Feeding the Adult

Many of the common health problems of nondomestic ruminants have recently been associated with direct or indirect dietary causes.¹¹ Chronic weight loss, rumen acidosis or rumenitis, laminitis, hoof overgrowth, and periodontal disease have all been attributed, at least in part, to historical feeding of all exotic bovids diets designed for domestic cattle. Cattle are grazing species, but many of the nondomestic Bovidae are intermediate or browse feeders. Browsers are adapted to eating the leaves and twigs of woody plants, intermediate feeders to both browse and grasses, and grazers to consuming grasses (see Table 63-1). All of these forages are fermented by the microbes of the ruminoreticulum, which produce fatty acids, providing energy to the ruminant. The grazer rumen is adapted for fermenting the high cellulose content in grasses through prolonged fermentation and particle retention, compared with the smaller, less muscular browser rumen. Consequently, browsers tend to eat less hay and are often fed higher amounts of pelleted concentrate to compensate for low hay consumption. High levels of easily digested carbohydrates such as starch and sugar, often found in pelleted concentrates, are too rapidly fermented in the rumen, leading to rumen acidosis. The ideal rumen pH range is 6.7 ± 0.5, and variation from this results in disturbance of the microflora. Altered and depleted rumen flora decrease the energy delivered to the ruminant, which results in weight loss. In response, many of these animals will receive increased amounts of concentrate, which compounds the problem. Rumen acidosis and resulting rumenitis may also lead to systemic acidosis, mineral imbalances, and laminitis or abnormal hoof growth.

Appropriately formulated pelleted feed for browsers should be based on a high-fiber forage meal such as aspen, alfalfa, soy or sunflower hulls, or cellulose powder, and should contain (1) a high-pectin, low-sugar energy source such as beet pulp; and (2) limited amounts of grain and corn.¹¹ A low-starch, high-fiber pelleted diet that meets these criteria has been recently formulated for browsing and intermediate ruminants (Wild Herbivore and Wild Herbivore Plus; Mazuri Zoo Feeds, PMI Feeds, St. Louis, MO). The recommended feed intake is 1.5% to 2.5% of body weight per day in addition to ad libitum grass or legume hay, and supplementation with natural nontoxic browse is recommended for all browsers. Grazers are generally fed commercial herbivore pelleted concentrate diet containing 12% to 18% protein and 16% to 25% acid detergent fiber at approximately 1% body weight per day in addition to hay. Salt blocks should be available at all times, and trace mineral salt blocks should be available to herds primarily on pasture or not receiving trace mineral balanced concentrates.

Adult bovids experiencing negative energy balance and weight loss from illness may require nutritional support during treatment. Commercially available products useful for boosting caloric intake include Low Odor MEGALAC Rumen Bypass Fat (Arm & Hammer, Church & Dwight Co., Inc., Princeton, NJ) and Wild Herbivore Boost (Mazuri Zoo Feeds, PMI Feeds, St. Louis, MO). These compromised animals may also benefit from transfaunation with rumen contents collected from a healthy conspecific. Tube feeding ruminants may be challenging because of the consistency and volume of feed they require; a commercial tube-feeding formula is available for herbivores (Critical Care, Oxbow Pet Products, Murdock, NB).¹⁰

The development of sophisticated chute systems for hoof stock has allowed for the handling of entire herds of nondomestic bovids rapidly and without chemical restraint.²⁵ Procedures such as venipuncture, vaccination, tuberculin testing, physical examination, treatment of minor conditions, hoof trimming, and reproductive procedures may be conducted without chemical restraint in an effectively designed chute system. In designing a restraint, considerations such as maneuvering animals from a pen into the chute, the ability to stop and sort animals within the system, the inclusion of movable rear walls for pushing resistant animals, the presence of a scale within the system, and multiple exit routes may be critical to creating a process that is efficient and safe, minimizing time and stress to the animals. Desensitizing animals to any chute system by incorporating movement through the system into the animals’ regular routine may greatly facilitate restraint. Many facilities housing large numbers of bovid and equid species are now using chute systems to facilitate preventive medicine, reproductive management, research, and extended treatment of animals, while alleviating the need for repeated chemical restraint.

Mechanical restraints are of three basic types: (1) box chutes or stanchions, (2) drop-floor chutes, and (3) crushes or squeeze chutes. Box chutes are the simplest and least expensive of the three, consisting of a simple pass-through enclosure with front and rear sliding barriers to retain the animal temporarily. Rear entry or exit restraints are not recommended for nondomestic bovids, as many of these animals are reluctant to enter an area with no perceived exit.

