Sexual maturity of ferrets is attained in the first spring after birth, at an age of 4–8 months. In the USA, the vast majority of ferrets are spayed or neutered before 6 weeks of age. Outside the USA, neutering is usually performed in the winter months, just before the ferret reaches sexual maturity. Females are induced ovulators and if not bred or spayed can develop severe estrogen-related pancytopenia F due to persistence of estrus, if not bred or spayed. Early neutering also tends to reduce the musky odor characteristic of Mustelids. In Europe use of an implant containing the GnRH agonist (deslorelin) has become common as a method of chemical neutering versus traditional surgery.
In the US, the anal scent glands are usually removed at the time of neutering; however, in some countries this is not legal. Removing the scent glands does not affect the ferret's musky odor, which is produced by the sebaceous glands.
Housing of Ferrets
Ferrets can be housed either inside or outside. When housed outdoors, ferrets should be provided with protection against the elements. Ferrets are highly susceptible to heatstroke because they cannot sweat, so housing should never be placed in direct sunlight.
Because of their inquisitive and lively nature, ferrets need a lot of room to play. Standard-sized ferret cages are generally not large enough for this activity, so ferrets should be provided with (supervised) time outside their cage. In addition, they should have plenty of toys (eg, balls, tunnels, foraging toys) for play and enrichment. Because ferrets are notorious escape artists and can squeeze through the tiniest of gaps, housing is ideally made from wire-mesh with grids not exceeding 1 inch, a sturdy floor, and a tight-fitting door that can be securely locked. The enclosure roof should be high enough to allow the ferret to stand on its hind limbs A litter box, feeding area, and sleeping area (nest box) should also be present. The litter box should be placed away from the feeding and sleeping areas.
Water can be provided in either a bowl or a bottle. Bottles are often preferred because ferrets tend to play with bowls, spilling the contents. The food and water bowls, as well as the litter box, should either be attached to the cage or heavy enough that the ferret is not able to tip them over.
Hammocks are favorite sleeping places of ferrets. A sleeping box lined with a t-shirt or similar can also work well. Hay, straw, and sawdust/wood shavings are not recommended as substrate in ferret housing because inhalation of dust may lead to chronic irritation of the upper respiratory tract.
Many ferrets are very sociable, although their wild counterpart (the pole cat) is a solitary living animal. Therefore, some veterinarians recommend keeping ferrets housed individually to prevent the potential stress of group housing. If ferrets are housed in groups, the size of the group should be limited to 3 or 4 animals.
Nutrition of Ferrets
Ferrets are carnivorous and require high levels of protein (35%–40%) in the diet. Fat content may vary, but both the carbohydrate (< 25%) and fiber (< 2.5%) proportions of the diet should be relatively low. High-quality commercial ferret food is available, although high-quality kitten food may be given as well. Feeding a more natural diet of whole rodents, rabbits, or pigeons or bone and raw flesh diets (BARF) has become popular in some countries. When feeding such raw meat–based diets, the food must be of human-grade quality and not contaminated with known pathogens such as Salmonella, Campylobacter, or both.
Clinical Care of Ferrets
Physical examination
Courtesy of Dr. N. J. Schoemaker.
Physical examination of the ferret is basically similar to that of the dog and cat. It is easiest to examine the ferret when it is held on the forearm. Biological data related to the ferret physical examination can be found in Vital Signs in Healthy Adult Ferrets. During abdominal palpation, a enlarged spleen can often be detected in adult ferrets. This splenomegaly is often due to extramedullary hematopoiesis, which is not clinically important. To exclude other causes (eg, lymphoma) and obtain a definitive diagnosis, transabdominal ultrasonography and cytologic examination of aspiration biopsy specimens may be warranted.
Sample collection
Blood
Courtesy of Dr. N. J. Schoemaker.
