Neat semen characters
Volume of semen ejaculate in Bengal bucks was significantly (P < 0.01) lower at 6 months (0.32 ± 0.02 ml), which increased gradually and significantly higher ejaculate volume was recorded during 11 to 12 months (0.67 ± 0.04 ml). Volume of semen ejaculates in the present study were similar to the reports of Furstoss et al. (2009); Sultana et al. (2013) and Kumbhar et al. (2019) in goats, but slightly lower than the observation by Chaudhari et al. (2018) in Surti bucks (0.7 ml) at 12 months of age.
The lowest spermatozoa concentration in the semen ejaculates was observed at 6 months of age (844.57 ± 23.12 x106/ml), but the concentration showed an increasing trend from 7 months onward and there was a significant difference (P < 0.01) among 8, 9, and 10 months of age, sperm cell concentration reached to 3176.14 ± 66.4 x106/ml at 12 months of age. Sperm cell concentration recorded in the present study was in close agreement with Chaudhari et al. (2018), who found 991 ± 20.48 x 106/ml sperm concentration in Surti bucks at 7 months of age. However, the values were higher than those reported by Thakur et al., (2005) in Chegu Pashmina bucks (1759 ± 79.79 x106/ml), Gogoi et al., (2008) in Beetal X Assam local (2751 ± 102.40 x106/ml). On the other hand, the value was lesser than the reports of Akpa et al. (2013) in Red Sokoto bucks (459.8 ± 72.27 x107). The concentration of sperm was linked positively with age, Kabiraj et al. (2011) opined that older bucks have more spermatogenic activity due to larger testicular size.
Mass motility of neat semen ranged from 2.64 ± 0.13 at 6 months of age to 3.71 ± 0.18 at 12 months. There was a gradual increase in the mass motility from 9 months onwards and a significant (P < 0.01) difference in mass motility has been observed between the ejaculates harvested during 6 to 7 months and 10 to 12 months. The results of the study are in agreement with Kumbhar et al. (2019) who observed mass motility of 3.78 ± 0.10, the highest value at 9.5 months of age. However, the value of the present study was lower (4.0 ± 0.16) than the observations of Kerketta et al., (2014) in goats found in the Rohilkhand region.
The individual motility (%) in fresh semen samples was lowest at 6 months of age (56.79 ± 1.24) which increased significantly over the period and reached to 80.71 ± 1.30% at 12 months of age. The present values recorded were in agreement with Akpa et al. (2013) who reported 80.0 ± 2.42% initial motility in 11 to 13 months old Red Sokoto bucks, while Gimenez, (2007) reported individual motility of buck semen ranged between 70 and 90%.
The percentage of non-eosinophilic live sperm cells in the ejaculates of Bengal bucks varied between 61.36 ± 1.11% and 83.14 ± 1.12% at 6, and 12 months of age, respectively. There was a significant (P < 0.01) increase in viable sperm count from 9 months to 11 months of age. A higher percentage of live sperm than the present study was reported in indigenous bucks at 12 months of age by Kumbhar et al, (2019), while the lowest values were reported in crossbred bucks (Kale et al., 1998); Surti bucks (Jadav et al., 2008) and Boer bucks (Suyadi et al., 2012). Factors like age, feeding, and breed had an impact on the viability of sperm (Leon et al., 1991).
The percentage of HOST positive spermatozoa in the ejaculates were in the range of 59.21 ± 1.73 to 80.71 ± 1.52 during 6 to 12 months of age in Bengal bucks. The population of HOST-positive sperm cells increased significantly (P < 0.01) in the ejaculates collected during 10 to 12 months of age than those of 6 to 8 months. The values of HOST-positive sperm count in the study were in accordance with that of Chaudhari et al. (2018) in Surti bucks at 7 to 12 months of age. However, lower values were reported by Kale and Tomar et al., (2000) in crossbred bucks; Narwade et al., (2018) in Saanen X Beetal bucks, and Deori et al., (2016) in Assam Hill goats.
