Contemporary perspectives to the traditional understanding of hyperketonemia in dairy cows

Abstract

This Ph.D. dissertation aims to provide to the body of literature and increase the understanding about hyperketonemia in dairy cows. Further knowledge is needed to better characterize the rumen and low BHB concentrations.Hyperketonemia is a transition disorder that affects dairy cows as they come into lactation. Hyperketonemia, associated with decreased milk production, impaired reproductive performance, and increased culling of cows, can be a costly disorder to dairy farmers and the dairy industry. Although hyperketonemia has been a prevalent disorder for several years, certain aspects of its association remain underexplored. Notably, the role of the rumen and exploring the use of beta-hydroxybutyrate (BHB) concentration as a continuous variable warrant further investigation. Thus, this dissertation aims to provide additional understanding of how these factors are associated to hyperketonemia. An overview of hyperketonemia and associated factors will be provided in the first two chapters of this thesis. These chapters aim to make relevant the need for more research about the role of the rumen in hyperketonemia. The third chapter is an introduction to the use of rumen metagenome and metabolome analysis to compare two groups of cows that differ based on milk production levels. The fourth chapter is a study that implemented metagenome and metabolome analysis from rumen fluid in cannulated cows to find associations with hyperketonemia status in those cows. The fifth chapter compares two commonly used methods for glucose quantification in dairy cow research. The sixth chapter focuses on modeling BHB on a continuous scale measured either at week 1 or 2 postpartum and its association with milk production, culling, and pregnancy. This dissertation contributes to the field and highlights the importance of the consideration of the rumen in its association to hyperketonemia and the caveats with using a cutoff value to separate cows into hyperketonemic and non-hyperketonemic groups. Future studies should consider more animals and samples to be able to better characterize associations with the rumen and hyperketonemia and should consider consequences of grouping hyperketonemic and non-hyperketonemic cows based on a cutoff value.