Standing sedation and chemical restraint with or without local or regional anesthesia are common techniques used to perform diagnostic and/or surgical procedures in farm animal species. Compared to general anesthesia, the ease of drug administration, minimal equipment requirements, low cost, shorter recovery time, and reduced potential for complications are advantages that make these techniques attractive to practitioners, particularly those who often do their work in the field or on the farm. Many minor surgical and diagnostic procedures may only require an animal to remain calm and motionless under the influence of standing sedation or chemical restraint for a short period of time. This is particularly true in the case of large or vigorous animals, where sedation or chemical restraint greatly minimizes the stress caused by forceful restraint. Drugs used for chemical restraint are often similar to the ones used for preanesthetic tranquilization or sedation (refer to Chapter 2). Higher doses of a single tranquilizer/sedative are often needed in order to produce desirable central nervous system (CNS) depression, whereas combinations of different classes of drugs are more likely to achieve the degree of sedation and restraint required for the procedure but with lower doses of each drug and thus reduction of the side effects of each drug.

3.1 Cattle

Xylazine produces varying degrees of CNS depression depending on the dose administered. Xylazine is frequently used alone or in combination with other drugs to produce standing sedation and chemical restraint. Intravenous (IV) administration of xylazine at 0.02–0.03 mg/kg induces standing sedation, while recumbency occurs at 0.1–0.18 mg/kg [1]. In adult cattle, intramuscular (IM) or IV administration of xylazine at 0.015–0.025 mg/kg produces standing sedation without recumbency; increasing the dose to 0.1–0.2 mg/kg causes recumbency and light anesthesia to occur [2]. However, at standing sedation doses, the analgesic effect of xylazine appears to be minimal. Doses up to 0.025–0.05 mg/kg IV are required to produce standing sedation in extremely anxious or unruly cattle [3]. Similarly, detomidine alone has been administered to produce dose‐dependent standing sedation and recumbency. Sedation produced with doses from 0.002 to 0.075 mg/kg IV is adequate to calm tractable and anxious cattle, while doses from 0.01 to 0.015 mg/kg IV are required for unruly cattle [3]. In Norwegian cattle, a higher dose of xylazine (0.55 mg/kg IM) was capable of inducing complete immobilization [4]. However, if adequate standing sedation cannot be achieved with what would be expected to be an appropriate dose of an α₂ agonist, a drug from a different class should be used to improve sedation instead of increasing the dose of the α₂ agonist to avoid profound ataxia and recumbency. Acepromazine (0.03 mg/kg IV) with or without xylazine (0.03 mg/kg IV) can be administered to facilitate penile extension for examination of preputial injury in bulls [1]. A combination of 10 mg of xylazine and 10 mg of acepromazine administered IV can produce sedation for standing procedures in manageable bulls and cows to facilitate placing the animal on a tilt table or to perform casting with ropes [5] (Figure 3.1).

Butorphanol is an opioid agonist/antagonist. It has agonistic effects on κ receptors but antagonist effects on μ receptors. The analgesic potency of butorphanol is approximately three to five times that of morphine. Butorphanol has a unique “ceiling effect”, that is, after the effective action has been attained, further increases of the dose do not increase or enhance the degree of desired pharmacologic effects [6]. Butorphanol is the most frequently used opioid in ruminants, and recommended doses are 0.02–0.05 mg/kg IV or subcutaneous (SC) every 4–6 hours [7]. Butorphanol alone was administered at 0.05–0.07 mg/kg IV to produce adequate standing sedation and analgesia for laparotomy [8]. However, butorphanol alone may cause slight CNS stimulation, especially when used in animals that are not in pain. Twitching of the facial muscles, lips, and head and nystagmus may be observed [9]. In adult dairy cows, IV butorphanol (10 mg) can be combined with acepromazine (7.5 mg) to produce sedation during standing cesarean section [10]. One study reported the effectiveness of xylazine (0.02 mg/kg IV) or detomidine (0.01 mg/kg IV) with or without butorphanol (0.05 mg/kg IV) for standing sedation in adult cattle. The result of the study showed that detomidine alone produced more profound sedation for 40–55 minutes than xylazine or xylazine–butorphanol. While butorphanol may enhance the analgesic effect of detomidine, its CNS‐stimulating effect at 0.05 mg/kg, as evidenced by nystagmus, seemed to offset the sedative effect of detomidine in three cows [11]. Ataxia and dysphoria were also reported in sheep when butorphanol was administered intravenously at 0.1–0.2 mg/kg [9].