Intact acrosome percentage was 57.57 ± 1.21 at 6 months of age, which increased significantly (p < 0.01) to 87.57 ± 1.34 at 12 months of age. Dorado et al., (2009), Ahmad et al., (2014), and Deori et al., (2016) reported a higher percentage of intact acrosome than the present study. The abnormal sperm count (%) showed a reverse trend with a significantly (P < 0.01) lower value of 9.22 ± 0.4 from 9 months of age onwards. The values of the study were close to Mahal et al. (2013) who recorded a normal sperm percentage of 87.20 ± 0.66 in 7 to 9 months and 89.20 ± 0.44 in the bucks aged 9 to 12 months. The percentage of abnormal sperm is negatively correlated with age in the present study similar to that of Zamiri and Heidari (2006).
Post freeze-thaw in vitro sperm characters
The post-thaw sperm motility was lowest (18.57 ± 0.82) at 6 months of age, which increased significantly (P < 0.01; 35.71 ± 1.3) at 12 months of age (Table 4). The percentage of post-thaw non-eosinophilic spermatozoa was found to be significantly (P < 0.01) lower at 6 months of age (23.29 ± 0.99). Although it increased significantly to 30.5 ± 0.72% at 8 months of age, no significant improvement was recorded thereafter. Similarly, the post-thaw HOST positive sperm cells (%) was significantly lower (21.57 ± 0.98) at 6 months of age but increased significantly (P < 0.01) to 28.56 ± 0.92 at 8 months of age and 37.43 ± 0.97 at 12 months of age (Table 4). The post-thaw acrosome intact sperm (%) was also significantly (P < 0.01) lower (45.57 ± 1.23) at 6 months of age which increased significantly from 9 to 11 months of age. Age of the bucks had a highly significant positive correlation with ejaculate characters as well as post thaw in vitro sperm characters, except with abnormal sperm count to which it had a highly significant negative correlation (Table 5).
Table 5
Correlation coefficient of semen parameters and age group of 6–12 months
Parameters | Age | Volume | Sperm conc. | Mass motility | Individual motility | Live count | HOST | Acrosome Integrity | Abnormal count | Post thaw Motility | Post Thaw-Live count | Post Thaw- HOST | Post Thaw- Acrosome Integrity |
Age | 1 | | | | | | | | | | | | |
Volume | .81** | 1 | | | | | | | | | | | |
Sperm conc. | .96** | .75** | 1 | | | | | | | | | | |
Mass motility | .62** | .56** | .60** | 1 | | | | | | | | | |
Individual motility | .93** | .73** | .89** | .56** | 1 | | | | | | | | |
Live count | .90** | .68** | .86** | .52** | .89** | 1 | | | | | | | |
HOST | .83** | .60** | .79** | .45** | .82** | .93** | 1 | | | | | | |
Acrosomal Integrity | .90** | .73** | .86** | .58** | .83** | .77** | .73** | 1 | | | | | |
Abnormal count | − .82** | − .65** | − .77** | − .52** | − .76** | − .74** | − .64** | − .82** | 1 | | | | |
Post thaw Motility | .87** | .69** | .83** | .55** | .83** | .79** | .69** | .79** | − .71** | 1 | | | |
Post Thaw-Live count | .83** | .651** | .80** | .49** | .78** | .79** | .70** | .77** | − .69** | .92** | 1 | | |
Post Thaw- HOST | .81** | .587** | .77** | .45** | .78** | .79** | .73** | .74** | − .66** | .83** | .90** | 1 | |
Post Thaw- Acrosome Integrity | .89** | .702** | .87** | .56** | .85** | .85** | .81** | .83** | − .66** | .79** | .77** | .766** | 1 |
**. Correlation is significant at the 0.01 level (2-tailed). |
The values of the present study for post-thaw progressive motility, viability, and HOST reactive sperm cells were in close agreement with that of Sharma and Sood, (2019) for Chegu goats. The average percentage of post-thaw intact acrosome was in accordance with Sinha (1989) and Lopes et al. (2021). However, Ramachandran et al. (2015) reported considerably lower values for post freeze-thaw sperm motility (28.82 ± 1.99), viability (41.01 ± 3.02) and HOST (41.01 ± 3.02) in Jamunapari bucks. Furthermore, Gangwar et al. (2014) also observed similar semen quality after thawing in Sirohi goats. On contrary to the present values, Deori et al. (2016) reported much higher values of post thaw sperm motility (55.39 ± 0.97), viability (71.01 ± 0.78), HOST reacted sperm cells (54.77 ± 0.55) and intact acrosome (82.16 ± 0.43) in Assam Hill goats. This might be due to variations in the breed and semen freezing methods.
