Notes on Azomite (AZM) and IPS Effects in Broiler Diets: Pellet Manufacture, Digestibility, and 21-d Performance

Overview

• Study evaluating the effect of Azomite™ (AZM) dacitic tuff breccia on pellet mill performance, broiler growth, and apparent ileal amino acid digestibility (AIAAD) when fed with inorganic phosphate sources (IPS) that vary between dicalcium phosphate (DCP) and tricalcium phosphate (TCP).
• Hypotheses:
  • AZM could reduce pellet mill energy use by lubricating the die and/or by promoting die scouring, while keeping production rate constant.
  • Diets containing AZM, especially with different IPS, would influence pellet quality, energy use, broiler performance (0–21 days), and AIAAD.
• Design summary:
  • 2 (IPS: DCP, TCP) × 2 (AZM inclusion: 0 vs 0.25%) factorial across 4 days of production in a Latin Square design.
  • Subjects: 320 one-day-old Ross 708 male broilers assigned to 32 pens (10 birds per pen).
  • Measurements: pellet mill motor load, production rate, hot pellet temperature, pellet durability, particle size, phytase activity, mineral content (Ca, P, etc.), 0–21 day feed intake (FI), body weight (BW) gain, FCR, and ileal amino acid digestibility (AIAAD) via titanium dioxide (TiO2) marker.
• Key outcomes reported:
  • TCP vs DCP: higher production rate, lower pellet mill motor load, and differences in pellet quality; AZM effects varied by IPS.
  • AZM (0.25%) generally decreased pellet mill motor load by about 1% overall and altered certain AIAAD and amino acid digestibilities, more notably with DCP.
  • AIAAD: cysteine digestibility increased with AZM in DCP diets; lysine, isoleucine, and valine showed tendencies to increase with AZM in DCP diets.
  • Broiler performance (0–21 d): no significant change in live weight gain (LWG); FCR increased slightly with AZM in DCP diets; TCP + AZM tended to improve FCR relative to DCP + AZM.
• Practical takeaway:
  • AZM can reduce pellet mill motor load and potentially reduce reliance on IPS, with some improvements to amino acid digestibility under certain IPS conditions, though growth performance over 21 days did not show clear improvement.

Experimental Design and Treatments

• Experimental setup:
  • 2 IPS options (DCP, TCP) × 2 AZM levels (0% vs 0.25%) in a Latin Square design across 4 manufacturing days.
  • Each treatment replicated within 4 days of production; one 454-kg batch per experimental unit.
• Animal and housing details:
  • 320 male broilers (Ross 708) allocated to 32 pens (8 replicates per treatment), 10 birds per pen.
  • Pen arrangement and blocking designed to minimize day-to-day variation.
• Diets and inclusion details:
  • Starter diets formulated to 90% of digestible amino acid requirements with corn, soybean meal, DDGS, and added AZM where applicable (0.25% in AZM treatments).
  • Treatments differed by IPS source (DCP vs TCP) and AZM inclusion (0 vs 0.25%).
  • Phytase included; fixed fat addition (soy oil) post-mixing to mimic industry practice.
• Production and sampling design:
  • Feed manufactured at WVU pilot mill with a California Pellet Mill and 4.8 × 38 mm die.
  • Steam conditioning at ~276 kPa (38 psi); mash conditioned at 80 °C for 30 s with a 42% auger rate; ambient temperature controlled by producing on warm days to reduce variation.
  • Latin Square arrangement allowed each treatment to occur in different run orders per replication day.
• Sample collection and analyses:
  • Post-pelleting samples collected for nutrient analyses (Ca, P, phytic acid, crude protein) and phytase activity.
  • Pellets analyzed for durability with New Holmen Pellet Tester; particle size assessed with Ro-Tap sieve shaker.
  • A portion of crumbled feed sent for phytase activity; others analyzed for mineral contents.
  • A subset of pelleted samples used to measure hot pellet temperature during production (
    multiple measurements per replication).
• Ethical considerations:
  • All animal procedures approved by West Virginia University Animal Care and Use Committee.