A combination of low doses of xylazine and ketamine can be used for chemical restraint. IV xylazine (0.05 mg/kg) and ketamine (0.2–0.4 mg/kg) or IM xylazine (0.025–0.05 mg/kg) and ketamine (2 mg/kg) produce chemical restraint with recumbency in combative or unruly ruminants. Opioid analgesics like morphine (0.05 mg/kg) or butorphanol (0.025 mg/kg) can be used with xylazine (0.025–0.05 mg/kg) and ketamine (0.05 mg/kg) administered either intravenously or intramuscularly for standing procedures [3]. A brief period of slight ataxia may occur following IV injection of this combination during standing sedation. Cattle receiving morphine appear to be more alert than those receiving butorphanol [3]. Ketamine can be given 10 minutes after a bolus of xylazine and morphine or xylazine and butorphanol to avoid significant ataxia [3]. A longer duration of sedation is produced when ketamine is administered intramuscularly immediately after IV xylazine and morphine or xylazine and butorphanol [12]. This combination is sometimes referred to as ketamine stun. The low‐dose combination of butorphanol, xylazine, and ketamine at 0.02–0.1, 0.02–0.0275, and 0.05–0.1 mg/kg, respectively, administered intramuscularly produces standing sedation. When increasing the doses of butorphanol, xylazine, and ketamine to 0.05–0.1, 0.025–0.05, and 0.3–0.5 mg/kg, respectively, chemical restraint with recumbency for 15 minutes is induced [1, 12]. Standing sedation produced by this low‐dose combination has been used for laparotomy in range cattle and endoscopy and head examination in rodeo bulls [5]. Using the high‐dose combination, chemical restraint with recumbency along with a casting rope and local or regional anesthetic techniques allows the performance of fracture stabilization, unilateral castration, and preputial resection/amputation in bulls [1]. Animals under the sedation of this combination normally appear to be alert but are not bothered by the surroundings and remain quiet for the duration of the procedures [3]. A similar combination of butorphanol, xylazine, and ketamine using a 5–10–20 ratio (5 mg of butorphanol, 10 mg of xylazine, and 20 mg of ketamine) can be administered intramuscularly or subcutaneously to produce effective standing sedation in tame cows and Brahman cows for cesarean section. If repeat dosing is required, half of the initial ketamine and a quarter of the initial xylazine doses can be given 30–40 minutes after the initial administration. Adequate sedation with a cooperative animal lasts 60 minutes with this 5–10–20 combination. In adult bulls, 10 mg of butorphanol, 20 mg of xylazine, and 40 mg of ketamine (10–20–40) IM or SC combined with local anesthetic nerve blocks can be used successfully to perform standing preputial surgeries [1, 3]. Increasing the dose of each drug to butorphanol 20 mg, xylazine 40 mg, and ketamine 80 mg (20–40‐80) can be used to produce standing sedation in large, unruly bulls. If deep sedation with recumbency is needed for the procedure, 20 mg of butorphanol, 25 mg of xylazine, and 250–500 mg of ketamine can be administered IV in cattle weighing 500–600 kg (1100–1320 lb) [5].

