Seasonal variation in semen quality of dorper rams using different collection techniques
Malejane, Cosmas Masankosa
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The aim of the study was to evaluate the seasonal variation in semen quality of Dorper rams using different semen collection techniques. The Dorper breed was used because of its renowned adaptability, hardiness, veld utilization, good mothering ability and high general global demand. The study was carried out on the University of the Free State campus, in Bloemfontein, South Africa from January 2012 to January 2013 (summer to summer). Eleven mature Dorper rams, recording a mean body weight of 69.6±9.2 kg and mean age of 18±4.7 months were used in this trial. The rams were clinically examined for breeding soundness prior to the study with the aid of a veterinarian, and then randomly divided into two groups. A group of 6 rams were trained for semen collection with the aid of the AV, while in the remaining 5 rams semen were collected using the EE. Two Dorper ewes were used as teasers during the training and for the entire duration of the trial in the AV group. A general management schedule for disease prevention was followed with water provided ad libitum throughout the trial and all rams fed a 2.5 kg maintenance diet (8.5MJ ME/kg) per day - the nutritional regime thus remained uniform and constant throughout the trial. A laboratory to perform the semen evaluation was set up adjacent to the semen collection area. Semen was collected weekly (Thursday) with the aid of the artificial vagina (AV) or electra-ejaculator (EE). Semen ejaculates were evaluated for semen volume, semen colour, semen pH, sperm wave motion, sperm motility, sperm cell concentration, sperm viability and morphology. Other parameters evaluated included libido (sex drive), body weight, body condition score, body temperature, scrotal circumference and scrotal volume. Climatological information for the study area during the experimental period, was obtained from the· Department of Agrometeorology (UFS weather station).The effect of method of semen collection technique (AV vs EE) and the seasonal changes on the above mentioned parameters were compared over seasons. The seasons were laid out as summer (December, January and February), autumn (March, April and May), winter (June, July and August), and spring (September, October and November). The semen and body parameter results were statistically analyzed with the aid of the PROC GLM procedures of SAS (1995). Parameters were considered significant at P<O.05.The results of this trial general showed that semen of Dorper rams may be collected using the AV and EE methods throughout the year. However a significant (P<O.05) difference in semen quality collected by the AV vs EE collection method was recorded. The AV collection method generally recording significantly better semen quality than the EE collection method. The rams were always eager to be collected using the AV method, while disinclination to further application of EE method was recorded in the Dorper rams throughout the year. Generally semen of significantly (P<O.05) better quality was also recorded in summer, autumn and spring (both semen collection techniques).The trial found that semen for Alar cryopreservation should not be collected in winter. The body parameters recorded in this trial generally were not significantly (P<O.05) different between the two treatment groups due to the maturity of the rams used and general uniform management of the rams. Therefore changes in semen quality in this trial could mainly be attributed to the season of the year and/or the semen .collection technique and not to a change in body parameters. The general tendency in the current trial was that the EE technique was the inferior method of semen collection - thus the AV is recommended as the most acceptable method of semen collection in Dorper rams. If the circumstances are such for the use of electro-ejaculation is necessitated, operators must strive to collect semen by applying electrical stimulation in the most humane possible way.