Drop-floor chutes are available commercially and consist of a ramp leading to, or a recessed area underneath, an adjustable V-shaped chute with sliding front and rear doors. When the animal is secured in the chute, the floor is dropped such that the animal is suspended by the hips and shoulders (Tamer Drop Floor Chute, Fauna Research, Inc., Red Hook, NY). Most bovids will refrain from struggling without foot purchase, allowing short procedures to be conducted. Width settings for each animal should be carefully established with drop-floor chutes to provide proper restraint, while not overly restricting the abdomen and chest, and duration of procedures should be limited to a few minutes. Drop-floor chutes may be portable or permanently installed.

Squeeze chutes vary from simple adaptations to an aisle way to highly adjustable hydraulic systems. Squeeze chutes developed for domestic cattle have been adapted to larger nondomestic bovids such as wild cattle and bison by adding “crash” gates—barred swinging front doors to prevent bypass of the head gate. Hydraulic squeeze chutes, available commercially (e.g., Hydraulic Tamer, Fauna Research, Inc., Red Hook, NY), provide the most flexible and rapid manipulation of large numbers of animals, as they are adjusted remotely while the animal is in the device. The padded walls of this restraint device are moved hydraulically to apply pressure to the hips and shoulders of the animal and may lift—achieving a result similar to a drop-floor chute—or close down over the animal to provide a darkened enclosed space. Doors installed in the restraint walls provide access for examination, treatment, and venipuncture.

Tranquilization and Sedation

Chemical restraint may be accomplished by two means: tranquilization and general anesthesia. Increasingly, neuroleptics of the butyrophenone and phenothiazine families have been used to attenuate the stress response in nondomestic ruminants undergoing intensive management for capture, translocation, isolation, or adaptation to environmental changes.^10,16,44 Licensed for use in humans as antipsychotic agents, these drugs act by blocking D2 dopamine receptors, thereby producing a state of lucid relief from anxiety. Most of the longer-acting formulations have an onset of action of 1 to 3 days, necessitating the addition of short-acting neuroleptics to produce immediate and long-term tranquilization. Table 63-3 lists common formulations and their onset and duration of action, and Table 63-4 lists suggested doses of neuroleptic drugs for tranquilization of pronghorns and bovids. Recommended dosages per kilogram of body weight are inversely proportional to body size. It should be noted that neuroleptic use may improve the ease of captive management of smaller hoof stock by increasing flight distance, but reducing the fear response may have the opposite effect in larger, more aggressive species, resulting in reduced avoidance behavior, reluctance to move, and aggression. Overdosing is known to produce behavioral side effects such as tardive dyskinesia, including abnormal facial and tongue posture, head pressing and other unusual movement patterns, and anorexia. Treatment of clinical signs of overdosing may be accomplished using low doses of xylazine, diazepam, or diphenhydramine.⁴⁴

Induction of General Anesthesia

General anesthesia is induced parenterally by intramuscular or intravenous routes. Intravenous administration may be performed on manually or mechanically restrained animals and provides the advantage of decreased induction and recovery time. However, in larger animals, intravenous administration of a mechanically restrained animal may result in difficulty in removing the rapidly-induced animal from the restraint device. In general, intramuscular induction of an animal with an appropriate regimen in a darkened, quiet enclosure provides a relatively rapid and smooth induction and may minimize the need for anesthetic supplementation because of longer duration of action. Administration of anesthetics intramuscularly (IM) may be conducted by hand, pole syringe, or projectile dart. The use of darts and remote injection systems has been previously reviewed²⁷ and requires careful planning and experience. Planning an anesthetic event should include considerations such as environmental temperatures, approach, enclosure size, obstacles, and the presence of other animals. Failure to deliver an appropriate dose accurately and quickly to an animal in the wild or in a large enclosure may result in excessive running or pacing injury, capture stress or myopathy, and death. Muscle masses of the rump, shoulder, and neck are preferred sites of remote injection. Failure of induction within an appropriate time (usually 5 to 15 minutes, depending on the regimen) may be caused by many factors, including dart failure, inappropriate dosing, and operator error. A partially anesthetized animal is susceptible to capture myopathy, so a decision to repeat induction should be made within 20 minutes of initial dart placement. Supplementation by remote means generally requires a full anesthetic dose, as the animal may be rapidly metabolizing the anesthetic because of stress and activity.