Standing sedation can be achieved with 0.005 mg/kg IV medetomidine alone in domestic ruminants [13]. Increasing the dose to 0.03 mg/kg and using an IM route of administration, lateral recumbency was induced for 60–75 minutes in domestic calves [14]. When delivered via tranquilizing gun at a higher dose (0.04 mg/kg), medetomidine has been used successfully to produce complete immobilization in capturing free‐ranging cattle [4, 15].

A combination of xylazine (0.3–0.5 mg/kg IM), ketamine (0.7–1.0 mg/kg IM), and Telazol (0.7–1 mg/kg IM) has been used to produce dose‐dependent chemical restraint and immobilization in free‐ranging cattle, for example Limousin, Scottish highland cattle, and American bison, for nonpainful procedures [16]. There are times when remote delivery of drugs to produce chemical restraint or immobilization is required for capture of wild or free‐ranging cattle, but the drug volume that can be delivered via a dart gun, pistol, or blow pipe is limited. Saddighi and Doherty [5] suggested that using a drug combination based on Telazol may be ideal under this situation because Telazol is available as a powder and can be reconstituted using xylazine and/or ketamine solutions. For example, by adding 1 ml of xylazine and 3–4 ml of ketamine into 500 mg of Telazol a small volume of drug mixture (4–5 ml) is created, which is sufficient to immobilize a 600‐ to 800‐kg (1320‐ to 1760‐lb) bovid. Caulkett et al. [17] reported that a medetomidine (0.06 mg/kg IM) and Telazol (1.2 mg/kg IM) combination produced immobilization and analgesia adequate for minor procedures for a period of 60 minutes [17]. Atipamezole (0.18 mg/kg) was administered to shorten the recovery time. A reversible combination of butorphanol, azaperone, and medetomidine (BAM) can be used to restrain and immobilize domestic and wildlife ruminants that are difficult to handle, such as rodeo stock or free‐ranging ruminants, e.g. bison, caribou, elk, or white‐tail deer [18–21]. BAM is commercially available as a premixed compound in two different mixtures: butorphanol 27.3 mg/ml, azaperone 9.1 mg/ml, and medetomidine 10.9 mg/ml or butorphanol 50 mg/ml, azaperone 50 mg/ml, and medetomidine 40 mg/ml (Wildlife Pharmaceuticals, Fort Collins, Colorado, USA; ZooPharm, Laramie, Wyoming, USA). Induction to recumbency is usually smooth with acceptable induction times, although repeated dosing with a partial or full dose of the combination may be required if the initial dose is not completely delivered. The quality of immobilization with this combination was reported to be good and allowed minor invasive procedures such as blood sampling, skin biopsy, and semen collection to be performed. In addition, a compounded higher concentration of α₂ antagonist, atipamezole (25 mg/ml), and an opioid antagonist, naltrexone (50 mg/ml), can be used to reverse the effects of medetomidine and butorphanol, and shorten the recovery to standing time. Respiratory depression and hypoxemia are common adverse effects associated with BAM, but the availability of the reversal agents to minimize the duration of recumbency and shorten the recovery to standing time have greatly improve the safety of the immobilization process, particularly for wildlife species [18–21].

Xylazine (0.1 mg/kg IV) and diazepam or midazolam (0.2 mg/kg IV) can be combined to produce short‐term chemical restraint with recumbency, and this combination was successfully used in a cow to place wires to stabilize a mandibular fracture. The duration of chemical restraint was 30 minutes and the cow stood approximately 60 minutes following drug administration. Additional analgesia with an opioid or a local anesthetic was not required for this procedure [22]. For procedures that require more intense analgesia, xylazine at 0.2 mg/kg and diazepam or midazolam at 0.1 mg/kg can be administered intravenously for a similar duration of recumbency. Tracheal intubation was performed in a calf receiving 0.1 mg/kg of xylazine and 0.2 mg/kg of diazepam (Figure 3.2). Table 3.1 summarizes the doses of drugs and drug combinations used for sedation and chemical restraint in cattle.