Text 19. Polecat-mink hybrid

A Polecat-Mink Hybrid, also known as khonorik by fanciers, is a hybrid between a European polecat and a European mink. Such hybridization is very rare in the wild, and typically only occurs where European mink are declining. The two species likely began hybridizing during the early 20th century, when northern Europe underwent a warm climatic period which coincided with an expansion of the range of the polecat into the mink's habitat.

Polecat-mink hybrids have a poorly defined facial mask; have yellow fur on the ears, grey-yellow underfur and long, dark brown guard hairs. They are fairly large, with males attaining the peak sizes known for European polecats (weighing 1,120-1,746 g and measuring 41-47 cm in length) and females being much larger than female European minks (weighing 742 g and measuring 37 cm in length). The majority of polecat-mink hybrids have skulls bearing greater similarities to those of polecats than to minks. Hybrids can swim well like minks and burrow for food like polecats. They are very difficult to tame and breed, as males are sterile, though females are fertile. The first captive polecat-mink hybrid was created in 1978 by Soviet zoologist Dr. Dmitry Ternovsky of Novosibirsk. Originally bred for their fur (which was more valuable than that of either parent species), the breeding of these hybrids declined as European mink populations decreased. Studies on the behavioral ecology of free ranging polecat-mink hybrids in the upper reaches of the Lovat River indicate that hybrids will stray from aquatic habitats more readily than pure minks, and will tolerate both parent species entering their territories. During the summer period, the diet of wild polecat-mink hybrids is more similar to that of the mink than to the polecat, as they feed predominantly on frogs. During the winter, their diet overlaps more with that of the polecat, and they will eat a larger proportion of rodents than in the summer, although they still rely heavily on frogs and rarely scavenge for food from ungulate carcasses as the polecat does.

Text 20. Vitamins in poultry nutrition

Vitamins play a very important part in poultry nutrition. The discovery of vitamins has been of practical importance to poultry keepers, as it is now possible to rear chicks at any time of the year regardless of climatic conditions and to keep laying hens in strict confinement without apparent loss of health and vitality. This has led to a complete reorganization of the poultry industry, based on the earlier hatching of chicks and the year around confinement of laying hens.

Vitamins of vitamin-forming substances are complex, organic compounds consisting of various combinations and proportions of carbon, hydrogen, oxygen and nitrogen, and possibly other elements. They are necessary for health, maintenance, growth, egg production and hatchability. A dozen or more vitamins are recognized for poultry.

Vitamin A is essential in poultry rations, not only for growth, production, reproduction and efficient feed utilization, but also for optimum vision and for maintaining the integrity of the mucous membrane. Vitamin A is found only in animal tissue, where it is stored largely in the liver.

Vitamin D is required by poultry for the proper metabolism of calcium and phosphorus in the formation of the normal bony skeleton, hard beaks, claws and strong egg shells. A deficiency of vitamin D, therefore, results in rickets. One of the primary actions of vitamin D appears to be concerned with increasing the absorption of calcium.

Vitamin E deficiency produces encephalomalacia, exudative diathesis and muscular dystrophy in chicks. It is also required for normal embryonic development in chickens, turkeys and ducks. Prolonged vitamin E deficiency produces testicular degeneration and lack of fertility in male chickens.

Vitamin К is required for the synthesis with the body of prothrombin, which is an important of the blood-clotting mechanism.