Many anesthetic regimens have been described for pronghorns and bovids,^{3,10,29 ,53} and these regimens generally consist of ultrapotent narcotics (carfentanil, etorphine, thiafentanil), with or without sedatives or tranquilizers (α₂-agonists, butyrophenones), dissociative cyclohexamines (ketamine or tiletamine), or both. The use of the mixed opioid agonist–antagonist butorphanol tartrate as a component of anesthetic cocktails has been recently reviewed.⁶ Historically, the ultrapotent opioid (narcotic) agents carfentanil citrate, etorphine, and thiafentanil oxalate have been the primary components of anesthetic cocktails used in nondomestic bovid species for many reasons: (1) Opioid agents have a relatively wide margin of safety for the patient and are highly potent, allowing for small volumes to be contained in remote delivery darts; (2) they are rapid acting and provide an efficient induction and minimize the risk of hyperthermia; and (3) they are reversible. However, ultrapotent opioids are associated with significant side effects such as suppression of respiration and GI motility, poor muscle relaxation, and renarcotization⁴⁶ and carry a risk to human safety, as the lethal human dose of some agents is as low as 20 micrograms (µg).²⁹ Ultrapotent opioids are Schedule II substances controlled by the Drug Enforcement Agency and thereby require the practitioner to possess special licensing and to follow defined possession, storage, and recordkeeping guidelines. Safety protocols and special training for handling narcotics and exposure emergencies must be maintained for all staff involved in ultrapotent narcotic procedures. Carfentanil citrate is the most potent of the three agents. Etorphine and thiafentanil oxalate may produce desirable effects such as improved muscle relaxation and decreased respiratory suppression in some species. Opioids, particularly carfentanil, may produce general anesthesia when administered alone; however, combination with other agents may reduce the narcotic dose, ease induction and recovery, increase muscle relaxation, and decrease respiratory suppression.

The α₂-agonists reported in bovid anesthetic regimens include xylazine, detomidine, and medetomidine. In general, bovids are more sensitive to the α₂-agonists compared with equids, and these agents may improve muscle relaxation, decrease narcotic doses, and ease induction and recovery. In smaller bovids and pronghorns, these drugs may be combined with cyclohexamines, benzodiazepines, butorphanol, or a combination, eliminating the need for an ultrapotent opioid. α₂-agonists, however, require 20 minutes to reach full effect when administered IM; approaching a recumbent animal prior to this time may result in spontaneous recovery and the need to re-administer the induction dose. α₂-agonists—particularly medetomidine—cause peripheral vasoconstriction, which may result in hypertension, bradycardia, poor mucous membrane color, and second-degree atrioventricular blocks. Use of parasympathomimetics such as atropine or glycopyrrolate to increase heart rate is controversial, as the resulting increased cardiac output may exacerbate hypertension. Medetomidine is available in highly concentrated formulations (Wildlife Pharmaceuticals, Inc., Fort Collins, CO), improving its usefulness for remote delivery in large species.

Dissociative anesthetics include the cyclohexamines ketamine hydrochloride and tiletamine (which is formulated in combination with the benzodiazepine zolazepam). These drugs are rapid acting, carry a high margin of safety, and are often used as adjuncts or supplemental anesthetics either intravenously (IV) or IM at 0.3 to 1.0 mg/kg. However, cyclohexamines are not reversible and thereby may affect duration of and recovery from anesthesia. When ketamine is used as a supplement, antagonism of reversible anesthetics should be delayed until 20 minutes after ketamine administration. This allows for ketamine metabolism and may prevent stormy recovery. Tiletamine, particularly when used without reversal of the zolazepam component (see Table 63-6), may be associated with prolonged recovery.

A partial list of suggested regimens for general anesthesia of bovids and pronghorns by species is presented in Table 63-5, and suggested reversal agents and doses are listed in Table 63-6.

