Digestible calcium equivalency of phytase and nutrient utilization of broiler chickens fed graded levels of limestone or phytase during the starter phase.

The current study aimed to quantify the digestible calcium (Ca) equivalency of a new phytase (HiPhorius) in broiler chickens. A total of 1,152 male Cobb 500 broiler chickens were used in an experiment in which 8 diets consisting of graded levels of Ca supplied with limestone or graded levels of the phytase were fed. The 8 dietary treatments were based on a corn-soybean meal diet containing 5.1 g/kg of Ca and 5.1 g/kg of phosphorus (P) as negative control (NC); the NC + 1.3, 2.6, or 3.9 g/kg of Ca from limestone; and the NC + 500, 1,000, 2,000, or 4,000 FYT/kg of phytase. Birds were fed the experimental diets for 3 d (from d 7 to 10) or 14 d (from d 7 to 21) to determine apparent ileal digestibility (AID) and apparent total tract retention (ATTR) of dry matter (DM), CP, Ca, and P. In the 10-day-old birds, increasing the levels of Ca decreased the AID of P and Ca (linear, P < 0.05). Increasing the levels of phytase quadratically improved (P < 0.05) the AID of Ca and P. The AID of DM and CP in the younger birds quadratically increased (P < 0.05) as the levels of Ca increased. There were linear and quadratic effects (P < 0.05) of increasing phytase level for the AID of DM and a linear effect (P < 0.05) for the AID of CP. In the 21-day-old birds, increasing Ca levels resulted in a linear decrease (P < 0.05) in the AID of CP and P, and a quadratic decrease (P < 0.05) in the ATTR of CP. Increasing phytase levels linearly and quadratically (P < 0.05) improved the AID and ATTR of CP, P, and the ATTR of Ca. The analyzed phytase activity in the diets supplemented with phytase ranged from 1,520 to 7,661 FYT/kg. The digestible Ca equivalence for dietary phytase at 1,520 to 7,661 FYT/kg ranged from 1.55 to 2.02 g/kg in the 10-day-old birds fed for 3 d and from 0.52 to 0.64 g/kg in 21-day-old birds fed for 14 d. The results showed the reduction in Ca level that could be accommodated by phytase supplementation, which is markedly different between the younger and older birds. Feeding duration influenced the impact of phytase supplementation on Ca and P digestibility, with better efficacy of phytase observed in the 10-day-old birds fed for 3 d. Also, the results showed the extra-phosphoric effects of phytase on the utilization of other essential nutrients such as protein and Ca.

Energy value of dry fat and stabilised rice bran for broiler chickens.

1. The ileal digestible energy (IDE), metabolisable energy (ME) and nitrogen-corrected ME (MEn) of dry fat (DF) and stabilised rice bran (SRB) were determined in two experiments with broiler chickens using the regression method.2. Chickens were fed a common broiler starter diet from d 0 to 17 and experimental diets from d 17 to 22 post hatching. Three diets were prepared; a maize-soybean meal reference diet (RD) and two test diets containing either DF at 50 or 100 g/kg replacement (Experiment 1) or SRB at 100 or 200 g/kg replacement (Experiment 2) of the energy-contributing ingredients in the RD. In each experiment, 192 chickens were randomly allocated to one of three dietary treatments in a randomised complete block design, comprising eight replicate cages with eight birds per cage.3. In Experiment 1, the IDE, ME and MEn linearly increased (P < 0.001) with increasing DF concentrations, while in Experiment 2, the IDE, ME and MEn of the diets were not affected by dietary supplemental SRB. The regression-derived IDE concentration for DF and SRB were 25.30 and 14.88 MJ/kg DM, respectively. The respective ME and MEn estimates (MJ/kg DM) were 25.32 and 24.78 for DF; 14.38 and 13.36 for SRB.4. In conclusion, the current data showed that broiler chickens utilised between 77% and 79% and 68% to 76% of the gross energy (GE) in DF and SRB, respectively, and this suggested a strong potential for these ingredients as dietary energy sources for broiler chickens.