In general, volumes of venous blood up to 1% of the body weight (approximately 1 mL per 100 g body weight) can be collected in healthy ferrets (eg, up to 6.5 mL from a 650 g ferret). The jugular vein (technique similar to that in cats) and the cranial vena cava are the recommended locations for venipuncture, especially if larger volumes are needed. The cranial vena cava approach is best performed under sedation, although this may not be needed in debilitated ferrets. For this procedure, the ferret should be placed in dorsal recumbency and the needle (26 gauge) inserted into the thoracic inlet, left from the manubrium, just cranial to the first rib and directed toward the right hindleg at a 30-degree angle. There is no risk of cardiac puncture from this technique. When sedating a ferret, it should be noted that isoflurane can artificially lower the PCV by up to 40%. Changes in plasma protein and the WBC count are not seen. Whenonly a small amount (up to 1 mL) of blood is needed, the lateral saphenous vein or cephalic vein can be used.
Urine
Collection of a voided sample is usually sufficient for urinalysis. Cystocentesis or catheterization is indicated only when microbial culture and sensitivity testing are necessary. These techniques usually require sedation. Cystocentesis technique is comparable to that for dogs and cats. Catheterization is more challenging because of the small body size and J-shaped penis in male ferrets. A 3 French urinary catheter or a 20–22 gauge jugular catheter may be used as a urinary catheter. Placing a 24-gauge venous catheter may help locate the urethral opening, which is located ventral to the J-shaped tip of the penis in males, and can help guide the urethral catheter into the urethra. Subsequent flushing of the catheter with saline (0.9% NaCl) solution may help advance the catheter. Advancing the catheter past the curvature at the level of the pelvic canal may be challenging; guidance per rectum may be helpful.
Anesthesia
Sedation
For nonpainful procedures, sedation may be sufficient to immobilize the ferret. Administration of 5% isoflurane in oxygen via a tight-fitting mask (placed over the mouth and nose) is often adequate. When the ferret is sufficiently calm, the concentration of isoflurane can be reduced to 2%. After isoflurane administration is discontinued, the ferret typically recovers quickly. Sedative drugs, such as medetomidine (100 mcg/kg, IM or SC), can also be used. An equal volume of atipamezole (5 mg/mL) is given after the procedure to antagonize the effects of the medetomidine. The combination butorphanol and midazolam (0.2–0.3 mg/kg, IM, each) also very effectively sedates ferrets. Although flumazenil can be used to antagonize the effects of midazolam, the half-life is much shorter than that of midazolam, so repeated doses of flumazenil may be necessary.
Anesthesia
Many different anesthesia protocols exist, and the choice is based on clinician experience, patient health status and the type of procedure to be performed. Aside from having the requirement for adequate sedation and immobilization, adequate analgesia is crucial. One protocol consists of premedication with medetomidine (100 mcg/kg, IM or SC) to allow for placement of an IV catheter. Propofol (1–3 mg/kg, IV) is then given to allow for endotracheal intubation. Anesthesia can then be maintained with 1%–2% isoflurane in oxygen. Another protocol consists of the combination of medetomidine (80 mcg/kg, SC or IM) with ketamine (5 mg/kg, SC or IM). Buprenorphine (10–30 mcg/kg, IM or SC) provides good postoperative analgesia. In addition, NSAIDs (eg, meloxicam, 0.2 mg/kg, every 24 hours, PO, IV, or SC) and tramadol (1–5 mg/kg, q 12-24 h, PO) may be suitable analgesics for the postoperative period. Because ferrets may be at risk for to gastritis and gastric ulcers, combining the use of an NSAID with an antacid (eg, omeprazole, 1–4 mg/kg, every 24 hours, PO; or ranitidine hydrochloride, 5 mg/kg, every 12 hours, PO) is often recommended.
Vaccination of Ferrets
Depending on the vaccine used, ferrets may be vaccinated for rabies and canine distemper every 1–3 years. There are 3 USDA-approved rabies vaccines for ferrets in the US (Defensor 1 or 3, IMRAB® 3, and Nobivac® 1-Rabies). Rabies vaccinations should only be given to ferrets at least 3 months of age. Ferrets should be vaccinated against canine distemper at ~8, 11, and 14 weeks of age. Currently, no canine distemper vaccines are approved for use in ferrets. Because some canine distemper vaccines may cause seroconversion and disease and other severe allergic reactions, most veterinarians only use the Nobivac PuppyDPv vaccine, because this vaccine has been reported to be safe. To prevent vaccine reactions, it is recommended to administer only one vaccine (ie, rabies or distemper) at a time.
