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EFFICIENCY - Feed conversion ratio (FCR) This EBV is an indication of the genetic ability of the animal to efficiently convert feed into body weight, as measured in Phase C growth tests. Please note that animals with a low FCR EBV are more efficient. Select bulls with low breeding values for efficient feed converters. - Kleiber Ratio This EBV is an indirect indication of the animal s genetic ability for feed conversion efficiency, as measured in Phase D growth tests. Animals with a higher breeding value are more efficient. Select bulls with above average Kleiber Ratio EBVs for good growth efficiency. - Feed Intake This EBV is an indication of the genetic ability of the animal for daily feed intake, as measured in Phase C growth tests. Animals with a high ADG EBV and a low feed intake EBV are more efficient and therefore desirable. - Feedlot Profit Index This EBV is an indication of the genetic ability of the animal to be profitable in a feedlot or similar environment. The EBV is a selection index that is composed of breeding values for feed intake, beginning weight and end weight, taken into account the relative economic weights of each. BODY MEASUREMENTS - Shoulder Height This EBV is an indication of the genetic ability of animals for shoulder height, as measured in Phase C and D growth tests. Select bulls with average shoulder height breeding values for medium frame type animals. - Body Length This EBV is an indication of the genetic ability of the animal for body length (measured from the shoulder bone to the pin bone), as measured in Phase C and D growth tests. Select bulls with above average body length breeding values and average shoulder height breeding values for relatively long animals. CONCLUSION Because EBVs are a combination of an animal s own performance, his relatives (pedigree) performance and the performance of his offspring in a single figure, it is a very accurate and very powerful tool in the hands of a breeder. Fast genetic progress can be obtained with the purposeful and balanced use of EBVs, without adverse effects on other traits. Worldwide, there is sufficient evidence to substantiate this claim. The question is: Do you do performance testing and use breeding values to your advantage? gewig teelwaardes. Selekteer gemiddelde volwasse teelwaardes vir gemiddelde grootte diere. - Gemiddelde daaglikse toename (GDT) Dié teelwaarde is n aanduiding van die dier se genetiese vermoë vir naspeense groei, soos gemeet in Fase C en D groeitoetse. DOELTREFFENDHEID - Voeromsetverhouding (VOV) Dié teelwaarde is n aanduiding van die genetiese vermoë van die dier om voer doeltreffend om te skalel na liggaamsgewig, soos gemeet in Fase C groeitoetse. Let asseblief op dat diere met n lae VOV teelwaarde meer doeltreffend is. Selekteer bulle met lae VOV teelwaardes vir doeltreffende voeromsetters. - Kleiberverhouding Dié teelwaarde is n indirekte aanduiding van die dier se genetiese vermoë vir voeromset doeltreffendheid, soos gemeet in Fase D groeitoetse. Diere met n hoër teelwaarde is meer doeltreffend. Selekteer bulle met bogemiddelde Kleiberverhouding teelwaardes vir goeie groeidoeltreffendheid. - Voerinname Dié teelwaarde is n aanduiding van die genetiese vermoë van die dier vir daaglikse voerinname, soos gemeet in Fase C groeitoetse. Diere met n hoë GDT teelwaarde en n lae voerinname teelwaarde is meer doeltreffend en dus wenslik. - Voerkraal Winsindeks Dié teelwaarde is n aanduiding van die genetiese vermoë van die dier om winsgewend te wees in n voerkraal of soortgelyke omgewing. Die teelwaarde is n seleksie-indeks wat saamgestel word uit teelwaardes vir voerinname, begin gewig en eind gewig, in ag genome die relatiewe ekonomiese gewigte van elk. LIGGAAMSMATES - Skouerhoogte Dié teelwaarde is n aanduiding van die genetiese vermoë van die dier vir skouerhoogte, soos gemeet in Fase C and D groeitoetse. Selekteer bulle met gemiddelde skouerhoogte teelwaardes vir mediumraam tipe diere. - Liggaamslengte Dié teelwaarde is n aanduiding van die genetiese vermoë van die dier vir liggaamslengte (gemeet van voor die skouerbeen tot agter die sitbeen), soos gemeet in Fase C and D groeitoetse. Selekteer bulle met bogemiddelde liggaamslengte teelwaardes en gemiddelde skouerhoogte teelwaardes vir relatief lang diere. Slot Omdat teelwaardes n dier se eie prestasie, sy verwantes (stamboom) se prestasie en die prestasie van sy nageslag in n enkele syfer kombineer, is dit n baie akkurate en baie kragtige instrument in die hand van n teler. Met die doelgerigte en gebalanseerde gebruik van teelwaardes kan vinnige genetiese vordering verkry word sonder negatiewe gevolge op ander eienskappe. Daar is wêreldwyd talryke bewyse om hierdie aanspraak te staaf. Die vraag is: Doen jy prestasietoetsing en gebruik jy teelwaardes tot jou voordeel? B E E F M A S T E R 2 0 1 2 53
