Efficacy and safety of dietary N,N-dimethylglycine in broiler production

N,N-dimethylglycine (DMG), the dimethyl derivative of the amino acid glycine, is a naturally occurring intermediary metabolite in the choline to glycine metabolism. The molecule was first reported in 1943 and is currently used for a variety of applications, including the enhancement of athletic performances in both man and racing animals. With respect to its biological activities, DMG is for instance suggested to enhance oxygen utilisation and to posses non-enzymatic anti-oxidant properties. The studies described in this thesis aimed to evaluate DMG as a feed additive in chickens for fattening. In a pilot study, broilers were challenged with both cold stress and a high energy feed in order to incite broiler ascites syndrome. This metabolic disease results from an imbalance between oxygen requirement and supply, and is an important cause of financial losses and a major welfare issue in the modern broiler industry. A low dosage of dietary DMG effectively attenuated progression towards ascites. We hypothesize that this effect results from reduction in endothelial damage and dysfunction caused by plasma free fatty acids, which were substantially lowered by DMG supplementation. Furthermore, DMG improved nutrient digestibility and reduced nitrogen emission, which can be attributed to an emulsifying effect of DMG at the gut level. A subsequent trial revealed dose-dependent effects of dietary DMG on technical performance, carcass yield, oxidative stress parameters and broiler ascites syndrome. However, the nature and magnitude of the effects depended on fatty acid profile of the basal ration. Herein, effects were most pronounced when fed a diet rich in poly-unsaturated fatty acids. Generally, effects showed a linear relationship with dose, except for progression towards broiler ascites syndrome, which showed a quadratic relationship with dietary DMG content. Next, a series of efficacy trials were performed on farms at different European locations, using broiler strains and rearing conditions common to each region. Basal flock efficiency showed a wide range between trials; still, DMG systematically improved broiler performance. Finally, a safety and tolerance trial demonstrated a wide safety range of DMG in the target species. Moreover, DMG did not accumulate in consumer parts of broilers when included in diets at the recommended dosage, and bioaccumulation in meat at tenfold dosage did not exceed DMG content in for instance spinach. In conclusion, current investigations clearly demonstrate a wide applicability of DMG as a new feed additive in broiler production, in which both economic efficiency and environmental load as well as animal welfare is enhanced without compromising consumer safety.