For proper plant growth, a regular supply of plant nutrients especially the essential ones, is necessary. Plants absorb a large number of elements from the soil, air and water during their growth period, but not all of these are essential. Only 16 elements have been found to be essential for all plants and four others have been found to be essential for some plants. Essential Elements for Plant Growth For element to be so classified, it has to fulfill the following criteria:  A deficiency of the element makes it impossible…

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The farmer has two main ways in which he can attempt to raise the performance of the animals. He can through their environment or try change their genetic make-up in other to increase their genetic potential. The various traits or characteristics of a pig for example are genetically controlled and inherited through genes, which contain the basic hereditary material. These genes can be manipulated to achieve genetic improvement by either increasing the frequency of favorable genes or combinations of genes by selection, or by introducing new genes into the population…

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Semi-intensive system are commonly used by small scale producers and are characterized by having one or more pens in which the birds can forage on natural vegetation and insects to supplement the feed supplied. It is desirable to provide at least two runs for alternating use to avoid build up of disease and parasites. As may be observed in the foregoing, varieties of subsystems have been adopted to take advantage of low-cost of the extensive system and the high productivity of the intensive as circumstances may dictate under different operation…

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There are many anatomical defects for example in pig which can affect performance. The majority of these are genetic in origin and therefore likely to be inherited from generation to generation. Tests are conducted to detect defects. These defects may be simple (i.e. controlled by one pair of genes) or complex (controlled by several pairs of genes). At the end of the test, the feed conversion efficiency is calculated, and the fat thickness is measure by an ultrasonic machine. Pigs are assessed on the basis of an index derived from…

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In the previous section, methods of pig improvement have been based on selection within breed. There is, however, another means by which the producer can attempt to genetically improve the performance. This involves cross-breeding which is the: Exploitation of the phenomenon of heterosis, which occurs when two breed, which are genetically different, are crossed. If the cross-bred individual shows an improvement in performance above the mean of both parents it is said to exhibit hybrid- vigor or the ability to combine in one or more individuals the desirable characteristics of…

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As an example of how testing and selection procedures can be integrated into a genetic improvement program, the national pig improvement program in Zimbabwe is described. This program is based on a pyramidal structure a small number of registered nucleus breeders assessed to be the herds genetically in the country, send their pigs to a central performance- test station. Approved boars and gilts pass out to multiplication herds, assessed to be the next rung down in terms of genetic merit, where their progeny is performance tested on the farm. Animal…

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