Interpretive Summary: Residual feed intake in beef cattle is associated with differences in protein turnover and nutrient transporters in ruminal epithelium.
By: Anne Wallace
A better understanding of how to maximize feed efficiency is needed to increase profits in beef cattle production. Residual feed intake (RFI) is a standard method to calculate cattle feed efficiency, but RFI can be affected by a variety of factors, including rumen-related function.
Researchers compared protein turnover and nutrient transporters in the ruminal epithelium of high RFI (least feed efficient) and low RFI (most feed efficient) cattle in this study published in the May 2019 Journal of Animal Science. Their goal was to look for associations between these cellular factors and feed efficiency.
Red Angus cattle (149 animals) were fed a finishing diet for 70 days. After calculating RFI, six high-RFI and six low-RFI animals were selected and compared. Blood samples were collected to measure insulin levels. Ruminal epithelial samples were also taken to look at the mammalian target of rapamycin (MTOR) signaling proteins. These proteins are involved in various cellular functions affecting feed efficiency, which include, regulation of insulin, glucose, and amino acid transport.
No difference was noted in blood insulin levels of high RFI and low RFI animals. However, there were significant differences in cellular synthesis and protein degradation in high versus low RFI animals. For example, low RFI animals had a lower abundance of some cellular synthesis proteins (i.e. MTOR, p-MTOR, RPS6KB1, EIF2A, EEF2K, AKT1, RPS6KB) and higher abundance of others (i.e., p-EEF2K, p-EEF2K: EEF2K, and p-EIF2A: EIF2A) compared to high RFI animals. Low RFI animals were additionally found to have a significantly lower abundance of some protein degraders (i.e., UBA1, NEDD4, and STUB1).
Although more in-depth studies are needed to understand better how these results may be useful for increasing feed efficiency in cattle. The data does support an association between cellular differences in ruminal epithelium protein turnover, nutrient transporters, and feed efficiency (in low and high RFI Red Angus steer). Further studies to better understand these cellular functions may maximize cattle feed efficiency, e.g., by altering the effectiveness of volatile fatty acid metabolism, are warranted.
To view the article, visit the Journal of Animal Science.