Maternal zinc supplementation enhanced skeletal muscle development through increasing protein synthesis and inhibiting protein degradation of their offspring.

Previous studies proved that maternal zinc supplementation had no significant effect on body weight (BW) of the offspring, but the effects of maternal zinc supplementation on skeletal muscle development of the offspring are poorly defined. Here, broiler breeders at 46 weeks old were allocated into three treatments with six replicates of 40 hens each and fed with diets supplemented with zinc from ZnSO4 at 0 (group Zn/C), 50 mg/kg (group Zn/L), and 300 mg/kg (group Zn/H) respectively for 6 weeks. The male offspring from each dietary treatment were divided into seven cages of ten birds each and fed with a commercial diet with supplemental zinc from ZnSO4 at 20 mg/kg. Results indicated that with the increase of zinc supplementation in hen's diet, the zinc levels were significantly elevated (P < 0.05) in the egg yolk. Compared with the control group, the breast muscle yield and muscle fiber width were significantly (P < 0.05) higher and larger in the broilers from group Zn/H at 2 and 5 weeks post-hatch, the phosphorylation of AKT at serine 473 residue (Ser 473), mammalian target of rapamycin (mTOR) at serine 2448 residue (Ser 2448), and FOXO at serine 256 residue (Ser 256) in skeletal muscles of the birds from various dietary treatments at two different age post-hatch were significantly (P < 0.05) increased. The phosphorylation of mTOR and FOXO was usually related to protein synthesis and degradation. In conclusion, supplemental zinc into the breeders' diet could increase protein synthesis and decrease protein degradation, which, in turn, enhance breast muscle development of the offspring.