The objective of this study was to determine the effects of in ovo injection of nicotinamide riboside (NR) on broiler embryonic myogenesis....Chicks injected with NR had greater Pectoralis major muscle weight and length...Injecting developing embryos at day 10 of incubation increased hatched chick Pectoralis major muscle morphometrics, which were partly because of the NR catalyzed increase in muscle fiber density.