The purpose of this research is to elucidate the role of amino acids for milk protein synthesis in lactating dairy cows in order to more accurately incorporate their supply into cost-efficient rations to maximize protein output and minimize nitrogen loss. This project is part of the Food4Foodure research program.
The gross efficiency with which protein is captured in milk by the dairy cow is generally low, resulting in excess output of urinary and fecal nitrogen into the environment. The relatively low average efficiency of nitrogen capture offers a great area for improvement. Optimizing the dairy cow's use of dietary protein would decrease associated cost for producers and minimize the environmental impact of dairy farms, thus improving the sustainability and public acceptance of dairy farming. Although a costly ingredient, there is great potential for manipulation of amino acid supply in dairy cow rations to optimize use and increase output of milk and protein yields.
There is an abundance of literature indicating the effects of protein and energy supply on milk yield and composition. However, the way in which essential amino acids (EAA) stimulate protein synthesis at the whole-body level and also the cellular level have yet to be fully characterized. Intermediary metabolism within the ruminant can greatly alter the true amino acid supply that is available to the mammary gland for milk protein synthesis. The rate of protein synthesis at the tissue level is regulated by precursor supply, with cellular machinery being responsive to specific nutrients and hormones. Recent work has implicated signalling pathways involved in mRNA translation in the response of milk protein yield to EAA and energy, but the details of their activity and function are far from complete. Detailed characterization of the molecular pathways responsible for milk protein synthesis would greatly affect the potential to improve animal efficiency all the way down to the cellular level.
The aim of this research is to gain a more comprehensive understanding of how supply of milk protein substrates – amino acid and energy – alter the metabolic response in the dairy cow and facilitate protein synthesis at the cellular level to maximize milk protein output and animal efficiency. Insight into the details of protein synthesis within the lactating animal will allow for more targeted nutrient delivery and opportunities to minimize the costs and the environmental footprint of the dairy industry.
Kelly Nichols obtained her BSc in Animal Biology and MSc in Dairy Nutrition & Metabolism at the University of Guelph in Guelph, Ontario, Canada. This PhD project falls under the research goal of ‘more-with-less by efficient nutrient use’ within the Feed4Foodure research program.