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.

 

Text 21. ANIMAL HUSBANDRY

Animal husbandry or pastoral farming is no less important than field husbandry. It comprises cattle-breeding; sheep-rearing and hog-growing, to say nothing of some minor branches, as poultry-breeding, rabbit-breeding, apiculture, etc.

Cattle can be roughly subdivided into draft cattle which has almost everywhere been replaced by various types of agricultural machinery; dairy cattle which provides dairy products (milk, butter, cream, cheese, etc.), beef cattle and dual purpose cattle.

The measure of merit of cattle is dependent upon the breed. The herds cannot be improved without the use of sires from pedigree stock.

Cattle-breeding on a scientific scale is not only aimed at improving the breed, but also at increasing the head of cattle; in stock-raising areas the herds are usually very big and the more heifers and calves are to be seen on the grazing lands, or in the corrals, the better the cattle-rearing farm is run.

One of the principal problems cattle-breeding faces is that of fodder or feeds. To choose the necessary feeds, rich enough in protein and other nutrient substances is not an easy thing.

As is well known, hay stands out as the main provender, but special crops are also grown for feeding cattle. They are mainly mangle, various leguminous plants, such as alfalfa, cow-peas, etc. Clover takes a vital part, while oilcake left over after the extraction of oil from linseed, cotton-seed and other varieties of oil-bearing seeds ranks particularly high in protein content. Most farms — both those going in for diversified (mixed) farming and those that specialize in stock-breeding — have ensilage towers where silo or ensilage is obtained through fermentation and stored. Ensilage is recognized to be an excellent feed by most cattle-breeders.

As a general rule, dairy products are processed on the farm. In the creamery milk is skimmed and churned into butter, while some part is turned into cream or sour cream. The production of cheese and canned milk is mostly effected at cheese factories and condenseries. After the bulk of the fat is removed from the milk, whey remains. It is still useful as a feed for domestic animals and also can be used for making curds.

Beef cattle is mostly sent to the slaughter-houses on hoof. Big meat­packing plants after the slaughter of cattle are engaged in curing, smoking, corning and especially canning the meat. Mechanization is implemented on a large scale in cattle-breeding. Particular significance belongs to it in feeding and milking. Automatic bunks (gravity belt, rationing feeder, etc.) are gradually being introduced.

Text 22. AQUACULTURE

Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions. Mariculture refers to aquaculture practiced in marine environments.

Particular kinds of aquaculture include fish farming, shrimp farming, oyster farming, algaculture (such as seaweed farming), and the cultivation of ornamental fish. Particular methods include aquaponics, which integrates fish farming and plant farming.

Fish farming

The farming of fish is the most common form of aquaculture. It involves raising fish commercially in tanks, ponds, or ocean enclosures, usually for food. A facility, which releases juvenile fish into the wild for recreational fishing or supplementing a species' natural numbers, is generally referred to as a fish hatchery. Fish species raised by fish farms include salmon, big eye tuna, carp, tilapia, catfish and cod.

Shrimp farm

Commercial shrimp farming began in the 1970s. About 75% of farmed shrimp is produced in Asia, in particular in China and Thailand. The other 25% is produced mainly in Latin America, where Brazil is the largest producer. Thailand is the largest exporter.

Shrimp farming has changed from its traditional, small-scale form in Southeast Asia in 1970s into a global industry which due to applied high technologies can produce more than 1,800,000 tonnes of shrimps and ship them worldwide. All farmed shrimp are of the family Penaeidae. And just two species of shrimp, the Pacific white shrimp and the giant tiger prawn, account for about 80% of all farmed shrimp. By reason of increasing ecological problems, repeated disease outbreaks, which result in decimation of shrimp populations across entire regions, in 1999 governments, industry representatives, and environmental organizations initiated a program aimed at developing and promoting more sustainable farming practices.

Oyster farming

Oyster farm or oyster bed is a place, especially on the sea bed, where oysters breed and grow naturally or are cultivated for food or pearls. The most popular edible marine mollusk of the genus Haliotis for farming is abalone which has an ear-shaped shell that is perforated with a row of respiratory holes. The shells are used for ornament or decoration. Abalone farming began in the late 1950s and early 1960s in Japan and China. Since the mid-1990s, this industry has become increasingly successful. Over-fishing and poaching have reduced wild populations of abalones. So, now abalone farming is the main supplier for abalone meat.

Algae

Microalgae are also referred to as phytoplankton, microphytes, or planktonic algae and constitute the majority of cultivated algae. Macroalgae, which are commonly known as seaweed, also have many commercial and industrial uses, but due to their size and specific requirements, they are not easily cultivated on a large scale and are most often taken in the wild.

 

Text 23. CALCIUM & PHOSPHORUS

Calcium

99 per cent of the calcium in the organism is in the skeleton and the teeth. It is deposited in certain areas of the bone as tricalcium phosphate crystals and gives the skeleton its rigidity; this calcium is not a permanent deposit, for bone is constantly being dissolved and redeposited. Several hundred milligrams of calcium are lost each day in the feces and urine. This amount must then be replaced through the diet. A calcium deficiency due to lack of dietary calcium is very rare. Calcium deficiency usually arises due to lack of adequate vitamin D, or to excessive amounts of other minerals that prevent calcium absorption. During pregnancy and lactation the demands for calcium rise immensely. If the calcium supply of the mother is not adequate for the maintenance of her normal needs, plus those of the growing fetus, calcium still will be supplied in sufficient amounts to the fetus at the expense of the stored calcium in the skeleton of the mother. The diseases resulting from insufficient calcium for the development and maintenance of bone are rickets and osteomalacia.