In the Northern Hemisphere, the typical production cycle of the American mink (Neovison vison, formerly Mustela vison) is divided into three phases during the year. The first phase occurs in late fall, when breeding animals are selected; these breeding animals are maintained over the winter months. These mink must be maintained in good body condition, although nutrient requirements in winter are lower than at other times of year. The second phase of the cycle spans reproduction through weaning of the kits. Mink are bred in early March. Implantation of the fertilized ova may be delayed, resulting in whelping after 40–75 days of gestation. Whelping occurs at the end of April and into mid-May. Lactating females and their kits are kept together until weaning, which occurs when kits are ~6–10 weeks of age. The third phase of the production cycle occurs after kits are weaned and lasts until pelting in the late fall.
Adult mink are housed individually in raised, wire-mesh pens. Provision of a hammock, platform, or shelf improves the environment, and the addition of suitable enrichment (eg, a golf ball, plastic tube, or chain) provides some novelty for mink and helps to minimize fur chewing and other stereotypies associated with boredom.
For pregnant females, a nest box with a hole for entry is attached outside the pen prior to whelping, and a wire or plastic mat (false bottom) is placed on the wire floor to prevent kits from falling through the bottom of the pen. The false bottoms should be cleaned of accumulated manure, especially as kits begin to leave the nest box. The false bottoms are removed once the kits are large enough not to fall through the pen floor. Wood used for the nest box should not be painted or treated with wood preservatives. The nest box should be sized to accommodate all the kits and the female; however, boxes that are too large may result in chilling of kits, which are altricial.
Males and growing kits also require a nest box for optimal comfort. Fine grassy hay, clean chopped straw, untreated dry hardwood shavings or sawdust, or fine wood wool are suitable nest materials. Sawdust or shavings from resinous woods should not be used because they may irritate the kits’ skin and upper respiratory system. Nest boxes should be cleaned and nest materials replaced as required, especially before whelping and throughout the nursing period. Mink are housed year-round in sheds that are semi-open to admit natural daylight and provide natural ventilation. It is important to provide good air circulation and shade in the warmer months, as well as a thorough, integrated pest control management system.
Mink are obligate carnivores. Feed is generally supplied as a wet paste placed on top of the wire mesh of the pen. Smaller farms may use a commercially prepared, dry, pelleted ration placed in feed hoppers. The feed ingredients that make up the wet ration can include chicken and fish by-products, liver, kidney, cooked eggs, processed meats, and a fortified commercial cereal. Acetic, glacial acetic, or phosphoric acid is added to the ration to minimize spoilage and extend the feed’s shelf life. During the late nursing, weaning, and postweaning periods, food is supplied on feeding trays or placed on an adjustable wire nest box cover to enable small kits to eat. Fresh water should always be available. Automatic, heated, recirculating watering systems with individual nipples are most commonly used in sheds. Watering cups fastened to the outside of the pen may be used as an additional water source.
Depending on how feed is provided, large freezers and cold storage facilities are necessary to freeze and store the protein portion of the ration. When feed is prepared on-farm, a day’s supply of meat by-products is thawed, commercially prepared cereal and vitamins added, and the combined ration ground and mixed with water to achieve a semisolid consistency that will remain on the wire of the pen without dropping through. Ready-mixed complete wet feed also may be delivered daily or every other day, depending on the season, either in bulk ready-to-feed or frozen blocks that are thawed as required.
Mink farmers usually keep one male for every four or five female breeders. Mink are seasonal breeders, with reproductive activity controlled by increasing daylight. Artificial lights in the sheds must be used with caution because they may adversely affect photoperiod and interfere with the normal reproductive cycle.
In the Northern Hemisphere, the breeding season begins in very late February or early March and lasts about 3 weeks. Breeding routinely occurs within 10 minutes after placing the female in the male’s pen. If fighting ensues, animals should be separated immediately. Ovulation is induced by breeding, and because mink experience delayed implantation, they can normally be rebred a second, third, or even fourth time. The most common schedules are double breedings (days 1 and 10 or days 1 and 2), triple breedings (days 1, 10, and 11), or quadruple breedings (days 1, 2, 10, and 11). Ova from two breedings have been known to develop in the same litter, but most kits come from the second, third, or fourth breeding. The implantation period can be altered by using artificial light after breeding.
Mink have one litter each year with 1 to 12 kits (average 5.5 kits/litter). Kits are blind, hairless, and weigh ~10 g when born. They grow rapidly throughout the summer to reach a weight of ~1,200 g (females) or 2,600 g (males) by November. Kits are separated at weaning and often housed in pairs (one male and one female, two males, two females, or one male kit with the adult female) and occasionally separated into single cages during the growth period. Although mink have been purpose-bred for more than 100 years, they are not domesticated, and adult mink are very agile, strong, and aggressive. Handling and moving mink requires the use of bite-resistant leather gloves or, preferably, moving crates or cages, which allow animals to be moved between cages without direct handling, minimizing animal stress.
Mink kits are vaccinated after weaning, at or after 8 weeks of age, with a 3- or 4-way vaccine containing Pseudomonas aeruginosa bacterin, Clostridium botulinum toxoid, and mink enteritis virus (a type of parvovirus), with or without a modified-live canine distemper virus vaccine. If kits don’t receive the distemper vaccine at this time, then they receive it when they are at least 10 weeks of age. Only one dose is administered to kits being raised for their pelt; however, it is recommended that animals kept as breeders be revaccinated in the winter before the breeding season. In the US, approved rabies vaccines are available for cats, dogs, ferrets, horses, cattle, and sheep; therefore, rabies vaccination for mink would be administered in an extralabel fashion.
Pelt collection (pelting) usually takes place in November. Typically, mink are killed by use of carbon monoxide inhalation in a sealed unit located in a well-ventilated area. Welfare certification programs for mink farming have been developed in the European Union as well as Canada and the US; however, not all countries mandate participation.