Research

Decreasing the prevalence of fatty liver in early lactation benefits both profitability and sustainability of the dairy industry. Apart from decreased milk production and increased veterinary cost-associated loss in profitability, fatty liver-induced compromised liver function in early lactation also results in longer calving intervals and decreased lifetimes of dairy cows, which jeopardize the sustainability of the dairy industry. Although the exact financial loss from fatty liver is difficult to quantify, the consequent decrease in liver function is costing U.S. dairy farmers over $150 million annually. If nutritional preventative strategies can effectively decrease the prevalence of fatty liver, when extrapolated to the 9.2 million cows in the US, each 1% decrease in fatty liver could mean a saving of $13.4 million annually. These savings become especially significant to economic sustainability for dairy producers with the current low milk price and high labor cost. We have identified a number of amino acids and their catabolites that function as neutraceuticals to improve liver function, health, and lactation performance. Currently, the lab is utilizing molecular and system biology approaches to elucidate the underlying mechanisms in the following projects:

• Influence of Branched Chain Amino Acids and Branched Chain Ketoacids on Liver Lipid Accumulation in Dairy Cows During Early Lactation. Zheng Zhou (PI), M. VandeHaar. USDA-NIFA (2021-67015-33383, $500,000, 01/01/2021-12/31/2025).

• Reducing risk of fatty liver in dairy cows by supplementing aromatic amino acids. Zheng Zhou (PI). Michigan Alliance for Animal Agriculture (AA-23-009, $24,990, 6/1/2023-5/31/2024).

Feeding 9 million dairy cows in the U.S. requires millions of acres of crops and accounts for half of dairy production cost. To sustainably feed people, it is essential to improve feed utilization by increasing the number of cattle in the herd with high feed efficiency. Over the past 60 years, genetic selection for cows with greater levels of milk production doubled the efficiency of converting feed to milk in the U.S. Such increase is primarily the byproduct of increasing milk production level. Although dairy cows have not reached their maximum production level, the margin for further improvement in milk production has diminishing returns in feed efficiency. Most of the variation in feed efficiency in dairy cows is due to differences in metabolism. By characterizing the contributions of post-absorptive nutrient metabolism, we are assessing the metabolic adaptations in efficient and inefficient cows to elucidate the mechanisms of feed efficiency. Additionally, the lab is also applying knowledge from these mechanistic studies by identifying biomarkers to differentiate efficient cows from inefficient cows, thereby providing practical tool for dairy farmers to make more informed decisions when selecting and culling cows towards higher feed efficiency from the following projects:

• Metabolic Efficiency of Nutrient Use Contributes to Individual Dairy Cow Variation in Feed Efficiency. Heather White (PI), Michael VandeHaar (Co-PI), Zheng Zhou (Co-PI). USDA-NIFA (2022-67015-36650, $650,000, 04/01/2022-3/31/2025).

• Metabolic adaptations in dairy cows with divergent residual feed intake. Zheng Zhou (PI), Michael VandeHaar (Co-PI), and Chi Chen (Co-PI). AgBioResearch ($200,000, 10/1/2024-9/30/2026).

• Identifying metabolic biomarkers as indicators of feed efficiency in lactating dairy cows. Zheng Zhou (PI). Michigan Alliance for Animal Agriculture (AA-21-177, $149,901, 6/1/2021-5/31/2023).

• Identifying feed efficient cows using urinary metabolism biomarkers. Zheng Zhou (PI). Michigan Alliance for Animal Agriculture (AA-23-008, $75,000, 6/1/2023-5/31/2024).