VN May 2022

Vetnews | Mei 2022 11 Article Azaperone canalsobe replaced in thedartmixturewithother sedatives and/or tranquilisers. Although these do not significantly shorten the induction times, they do improve muscle relaxation and the quality of immobilisation. Traditionally, azaperone was added to the dart mixture to alleviate some opioid-induced hypertension observed in large ungulate species like elephants and rhinos. This alleviation is primarily due to the peripheral vasodilation caused by azaperones' blocking of alpha1-adrenergic receptors in the periphery. Xylazine, medetomidine, detomidine, or midazolam have been used instead of azaperone, although the literature is still lacking regarding the physiological effects of using these drugs in the dart. It is reported that the addition of xylazine produces quicker inductions compared to azaperone, although increased salivation may be observed. Standing sedation in captive black rhinos has also been achieved using combinations of butorphanol anddetomidine aswell asmedetomidine andmidazolam. However, more research is required in the field of standing sedation of this species to determine which combination provides the safest sedations. Regardless of the tranquiliser and/or sedative added to the opioid for total chemical immobilisation, it is always advisable to include at least 2000 IU of hyaluronidase in the drug mixture to reduce the induction time as much as possible. An important consideration when immobilising black rhinos is that they appear much more sensitive to butorphanol's effects than white rhinos. Butorphanol isoftengiven inwhite rhinos toalleviate respiratory depression at a dose rate of 10 – 15 mg butorphanol per mg of opioid given intravenously (IV). However, this same dose may bring a black rhinotoitsfeetquiteeasily.Itisadvisabletotitratethebutorphanoldose with 5 mg butorphanol IV until the desired effect is achieved. Similarly, the opioid effects in black rhinos are rapidly reversed by administering either diprenorphine or naltrexone. In animals to be transported after immobilisation, diprenorphine should be used instead of naltrexone since the latter cancauseanimals tobecomealert andhighly aggressive very quickly. Black rhinos can be kept immobilised with potent opioids for several hours, although repositioning animals approximately every 30minutes is critical. Good blood flow to the legs must always be maintained. Suppose animals are to be transported after immobilisation or wild animals are to be kept in confinement. In that case, it's essential to consider an appropriate tranquiliser and/or sedative and to administer this before reversal of immobilisation. Azaperone is suitable for short- term sedation and can work for up to 3 hours. Midazolam is also relatively short-acting and has been used quite successfully. Although haloperidol can be used, care should be taken with high doses as animals are susceptible to extrapyramidal symptoms. Zuclopenthixol- acetate is an effective long-acting tranquilliser in black rhinos and is particularly useful in wild animals that are first brought into boma confinement and during transport. It takes about an hour to take effect after intramuscular administration, but its effects can last for up to 72 hours. Due to their conservation status and the nature of black rhinos, care should always be taken when planning and executing a chemical immobilisation operation. It is essential that drug protocols are customised to the animals and the situations and that all the personnel involved are knowledgeable on what these protocols entail. Complications should always be anticipated, and drug protocols adapted accordingly. Potent opioids have made it much more achievable to safely capture and handle this iconic species. Still, cognisance should always be taken that improper dosing can lead to serious adverse effects. v For more information on the potent opioids and their doses in different species, visit theWildlife Pharmaceuticals website at www.wildpharm.co.za or contact themat specialist@wildpharm.co.za. Dr Hayden Cuthill with an immobilised black rhino Dehorned black rhino