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Tandem Selection
Tandem selection is a method of artificial selection in which useful traits are selected for sequentially. For instance, one could select for both increased milk yield and increased milk fat content in cows via tandem selection by first selecting those with the best of one trait, production of high milk yield, and then when that trait is at a satisfactory level, by starting to select for those cows that produce milk with the greatest milk fat content instead. However, for cows to produce milk with greater fat content, yield may have to go down due to limits of the cows metabolism. So while cows are being selected based on increased milk fat content, the yield of milk they are producing may also go down, thus reversing the selection process previously performed to increase it. Therefore, tandem selection has a major disadvantage to other major types of artificial selection for multiple traits, such as culling and index selection Index selection is a method of artificial selection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artificial Selection
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together. Domesticated animals are known as breeds, normally bred by a professional breeder, while domesticated plants are known as varieties, cultigens, cultivars, or breeds. Two purebred animals of different breeds produce a crossbreed, and crossbred plants are called hybrids. Flowers, vegetables and fruit-trees may be bred by amateurs and commercial or non-commercial professionals: major crops are usually the provenance of the professionals. In animal breeding, techniques such as inbreeding, linebreeding, and outcrossing are utilized. In plant breeding, similar methods are used. Charles Darwin discussed how selective breeding had been successful in producing chang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milk
Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modulating components in milk contribute to milk immunity. Early- lactation milk, which is called colostrum, contains antibodies that strengthen the immune system, and thus reduces the risk of many diseases. Milk contains many nutrients, including protein and lactose. As an agricultural product, dairy milk is collected from farm animals. In 2011, dairy farms produced around of milk from 260 million dairy cows. India is the world's largest producer of milk and the leading exporter of skimmed milk powder, but it exports few other milk products. Because there is an ever-increasing demand for dairy products within India, it could eventually become a net importer of dairy products. New Zealand, Germany and the Netherlands are the largest export ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crop Yield
In agriculture, the yield is a measurement of the amount of a crop grown, or product such as wool, meat or milk produced, per unit area of land. The seed ratio is another way of calculating yields. Innovations, such as the use of fertilizer, the creation of better farming tools, new methods of farming and improved crop varieties, have improved yields. The higher the yield and more intensive use of the farmland, the higher the productivity and profitability of a farm; this increases the well-being of farming families. Surplus crops beyond the needs of subsistence agriculture can be sold or bartered. The more grain or fodder a farmer can produce, the more draft animals such as horses and oxen could be supported and harnessed for labour and production of manure. Increased crop yields also means fewer hands are needed on farm, freeing them for industry and commerce. This, in turn, led to the formation and growth of cities, which then translated into an increased demand for foodstuf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milk Fat
Butterfat or milkfat is the fatty portion of milk. Milk and cream are often sold according to the amount of butterfat they contain. Composition Butterfat is mainly composed of triglycerides. Each triglyceride contains three fatty acids. Butterfat triglycerides contain the following amounts of fatty acids (by mass fraction):The quote values vary by 1–3% according to the source: Butterfat contains about 3% trans fat, which is slightly less than 0.5 grams per US tablespoon. Trans fats occur naturally in meat and milk from ruminants. The predominant kind of trans fat found in milk is vaccenic fatty acid. Trans fats may be also found in some industrially produced foods, such as shortenings obtained by hydrogenation of vegetable oils. In light of recognized scientific evidence, nutritional authorities consider all trans fats equally harmful for health and recommend that their consumption be reduced to trace amounts. However, two Canadian studies have shown that vaccenic acid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metabolism
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the conversion of food to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of metabolic wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transportation of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary (or intermediate) metabolism. Metabolic reactions may be categorized as '' catabolic'' – the ''breaking down'' of compounds (for example, of glucose to pyruvate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Culling
In biology, culling is the process of segregating organisms from a group according to desired or undesired characteristics. In animal breeding, it is the process of removing or segregating animals from a breeding stock based on a specific trait. This is done to exaggerate desirable characteristics, or to remove undesirable characteristics by altering the genetic diversity of the population. For livestock and wildlife, culling often refers to the act of killing removed animals based on their individual characteristics, such as their sex or species membership, or as a means of preventing infectious disease transmission. In fruits and vegetables, culling is the sorting or segregation of fresh harvested produce into marketable lots, with the non-marketable lots being discarded or diverted into food processing or non-food processing activities. This usually happens at collection centres located at, or close to farms. Etymology The word ''cull'' comes from the Latin verb '' coll ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Index Selection
Index selection is a method of artificial selection in which several useful traits are selected simultaneously. First, each trait that is going to be selected is assigned a weight – the importance of the trait. I.e., if you were selecting for both height and the coat darkness in dogs, if height were the more important of the two one would assign that a higher weighting. For instance, height's weighting could be ten and coat darkness could be one. This weighting value is then multiplied by the observed value in each individual animal and then the score for each of the characteristics is summed for each individual. This result is the index score and can be used to compare the worth of each organism being selected. Therefore, only those with the highest index score are selected for breeding via artificial selection. This method has advantages over other methods of artificial selection, such as tandem selection Tandem selection is a method of artificial selection in which useful traits ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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