Bull selection based on QTL for specific environments Fabio Monteiro de Rezende Universidade Federal Rural de Pernambuco (UFRPE) - Brazil

Introduction How selection is done in Brazil –Dairy cattle. –Beef cattle. Result of these selection –Improved production. Problems caused by phenotypic selection –Negative effect on others traits –Results below expected

Potential GxE interaction can be quantified by considering as different traits the dairy performance of relatives in each country. Small difference between daughter responses and sire breeding in sub-tropical regions. Actual gain depends on the genetic value of the candidate germ plasm and its performance in production environments. To evaluate germ plasm importation options, quantifying potential interactions between US sires and Brazilian herd environments is essential.

With the milk production increasing, the quality of health and reproduction are declining. The infertility has a large impact on competitiveness and the sustainability of the dairy cattle industry. Studies designed for identification of QTL are based on crosses of genetically distinct breeds or inbred lines.

Objectives Help to increase herd productivity: –Selecting bulls that have higher genetic values in the target environment. Make this selection viable: –Show producers how much better is this selection, and make it popular and cheaper.

Increase profits –Identify the investment and the additional productivity. Combine traits that are negatively correlated: –Milk yield and protein concentration. –Milk yield and reproduction.

Materials and Methods Animals in different environments Ranking these animals according to the records –Records of milk yield, quantity of protein, fertility. Identify the QTLs for specific traits –Compare information inside the environment

Ranking the QTLs –Determine which QTL has the greatest effect for each trait in each environment. Evaluate the most important QTLs, and their effects, between different environments

Identify the QTLs with similar (favorable) effects in both environments. –These QTLs should be useful in both environments. Identify the QTLs that differentially affect performance in the target environment. –These QTLs should be selected only for bull that would be used in specific environments –They are responsible for increased production only in those specific conditions (environments).

Materials and Methods from M. S. Ashwell’ paper Resource Population. –Semen from 10 Holstein families was selected from progeny- tested animals. –Two research groups conducted independent genome scans. Genotyping. –For each individual genome scan, microsatellite markers were selected at approximately 20-cM intervals from published bovines maps.

Phenotypic Data. –Data for milk yield and composition, SCS and productivity life (PL) collected were processed in genetic evaluation procedure. –The female fertility trait is new genetic evaluation. –Pregnancy status is determined from the date of last breeding and is verified using the next calving date. Statistical Analysis. –Data from a total of eight traits were analyzed using a regression approach originally described in –Data included daughter deviations for milk, fat, and protein yield, fat and protein percentage, SCS, and PL, weighted by their respective reliabilities.