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 (Turnbaugh et al., 2006), obese and nonobese humans (Ley et al., 2006), and energy metabolism in birds (Torok et al., 2008 and Stanley et al., 2013). 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
