Effects of commercial in ovo injection of 25-hydroxycholecalciferol on bone development and mineralization in male and female broilers

Improved bone development and mineralization in broilers have been attributed to the use of 25-hydroxylcholecalceiferol [25(OH)D-3] as a dietary supplement. In this study, effects of the in ovo injection of 25(OH)D-3 delivered in commercial diluent on 18 d of incubation (doi) on subsequent bone development and mineralization in male and female Ross x Ross 708 broilers were investigated. The variables investigated included bone mineral density and breaking strength, bone ash concentration, and calcium and phosphorus bone ash concentrations. In a single-stage incubator, with 6 treatments on each of the 10 tray levels, a total of 2,400 experimental broiler hatching eggs were evenly and randomly set. Eggs were treatment-injected and transferred to corresponding hatching baskets on 18 doi. Experimental treatment groups were those that received 0.2, 0.6, 1.8, or 5.4 mu g of 25(OH)D-3 that were delivered in 100 mu L of commercial diluent. Noninjected and diluent-injected controls were also included. on 21 doi, chicks were pulled and placed in corresponding floor pens, and on each of d 0, 14, and 28 posthatch (poh), 2 birds of each sex from each pen were randomly selected for necropsy and extraction of both of their tibia bones. Bones from the right leg were subjected to mineral density analysis and those from the left leg were used to determine breaking strength and residual bone ash concentration. Furthermore, ash calcium and phosphorus concentrations on d 14 and 28 poh were determined. There was a treatment x sex x age interaction for bone breaking strength. Bone breaking strength in male birds on d 28 poh was higher in the 0.20, 0.60, and 1.80 mu g of 25(OH)D-3-injected treatment groups than in the diluent-injected control group. In conclusion, although the in ovo injection of 25(OH)D-3 had no positive effect on the bone development of Ross x Ross 708 broilers through d 28 poh compared with noninjected controls, it may provide a benefit to those subjected to an injection of commercial vaccine diluent.