Abstract #1

# 1
Effects of dietary fatty acids on nutrient digestion, energy partitioning, and milk fat synthesis.
A. L. Lock*1, J. de Souza1, 1Michigan State University, East Lansing, MI.

Our understanding of fatty acid (FA) digestion and metabolism in dairy cows has advanced significantly in the last few decades. We now recognize that FA, both of dietary and rumen origin, can have different and specific effects on feed intake, rumen metabolism, small intestine digestibility, milk component synthesis in the mammary gland, and energy partitioning between the mammary gland and other tissues. We will present research focusing on specific FA and how dairy cows respond differently to combinations of FA. Recent research has highlighted differences in intestinal digestibility among palmitic acid (C16:0), stearic acid (C18:0), and oleic (cis-9 C18:1) acids, which impacts the amount and profile of absorbed FA available for metabolic purposes. C16:0, C18:0, and cis-9 C18:1 usually comprise the majority of FA present in milk fat and adipose tissue of dairy cows. In addition, these FA comprise the major FA in a wide range of commercially available fat supplements. While these FA have different functions in metabolism, they may also interact with each other by competitive or complementary mechanisms under different physiological conditions. In the mammary gland, milk FA are derived from 2 sources: <16 carbon FA from de novo synthesis in the mammary gland and >16 carbon FA originating from extraction from plasma. 16-carbon FA originate from either de novo or preformed sources. Milk lipid synthesis in the mammary gland is dependent upon the simultaneous supply of short/medium-chain FA and long-chain FA. C16:0 has a higher preference as a substrate to start triglyceride synthesis than C18:0 or cis-9 C18:1. Also, if the amount of preformed FA surpasses the capacity of the mammary gland, these might be redirected to other tissues (e.g., adipose tissue) altering energy partitioning. In the future, the opportunity and challenge will be to continue to improve our understanding of how and which FA affect nutrient digestion, energy partitioning, and milk systhesis in lactating dairy cows and effectively apply this knowledge in the feeding and management of todays high producing dairy cows.

Key Words: energy partitioning, fatty acids, milk fat synthesis

Speaker Bio
I am an associate professor in the Department of Animal Science at Michigan State University. Originally from a dairy farm in the southwest of the United Kingdom, I received my PhD from the University of Nottingham and completed a post-doc at that institution as well as at Cornell University. I had a research and teaching appointment at the University of Vermont from 2006 to 2009 before moving to my current research and extension appointment at Michigan State University in the fall of 2009. My research and extension programs focus on both dairy production and human nutrition and health, and the interface between these two disciplines. The central theme is fatty acid digestion and metabolism in the dairy cow and the impact of bioactive fatty acids on animal production and human health. Current efforts concern the effect of diet on the production of biohydrogenation intermediates in the rumen, dietary strategies for maximizing milk fat synthesis, applying this knowledge to improve our ability to troubleshoot on farm issues related to milk fat depression, fatty acid absorption in the small intestine, fat supplementation opportunities, and the potential for omega-3 fatty acids to promote dairy cattle metabolism and health. The impact of milk and dairy products on human health, in particular the role of milk fat is also of special interest.