Feeding the Hospitalized Snake

Introduction

Depending on their age and size, snakes may be fed multiple times in one week or every 2 to 4 weeks. If nutritional support is truly needed, then assisted feeding is indicated in the hospitalized snake. Tube feeding is commonly performed in critically ill snakes after fluid therapy and supplemental heat is provided.

Reptiles are ectothermic or poikilothermic therefore body temperature varies with environmental temperature rather than changes in internal metabolism. To minimize stress, provide patients with an appropriate temperature gradient and meet their other environmental requirements. For instance, corn snakes (Elaphe guttata) are temperate zone species from the southeastern United States that enjoy vertical space for climbing and some humidity, whereas ball pythons (Python regius) are terrestrial species from arid countries in Central and west Africa (Table 1). In contrast, garter snakes (Thamnophis spp.) inhabit much of the US, living along the edges of ponds, streams and rivers. See Hospitalizing Non-Traditional Pets for more specific advice.

Table 1. Husbandry requirements of the three popular snake species
	Ball python	Corn snake	Garter snake
Preferred optimum temperature zone	27-29°C (80-85°F)	21-31°C (70-88°F)	18-26.6°C (65-80°F)
Warm spot	31-35°C (88-95°F) on substrate with cooler gradient	35°C (95°F) on rock or perch with cooler gradient	29°C (85°F) on rock, with much cooler gradient
Nighttime low	25.6-26.6°C (78-80°F)	2-5°C (10-15°F) drop at night	5-15°F drop at night
Humidity	Damp mulch/moss in hide box	40-60%	40-75%
Terrestrial versus arboreal	Terrestrial	Some vertical space needed	Primarily terrestrial, open spaces
Natural food	Rodents	Rodents	Fish, frogs, earthworms

 

Recognizing true anorexia

Defining anorexia in snakes can be tricky. Fasting may be expected in some species during certain times of the year. For instance many gravid females and actively breeding males eat less or go off feed entirely. Some species also fast for weeks or months as an adaptation to excess heat or cold, drought, or lack of food. This dormancy in reptiles is called “brumation” as opposed to true hibernation. Some snakes, particularly large boas and pythons as well as some species of rattlesnake, may not eat for extended periods of time. Research in the ball python, rat snake, (Elaphe obsolete), and Western diamondback rattlesnake (Crotalus atrox) have shown these species are able to successfully tolerate starvation by reducing their resting metabolic demands by up to 72%. Fat bodies are catabolized for energy while critical protein stores are spared (McCue 2007, Blem 1990). Since brumation is associated with slowed metabolism, little energy is consumed and very little weight loss occurs (Whittier 1996).

Many temperate zone snakes must be cooled to induce successful reproduction, however brumation is not without risk and should only be practiced by experienced owners. Prolonged or multiple fasts in less than ideal conditions can be debilitating, and brumation can lead to starvation in thin or sickly reptiles. Regular weighing is therefore recommended for fasting reptiles.

 

Is nutritional support indicated?

When trying to determine if nutritional support should be initiated in an anorectic snake, the first question to ask is:  Does this species normally brumate in the wild?

During brumation, a healthy specimen will lose relatively little body weight, but improper or prolonged fasting can lead to starvation and debilitation. So the next questions to ask are: Is there weight loss? and  What is the snake’s body condition? Muscle and small to moderate amounts of fat should be palpable over the vertebral processes. Also obtain a detailed dietary and clinical history. Look for evidence of disease on physical examination.

Laboratory diagnosis of starvation can be difficult. Blood glucose and electrolyte levels decrease inconsistently. Low albumin levels may also suggest malnutrition. Plasma triglycerides were found to correlated positively with body condition in female garter snakes emerging from brumation (Whittier 1996).

Imaging may also prove helpful. Use radiographs to rule out gastrointestinal obstruction or impaction. Ultrasound may be used to look for the presence of intracoelomic fat bodies.