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Back to basics the because it s all in genetics ANINA VAN VUUREN Petana Beefmasters Genetics has long been the basic principle on which every stud or commercial breeder builds his business, on purpose or intuitively. They breed their stock, crossbreed, mate, do corrective mating and generate various performance indexes that measure traits that are of interest to them and that are utilised as tools in selection criteria. All in an effort to produce superior progeny or capture specific traits that give their herd an advantage and to stay competitive in the ever developing marketplace. They use indexes to make informed management decisions or inform prospective buyers regarding specific traits of individual animals. They further simply use the selected traits of the animal they see in front of them (or in the world of genetics described as the phenotype of that animal). Conventional performance indexes are irreplaceable tools. However, the unique but fixed genetic makeup of any given individual contributes only half of its outcome while the rest is determined by the environment of that individual. Thu s the influence of factors such as food availability or even disease determine how genetic traits are manifested. Breeders further need to invest in an animal for long periods of time while it is growing to maturity and producing offspring before breeding indexes can be generated, thu making it sometimes an uncertain investment. The advances of now commercially available but still fledgling technology and the advanced indexes generated from these analyses enable breeders to see the genetic profile of animals. Or at this stage at least some of it. This is called genomics and various articles about genomics have lately been seen in the popular press. This topic has also been discussed in the Beefmaster Journal of 2011. The benefit of genomics is that it will enable breeders to compare important traits across breeds but also between herds and individuals across different environmental boundaries. Secondly, indexes for specific and important traits can be generated in young non-breeding animals. Genomics is still a very complicated and costly affair and much more genetic data needs exploring but it is an imperative emerging tool to breeders. The subject terminology associated with genetics and genomics however is worth reviewing. Herewith then a short but basic summary of Genetics 101 (for mammals) (specially for all of those that attended Oom Gert se plek rather than their genetic practical across the street on Friday afternoons at TUKS). B E E F M A S T E R 2 0 1 2 57
GENETICS Classical Evolutionary Mitosis Meiosis Rules of inheritance Chromosomal mapping Molecular Cytogenetics Structure of DNA Control of gene expression Mechanisms of change Change in gene frequansies in populatios Cells are the building blocks All organisms are composed of cells which are fundamental structural units that house genetic material and the biochemical organisation that accounts for the existence of life. Different cells shows tremendous diversity in structure and metabolic capabilities, yet the similarity among these diverse cell types are more profound than the differences. Some of the main properties in common are the following: 1. All cells store information in genes made of DNA. 2. The genetic code used in the genes of all cells is, with minor exceptions, the same. 3. All cell types decode the genes in their DNA by an RNA system that translates genetic information into proteins. 4. Proteins governs function and structure in all cells. Animals such as mammals are composed of about 200 different cell types. Each type has become specialized during embryological development to perform a particular function in one of the many tissues of the animal. Stem cells are undifferentiated tissue cells that can become any type of specialized cell and is used in modern day medical applications such as cell replacement therapy. Stem cells are for example harvested from the embryonic cord of a newborn. Where are those genes? Higher organisms are eukaryotes (as appose to prokaryotes) which means that they have a true nucleus and the genetic material is separated from the remainder of the cell contents by a nucleur envelope. The cytoplasm also contains various other cell structures within a plasma membrane. The chromosomes within the nucleus of the cell structure is normally spread out or diffused but will become thick and structured ONLY during cell division stages (mitosis & meiosis) by processes of coiling and shortening (and the nucleus membrane dissolve). The familiar picture of paired chromosomes is a karyotype and is photographed during mitosis. Similar (homomorphic) chromosomes pairs can be identified (autosomal). However, the different pairs of chromosomes differ in size. A potential exception is the sex chromosomes (XY) which in some species are of unequal size (heteromorphic). Females are XX while males are XY. Figure 1: The karyotype of a human male (XY). Note the difference in size of the last pair of chromosomes; X being the larger and Y the smaller. What are the patterns of inheritance? Genes are located on the chromosomes and is responsible for the expression of specific traits. Their position (loci) and order on the chromosome can be mapped through a complicated laboratory processes. The genotype of an organism refers to the genes it possesses. The phenotype refers to the observable traits and attributes of an organism. 58 B E E F M A S T E R 2 0 1 2
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