Bull selection based on QTL for specific environments

1
Bull selection based on QTL for specific
environments

• Fabio Monteiro de Rezende
• Universidade Federal Rural de Pernambuco (UFRPE)
  - Brazil

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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

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• 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.

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• 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.

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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.

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

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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

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• 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

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• 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).

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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 .

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• 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 1992.
• Data included daughter deviations for milk, fat,
  and protein yield, fat and protein percentage,
  SCS, and PL, weighted by their respective
  reliabilities.