 

Dietary strategy

All snakes are carnivores with relatively larger snakes consuming vertebrates and smaller ones eating invertebrates. The carnivore gastrointestinal tract is relatively short and simple. Dietary energy is derived from fat and protein.

The preferred prey item will vary with the species but may include appropriately sized rodents, rabbits, fish, and birds. Most species commonly kept as pets may be fed rats and mice purchased frozen from commercial suppliers and thawed prior to feeding. Pythons, boas, rat snakes, corn snakes, gopher snakes (Pituophis catenifer), bull snakes (Pituophis catenifer sayi), and pine snakes (Pituophis melanoleucus) generally eat rodents and chicks. Kingsnakes feed on other snakes in the wild but usually eat rodents in captivity. Water snakes feed on amphibians, crayfish, fish, and invertebrates. Garter snakes and ribbon snakes (Thamnophis spp.) as well as DeKay’s brown snake (Storeria dekayi) will also eat slow-moving invertebrates. Green snakes (Genus Opheodrys) may be fed a variety of invertebrates including crickets.

Although wild-caught adult snakes may refuse prey, those born in captivity generally accept commonly available prey. For example, garter snakes can be fed young mice (appropriately sized “pinkies” and “fuzzies”) scented with fish (common fish for this purpose are frozen silversides sold in pet shops as fish food).

 

Before you feed the snake…

Most reptiles will not waste away if they miss a meal or two. A more common clinical mistake is to feed reptile patients too quickly. Make sure the patient is hydrated and warm before initiating nutritional support.

• Provide your patient with an appropriate temperature gradient and humidity. (See Hospitalizing Non-Traditional Pets for more specific advice).
• Dehydration is common in sick reptiles. The dehydrated reptile will be depressed and anorectic with sunken eyes and dry loose skin folds. Maintenance fluid replacement has been estimated at 20-40 ml/kg/day for snakes.

 

What should be fed?

Snakes with loss of body weight and body condition that are still clinically healthy, may be fed solids. For advice on promoting self-feeding see below. When force-feeding a snake, skin the prey item and trim incisors and claws. If water-soluble lubricant is used, take care not to occlude the glottis with this material. The bolus is then gently milked down the esophagus.

Critically ill reptiles should be tube feed a formula that is easily digestible and highly absorbable like Emeraid Carnivore.

 

How to tube feed a snake

1. Weigh the patient on a gram scale.
2. Restore fluids and electrolytes, when indicated. House the patient at its preferred temperature gradient (see Basic Husbandry).
3. Calculate maintenance daily caloric requirements (MER), which are estimated as 32 (BW^0.75)where body weight (BW) is in kilograms (Table 2). Maintenance energy requirements are expressed in kilocalories per day and are based on values at 86°F (30°C) (Donoghue 2006).Of course all reptiles metabolic rates are not created equal. Larger snakes tend to have slower metabolic rates. Species that utilize a “sit and wait’ predation style such as pythons also have slower metabolism than more active species. Variations in metabolism have also been documented with seasons, gender, age, and habitat (Nagy 1999).Table 2. Estimated daily maintenance caloric requirements (1XSMR) in reptiles based on 32 (BW^0.75)*
   

   Body weight (grams)	Daily caloric requirements (kcal/day)
   5	0.60
   10	1.01
   25	2.01
   50	3.38
   75	4.59
   100	5.69
   150	7.71
   200	9.57
   300	12.97
   400	16.10
   500	19.03
   600	21.82
   700	24.49
   800	27.07
   900	29.57
   1000	32.00
   2000	53.82
   3000	72.94
   4000	90.51
   5000	107.00
   10,000	179.95
   15,000	243.90
   20,000	302.64
   25,000	357.77
   30,000	410.20
   * BW stands for body weight in kilograms; based on values at 86°F (30°C) (Donoghue 2006)

