Muna M. M. Ahmed and A. Abdel Gadir
Faculty of Animal Production, P. 0. Box 32 Khartoum North, Sudan.
SUMMARY
Semen was” collected from six Saanen bucks using an artificial vagina. Collection was done at weekly intervals throughout the seasons of one year. The bucks were imported from bland and were allowed one year acclimatization period under the dry-arid climate of Khartoum. Three different types of diluents were used for processability and freezability of the semen. These were skimmed-milk diluent for short-term storage at +5 °C. The other two diluents were intended for deep freezing of semen in liquid nitrogen. Both diluents composed of the same constituents (tris-egg-yolk) but one was used for the one-step method of dilution and the other for the two-steps method of dilution. Percentage motility of spermatozoa that survived after freezability were not significant between the two methods. However, percentage motility of spermatozoa processed with milk was significantly high. For all types of diluent, the effect of season has shown that percentage motility of spermatozoa was lowest in Summer compared to Autumn and Winter.,
INTRODUCTION
Semen evaluation is used to predict the breeding value of a sire used in
natural service or artificial insemination (Rice, 1970; Sorensen, 1979). In line with the ongoing attempt to upgrade the indigenous breeds, Khartoum State Ministry of Agriculture has imported a herd of Saanen goats from the Netherland in 1993. However, understanding the effect of genetic-environment interaction on the reproductive performance represents the first challenge for any gain anticipated from this exotic breed. However, perhaps the most important single technique ever deviced for genetic improvement of animals on large scale is artificial insemination (AI). Processing the semen of Saanen
breed locally would provide a permanent source of high quality semen. It is also economically feasible for small holders to make use of AI. The present study was carried out with the objective to evaluate the processability and freezability of semen collected from Saanen bucks at different seasons of the year.
MATERIALS AND METHODS
Semen was collected from six Saanen bucks throughout the seasons of the year at weekly interval. Collection was done by using an artificial vagina (AV). Three types of diluent were used to extend the semen : These were skim-milk diluent for short term storage at +5 0C. Beside two deep freezing extenders which were Tris-egg-yolk diluent for one step method of dilution and tris-egg-yolk diluent for two steps method of dilution. The constituent of each diluent is shown in Tables 1, 2 and 3.
The collected semen was maintained at 30 oC untill diluted. Each of the milk diluent and tris-based diluent (one-step method) was added to the semen in the ratio of 1:4. For the two-step method diluent, Di fraction was added to the semen at 30 oC to achieve only half of the final pre-freezing rate. After cooling for 60 minutes to +5 oC, the semen was extended further to the final rate with D2 containing the glycerol (Table 3). The pre-freezing percentage motility of spermatozoa was estimated by placing a drop of chilled (at 5oC) diluted sample in a warm slide and examined with a cover slip under a light microscope. The semen was then aspirated into 0.5 ml polyvinyl straws. Semen samples extended with tris-base diluent were equilibrated with the diluent components over one hour, frozen first in nitrogen vapour and gradually immersed in liquid nitrogen for long-term storage. One straw per buck per batch was thawed in a water bath at 35 oC for 21 seconds. The freezability was expressed as a percentage of sperm surviving the deep freezing process.
RESULTS
The average motility of spermatozoa extended with skimmed-milk diluent and chilled to + 5 oC was 65.11%. A sigificantly higher motility percentage was obtained in Autumn than either Summer or Winter (Table 4).
The freezability of unwashed spermatozoa varied significantly with seasons (Tables 5 and 6). Satisfactory results were obtained in Autumn and Winter. An average of 30.03% and 33.44% spermatozoa survived the deep-freezing process for the one-step and the two-steps method of dilution respectively. However, no significant differences between the two methods were detected.
Table 1 : Skimmed milk diluent for buck semen.