Biometry of castrated kids testicles and evaluation of sperm obtained from cauda epididymis
Male kids were castrated from age two onwards to study the testicular parameters vis-a-vis sperm quality obtained from cauda epididymis at different age intervals. It was observed that the viable spermatozoa were collected from the cauda epididymis from 5 months onwards. Testicular length (mm) of both right and left with epididymis was significantly (P < 0.05) higher at 4 months than those of 2 and 3 months of age. Similarly, the mean values of testicular weight (g) and epididymal weight (g) of the right and left showed significant (P < 0.05) increased from 3 months onwards and thereafter it did not increase during the 4th and 5th months. Mean epididymal length (mm) of both right (43.47 ± 0.37) and left (42.25 ± 0.27) at 2 months increased (P < 0.05) gradually till 5 months of age to 88.8 ± 0.02 and 87.7 ± 0.56 (Table 7). The increase in testicular measurements with the advancement of age was in accordance with the earlier observations (Gogoi et al., 2005; Akpa et al., 2013; Kumbhar et al., 2019) in different goat breeds. Yaseen et al. (2010); Kabiraj et al. (2011), and Baldaniya et al. (2020) also reported a similar trend in the values of testicular length, testicular weight, and epididymal weight in different breeds of bucks. However, Oyeyemi et al. (2012) observed a lower length (7.66 ± 1.05 cm) of epididymis than the present findings. The differences might be due to breed, age, body condition, feed, and health conditions.
Table 7
Biometry of castrated kids testicles and evaluation of sperm obtained from cauda epididymis
Parameters | 2 month | 3 month | 4 month | 5 month |
TLR(mm) ± SE | 25.74a ± 0.55 | 29.21b ± 0.43 | 57.25c ± 0.54 | 57.65c ± 0.34 |
TLL(mm) ± SE | 26.86a ± 0.15 | 29.21b ± 0.03 | 58.06c ± 0.23 | 58.8c 3 ± 0.02 |
TWR(g) ± SE | 3.12a ± 0.03 | 5.4a ± 0.45 | 21c ± 2.1 | 26.36d ± 0.17 |
TWL(g) ± SE | 3.63a ± 0.06 | 5.5a ± 0.01 | 22.64c ± 1.76 | 28.3d ± 0.75 |
EWR(g) ± SE | 0.99a ± 0.04 | 1.16a ± 0.02 | 4.21b ± 0.29 | 4.4b ± 0.51 |
EWL(g) ± SE | 1a ± 0.02 | 1.05a ± 0.01 | 3.69b ± 0.06 | 4.3b ± 0.2 |
ELR(mm) ± SE | 43.47a ± 0.37 | 46.19b ± 0.23 | 78.84c ± 0.36 | 88.8d ± 0.02 |
ELL(mm) ± SE | 42.25a ± 0.27 | 45.63b ± 0.45 | 77.22c ± 0.08 | 87.7d ± 0.56 |
Means with different superscripts in a row differ significantly P < 0.05 |
TLR : Right testicular length; TLL Left testicular length; TWR : Right testicular weight ; TWL: Left testicular weight; EWR: Right epididymal weight; EWL : Left epididymal weight; ELR: Right epididymal length; ELL : Left epididymal length |
Castration study revealed that cauda epididymis of Bengal kids contained viable sperm cells at 5 months of age, and the blood testosterone levels also reached the peak at the same period. But semen ejaculates containing adequate numbers of matured, viable and motile sperm cells could be collected only at the age of six months. Further, semen ejaculate characters and their cryo-survivability were optimal at 11–12 months of age with almost stable body weight, and scrotal/ testicular biometry. Based on the above facts, it can be concluded that the Bengal bucks attained puberty at 5–6 months and sexual maturity at 11–12 months of age. Hence, these criteria may be considered while selecting Bengal bucks for breeding purposes/semen donation for gaining optimum breeding efficiency.