4. To minimize the risk of metabolic problems, feed debilitated patients no more than 50-75% of their calculated MER for the first two to four feedings. Then begin to increase the calories fed gradually.Also keep mechanical limitations in mind when tube feeding. The stomach capacity of the snake is estimated at 2%-5% of body weight. So the stomach of a 100 gram snake should theoretically be able to hold somewhere between 2-5 ml of formula.
5. Select a relatively wide bore tube. Whenever possible, the tube should be long enough to reach the stomach located approximately at the halfway point of the snake. Tubes made specifically for gavage feeding may be particularly useful for larger reptiles since they are often quite long with weighted tips to prevent the tube from doubling back on itself.
6. Use a speculum to hold the mouth open. Rubber spatulas, some bird speculums, or padded hemostats can all serve well. Take care not to injure the teeth.
7. Snakes can be particularly confusing when it comes to determining the frequency of tube feeding since they normally eat relatively large meals infrequently. A variety of schedules have been used successfully in healthy snakes (Donoghue 2006). When approximately 100% of calculated energy requirements may be given at one meal, then tube feedings are often performed on a weekly basis. Research suggests snakes may be assist fed large volumes with minimal or no gastrointestinal upset (Secor 1994, Stark 2002, Starck 2001).
   Transitional epithelium in Burmese pythons (Python molurus bivittatus) allows enormous changes in size (up to 3 times fasting values by Day 2 post-feeding) without cell proliferation (Starck 2001). Intestinal villi are inflated via a blood and lymph pressure pump system that requires little metabolic investment and therefore works even in the starved snake. Studies in healthy sidewinder rattlesnakes (Crotalus cerastes) showed remarkable metabolic changes. Levels of amino acid transporters up to 22-times fasting levels within 1-3 days after feeding and a 2-fold increase in intestinal mass within 1 day of feeding (McCue 2007).
8. Hold the cranial half of the snake up for a few minutes after a feeding to minimize the risk of regurgitation, particularly if the tube used was not long enough to reach the stomach.
9. Minimize handling for at least several hours after tube feeding
10. Monitor the patient for stool production. Liquid diets designed for assist feeding are highly digestible, therefore stools will be produced less frequently and volume will be lower. Clients sometimes need assurances that these signs are normal and not indicative of constipation in their reptile.

Visit LafeberVet’s video clip on Nutritional Support in the Reptile for a demonstration of tube feeding a snake.

 

Potential complications

Regurgitation can sometimes be a problem in tube fed snakes. Regurgitation may be caused by large volume, a hyperosmolar meal, stress or disease (Donoghue 2006). As a general rule, tube feeding is continued if the patient regurgitates using smaller volumes of more dilute formula.

Although the gastrointestinal tract of the debilitated snake can almost certainly handle a large first meal, a risk of “refeeding syndrome” is believed to exist in reptiles as seen in mammals.  Over-feeding of a starved, critically ill patient can lead to life threatening falls in potassium and phosphorus levels. Rapid administration of calories, particularly carbohydrates, predisposes a patient to refeeding syndrome.

 

The self-feeder

To stimulate voluntary feeding:

• House the snake at a temperature gradient appropriate for the species.
• The presence of basking lights and water baths can also increase the appetite.
• A hide box may also prove helpful. Hide box suitability can vary with the species but they are usually relatively small so when the snake curls up its body touches the box sides. Depending on the species, hide box environment may be dry or humid.
• Many snakes are crepuscular, and should be offered prey during the late afternoon or evening.

Offer hospitalized patients pre-killed, warm, whole prey via tongs. Select a natural prey item for the species. For the sluggish snake, “slap feeding” may prove helpful. Using tongs, prey is tapped or lightly slapped alongside the mouth until the snake strikes at its prey.

Many rodent-feeding snakes eat once weekly. Active snakes, like the garter snake, may need more frequent meals. A baby snake may feed every other day. In many instances, breeders will also feed females more frequently as the breeding season approaches.

 

Water

Unless the snake has neurologic deficits or is extremely weak, make water available at all times. Snakes will drink from bowls, but whenever possible also provide a large, sturdy, shallow container that allows easy entry and exit for soaking. Soaking enhances water uptake, stimulates eliminations, and aids shedding.

 

References