The objective of this study was to determine the effect of nicotinamide riboside (NR) concentration on avian embryonic myogenesis. Fertilized broiler eggs (n=60; Cobb 500) were randomly assigned to 1 of 4 treatments: 0.0, 2.5, 5.0, or 10.0 mM NR in sterile saline. At day 10 of incubation, 100ml of treatment solution was injected into the egg yolk. Eggs were incubated at 37 ± 3°C and a relative humidity of 40 ± 2%. At day 19 of incubation, embryos were euthanized by prolonged exposure to CO2 gas and decapitation. Measurements including: embryo weight; crown-rump length; chest circumference (CC); and left Pectoralis major (PM) weight, length, width, and depth were collected. There was no treatment effect for embryo weight (P=0.99). Embryos treated with 10.0 mM NR had longer crown-rump measurements than all other treatments (PP>0.36). Embryos from the 5.0 and 10.0 mM treatments had larger CC and PM weight and width than 0.0 mM embryos (PP>0.38) from each other. Embryos injected with 2.5 mM of NR did not differ in CC or PM weight and width when compared to other treatments (P>0.06). All NR treatments had longer PMmuscles than the saline treatment (PP0.41). Embryos treated with 10.0 and 2.5 mM NR had thicker PM muscles than saline injected embryos (PP=0.58). Embryos injected with 5.0 mM NR did not differ in PMthickness compared to other treatments (P>0.06). Injecting up to 5.0 mM NR into the yolk of the developing embryo had no effect on body weight but increased PM measures; thus, indicating NR influenced avian myogenesis.