402 Awardee Talk - Efficiency of nutrient use in ruminants: Current understanding and emerging questions

Abstract

Abstract Because feed costs represent a large proportion of total costs for ruminant production systems, improving the efficiency of nutrient utilization is an important goal for improving profitability and sustainability. Research on nutrient utilization in ruminants dates back to the 1800s when the first nutrient balance experiments were conducted. The concept of efficiency is complex and can be expressed in many ways. Different approaches should be used when examining economic efficiency vs. biological efficiency, growing vs. mature animals, or answering research questions vs. use in a production setting. Additionally, animal efficiency can be examined at different scales of complexity including animal, tissue, cell, or molecular levels, and at the level of total feed, feedstuff, or specific nutrient. Some of the facets that have been shown to be associated with animal efficiency include body composition, feed intake and digestion, heat production, blood metabolites and hormones, tissue mass, cell proliferation, protein turnover, ion transport, mitochondrial function, mRNA or protein expression profiles, and genomic polymorphisms within the animal, and composition and diversity of the gastrointestinal microbiome. Large amounts of information are being generated at the genomic, transcriptomic, and proteomic levels which will add to our knowledge about what factors are associated with animal efficiency. Nutrients, such as amino acids, play an important role to meet requirements for maintenance and production and have many other physiological functions regulating metabolism in the animal. There is potential to develop nutrient supplementation, or feeding, strategies to alter metabolism and improve nutrient utilization. Future research is needed to better define the mechanisms influencing efficiency of utilization of individual nutrients, rather than feed dry matter, and to develop management, nutritional, or animal breeding approaches to improve animal efficiency through altering whole animal, tissue, cellular, and molecular facets known to be associated with differences in animal efficiency.