Synthesis of milk proteins in dairy cattle:
Dairy cows exposed to heat stress severely reduce feed intake and results in a dramatic decline on milk and milk protein synthesis. The drop in intake accounts for a portion (approximately 40%) of the decrease in milk synthesis. The remaining loss in production is explained by changes in absorption and utilization of nutrients (e.g. VFA, amino acids, and fatty acids). These changes in metabolism reduce the conversion of nutrients into milk. In addition to heat stress, excess supply of amino acids increases oxidative stress and muscle protein degradation. The rationale that underlies this research is that understanding how heat stress and amino acids affect the milk and milk protein synthesis is expected to lead to critical knowledge. This in turn is expected to lead to novel nutritional strategies to reduce the negative impact of heat stress in cattle. Our contribution is expected to explain metabolic adaptation of the dairy cow in response to heat stress.
Nutrient manipulation to maximize rumen microbial growth:
Dairy cattle fed to current industry standards retain 25% of the nitrogen intake in milk (nitrogen-use efficiency) and 50% of the nitrogen intake is excreted in urinary urea-nitrogen. Lowering rumen degradable protein has been used to reduce urinary nitrogen excretion and to increase capture of nitrogen by rumen microbes. The bacterial community composition can adapt to different rumen conditions even among cows fed different diets. Investigations have confirmed that cows consuming a diet with low rumen degradable protein increase the recycling of urea to the rumen and reduce urinary excretion of urea. It is expected that the rumen function and the microbial activity will be maintained in cows consuming diets with low rumen degradable protein. The overarching goals of our work are to increase nitrogen retention in product, and reduce nitrogen waste through a better understanding of the role of dietary protein intake in key biological functions.
Pasture-based dairy production:
There is limited research and extension information available from the southeastern U.S. to assist organic dairy producers to make informed decisions regarding forage selections and their relationships with cattle productivity. This research seeks to address this need through a long-term goal of developing practical, research-based recommendations for organic forage management to maximize herd productivity, and profitability in the southeastern U.S. This knowledge will be used to develop decision-making tools and educational materials that will be disseminated through a series of extension programs.