Interpretive Summary: Addition of dietary methionine but not dietary taurine or methyl donors/receivers to grain-free diet increases postprandial homocysteine concentrations in adult dogs

By: Dr. Emily Taylor

Grain-free diets have been popular in the pet industry for over a decade; however, recently, they have been associated with canine dilated cardiomyopathy (DCM). Research has linked DCM with a deficient of taurine in cats, which may be a possible cause for DCM in large breed dogs.  Methionine and cysteine, amino acid precursors to taurine synthesis in dogs, is very low in ingredients used to replace grains. To date, there has been no research evaluating the plasma and whole blood taurine concentration of dogs when feeding grain-free diets supplemented with nutrients involved in the biosynthesis of taurine. Therefore, the objective of the current study was to investigate the effects of supplementing a complete grain-free dry dog food with either methionine (MET), taurine (TAU), or methyl donors (choline) and methyl receivers (creatine and carnitine; CCC) on postprandial AA concentrations. 

Nine post-meal blood samples were collected on eight healthy beagle dogs fed one of three treatment diets or the control grain-free diet (CON). These samples were collected at 15, 30, 60, 90, 120, 180, 240, 300, and 360 min. Methionine concentration from 30 to 360 min and homocysteine concentration from 60 to 360 min were greater in dogs fed MET when compared to the CON, TAU, and CCC. Taurine concentrations were greater over time than dogs fed the CON; however, they did not differ from dogs fed MET and CCC. In addition, most AAs were significantly elevated at six h post-meal when compared to fasted samples across all treatments. 

Additional methionine supplementation on top of a complete and balanced grain-free dog diet led to increased plasma and whole blood methionine and plasma homocysteine concentration; however, plasma taurine concentration was not different from the control. In addition, supplementation of creatine, carnitine, and choline in grain-free diets may play a role in sparing the methionine requirement without increasing homocysteine concentration. Researchers believe that supplementing these nutrients could also aid in the treatment of disease that causes metabolic or oxidative stress, including cardiac disease in dogs.

This article is available in the Journal of Animal Science.