Prenatal nutritional manipulation by in ovo enrichment influences bone structure, composition, and mechanical properties

The objective of this study was to examine the effect of embryonic nutritional enrichment on the development and properties of broiler leg bones (tibia and femur) from the prenatal period until maturity. To accomplish the objective, 300 eggs were divided into 2 groups: a noninjected group (control) and a group injected in ovo with a solution containing minerals, vitamins, and carbohydrates (enriched). Tibia and femur from both legs were harvested from chicks on embryonic days 19 (E19) and 21 (E21) and d 3, 7, 14, 28, and 54 posthatch (n = 8). The bones were mechanically tested (stiffness, maximal load, and work to fracture) and scanned in a micro-computed tomography (mu CT) scanner to examine the structural properties of the cortical [cortical area, medullary area, cortical thickness, and maximal moment of inertia (I-max)] and trabecular (bone volume percent, trabecular thickness, and trabecular number) areas. To examine bone mineralization, bone mineral density (BMD) of the cortical area was obtained from the mu CT scans, and bones were analyzed for the ash and mineral content. The results showed improved mechanical properties of the enriched group between E19 and d 3 and on d 14 (P < 0.05). Differences in cortical morphology were noted between E19 and d 14 as the enriched group had greater medullary area on E19 (femur), reduced medullary area on E21 (both bones), greater femoral cortical area on d 3, and greater I-max of both bones on d 14 (P < 0.05). The major differences in bone trabecular architecture were that the enriched group had greater bone volume percent and trabecular thickness in the tibia on d 7 and the femur on d 28 (P < 0.05). The pattern of mineralization between E19 and d 54 showed improved mineralization in the enriched group on E19 whereas on d 3 and 7, the control group showed a mineralization advantage, and on d 28 and 54, the enriched group showed again greater mineralization (P < 0.05). In summary, this study demonstrated that in ovo enrichment affects multiple bone properties pre- and postnatally and showed that avian embryos are a good model for studying the effect of embryonic nutrition on natal and postnatal development. Most importantly, the enrichment led to improved mechanical properties until d 14 (roughly third of the lifespan of the bird), a big advantage for the young broiler. Additionally, the improved mineralization and trabecular architecture on d 28 and 54 indicate a potential long-term effect of altering embryonic nutrition.