult Nili-Ravi buffalo bulls, Swamp buffalo bulls and Murrah buffalo bulls (Javed et al., 2000; Koonjaenak et al., 2007; Bhakat et al., 2015). However, results of seasonal influence on mass motility of buffalo bulls in present study are contrary with the findings of Younis et al. (1998). Mass motility was observed better in Sahiwal district compared to Bahawalpur district showing the better semen produced in Sahiwal district in present study.

Individual sperm motility in buffalo bulls was 66.02+-2.02% and 49.72+-2.02% in Sahiwal and Bahawalpur districts, respectively. Rehman et al. (2012) and Younis et al. (1998) documented individual sperm motility in buffalo bulls congruent with the findings of present study in Sahiwal district. Contrarily, Javed et al. (2000) recorded individual sperm motility (59.50+-1.09 %) in adult Nili-Ravi buffalo bulls. Increased individual sperm motility was reported by Kiani et al. (2014) in Kundhi buffalo breeding bulls and in Swamp buffalo bulls by Koonjaenak et al. (2007). In present study although non-significantly, but decreased individual sperm motility was observed in winter compared to autumn, spring, dry summer and humid summer in Sahiwal district. Similarly seasonal variations did not influence individual sperm motility in Bahawalpur district. Javed et al. (2000) recorded low individual sperm motility in winter.

Decreased individual sperm motility in winter was also found by Singh et al. (1992) in Murrah buffalo bulls. Younis et al. (1998) and Heuer et al. (1987) observed increased individual sperm motility in peek breeding season (autumn) in Nili-Ravi buffalo breeding bulls. According to Koonjaenak et al. (2007) seasonal variations do not influence individual sperm motility. Individual sperm motility was observed higher in Sahiwal district compared to Bahawalpur district demonstrating the better quality semen produced in Sahiwal district than Bahawalpur district in the present study. This may be attributed to the more favorable climatic conditions of Sahiwal district than Bahawalpur district for better quality semen production. In the present investigation, sperm concentration of 1023.27+-24.36 million/mL and 854.27+-24.36 million/mL was observed in Sahiwal and Bahawalpur district respectively.

Javed et al. (2000) published the sperm concentration of 1050+-40 million/mL in adult Nili-Ravi buffalo breeding bulls in Sahiwal district which is in close agreement with the finding of present study in Sahiwal district. Similar results (1016.68+-21.25 million/mL) were observed by Bhakat et al. (2015) in Murrah buffalo bulls. However Younis et al. (1998) observed the higher value of sperm concentration (1160+-60 million/mL) and similar results were found by Koonjaenak et al. (2007). Seasonal effect on the sperm concentration was found significant in both the district. Significantly low sperm concentration was observed in winter. Sperm concentration was highest in autumn in both the districts and is supported by the findings of Javed et al. (2000) and Younis et al. (1998) in Nili-Ravi buffalo bulls.

Higher sperm concentration during the milder seasons is also documented by Zafar et al. (1988) and Dumitrescu et al. (1988) supporting our findings. Bhosrekar et al. (1992) and Koonjaenak et al. (2007) reported the non-significant effect of season on sperm concentration in Swamp buffalo is contrary to the findings of present study in both districts. However, Bhakat et al. (2015) documented the significant effect of season on sperm concentration supporting the results of present study. In the present study overall higher sperm concentration in Sahiwal district compared to the Bahawalpur district might be due to enhanced spermatogenesis in Sahiwal district due to favorable climatic conditions which also lead to increase the diameter and thickness of seminiferous tubules (Ibrahim et al., 2013).In conclusion, semen quality of Nili-Ravi buffalo breeding bulls is superior in autumn and spring and bulls in Sahiwal district produce superior quality semen compared to Bahawalpur district.

Acknowledgements: Authors gratefully acknowledge the cooperation of Directorate of Breed Improvement, Livestock and Dairy Development Department, Punjab, Pakistan at semen production units during the course of the study.

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