Abstract
The objective of this study was to determine the effects of in ovo injection of high-yield broiler embryos with nicotinamide riboside (NR) on pectoralis major muscle (PMM) development, growth, and gene expression. Fertilized Cobb 700 broiler eggs were randomly assigned to one of four treatments within a 2 × 2 factorial design. Factor 1 consisted of NR dose (DOS) with eggs receiving 0 or 2.5 mM NR. Factor 2 consisted of injection location (LOC), with treatments injected into either the yolk sac or albumen. At day 10 of incubation, 100 μL of the assigned NR dose was injected into the yolk sac of the developing embryo and chicks were euthanized within 24 h of hatching. Chick PMM and individual fiber morphometrics, and expression of genes associated with cell cycle progression were analyzed. There were DOS × LOC interactions for hatched chick PM weight and length (P < 0.04). When NR was injected into the albumen, PMM weight decreased (P < 0.05); when NR was injected into the yolk, PMM weight increased (P < 0.05). Pectoralis major length was not affected (P > 0.05) when NR was injected into the albumen but was increased (P < 0.05) when NR was injected into the yolk. There was a DOS × LOC interaction (P = 0.04) for muscle fiber density and tended to be a DOS × LOC interaction (P = 0.07) for muscle fiber CSA. Pectoralis major muscle fiber density was not affected when NR was injected into the albumen (P > 0.05), but density increased when NR was injected into the yolk (P < 0.05). There were DOS × LOC interactions for hatched chick COXII, cyclin D, and SIRT1 expression (P ≤ 0.04), which may indicate NR improves skeletal muscle development and growth by enhancing myoblast proliferation during embryonic development.