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| Author(s): |
Fernanda Marcondes de Rezende
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Pirassununga. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Zootecnica e Engenharia de Alimentos (FZE/BT) |
| Defense date: | 2009-03-27 |
| Examining board members: |
Paulo Roberto Leme;
Heidge Fukumasu;
Simone Cristina Méo Niciura
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| Advisor: | José Bento Sterman Ferraz |
| Abstract | |
Data on of 3,844 Nellore cattle, reared under pasture conditions on two different farms in southwestern Brazil, 1,889 of them measured by ultra-sound for carcass traits and 674 bulls finished in a feedlot for 90 to 120 days and slaughtered around 24 month of age were analyzed to verify the association with genetic markers (DNA Single nucleotide polymorphism or SNP) with the objective of detecting association of those markers with traits economically important relevant for Brazilian beef business. Growth traits considered were birth weight (PNAS), weaning weight (PDES), yearling weight, measured at 18 mo (PSOB), weight gain after weaning (GP345), visual scores for carcass conformation (CONF), finishing (PREC) and muscle (MUSC). Carcass traits, measured by ultra-sound were ribeye area (AOL_US), backfat (EGS_US) and fat depth at rump (EGP8). Additionally, carcass traits measured after slaughter were hot carcass weight (PCQ), ribeye area (AOL), fat depth on Longissimus muscle (EGS). Meat quality traits were measured after 7, 14 and 21 days of ageing: weep loss (PEX7, PEX14 and PEX21), shrink loss (PCO7, PCO14 and PCO21) and tenderness (MAC7, MAC14 and MAC21). Total lipids and cholesterol content on samples aged for 7 days, were, also, included on the analysis. The genotypes of DNA markers were carried out in laboratories licensed by a private company using its micro-array panels. Allele substitution effects were estimated in single or multi-polymorphism analysis. Additive and dominance effects were also estimated. Many DNA polymorphisms analyzed showed to be fixed or the frequencies for one of the alleles were too high, more than 99 %. In those cases, analysis could not be performed. However, for many others polymorphisms there was observed variability on allele frequencies what make possible to do the association analysis. All traits analyzed were influenced by, at least, two polymorphisms with statistically significant (P≤0,05) or suggestive (0,05<P≤0,20) effects, thus DNA polymorphisms can be used as additional and auxiliary criteria on selection process of those 24 traits related to animal growth, carcass and meat quality in Nellore cattle. As allele substitution effects explain only a small part of the phenotype, the results of this paper suggest that the effect of those markers should be considered together. (AU) | |