TABLE 63-5

Combinations of Chemical Restraint Agents Used for Induction of Anesthesia in Selected Species of Antilocapridae and Bovidae*^{3,8,10,29,31,53}

	CARF	ETOR	THIA	XYL	MED	DET	KET/AZAP
ANTILOCAPRIDAE
Pronghorn	0.05			1.0
		0.1		1.0
					0.3		5 K
			0.1	0.5
AEPYCEROTINAE
Impala	0.02–0.03			± 0.1–0.2
		0.08–0.10		0.1–0.3
			0.08
			0.04	0.5–0.1	Or 0.025–0.05
					0.20–0.25		3–5 K
ALCELAPHINAE
Hartebeest	0.01			0.15
Wildebeest	0.008			0.08
			0.03	0.1
Bontebok/blesbok	0.015–0.025			0.2–0.35			1.5–2.5 K
		0.020–0.025		0.2–0.3			0.2–0.3 K
			0.03				0.5 A
					0.05–0.09		1.0–1.3 K
Tsessebe			0.03	0.1			0.3 A
ANTILOPINAE
Springbok	0.03
		0.05–0.10		0.15–0.25
				0.5			9.0 K
Blackbuck	0.05
		0.1
					0.25		2.0 K
Addra gazelle	0.015–0.02			±0.20
		0.03–0.06
					0.06–0.10		1.8–4 K
Slender-horned gazelle	0.03–0.05			0.10–0.25
Grant gazelle	0.035
Thomson’s gazelle	0.02–0.03
		0.05–0.07		0.2–0.45			0.2–0.45 K
Gerenuk					0.06–0. 07		1.5–2.0 K
			0.04				3.5 K
Dik-dik		0.01		0.4
Suni		0.01		0.4
				0.2–0.4			15 K
Klipspringer		0.01		0.4
		0.05
					0.16		2.1 K
Saiga	0.05–0.1
BOVINAE
Bison	0.004–0.008			0.05–0.10
		0.01		0.05
				0.5–1			4 K
					0.05–0.08		1.5–2.5 K
Gaur, gayal, banteng	0.006–0.01			0.1–0.2
		0.01–0.02
Nilgai	0.02
		0.03
Anoa	0.008–0.012			0.06–0.12
African buffalo	0.005			0.05
		0.015		0.1–0.15
			0.01–0.025		±0.05–0.1
Giant eland	0.008					0.03
	0.005–0.007			0.05–0.10
Common eland	0.01–0.016			0.15–0.20
		0.02		0.40
			0.03–0.07	0.1
				0.8			4 K
Nyala	0.015–0.025			0.10–0.25
		0.04		0.30
			0.045		0.05		3–4 K
			0.08	0.3
Sitatunga	0.04			0.3
Tibetan yak			0.02	0.15
Bongo	0.01–0.025			0.1–0.25
	0.01			0.15–0.2			0.5 K
		0.02–0.05		0.05–0.15
Greater kudu	0.02–0.25			0.2–0.25
		0.02–0.03		0.2–0.3
			0.05	0.25
CEPHALOPHINAE
Maxwell duiker	0.025
		0.02		1
				0.2–0.3			15–25 K
Blue duiker		0.01		0.40
				0.3			15 K
					0.2		2.2 K
Yellow-backed duiker	0.02–0.03			0.2
		0.02		1
Common duiker			0.01–0.02	0.5
HIPPOTRAGINAE
Addax	0.025			± 0.15–0.25
		0.03–0.04				0.02
					0.05–0.06		1.0 K
Roan	0.015–0.02			0.15–0.2
		0.025		0.15–0.25
			0.01–0.02		0.005–0.006		0.3–0.6 K
Sable	0.015–0.02			0.15–0.2
		0.015–0.025		0.1–0.2			±0.15–0.2 K
			0.03	0.1–0.2
Scimitar-horned oryx	0.015–0.03			0.15–0.3
		0.025		0.15
		0.05			0.005
Gemsbok	0.01–0.02			0.1–0.2
		0.03		0.25
		0.015		0.15–0.25			0.15–0.25 K
			0.02–0.04		0.02–0.04		1.0 K
Arabian oryx	0.03–0.04			0.25
		0.03–0.04		0.3
		0.04			0.005
		0.045–0.05				0.045–0.05
					0.03–0.06		1.2–2 K
REDUNCINAE
Waterbuck	0.01–0.025			0.10–0.25
		0.03		0.25
			0.03–0.05	0.2
Red lechwe	0.02
	0.01			0.1
		0.02–0.05		0.1–0.4			0.1–0.4 K
Nile lechwe	0.02			0.25			1.0–2.0 K
			0.02				1.5–3.0 K
Uganda kob	0.035			0.35
Reedbuck			0.05–0.07	0.2			±0.1 A
Rhebok	0.01			0.4
		0.01		0.4

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Sphenisciformes (Penguins)
2. Tubulidentata (Aardvark)
3. Caudata (Urodela)
4. Gruiformes (Cranes, Limpkins, Rails, Gallinules, Coots, Bustards)

Stay updated, free articles. Join our Telegram channel

Join