Technical aspects of improved semen collection procedures in African rhinoceroses (Ceratotherium simum; Diceros bicornis) under field conditions

Wild rhinoceros populations are threatened by ongoing poaching pressure and habitat loss. Establishing reservoirs of gametes of as many individuals as possible may assist to preserve genetic diversity and could be applied in assisted reproductive techniques in the future. However, for routine implementation of semen collection during any male rhinoceros immobilisation event, current methods and protocols need simplification and improvement.
This study aimed to establish field-friendly methods of semen collection in white (Ceratotherium simum; WR) and black rhinoceroses (Diceros bicornis; BR) that can be performed opportunistically given the usual time constraints.
Sixty-two game-farmed WR and seven wild BR were immobilised for planned management interventions. Semen collection was performed using electro-stimulation with a battery powered electro-ejaculator and specifically designed rectal probe. Furthermore, in ten WR and two BR, urethral catheterisation was performed with a 10FG nasogastric tube passed retrograde up the urethra as a method of semen collection.
Semen-rich fractions were collected from 47/62 WR and 6/7 BR following electro-stimulation. Of these, 10 WR and two BR samples were obtained by urethral catheterisation. The duration of semen collection was 16.4 ± 7.3 (3-30) and 25.8 ± 6.0 (19-33) min requiring 5.2 ± 2.3 and 6.0 ± 0.7 stimulation sets for WR and BR, respectively. Semen volumes, sperm concentrations, motile and viable sperm were 1-64 and 9-18 ml, 68.4 ± 54.2 and 23.7 ± 26.7x106/ml, 51.0 ± 14.2 and 55.0 ± 17.3, and 79.9 ± 15.0 and 88.3 ± 8.4% for WR and BR, respectively. Urethral catheterisation, when implemented, reduced the time required for semen collection. Operator experience influenced sampling efficacy.
Equipment and methods described in this study improved semen collection in free-ranging rhinoceroses and can be combined with routine immobilisations, despite time constraints.