In ovo feeding of nicotinamide riboside affects broiler pectoralis major muscle development

The objective of this study was to examine the effect of nicotinamide riboside (NR) on pectoralis major muscle (PM) development and growth. Fertilized Cobb 500 broiler eggs (N = 156; average weight of 70.3 g) were ordered by weight, and within each four egg strata, eggs were randomly assigned to treatments within a 2 × 2 factorial arrangement. Factor 1 consisted of NR treatment with eggs receiving 0 or 250 mM NR. Factor 2 consisted of injection location, with treatments injected into either the yolk sac or albumen. Eggs were incubated at a temperature of 37 °C and a relative humidity of 40 ± 2% for the first 18 d of incubation and humidity was increased to 60 ± 2 °C for the final 3 d. On day 10 of incubation, eggs were injected in their designated location with 100 µL of 0.9% sterile saline containing the assigned NR dose. Chicks were hatched, euthanized, and morphometric measurements of the body and left PM were collected. The left PM was also analyzed for muscle fiber cross-sectional area (CSA) and density. There were no treatment × location or main effects for all body morphometric measurements (P > 0.07), except chest width of chicks from eggs injected in the yolk were wider (P = 0.01) than chicks from eggs injected in the albumen. There were only treatment × location interactions for PM weight and length (P < 0.01). When NR was injected into the albumen, PM weight did not differ (P = 0.09); however, when NR was injected into the yolk sac, PM weight increased (P < 0.01). When NR was injected into both locations, PM length increased (P < 0.01), but increased to a greater extent when NR was injected into the yolk sac. There were treatment main effects for PM width and depth (P < 0.01), with NR injected chicks having PM with greater width and depth. There were no treatment × location or main effects for PM fiber CSA (P > 0.06). There was a treatment × location interaction (P < 0.01) for fiber density. When NR was injected into the albumen, fiber density did not differ (P = 0.09); however, when NR was injected into the yolk sac, fiber density increased (P < 0.01). Injecting NR into the yolk sac of the developing embryo at day 10 of incubation increased PM development which was due to an increase in muscle density.