Interpretive Summary: Effects of guanidinoacetic acid supplementation on nitrogen retention and methionine flux in cattle
By Anne Zinn
Creatine stores high-energy phosphate bonds in muscle and is synthesized in the liver through methylation of guanidinoacetic acid; supplementation of guanidinoacetic acid may therefore increase methyl group requirements, which may affect methyl group utilization. A study recently published in the Journal of Animal Science evaluated the metabolic responses of growing cattle to postruminal supplementation of guanidinoacetic acid, in a model where methionine was deficient, with and without methionine supplementation. The research team from Kansas State University hypothesized that guanidinoacetic acid supplementation to Metdeficient cattle would induce a methyl group deficiency and that methionine supplementation would reduce the methyl group deficiency. Additionally, it was thought that guanidinoacetic acid might improve nitrogen retention when methionine was supplemented.
Overall, results of the present study demonstrated that guanidinoacetic acid supplementation may improve protein deposition when methyl group sources are supplemented concurrently or provided in adequate amounts by the basal diet. Additionally, increases in plasma creatine in association with no increase in urinary excretion of guanidinoacetic acid in response to postruminal supplementation of guanidinoacetic acid suggests that guanidinoacetic acid can be an effective way to increase creatine availability to cattle. It is worth noting that supplementation of guanidinoacetic acid did not significantly increase methylation reactions, which suggests methylation reactions other than guanidinoacetic acid synthesis may have been reduced by guanidinoacetic acid supplementation. The administration of guanidinoacetic acid, when methyl groups are not limiting, could potentially improve lean tissue deposition and cattle growth, but further research is necessary to fully understand the nature and extent of these alterations following guanidinoacetic acid provision to cattle.
The full paper can be found on the Journal of Animal Science webpage.