Genomic Selection Has Changed Dairy Sire Selection

Heifers

Take Home Messages

  • Use of genomic markers has reduced the generation interval, defined as the average age of parents when their offspring are born.
  • The generation interval of sires of bulls has decreased from approximately 7 to 2.5 years, while dams of bulls has decreased from 4 to 2.5 years.
  • Genomic selection has increased the rate of improvement in economically important traits such as daughter pregnancy rate, productive life, and somatic cell score.
  • Progeny-tested sires remain in demand and continue

Genomics and Reproductive Performance

Curious Jersey Cows

Where We Are Coming From: The Problem

For decades dairy production systems have faced the challenge of attaining adequate fertility levels. Insufficient reproductive performance will result on reductions on the proportion of cows at their peak production period, increments in insemination costs, and delayed genetic progress. Moreover, impaired fertility is one of the most frequent reasons for culling and increased days open are associated with a greater risk of death or culling in the subsequent lactation.

An historical trend for …

The Big Picture: Genomics, Humans, and Animals

Various breeds of cattle

Take Home Messages

  • The completion of the Human Genome Project, along with DNA sequencing of numerous other species has facilitated a flurry of genomic research.
  • Scientists are currently investigating how SNPs are associated with disease in humans and animals, along with production traits and fertility in livestock.
  • Genomic testing has been embraced by people to study their own health traits and ancestry, and to select for cattle that best fit the herd management strategy.

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Novel Reproductive Traits for Genomic Selection

Holstein Cows

Fertility is a key component of modern dairy production systems. However, a trend for declining dairy fertility has been evident in diverse production systems. Although fertility traits are strongly influenced by the environment, there is evidence for genotypic variation providing opportunity for selection. There are current efforts placed in collection of high numbers of accurate novel fertility phenotypes associated with the corresponding genotypes. Large scale evaluations are testing potential associations between direct measures of fertility and genomic variation on dairy …

Exploring the Best Combinations of Genomics, Semen Type, and Culling in Dairy Cattle

dairy calves

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Introduction

Commercially affordable sexed semen (since 2006) and genomic testing (since 2009) have added to the options that dairy farmers should consider when looking to increase profitability. These technologies, combined with good overall management, and older technologies such as embryo transfer or beef semen, lead to an expanded number of choices regarding genetic selection, breeding and …

Genética y Genómica: Una Introducción


¿Cuál es la diferencia entre “Genética”, “Genómica”, y “Genoma”?”

La genética es una rama de biología enfocada en la herencia y la variación de los organismos. En términos más simples, la genética se centra en las características o rasgos que se transmiten de padres a hijos, de una generación a otra.

La genómica es una disciplina científica enfocada en el mapeo genético, la secuenciación de ADN, y el análisis del genoma completo de un organismo, incluyendo organizar los resultados en …

Genetics and Genomics: An Introduction

 

This article is part of our series of original articles on emerging featured topics. Please check here to see other articles in this series.

What is the difference between “Genetics,” “Genomics,” and “Genome?”

Genetics is a branch of biology focused on heredity and variation of organisms. In simpler terms, genetics focuses on the characteristics or traits that are passed from parents to children, from one generation to another.  

Genomics is a scientific discipline focused on genetic mapping, DNA sequencing, and …

Use of SNP for Whole Genome Selection in Cattle, Page 3

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SNP Evaluation Systems (continued)

SNP Chips

As mentioned earlier, there is a SNP about every 700 base pairs in the Bos taurus genome, and since the genome is about 2.8 billion base pairs in length, there are about 4 million SNPs. There are too many SNPs to deal with all of them practically, so smaller samples of SNPs are used. Specific SNPs can be …

Use of SNP for Whole Genome Selection in Cattle, Page 4

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SNP Evaluation Systems (continued)

Genomic Selection and Genetic Progress

There are three practical ways of increasing genetic progress: 1) increase accuracy of selection; 2) increase selection intensity; and 3) decrease generation interval, which also results in more selection steps per unit time. Whole genome selection is one of the few tools that can affect all three of these components affecting genetic progress. Accuracy clearly …

Use of SNP for Whole Genome Selection in Cattle, Page 5

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SNP Evaluation Systems (continued)

Limitations of SNP Selection

The main limitation of SNP selection is having good phenotypic information from a large number of animals in the population of interest (Hayes et al. 2009). For example, accuracy improved markedly when the number of progeny-tested American Holstein bulls increased from 1,151 to 3,576 (VanRaden et al. 2009). Very few populations of cattle have thousands of …