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| Author(s): |
Andrea Renata da Silva Romero
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Jaboticabal. 2021-04-12. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal |
| Defense date: | 2021-02-25 |
| Advisor: | Henrique Nunes Oliveira |
| Abstract | |
Ticks are responsible for the spread of pathogens such as Babesia bigemina and Anaplasma marginale that cause the diseases babesiosis and anaplamosis, respectively. The constant presence of the tick in national herds leads to economic losses and difficulty in the inclusion of taurine breeds, as they are animals more susceptible to parasitic diseases than indicine cattle. Thus, the objective of this study was to estimate components of variance, accuracy of prediction, and to conduct a genome-wide association study (GWAS) for the levels of infection of B. bigemina (BigIL) and A. marginale (AmIL). In chapter two, analyses for BigIL were performed using 1,882 animals (1,716 Braford and 166 Hereford) with genotypes imputed to a panel of ~777,000 markers. The variance components were obtained using the Bayesian approach. For the estimation of genomic breeding values (GEBV), tick count (CC) phenotype and levels of B. bovis infection (BovIL) were included in the multivariate model aiming at gains in BigIL prediction accuracy. Genomic prediction and GWAS analyses were performed using genomic best linear unbiased prediction method (GBLUP). Low heritability was observed for BigIL (0.090) indicating greater environmental influence than genetic. The estimate of the genetic correlation between BigIL and CC was low (0.240), in contrast to the correlation between BigIL and BovIL which was high (0.624). The genetic correlation values may have contributed to an increase in accuracy when comparing the univariate (0.246±0.189) and multivariate (0.606±0.180) models. GWAS results showed a polygenic inheritance of BigIL. In the regions close to the SNPs that explained most of the additive variance were identified 35 genes previously related to the immune response located on chromosomes 1, 4, 5, 7, 10, 13, 18, 20, 27, 29. In chapter three, the variance components were estimated by Bayesian analysis and the method used for GWAS and estimation of the values was the best linear biased genomic predictor (GBLUP) using the multivariate model. The estimates of heritability and prediction accuracy were 0.090 and 0.180, respectively. The genetic correlation between AmIL and BigIL was high 0.793, while the correlations between AmIL and BovIL and tick count were close to zero. Exploring the top 10 regions of GWAS, candidate genes were found related to host-pathogen interaction and response to inflammation, located on chromosomes 2, 5, 8, 10, 13, 15, 17, 20, 24, and 29, overlapping with QTL previously described for susceptibility to tuberculosis in cattle and QTL with somatic cell score were identified. Thus, the results obtained in the present work can contribute to the establishment of selection strategies that result in animals that are able to maintain lower levels of infections by agents that cause Bovine Parasitic Sadness. (AU) | |
| FAPESP's process: | 17/21000-0 - Genomics studies of resistance to bovine Anaplasmosis in Braford animals |
| Grantee: | Andrea Renata da Silva Romero |
| Support Opportunities: | Scholarships in Brazil - Doctorate |