| Components | Amounts |
| Glucose (g) | 0.2 |
| Skimmed milk (g) | 10 |
| Streptomycin (mg) | 50 |
| Penicillin (IU) | 50.00 |
| Bi-distilled water to (ml) | 100 |
Table 2 : Tris – egg – yolk – glucose diluent for the one
| step method of dilution | |
| Components | Amounts |
| Tris (hydroxymethyl) aminomethane (g) | 3.756 |
| Glucose (g) | 0.625 |
| Citric acid (g) | 2.17 |
| Egg-yolk (m1) | 2.5 |
| Glycerol (ml) | 5 |
| Penicillin (IU) | 100.000 |
| Streptomycin (mg) | 100 |
| Glass distilled water to (ml) | 100 |
Table 3 : Tris – egg – yolk – glucose diluent for the two
steps method of dilution
| Components犀利士 g> | Amounts D1 D2 | |
| Tris (hydroxymethyl) | ||
| aminomethane (g) | 3.634 | 3.634 |
| Glucose (g) | 0.5 | 0.5 |
| Citric acid (g) | 1.99 | 1.99 |
| Egg-yolk (ml) | 2.5 | 2.5 |
| Glycerol (m1) | 14 | |
| Penicillin (IU) | 50.000 | 50.000 |
| Streptomycin (mg) | 50 | 50 |
| Glass distilled water to (ml) | 100 | 100 |
Table 4 : Effect of season on the motility of Saanen bucks
spermatozoa diluted with milk and chilled to +5 °C.
| Source of variation | N | Motility % |
| Overall mean ±sd | 46 | 65.11±9.47 |
| Season : | ||
| Summer | 7 | 51.43+6.39B |
| Autumn | 21 | 69.05+7.34A |
| Winter | 18 | 65.83±7.63A |
Means with different superscripts differ significantly (p <0.01).
Table 5 : Effect of season on the motility of Saanen bucks spermatozoa processed with Tris-egg-yolk-glucose diluent and diluted in One-step.
Source of N Motility at Post-thawing
variation +5°C motility %
overall
mean±sd 98 61.33±7.48 30.03±12.61
Season :
Summer 12 57.08±7.7. 17.08±5.19B
Autumn 36 63.19±6.36 33.33±13.02A
Winter SO 60.00±7.68 30.80±11.59A
Means with different superscripts within the same column differ significantly (p < 0.01).
Table 6 : Effect of season on the motility of Saanen spermatozoa processed with Tris-egg-yolk-glucose diluent and diluted in two-steps.
Source of N Motility at Post-thawing
variation +5oc motility %
overall
meantsd 93 61.41±8.05 33.44±11.12
Season :
Summer 16 56.25+4.5113 20.94±5.92B
Autumn 30 60.17±3.80A 38.17±10.68A
Winter 47 63.40±8.82A 34.89±4.65A
Means with different superscripts within the same column differ significantly (p <0.01).
DISCUSSION
The percentage of spermatozoa that survived freezability (30.03% and 33A4% for the one and two-steps methods of dilution) was lower than that (46%) obtained by Loubser and Van Miekerk (1983) for washed Angora spermatozoa. This would illustrate the fact that washing spermatozoa before freezing would give better results. According to Mune (1987), washing would remove the enzyme phospholipase present in the semen, which attacks the lecithen of egg-yolk releasing lysolecithen that is toxic to spermatozoa.
The effect of season on spermatozoa motility showed significant lower motility in the semen collected during Summer than Winter and Autumn. Similar findings were obtained by Westhnysen (1978), Loubser and Miekerk (1983). It is recommended that washing of semen could completely reverse the seasonal variation in the unwashed deep-freezing spermatozoa (Corteel, 1977).
REFERENCES
Chemineau, P.; Cagnie, Y.; Guerin, V.; Orgeur, P. and Vallet, J. C. (1991). Training manual of artificial insemination in sheep and goat. FAO, Rome, Italy.
Corteel, J. M. (1977). Collection, processing and artificial insemination of goat semen. In Gall, C. ed. Goat production Acad. Press London. P. 171 – 191.
Evans, G. and Maxwell, W. M. C. (1987). Salamon’s artificial insemination on sheep and goat. Butterworth. London. pp. 85 – 116.
Loubser, P. G. and Van Miekerk, C. H. (1983 b). Seasonal change in sexual activity and semen quality in Angora ram. 2. Semen volume, quality and freezability. S. Afri. J. Sci. 13 (3) : 161 – 163.
Mune, J. F. (1987). Artificial insemination in goats. IV in Conf. on goat 13-8, March 1987, Brazilia, Bro. pp. 733 – 743.
Rice, A. S. (1970). Breeding and Improvement of Farm Animals, 6th ed., MGraw Hill Books Co., New York 300 pp.
Sorensen, A. M. (1979). In : Animal Production Principles and Practices “Ovulation Control” MCGraw IIill Books 299 pp.
Westhnysen, J. M. (1987). Observation on the deep-freezing of Angora goat semen. S. Afi. J. Ani. Sci. (8) : 111-113.
Authors:
Dr. Muna Mahgoub Mohamed Ahmed
Ahmed Abdel Gadir
University of Juba, Khartoum, Sudan.
Download As : PDF