Seasonal variation in semen quality of Dorper rams using different collection techniques
The aim of the study was to evaluate the seasonal variation in semen quality of Dorper rams using different semen collection techniques. The study was carried out from January 2012 to January 2013. A general management programme for health control was followed, with water being provided ad libitum throughout the trial, and all rams being fed a 2.5 kg maintenance diet per day. 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 the trial. A group of six rams were trained for semen collection with the aid of the artificial vagina (AV), while in the remaining five rams, semen was collected using the electro ejaculator (EE). Immediately after collection, ejaculates were evaluated macroscopically and microscopically for semen volume, semen colour, semen pH, semen wave motion, sperm motility, sperm cell concentration, sperm viability and morphology. The results of the trial generally showed that semen in Dorper rams may be collected using the AV or EE methods throughout the year. However, an overall significant better semen quality collected by the AV versus the EE collection method was recorded. Generally, semen of significantly higher quality was recorded in summer, autumn and spring (both collection techniques). The tendency in the current trial was that the EE technique of semen collection was the less reliable method. Consequently the AV is recommended as the more acceptable method of semen collection in the Dorper. Winter is not generally recommended for semen collection, especially when using the EE.
Keywords: Artificial vagina, electro-ejaculator, season, semen quality