AUTHOR=Roşu Ovidiu , Melega Iulia , Evans Alina L. , Arnemo Jon M. , Küker Susanne 

TITLE=Evaluation of Medetomidine-Ketamine for Immobilization of Feral Horses in Romania

JOURNAL=Frontiers in Veterinary Science

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2021.655217

DOI=10.3389/fvets.2021.655217

ISSN=2297-1769

ABSTRACT=<p>Feral horses are immobilized for a variety of reasons including population control via contraceptives. Although opioid combinations have been successfully used for immobilization of feral horses, there is a need for combinations using drugs that are more readily available and present less of a human health hazard. We evaluated the chemical immobilization with physiological measurements and blood gas analyses of 91 free-ranging feral horses (<italic>Equus ferus caballus</italic>) remotely immobilized with a combination of 30 mg medetomidine and 775 mg ketamine in a single disposable 6 ml dart. During immobilization, heart rate, respiratory rate, rectal temperature, capillary refill time and peripheral oxygen hemoglobin saturation (SpO<sub>2</sub>) were evaluated. In eight horses, arterial blood samples were analyzed to evaluate the blood gases, acid-base status and hematologic variables. Targeted horses presented a wide range of age, size and body condition. Eighty-one horses had an uneventful mean induction of 7.2 min. Eighty-nine horses were immobilized in lateral recumbency with good muscle relaxation and a median recumbency time of 67 min. Ten horses required supplemental ketamine intravenously (x̄ = 434 mg) due to incomplete immobilization. In 58 horses the effects of medetomidine were antagonized with atipamezole intravenously. Increased respiratory rate (&gt;20 breaths/min), increased heart rate (&gt;45 beats/min) and decreased SpO<sub>2</sub> &lt; 90% were noted in more than half of the individuals, while increased rectal temperature (&gt;39.0°C) was recorded in six animals. Blood parameters showed hypoxemia (&lt;90 mmHg, <italic>n</italic> = 8), hypercapnia (&gt;45 mmHg, <italic>n</italic> = 5), high glucose levels (&gt;134 mmol/L, <italic>n</italic> = 3), increased blood lactate (&gt;1.5 mmol/L), total carbon dioxide, bicarbonate and base excess which further increased in the second sample, whereas SpO<sub>2</sub> and calcium values decreased. Recoveries were smooth, with one (<italic>n</italic> = 86) or more (<italic>n</italic> = 5) attempts of standing. Eighty-nine recoveries were uneventful, besides one male that showed signs of monoparesis of the left front leg and one mare with signs consistent with exertional myopathy. In conclusion, medetomidine-ketamine provided a reliable immobilization in feral horses over a wide range of body mass and age. However, based on the observed hypoxemia during immobilization, oxygen supplementation is strongly recommended for this protocol.</p>