Protein Source and Nutrient Density in the Diets of Male Broilers from 8 to 21 Days of Age: Effects on Tibia Dimension, Breaking Strength, and Mineral Density

The effects of supplemental protein source, and amino acid (AA) and apparent metabolizable energy (AME) densities in the diets of broilers on their growth performance and intestinal development were reported in companion studies. The effects of protein source, and AA and AME densities on the tibias of male Ross × Ross 708 broiler chicks were investigated in the current study. A completely randomized block design with a 2 × 2 × 2 factorial arrangement of treatments was applied (10 blocks, 8 treatments/block, 14 chicks/pen). Diets fed from 8 to 21 days of age (d) were formulated to contain two protein sources [high inclusion of distiller’s dried grains with solubles diet (hDDGS) or high inclusion of meat and bone meal diet (hMBM)], two AA densities (moderate or high) and two AME densities (moderate or high). Tibias from 2 chicks/pen at 21 d were sampled. Chicks fed a high AA diet exhibited longer tibias than did chicks fed a moderate AA diet. Chicks fed hDDGS diets with a high AME density exhibited larger tibia circumferences as compared to those fed hMBM diets with a high AME density. Dietary treatment did not affect tibia breaking strength, ash content, or calcium, phosphorus, potassium, zinc, manganese, and magnesium concentrations in the tibia. Because feeding chicks high AME diets increased their BW, the weights of their tibia, and tibial calcium and phosphorus weights relative to BW were decreased. In birds fed high AA diets, the feeding of hMBM diets improved tibia breaking strength relative to BW when compared to the feeding of hDDGS diets. In conclusion, either hDDGS or hMBM diets can be fed to male broilers from 8 to 21 d without affecting mineral deposition in their tibias. In addition, high AME diets may improve broiler BW without affecting tibia strength.