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Management Perspectives Polled or Scurred: Do You Know the Difference? The popularity of polled In other words, the abcattle breeding is a subsence of the polled gene ject that needs no further (i.e., horned) masks the explanation – especially in presence of the scur gene. the Red & White breeders’ The polled gene is domicircle. Polled has been a nant to the horned gene. popular niche in Red & The gene for scurs is exWhites for some time, and pressed differently from the majority of bloodlines the genes for polled/ building the polled gene horns. The way this gene expansion trend still disis expressed depends on play a strong Red base. the sex of the animal. In Not at all unexpected, males, the scur gene is or untypical when a single dominant, meaning that trait becomes the focus scurs will be present if of intense breeding, other even only one copy of the genetic-related discovergene is present. ThereScurs are small, loose, horny growths in the ies happen. CV, BY, hapfore, it is more easily deskin where horns would normally develop, lotypes and other undesirtected in the bull. such as those visible on this bull. Scurs are able traits have surfaced In females, the gene is determined by a different gene than polled. in the Holstein breed, for recessive, meaning that example. Recently, with the intensity of breeding for the she must possess both genes for scurs in order for scurs to polled gene, breeders have reported the increased incidents be present. If a cow possesses only one scur gene, she will of animals with scurs. What does this mean? It is important not have scurs herself, but has a 50 percent chance of passto have an understanding if you are looking at breeding – ing the scur gene on to her calf. and especially if marketing – polled animals. Table A depicts the inheritance patterns and phenotypic exWhat are scurs? pressions that can be expected in the various combinations Scurs are small, loose, horny growths in the skin where of polled and scur gene inheritance. Genetic combinations of horns would normally develop. Scurs can most easily be polled parents (PP as homozygous and Pp as heterozygous), identified by touch; unlike horns, they are not attached to scurred parents (SS as homozygous, Ss as heterozygous and the skeleton of the animal. Scurs can be wiggled and moved, ss as a non-carrier), and horned parents (pp) are represented. regardless of age and size. The size and length of a scur can vary rather significantly, Table A: with the larger instances often seen in males, believed to Genetic Makeup of be influenced by the presence Cows Bulls of testosterone. Animal Scurs have been common in many beef cattle breeds Polled with Scurs Smooth Polled PPSS for decades. However, only Possible to have scurs?? All male offspring polled with scurs recently, logically due to the focus on breeding polled catPolled with Scurs PPSs Smooth Polled tle, has the gene even gained Can sire polled offspring +/- scurs awareness in dairy breeds. What is the relationship Smooth Polled PPss Smooth Polled with the polled gene? All offspring will be smooth polled The gene that determines Polled with Scurs if an animal will have scurs PpSS Polled with Scurs is not the same gene as that Can sire smooth polled daughters. which determines if it is Polled with Scurs polled. It is a common misPpSs Smooth Polled understanding that scurs are Can sire polled offspring +/- scurs. somehow a partial expression Ppss Smooth Polled Smooth Polled polled gene, but this is incorrect. ppSS Horned Horned The presence of the genetic allele for scurs in cattle can ppSs Horned Horned only be seen in a polled anippss Horned Horned mal, because horns will otherwise cover up the scurs1. 1 Long, C.R. (1978). “Inheritance of the horned, scurred and polled condition in cattle”. Journal of Heredity 69: 395-400. by Ed Peck Testing for polled should be considered There are many reasons mistakes could happen in classifying a calf as polled or horned. The scur gene, human error, poor judgment, and a varying degree of genetic influence on horn growth strongly suggest testing for the polled gene should be a mandatory when marketing or buying elite, highvalue polled animals. There currently are two different tests available on the market, and the differences are important. The Geneseek/Igenity test is the test available directly through Neogen Corporation after the acquisition of the Igenity brand. It is this test that is currently offered through Holstein Association USA. This test is based on haplotypes, meaning it tests several points along the chromosome to evaluate the potential presence of the polled mutation, rather than testing for the mutation directly. Therefore, it is less than 100 percent accurate, and should be considered as an indicator of the likeliness the animal carries the polled mutation, but not a definitive confirmation. In 2011, GeneControl out of Germany introduced a new test based on the discovery that there are two different mutations that can cause the polled condition in cattle. To cut through some of the scientific technicalities on what is required to use the term “proven” in this area of genetics, the new GeneControl test directly measures what scientists regard as the causal mutations for polled. This means the GeneControl test can be considered 100% accurate for the two known types of polled. If there are more types of polled yet to be discovered the GeneControl test of course will not be any good for them. Unfortunately, at this time, there is no test available for testing an animal – male or female – for the scur gene. Summary points to remember 1. Polled and scurred are different genes that interact to give different phenotypes, generally classified as smooth polled, polled with scurs or horned. 2. In order to have scurs an animal has to be polled. A horned animal can carry the scurred gene, but the scur itself will be hidden by the horn. 3. The scurred gene is considered to be dominant but is heavily influenced by the sex of the animal. In order to show the scurred phenotype males typically require only one copy of the scurred gene while females typically require two copies. 4. It is expected that there are many genes other than polled and scurred that influence horn shape and size in smaller ways. These other genes are likely the reason why there is a large amount of variation in scur shape and size. There is little doubt the demand for polled genetics will continue to grow. Many predict it will become the way of breeding all dairy cattle in the future, and it is hard to argue the logic. For breeders and buyers involved in this rapidly growing segment, it is very important to understand the genetic dynamics we know today, and will continue to learn as bloodlines carrying the polled gene are both intensified and expanded. Breeders should be prepared to answer the questions buyers will want to know – and have a right to ask. Buyers should most definitely ask the questions and consider the knowledge and understanding they gain in their investment risks. Recent insights in the industry Following are recent conclusions in the Red & White industry that can help put some context to the polled/scur situation: • Clerinda Balti-Red-ET was initially marketed as a polled bull, before the development of the GeneControl test. Following numerous reports of only horned calves from horned dams, he was tested and confirmed to not be a carrier of either of the two known polled mutations. He has since been designed as “Tested Free of Polled” by Holstein Canada and his polled status has been rescinded by Holstein Association USA. It remains unknown why Balti never grew horns as he was not physically dehorned. More research is needed to determine why Balti never grew horns. He is believed to be a carrier of the scur gene, which led to the confusion of being polled. There is no genetic test for scurs so this cannot be confirmed. • Aggravation Lawn Boy P-Red is the most common source of the polled gene in the Holstein population. Lawn Boy is a proven carrier of the polled gene, and also appears to be a carrier of the scurred gene. Therefore, he can sire polled, polled/scurred, scurred, or horned offspring. • Sandy-Valley Colt P-Red-TW is a more recent, heavily influential polled sire. As a Lawn Boy son himself, he too is a polled carrier and also considered to be a carrier of both the scurred gene.