Detrimental Impact of an Alpha2-Adrenergic Agonist on Semen Collection in the Giant Panda (Ailuropoda melanoleuca)
Copper Aitken-Palmer1, DVM, MS; Carlos Sanchez2, DVM, MS; Chengdong Wang3, DVM; Rong Hou3, MS; Zhihe Zhang3, PhD; David Wildt1, PhD; JoGayle Howard1, DVM, PhD
1Center for Species Survival, Smithsonian’s National Zoological Park, Washington, DC, USA; 2Department of Animal Health, Smithsonian’s National Zoological Park, Washington, DC, USA; 3Chengdu Research Base of Giant Panda Breeding, Chengdu, Sichuan, P.R. China
Many male giant pandas (Ailuropoda melanoleuca) in breeding centers do not breed naturally. As a result, the few breeding males are genetically over-represented in the global ex situ population. To maintain and improve genetic diversity, semen collection and artificial insemination are crucial techniques for proper giant panda genetic management. Historically in China, ketamine alone has been used as the anesthetic agent for semen collection in the giant panda, but poor muscle relaxation and vomiting during the procedure (possibly related to insufficient dosage of ketamine) have led to recent changes. To develop an optimal protocol for semen collection by electroejaculation, alternative anesthetic dosages and combinations were assessed. Adult (>6 yr) male giant pandas were anesthetized with either: 1) ketamine (8–10 mg/kg, i.m.) for induction and isoflurane gas (1–5%) for maintenance (n=five males); or 2) combined ketamine (6 mg/kg, i.m.) and xylazine (0.8 mg/kg, i.m.) for induction and isoflurane gas (1–5%) for maintenance (n=five males). Both protocols resulted in safe and effective anesthesia in the giant pandas. Anesthesia using ketamine/xylazine/isoflurane improved the speed of anesthetic induction (5 to 8 min) and overall muscle relaxation, but resulted in a lower (p<0.05) number of ejaculated sperm (915±300×106 total sperm) compared to ketamine/isoflurane (8–12 min; 3,155±800×106 total sperm). Examining urine samples collected by cystocentesis immediately after induction of anesthesia and before electroejaculation revealed that sperm were lost into the bladder within 10 min after ketamine/xylazine administration (41±11×106 sperm/ml of urine) compared to ketamine (1±0.6×106 sperm/ml of urine). These results indicate that the addition of the alpha2-adrenergic agonist xylazine causes muscle relaxation and subsequent sperm loss into the bladder. Therefore, to ensure maximal sperm quality using electroejaculation, ketamine combined with xylazine is not the optimal anesthetic protocol when semen collection is the primary purpose of the procedure.