Improving Broiler Performance and Digestibility Through Feed Enzymes and Production Rate Aids Utilized in Pelleting.

Improving Broiler Performance and Digestibility Through Feed Enzymes and Production Rate Aids Utilized in Pelleting. Kristina Marie Bowen Enzymes are commonly added to poultry diets to improve performance parameters that may in turn decrease costs to the producer. Pellet mill production rate aids are also utilized to reduce feed manufacture costs and may have additional benefits when fed to poultry that are associated with the increase in production rate. Past research has shown that Azomite (AZM) can increase pellet mill production rate in diets that include inorganic phosphate sources (IPS) of dicalcium phosphate (DCP) or tricalcium phosphate (TCP). In the first experiment the authors hypothesized that if production rate were held constant then pellet mill energy consumption would decrease for diets that contained AZM due in part to a lubricating and/or pellet die scouring effect. This could decrease dietary amino acid exposure to frictional heat and pressure within the pellet die, maintaining amino acid conformation, and amino acid digestibility. The objective was to determine the effect of AZM (0.25%) in diets with DCP and TCP on pellet mill energy consumption, subsequent live bird performance, and apparent ileal amino acid digestibility (AIAAD) when fed to broiler chicks for 21 days. Feed was manufactured in a 2 (IPS) x 2 (AZM inclusion) factorial across 4 days in a Latin square design. Post manufacture, three hundred twenty-day-old Hubbard × Ross 708 males (0.038kg  0.0014 SD) were allocated by weight to 8 replicates per treatment, 10 chicks per raised wire cage, in a randomized complete block design. Dietary treatments were arranged in a 2 x 2 factorial: DCP with or without AZM and TCP with or without AZM. On d21 ileal contents were collected for amino acid and titanium dioxide analysis. Statistical analysis (Glimmix, SAS 9.4) was performed on the factorial arrangement of treatments and multiple comparisons were made of all treatments with post-hoc test by Tukey’s. Pellet mill motor load decreased by 5% in diets containing TCP compared to DCP (P<0.001), and 1% when AZM was included (P<0.001). An IPS × AZM inclusion interaction occurred for pellet durability (P<0.001) and hot pellet temperature (P<0.05). Pellet durability was increased in diets containing DCP when AZM was included, while TCP were unaffected. Hot pellet temperature increased for TCP diets with AZM, whereas DCP diets did not change. Apparent ileal digestibility of lysine, cysteine, and isoleucine were affected by the interaction of IPS and AZM inclusion (P<0.05), demonstrating that processing with AZM increased digestibility in DCP diets but not TCP diets. Despite increased amino acid digestibility, AZM in DCP diets increased feed conversion ratio (FCR) by 0.02 (1.284 vs 1.303, P<0.05). However, AZM did not affect FCR in TCP diets (1.294 vs 1.285, P>0.05). Decreased pellet mill motor load that resulted from AZM inclusion suggests that feed was subjected to less frictional heat and/or pressure within the pellet die. This reduction in frictional heat and pressure likely preserved amino acid conformation, but the improvement was not translated to growth efficiency. Mixer added phytases must retain efficacy post conditioning and pelleting. Heat from saturated steam and friction upon pellet die extrusion may deactivate phytases. In addition, increasing phytase concentrations in diets may increase nutrient release from phytate. In this second experiment the objective was to assess two commercially available phytases that were concentrated at 500, 1,000, or 2,000 FTU/kg in mixed mash post steam conditioning at 82°C for 30 sec and extrusion through a 4.8 x 38mm pellet die on 0 to 44d Ross 708 male broiler performance, mineral digestibility, and tibia ash responses. The phytase sources were both derived from E. coli and expressed in Trichoderma Reesei, (QB) and expressed in Pichia pastoris, (OP). A 3 (Phytase level) × 2 (Phytase source) factorial arrangement of treatments within a randomized complete block design was utilized. A positive control and negative control diet based on available phosphorus (P) and total calcium (Ca) were also manufactured and analyzed within a multiple comparison. Crumbled and pelleted diets were fed to 8 replicate pens of 30 chicks in three phases. Live performance, d20 and d44 tibia ash, d44 hot boneless, skinless breast weight and mineral digestibility were measured. Day 44 live weight gain (LWG) and both d20 and d44 tibia measures increased for all phytase concentrations relative to the negative control (P<0.05). Phytase sources did not differ in their effect on live performance or breast yield with the exception of live weight at 20 days where birds provided with OP were heavier (P<0.05). Calcium digestibility was increased for birds fed OP relative to QB (P<0.05). Phosphorus digestibility increased when either source was fed and was higher with OP compared to QB at 500 FTU/kg (P<0.05). Day 20 tibia ash percentage increased for 1,000 and 2,000 FTU/kg concentrations for both phytase sources while mg tibia ash increased with all levels of both sources compared to the control (P<0.05). Mg tibia ash was higher with OP compared to QB at the 500 FTU level (P<0.05). Both phytase sources increased d44 percent and mg tibia ash relative to the negative control with OP exceeding QB at 1,000 and 2,000 FTU for tibia ash percent and at 2,000 FTU for mg tibia ash (P<0.05). The assessed phytase sources showed similar benefit to live performance and breast yield but varied in response to tibia ash and mineral digestibility at different concentrations.