| Grant number: | 16/15066-5 |
| Support Opportunities: | Scholarships in Brazil - Master |
| Start date: | April 01, 2017 |
| End date: | February 28, 2018 |
| Field of knowledge: | Agronomical Sciences - Animal Husbandry - Genetics and Improvement of Domestic Animals |
| Agreement: | Coordination of Improvement of Higher Education Personnel (CAPES) |
| Principal Investigator: | Gerson Barreto Mourão |
| Grantee: | Eula Regina Carrara |
| Host Institution: | Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil |
Abstract Heat stress is a common cause of physiological changes in dairy cows, with negative consequences on milk production, milk quality, and on the reproductive efficiency of these animals. The use of genomic tools can assist the selection of less sensitive animals to heat stress and help to accelerate the genetic gain. Thus, it is proposed: i) to identify less sensitive cows to heat stress by using a genomic approach; ii) to identify molecular markers associated with phenotypes susceptibility to heat stress; iii) to assess whether of these markers can be used to predict cows' breeding values for production and milk quality traits. Phenotypes for production and milk quality traits of 6,800 Holstein cows as well as the genotypes of 1,168 these cows will be used. The genotypes were obtained in low density (6k, 6,909 single nucleotide polymorphism) and medium density panels (30k) for 768 and 400 cows, respectively, and imputed to 60,671 SNP. Temperature and humidity data (from two days before the day of milk control) will be collected from weather stations near to the farms studied and used to calculate the temperature and humidity index (THI). Genetic analysis will be performed in two steps. First, a random regression model will be fitted to evaluate the sensitivity of milk yield and milk composition traits to changes in THI. Subsequently, breeding values estimated for THI intercept and THI slope in random regression model for the genotyped animals will be considered as phenotypes in the association study, which will be developed by using the Bayes CÀ regression method. The sum of the effects of SNP according to the genotype will be considered the genomic value of each individual. The genotyping of 825 cows and the imputation procedure were developed in previous projects supported by FAPESP (10/12929-6; 12/15948-7). This is a complementary study in the research line of dairy cattle animal breeding and it is expected that it will contribute to the understanding of the adaptive metabolism of animals to heat stress through the identification of SNPs associated with adaptation mechanisms and the incorporation of this information in sire selection. (AU) | |
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