Project Number: 5030-32000-238-000-D
Project Type: In-House Appropriated
Start Date: Oct 1, 2021
End Date: Sep 30, 2026
Objective 1: Compare Holstein cattle with a 1964 mastitis-resistant genetic background with modern mastitis-susceptible genetic background, identify genetic and immunologic traits that account for improved resolution of clinical mastitis against common mastitis pathogens and disease resistance through the periparturient period. Sub-objective 1.A: Compare the immune response to infection with Staphylococcus aureus between the two populations of Holsteins in both the acute and chronic phases of the disease. Sub-objective 1.B: Determine the impact of 1964 genetics on the proteome of innate immune cells during the periparturient period in comparison to cows with modern genetics. Objective 2: Facilitate the development of antibiotic alternatives to prevent and treat mastitis by identifying, isolating, and testing important components of bovine mammary gland dry secretions. Sub-objective 2.A: Fractionate components of mature bovine mammary gland dry secretions to identify portions that may be further developed as non-antibiotic mastitis preventive or treatment. Sub-objective 2.B: Determine if there are unique antimicrobial components to the 1964 cows’ dry secretion.
Mastitis is the most prevalent infectious disease in dairy herds and the costliest disease for dairy producers. Newer estimates of mastitis' economic impact on the dairy industry calculate a single clinical mastitis case costs an estimated $586. Antibiotics and proper cow management are the mainstays for mastitis treatment and control. Dairy cattle with mastitis plus antibiotic dry treatments account for more antibiotic usage than all other dairy cattle diseases combined. To reduce antibiotic use, we need to understand better how the immune system fails to eliminate mastitis infections. A unique resource, available through a collaboration with researchers at the University of Minnesota, is a herd of Holsteins that have not been subjected to selective breeding since 1964. These 1964 cows were compared to cows with modern genetics for their ability to respond to an experimental mastitis challenge with Escherichia coli. The 1964 cows were able to clear the infection almost immediately and had fewer clinical signs of infection. A long-term goal is to identify genetic traits that allow the 1964 cows' immune system to protect the host better. Identification of these immunological traits may allow us to bring back these immunological advantages into modern dairy cows. We will use experimental mastitis models, bacterial inhibition tests, and proteomic assays to determine differences between modern and 1964 cows' ability to recognize and destroy pathogens. We will challenge cows with Staphylococcus aureus, isolate antibacterial components in dry secretion, and demonstrate protein changes between modern and 1964 cows during the periparturient period. Isolation and identification of traits that grant greater resistance to mastitis will be used to genetically breed for more resistant animals or products using isolated compounds as therapeutics.