Diet Formulation and Composition Details

• Diet formulation targets and ingredients:
  • Corn and soybean meal-based starter diets plus DDGS; formulated to meet ~90% of digestible amino acids requirements.
  • AZM substituted for corn at 0.25% where applicable.
• Table of formulated and analyzed nutrients (highlights):
  • ME: 3,000 kcal/kg for both DCP and TCP diets.
  • Crude protein: ~20.10–20.12% (analyses ~21.2–21.5% depending on treatment).
  • Total calcium: TCP diets higher than DCP diets (e.g., up to ~31.0% Ca in AZM-treated TCP).
  • Total phosphorus: TCP diets higher than DCP diets (up to ~18.1% P in AZM-treated TCP).
  • Nonphytate phosphorus: ~0.39–0.47% across treatments (slightly higher in some AZM/DCP combos).
  • Phytase activity: ~390–470 FTU/kg depending on treatment and day of manufacture.
• 1% fat addition and mineral premix:
  • Soy oil added at mixer (1.0%); remainder added post-pelleting.
  • Premix provided micronutrients and vitamins; phytase top-dressed at 1,000 FTU/kg.
• AOAC methods and nutrient analyses used for validation (Ca, P, phytic acid, crude protein, etc.).

Pellet Manufacture and Quality Measures

• Equipment and process specifics:
  • 40 HP CPM conditioner and pellet mill; 4.8 × 38 mm die; steam conditioned to target 80 °C for 30 s at 42% auger rate.
  • Hygieniser present but not activated; feed passed through during manufacturing.
• Key production metrics:
  • Production rate (MT/hr) and production rate (kg/min) measured during manufacture.
  • Pellet mill motor load recorded via PLC at target conditioning conditions.
  • Hot pellet temperature measured during extrusion; standardized data collected.
• Pellet quality indicators:
  • Pellet durability: measured with New Holmen Pellet Tester; results expressed as percent durability.
  • Particle size distribution: assessed with Ro-Tap Ro-Tap Shaker; mean geometric size recorded with standard deviation.
• Observed effects by IPS and AZM:
  • TCP diets increased production rate by ~2% versus DCP (P = 0.039).
  • Pellet mill motor load decreased by ~5% for TCP vs DCP (P < 0.001).
  • AZM inclusion reduced pellet mill motor load by ~1% (P < 0.001).
  • AZM increased pellet durability in DCP diets; TCP diets showed no change in durability with AZM (P < 0.001 for IPS effect; interaction for IPS × AZM on durability).
  • Hot pellet temperature increased with AZM in TCP diets but not in DCP (P = 0.019 for IPS × AZM interaction).
• Die scouring and lubrication hypotheses discussed:
  • TCP’s angular particles are more abrasive and may scour the die, increasing production rate and potentially lowering motor load.
  • AZM may provide lubrication (surface fractioning) and die scour, reducing frictional heat and preserving protein/AA conformation.
  • Interaction between IPS and AZM suggests AZM’s benefits are more evident with DCP than with TCP for some pellet quality measures.

Apparent Ileal Amino Acid Digestibility (AIAAD)

