- Title
- Characterisation and cryopreservation of semen from indigenous Namaqua Afrikaner sheep breed, in comparison with Dorper and Dohne Merino breeds
- Creator
- Letsoalo, Phutiane Thomas
- Subject
- Merino sheep Dorper sheep Semen
- Date Issued
- 2017
- Date
- 2017
- Type
- Thesis
- Type
- Masters
- Type
- Animal Science
- Identifier
- http://hdl.handle.net/10353/11707
- Identifier
- vital:39099
- Description
- The aim of this study was to characterise and cryopreserve semen of the indigenous Namaqua Afrikaner breed, and to compare it to that of Dorper and Dohne Merino sheep, whose semen is commercially frozen on a large scale. The study was conducted between January and August 2015. September 2013-born Namaqua Afrikaner (12), Dohne Merino (12) and Dorper (9) rams were used in the study. The rams were kept under kraal conditions with adequate shade, and they received a high protein, high energy diet. Originally it was envisaged to collect semen samples using the artificial vagina (AV) method, which proved to be problematic with the Namaqua Afrikaner rams. Semen samples were subsequently collected twice a week by either AV (Dohne Merino and Dorper) or electro-ejaculation (EE; all three breeds). Macroscopic sperm traits were assessed and sperm concentration determined immediately after collection. Each semen sample was diluted with Triladyl® (1:3) and subsequently frozen in liquid nitrogen vapour in straws. Frozen straws were thawed and evaluated at 7, 30 and 90 days after cryopreservation. A droplet (0.5 ml) from each thawed sample was assessed microscopically for post-thaw motility and percentage live sperm. Nigrosin-Eosin smears were prepared of fresh, diluted and frozen-thawed semen samples for determination of percentage live sperm. Data of all the traits were analysed with the GLM and CHI-SQUARE procedures of the SAS statistical package. Breed had a significant effect on ejaculate volume of fresh semen collected either via electro-ejaculation or artificial vagina. Dorper rams (1.37 ± 0.08 ml) and Dohne Merino rams (1.20 ± 0.08 ml) produced ejaculates with higher (P <0.05) semen volume than Namaqua Afrikaner rams (1.09 ± 0.08 ml) when using the EE. With the AV method, Dohne Merino rams (1.46 ± 0.08 ml) produced a higher (P <0.05) ejaculate volume than Dorper rams (1.22 ± 0.08 ml). Motility of the frozen-thawed semen samples was lower than that of the fresh and diluted samples for all breeds and collection methods. Furthermore, motility 3 hours after thawing was also lower than motility assessed immediately after thawing for all breeds and collection methods. Motility of frozen-thawed semen collected with an AV and evaluated at 7, 30 and 90 days after freezing was significantly higher than that collected via EE. Dorper rams had the lowest sperm concentration (1.10 ± 5.29x109 sperm/ml) and the Namaqua rams the highest sperm concentration (1.22 ± 5.20x109 sperm/ml) (P ˂0.05). The AV samples had a higher (P >0.05) sperm concentration (1.20 ± 3.68x109 sperm/ml) than the EE samples (1.11 ± 3.51x109 sperm/ml). The percentage live sperm in the fresh semen samples did not differ among Namaqua Afrikaner (67.76 ± 1.94percent), Dohne Merino (68.59 ± 1.94percent) and Dorper (72.82 ± 1.98percent) rams. The percentage live sperm for all three breeds dropped considerably after freezing to 17.76 ± 2.03percent, 17.86 ± 2.03percent and 22.72 ± 2.07percent respectively. It remained constant for all the breeds from 7 until 90 days after freezing, indicating that length of storage should not have an effect on percentage live sperm for semen collected via AV or EE. Percentage live sperm of the frozen-thawed semen of the Namaqua rams was lower than that of the Dorper rams, indicating that the Namaqua semen collected via EE did not freeze as well as that of the Dorper semen. In conclusion, neither fresh nor frozen-thawed Dorper and Dohne Merino semen collected via EE did differ significantly. Furthermore, except for semen volume, Dorper and Dohne Merino semen collected via AV did not differ significantly whether evaluated as fresh or frozen-thawed semen. However, both Dorper and Dohne Merino rams produced semen with higher motility and a higher percentage live sperm post-thaw when the semen samples were collected via an AV than via EE. From these results it can therefore be postulated that if Namaqua semen were collected via AV it could have a higher post-thaw percentage live sperm than if semen was collected via EE. Advanced further studies are necessary to investigate the reason for the lower post-thaw survival rate of sperm of the Namaqua Afrikaner rams. This is necessary as semen stored in a cryobank for breeding and conservation purposes for this endangered breed has to be of high quality. Such resources as cryobanks are expensive and funds cannot be wasted on preserving inferior samples that could not fertilize an ovum when needed. The low percentage of live sperm obtained with the frozen-thawed samples in this, as well as other studies on indigenous breeds, is an indication that further research is needed into more suitable freezing protocols. It can be concluded that Namaqua Afrikaner semen cannot be frozen successfully for the purpose of storage in a cryobank, when using a freezing protocol based on Triladyl® as extender. Furthermore, any increase in post-thaw survival rate of sperm will be beneficial and it is therefore suggested that all efforts be made to solve the problem of the Namaqua Afrikaner rams that do not want to ejaculate into an artificial vagina.
- Format
- 106 leaves
- Format
- Publisher
- University of Fort Hare
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- University of Fort Hare
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