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~ nirocluction Fur-bearing species are the most recently domesticated group of animals; moreover, their domestication has been accom- plished over a relatively short period of time. Since mink and foxes are by nature carnivorous, their feeding has involved dif- ferent types of ingredients and different storage and handling practices than those used with most other species of farm animals. Also, the major marketable product in the fur indus- try is the pelt, the production of which involves certain consid- erations that are different from those emphasized with those species that contribute mainly to the production of human food. Mink (Mustela bison) are predominant among the several species of animals that are raised for their fur. Although the size of the fur industry has fluctuated widely in response to varying economic and social pressures, it has formed a small but significant part of the American agricultural economy for several decades. There has been an increase in the number of animals raised since 1977, following a brief decline. In 1979, the mink pelts produced in the United States totaled approx- imately 3.4 million, with a gross "farm gate" value of about $140 million. In fact, mink pelts are a significant trade item, worldwide, totaling 20 million with an approximate market value of $800 million in 1979. The mink industry has been served by significant research programs in the United States, Canada, and several other countries, notably the Scandina- vian bloc, and data from these form a major data base for this publication. Numerous color phases of mink have been devel- oped; however, the nutritional requirements of these types have generally been considered to be similar and are so reported, unless differentiation is specifically mentioned. Foxes were raised commercially earlier than mink, but their ranch production in the United States has declined greatly since about 1948. The most common species grown include the silver fox /(Vulpes julva) and the blue fox /tAlopex lagopus). There has been increased production of both silver and blue foxes recently in Europe. Information in this publication relates to the silver fox unless the blue species is specifically named. The efficient production of fur has some points in common with the production of other animal products. It is contingent on the economical maintenance of breeding animals, repro- duction resulting in birth of large litters, excellent lactation performance, rapid growth of the young animals, and desir- able qualities in the fur including density and often subtle dif- ferences in color. The relationship between nutrition and the first four of these items is evident. Desirable qualities in the fur result from careful selection and exploitation of mutant genes, but the extent of their development is largely dependent on nutrition. Data on the nutrient requirements of mink and foxes are ob viously incomplete, and a continuing program of nutrition research with these species is essential for the completion of a comprehensive information base. Much of the information that is available relates to the growth period for young and pelter mink. More data are needed on reproduction and lacta- tion requirements. More precise figures are also required on feed intake by both mink and foxes; the practice of feeding these species wet diets on the cage wire increases the difficulty of assessing actual intakes, as contrasted with feed disap- pearance. Supplies of fresh meat and fish for use in fur-bearer diets are becoming both scarce and expensive. Two alternatives exist: (1) greater dependence may be encouraged on wastes and by- products (scraps, trimmings, viscera, etc.), in which case in- formation should be assembled on their specific nutrient con- tents, and (2) research should continue on the formulation of diets totally from dry ingredients.
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