Organic dairy cows at Morris.

2020-21 Rapid Ag: Reducing Mastitis in the Dairy Cow by Increasing the Prevalence of Beneficial Polymorphisms in Genes Associated with Mastitis Resistance

April 3, 2019

Principal Leader

Brian Crooker

Department

Department of Animal Science

The Problem

Mastitis, a mammary gland infection, is the most expensive health-cost component for the dairy industry ($1.7 to 2 billion annually, about 11% of annual U.S. milk production) due to lost milk yield and increased labor and drug costs (1). The contemporary Holstein cow has a less robust immune system and is more susceptible to disease and metabolic disorders than her ancestors (2). Efforts to reverse the unintended negative impacts of previous selection practices through altered selection priorities (greater emphasis on health and fertility traits) and marker assisted selection programs (CDCB, 2017 https://www.uscdcb.com/eval/summary/trend.cfm) have been beneficial but additional, more-focused gene-assisted selection efforts are needed. A better understanding of genetic polymorphisms beneficial to mastitis resistance would strengthen gene-assisted selection efforts designed to enhance the prevalence of beneficial genes and quicken the pace towards reducing incidence and severity of mastitis in the dairy cow.

Background

Keeping cows healthy minimizes the need for therapeutic interventions which can reduce use of antibiotics, reduce the cost of producing milk, and contribute to a continued supply of safe, wholesome milk for consumers. Mastitis, a mammary gland infection, is the most expensive healthcost component for the dairy industry ($1.7 to 2 billion annually, about 11% of annual U.S. milk production) due to lost milk yield and increased labor and drug costs (1). The contemporary Holstein cow has a less robust immune system and is more susceptible to disease and metabolic disorders than her ancestors (2) due in part, to a reduced prevalence of genetic polymorphisms that support a strong immune response and an increased prevalence of detrimental polymorphisms (3,4). We will use unselected Holsteins that represent the 1964 ancestors of the contemporary Holstein to identify genomic polymorphisms in genes that contribute to a robust immune system. Prevalence of these beneficial and detrimental polymorphisms in the DNA of contemporary Holsteins will be determined and the information used to identify polymorphisms for inclusion in updated versions of gene-assisted selection strategies designed to strengthen immune function and increase mastitis resistance.

Project Goals and Objectives

Our premise is that previous selection practices have successfully increased the presence of genetic polymorphisms associated with increased milk yield but have decreased the presences of polymorphisms associated with disease resistance. Our overall goal is to increase the presence of genetic polymorphisms in the Holstein cow to strengthen immune function and increase mastitis resistance. Key objectives to achieve this goal include  

  1. Determining differences in mammary gene expression when unselected and contemporary Holsteins are subjected to an intramammary Escherichia coli challenge
  2. Sequencing these differentially expressed genes to identify potentially beneficial polymorphism differences between unselected and contemporary Holstein genotypes
  3. Determining the relative presence of these polymorphisms in a larger population of unselected and contemporary Holsteins to identify polymorphisms that would be important to include in geneassisted sire selection programs

Throughout this effort we will be informing the industry, lay and scientific communities of our progress towards achieving these objectives.

References

  1. Jones, G. M. and T. L. Bailey. 2009. Understanding the basics of mastitis. http://pubs.ext.vt.edu/404/404-233/404-233.html
  2. Egger-Danner et al. 2015. Invited review: Overview of new traits and phenotyping strategies in dairy cattle with a focus on functional traits. Animal 9:191-207.
  3. Siebert et al. 2017. Genetic variation in CXCR1 haplotypes linked to severity of Streptococcus uberis infection in an experimental challenge model. Vet. Immuno. Immunopath. 100:45-52.
  4. Curone et al. 2018. What we have lost: Mastitis resistance in Holstein Friesians and in a local cattle breed. Res. Vet Sci. 116:88-98.