Sperm Motility and Viability of Chilled Ram Semen Collected by Artificial Vagina and Electroejaculation

The current study aimed to evaluate motility and viability of chilled ram semen collected by artificial vagina and electroejaculation during the non-breeding season. A total of 18 ejaculates from clinically healthy rams in a non-breeding season were collected by artificial vagina (AV; n = 9) and electroejaculation (EE; n = 9) and submitted to preliminary evaluation. After that all ejaculates were diluted through a Tris-based extender containing low concentration (5%) of glycerol and egg yolk and stored at 5°C for 48 hours. Motility and viability of semen samples were evaluated at 0, 6, 24 and 48 h of storage. Estimation of motility was carried out by a microscopic digital system, and viability was assessed by the one-step eosin-nigrosin staining technique. Until 6 h of storage, the differences between motility and viability of semen collected by AV or EE were non-significant, while at 24 and 48 h the parameters were higher (P < 0.05) in semen collected by AV. The increasing time of storage correlated negatively with the evaluated parameters (P < 0.05). In conclusion, the chilled semen from ram in the non-breeding season collected by AV demonstrated better motility and viability until 48 h, compared with the semen collected by EE, and could be recommended for artificial insemination up to 24 h after storage at 5°C. The time of storage had a negative effect on sperm motility and viability (P < 0.05). Correspondence to Stanimir Yotov, Department of Obstetrics, Medicine, Trakia University, Student campus, 6000 Stara Zagora, Bulgaria. E-mail: stanrad@abv.bg Introduction insemination of animals with liquid semen preserved at 0–5°C for an extended period or use of frozen semen (Salmon and Maxwell, 2000; Joshi et al., 2001; Abulizi et al., 2012). Maintenance of the spermatozoa biological potential and their genetic information after storage in low temperatures is crucial for sheep breeding practice (Gundogan, 2009). Many reasons can affect the quality of ejaculates intended to chilling or freezing but one of the most important is the method of semen collection (Maxwell and Watson, 1996; Maxwell et al., 2007; Jimenez-Rabadan et al., In ram, the main semen collection techniques are The semen collection with AV is similar to a natural service and is easy to apply, but requires an extended training period of rams and not all animals can be successfully trained (Wulster-Radclife et al., 2001). Electroejaculation has some advantages because it is a quick method, appropriate for use in non-trained males or those with problematic sexual behaviour, and the collected semen has an increased volume compared with ejaculates collected by AV (Mattner and Voglmayr, 1962; Marco-Jimenez et al., 2005; Jimenez-Rabadan et al., 2012). Different studies have presented the effects of both methods on small ruminant semen quality (Matthews et al., 2003; Marco-Jimenez et al., 2005; Ledesma et al., 2015). Electroejaculation is very variable and the collected semen is often contaminated with 1990). In a study by Marco-Jimenez et al. (2005), electroejaculation resulted in a lower recovery electrical stimulation and the fresh semen quality was except for the concentration of spermatozoa. However, a higher number of stable and functional spermatozoa were found for frozen-thawed spermatozoa collected contrast, other authors (Matthews et al., 2003; Bopape et al., 2015) recorded better percentage of motile and live sperm cell semen collected by AV compared with EE, and Jiménez-Rabadán et al. (2012) indicated a higher sperm quality after thawing of cryopreserved Ram spermatozoa are sensitive to extreme temperature changes during cooling and freezing which induce damage to the sperm plasma membrane or structural changes leading to a capacitation process (Hammerstedt et al., 1990; Salamon and Maxwell, 1995; Watson, 1990). The cryopreserved sperm cells, increased to achieve normal fertilization rates because of the lower viability, reduced motility and increased abnormal apical ridge (Shannon and Vishwanath,