Interpretive Summary: Metabolic studies reveal that ruminal microbes of adult steers do not degrade rumen-protected or unprotected l-citrulline
By: Anne Wallace
The amino acids L-citrulline (Cit) and L-glutamine (Gln), although non-essential, play important roles biochemically in the gut. Animal studies suggest oral supplementation of these amino acids in feed benefits gut integrity and health. However, Cit and Gln are absorbed in the small bowel, and may be degraded by rumen microbes before they can be absorbed.
Rumen microbes extensively degrade amino acids, however their effect on Cit and Gln are not well studied. In this January 2020 Journal of Animal Science study, researchers evaluated the degradation of dietary Cit and Gln by rumen microbes in adult Angus × Hereford steers. Their goal was to determine whether rumen-protective processing of these amino acids are needed. They hypothesized that adult steers ingesting rumen-protected Cit and Gln would have increased blood levels over steers ingesting non-protected Cit and Gln.
Both in vivo and in vitro studies were conducted. Results unexpectedly found that rumen microbes did not significantly degrade the non-protected Cit and Gln over the protected forms, as evidenced by blood level concentrations.
Overall, the results of this study suggest that Cit and Gln do not need to be administered in a rumen-protected form to adult Angus × Hereford steers. Additionally, Cit and Gln were not degraded significantly in the rumen of steers, suggesting that not all amino acids may be degraded extensively win the rumen, as was previously thought. More studies looking at the need for rumen-protection in other amino acids may be warranted.