Feed efficiency and the microbiota of the alimentary tract

There is considerable variation in the efficiency that cattle convert feed for maintenance and product (body weight gain, milk, and conceptus). Both intake and gain are polygenic traits and to better understand factors that contribute to variation in feed efficiency more defined phenotypes are needed. Several studies have associated differences in the microbiota of the alimentary tract between obese and non-obese rodents, obese and non-obese humans, and energy metabolism in birds. These finding suggest that there is a potential relationship between the microbiota of the alimentary tract and feed efficiency in beef cattle. Considerable research has been conducted on the rumen microbiota, but less consideration has been given to the rest of the alimentary tract. Changes in the microbial community of the rumen-reticulum complex with changes in diet as well as across species of ruminants have been documented. The observed diversity in the microbiota has been limited to those organisms that can be cultured. The rumen is an anaerobic environment and many of the strict anaerobes are difficult to culture in vitro. The concern has been that relative differences in microbial species may have been a function of the ease of culturing some species in vitro and that the ability to grow in vitro is not indicative of their relative proportion of the rumen-reticulum microbiota. Using next-generation sequencing provides a tool to estimate the makeup of the microbiota by identifying bacteria by their DNA sequence rather than enumerating them through culture techniques. Two studies were conducted as part of the Agriculture and Food Research Initiative Competitive Grant 2011-68004-30214 from the USDA National Institute of Food and Agriculture to determine the relationships between the microbiota and feed efficiency. The results of this research have been reported by Myer et al. and Freetly.