CHARACTERISATION AND CRYOPRESERVATION OF SEMEN OF THE INDIGENOUS NAMAQUA AFRIKANER SHEEP BREED

 

P.T. Letsoalo1#, E. Kilian1, A. Baca1, H.I.P. Olivier1, M.A. Snyman1 & V. Muchenje2

1Grootfontein Agricultural Development Institute, Private bag X529, Middelburg EC, 5900, South Africa

2Department of Livestock and Pasture Science, Faculty of Science & Agriculture, University of Fort Hare

5700, South Africa

#Corresponding author: Thomas Letsoalo

 

Background: The Namaqua Afrikaner is one of the oldest sheep breeds in South Africa. This indigenous fat-tail breed is listed as endangered on the Endangered Species list of Food and Agriculture Organisation. Grootfontein Agricultural Development Institute implemented a program in 2006 involving the conservation and improvement of South African sheep breeds (GADI-Biobank). The two departmental Namaqua Afrikaner flocks, as well as one privately owned flock, are part of this program. These flocks comprise most of the remaining purebred Namaqua Afrikaner sheep in the country. This study forms part of the establishment of a cryopreservation bank for the Namaqua Afrikaner part of the GADI-Biobank.

 

Aim: The aim was to investigate the quality of fresh and frozen semen of Namaqua Afrikaner sheep, compared to that recorded for semen obtained from the Dohne Merino and Dorper breeds that are cryopreserved on a commercial scale.

 

Methodologies: 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 on measured levels. Rams were exercised regularly for the entire trial period. 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 breeds). Macroscopic sperm traits were assessed and sperm concentration determined immediately after collection. Each sample was diluted with Triladyl® (1:3) and subsequently frozen in straws. Nigrosin-Eosin smears were made of fresh and diluted semen samples for survivability (% live) and mortality (% dead) evaluation. Frozen straws were thawed and evaluated at 7, 30 and 90 days after cryopreservation. A droplet (0.5mL) from each thawed sample was assessed microscopically for post-thaw motility and the percentage live sperm. Nigrosin-Eosin smears were also made for evaluation of % live sperm. Data were analysed with the GLM and CHI-SQ procedures of the SAS statistical package.

 

Results: No breed differences were observed in sperm concentration or motility. Dorper rams had higher semen volume than Namaqua rams. Dorper rams had higher % live sperm at 7, 30 and 90 days than Namaqua rams. Semen volume and motility of the fresh and diluted semen samples did not differ between collection methods. Sperm concentration, motility of frozen-thawed semen samples and % live sperm was higher (P<0.05) with the AV method.

 

Discussion: Namaqua Afrikaner sperm traits did not differ in quality from Dohne Merino or Dorper semen before cryopreservation, but % live sperm after cryopreservation was lower than that of Dorper semen. Results indicated that semen quality post-cryopreservation was improved when semen samples were collected by means of the AV method, when compared to the EE method. 

 

Conclusions: Further research is required to investigate the phenomenon that Namaqua Afrikaner rams do not want to ejaculate into an AV. 

 

Published

Proceedings 49th SASAS congress, Stellenbosch