LAUSR

The objective of the current study was to compare the effects of dietary enzymes and nutrient restriction on performance and bone mineralization in birds fed wheat- or sorghum-based diets. A total of 720 d-old male broiler chicks were randomly allocated to 8 treatments, with 6 replicates per treatment and 15 birds per replicate. Birds were reared in floor pens from 0 to 35 d. The study used a 2 × 4 factorial arrangement with 2 grains (sorghum or wheat) and 4 diets: positive control (no enzyme and ME, digestible Lys, Ca, and P sufficient, negative control (NC; no enzyme and reduced ME [-100 kcal/kg], digestible AA [-2%], Ca [-0.12 percentage points], and available P [-0.18 percentage points in the starter phase and -0.22 percentage points in the grower phase]), NC + nonstarch polysaccharide-degrading enzymes + phytase (500 phytase units [FTU]; NCCP), and NC + phytase (1,000 FTU; NCP). From 0 to 35 d, birds fed wheat-based diets had greater G:F (4.5%), BW gain (9.2%), breast meat yield (6.8%), and tibia ash (2.0%) compared with birds fed sorghum-based diets. Across grain types, the NCCP treatment improved BW gain ( < 0.001), feed intake ( < 0.001), G:F ( < 0.05), and livability ( < 0.001) compared with the NC treatment. Birds fed NCP had greater BW gain ( < 0.001), feed intake ( < 0.001), G:F ( < 0.001), and livability ( < 0.001) compared with birds fed NC. Birds fed the NCP diet had greater BW gain ( < 0.001), toe ash ( < 0.01), and tibia ash ( < 0.001) compared with birds fed the NCCP diet. There was a grain × diet interaction for feed intake ( < 0.01), BW gain ( < 0.001), tibia ash ( < 0.01), and tibia breaking strength ( < 0.05). The influence of enzymes was more pronounced in sorghum-based diets than in wheat-based diets. Birds fed wheat-based diets had greater ileal digestibility of His, Met, Val, Phe, Ile, Leu, Trp, Glu, Pro, Ala, Tyr, and Cys compared with those fed sorghum-based diets ( < 0.05). Across grain types, NCP had greater apparent ileal digestibility of Met, Lys, Ser, Pro, Gly, and Cys than NC ( < 0.05). The results suggest that wheat is superior to sorghum for broilers, as expected, but that enzyme supplementation has the capability to restore the compromised bird performance due to feeding sorghum. In addition, compared with nonstarch polysaccharide-degrading enzymes and phytase (500 FTU/kg feed) added in concert, phytase supplemented at 1,000 FTU/kg resulted in a further improvement of some of the performance and bone mineralization parameters in male broilers fed sorghum-based diets.