30 Effects of exogenous oxytocin on semen characteristics in banteng (Bos javanicus) and lowland anoa (Bubalus depressicornis)

Developing semen-collection protocols that maximise the total sperm output during a single collection from an endangered species is critical for strategic biobanking practices. The hypothesis tested in the present study was that the administration of exogenous oxytocin before semen collection by electroejaculation (EEJ) would significantly increase the total sperm count of the ejaculate obtained from both banteng and lowland anoa. Ejaculates from 13 banteng (n = 14) and 12 lowland anoa (n = 13) were collected via EEJ. Animals were anaesthetised using the attending veterinarian’s preferred protocols, and animals were administered oxytocin intravenously (banteng n = 6, 50 IU; lowland anoa n = 2, 25 IU) 10 min before semen collection. Testes were measured with callipers and total testes volume was calculated with the following equation: V = L × W² × 0.524 (V = total volume, L = length, and W = width). To collect semen, a Teflon rectal probe (banteng: 60 mm diameter and 110 mm electrode length; lowland anoa: 38 mm diameter 100 mm electrode length) and electro-stimulators were used to administer stimuli in sets of 10, at 2 to 5 V. Ejaculates were collected in a plastic collection cup and transferred into 15 mL conical tubes (banteng) or a 1.5 mL microcentrifuge tube (lowland anoa) and maintained at 23°C until processed. Semen was assessed for volume, pH, osmolarity, sperm concentration, total sperm count, percentage of motile sperm, status (on a scale of 0–5 [0 = no forward progression, 5 = rapid and straightforward progression]), and sperm/cm³ of testes. Statistical analyses were performed using GenStat 21st edition. Differences in banteng ejaculate characteristics between oxytocin-treated and untreated bulls were evaluated using the nonparametric Kruskal-Wallis test. Due to the limited sample size for lowland anoa, ejaculate characteristics were assessed using descriptive statistics. Significant (P < 0.05) differences were observed in sperm concentration, total sperm count, and sperm per cubic centimetres of testes between oxytocin-treated (2,138 ± 884 10⁶ sperm/mL, 32,070 ± 8812 10⁶ sperm, 91 ± 40 10⁶ sperm/cm³ of testes) and untreated (309 ± 69 10⁶ sperm/mL, 2,702 ± 763 10⁶ sperm, 7 ± 2 10⁶ sperm/cm³ of testes) banteng. In addition, semen could be observed on the prepuce before the start of semen collection in three of the oxytocin-treated banteng. In contrast to banteng, all semen characteristics were numerically similar between oxytocin-treated and untreated lowland anoa bulls. These findings indicate that the administration of oxytocin to banteng before semen collection significantly increases total sperm output, thus maximising the number of banteng spermatozoa available to biobank. The presence of semen on the prepuce after oxytocin treatment, but before EEJ, suggests this may be a useful agent to administer before other semen-collection techniques, such as urethral catheterisation. Additional collections on lowland anoa are required to determine the effect of exogenous oxytocin on semen characteristics, and to evaluate potential differences in efficacy between species.