• Measurement method:
  • On day 21, ileal digesta collected from 4 birds per pen, pooled, freeze-dried, and analyzed for amino acids and TiO2 marker.
  • AIAAD calculated using TiO2 concentrations and AA/N concentrations:
  • Formula:
    ext{AIAAD}(
    ext{%) } = igg[1 - igg(rac{TDi}{TDO}igg)igg(rac{NO}{Ni}igg)igg] imes 100
    where
  • $TDi$ = TiO2 in diet (g/kg DM),
  • $TDO$ = TiO2 in ileal digesta (g/kg DM),
  • $Ni$ = nitrogen or amino acid in diet (g/kg DM),
  • $NO$ = nitrogen or amino acid in ileal digesta (g/kg DM).
• Main results:
  • IPS × AZM interaction for cysteine digestibility (P = 0.034): cysteine AIAAD increased in DCP + AZM vs DCP − AZM; TCP diets showed no AZM effect.
  • Lysine, valine, isoleucine: trend-level increases with AZM in DCP diets (lysine P = 0.058; isoleucine P = 0.070; valine P = 0.097).
  • Overall, TCP diets without AZM showed higher digestibility for some amino acids (glutamic acid, cysteine, lysine) compared with DCP without AZM (e.g., cysteine P = 0.042; lysine P = 0.041 for certain comparisons).
• Explanations offered:
  • Reduced exposure to fricitional heat due to AZM and/or die-scouring effect could preserve AA conformation, improving digestibility.
  • Maillard browning (heat + low moisture) can reduce AA digestibility, particularly for lysine; AZM’s lubricating/ scouring effects may minimize such damage.
  • Moisture effects: moisture around extrusion may mitigate lysine loss; reported literature indicates moisture above 15% can reduce lysine loss during extrusion-cooking.
• Additional context:
  • Authors propose natural microflora regulation and toxin interactions as potential in-feed effects of AZM that could indirectly influence digestion and digestibility, though mechanisms remain speculative.

Bird Performance (0–21 Days)

• Growth and feed efficiency outcomes:
  • No significant effect of IPS or AZM on 0–21 day LWG per bird (P > 0.05).
  • AZM increased FCR by 0.02 in DCP diets (P = 0.004): DCP without AZM vs DCP with AZM showed worse feed efficiency when AZM was included.
  • TCP diets showed a tendency toward better FCR with AZM inclusion compared with DCP + AZM (P = 0.008 for a contrast), suggesting some SSP (system) interaction favorable to AZM under TCP conditions.
• Feed intake (FI) observations:
  • A trend toward higher FI with AZM (P = 0.067), suggesting AZM could influence palatability or appetite under some IPS contexts.
• Performance interpretation:
  • While digestibility (AIAAD) improved for certain amino acids with AZM in DCP diets, this did not translate into improved 21-day growth performance under the conditions tested.
  • Authors suggest that a longer grow-out period might be needed to detect growth or efficiency benefits linked to improved amino acid digestibility.
• Practical implications:
  • AZM can modestly improve digestibility of specific amino acids in DCP diets, and may reduce energy demand of pelleting; however, it does not necessarily improve short-term growth performance in 21 days.

Statistical Design and Data Analysis Highlights

• Statistical framework:
  • Diets arranged in a 2 × 2 factorial design (IPS × AZM) across four manufacturing days using a Latin Square to control day effects.
  • Experimental unit for feed manufacturing: one 454-kg batch; for bird performance: cages with 10 birds each served as experimental units.
  • Mixed-model approaches (GLIMMIX in SAS) used for pellet-related responses and growth performance; Tukey’s test for post-hoc multiple comparisons; significance at P ≤ 0.05, trends at P ≤ 0.10.
• Key contrasts and interactions:
  • IPS × AZM interaction significant for pellet quality and hot pellet temperature (P < 0.001 and P = 0.019, respectively).
  • IPS × AZM interaction significant for AIAAD of cysteine (P = 0.034).
  • TCP diets without AZM vs with AZM showed differences in production rate, motor load, and pellet durability correlations.

Conclusions and Practical Implications

• Major conclusions drawn by the authors:
  • Pellet mill motor load decreased by 5% when comparing TCP to DCP diets, likely due to die scouring by the angular TCP particles.
  • AZM inclusion at 0.25% reduced pellet mill motor load by about 1% in diets containing either DCP or TCP.
  • AZM improved AIAAD for cysteine in DCP diets and tended to improve digestibility of lysine, isoleucine, and valine in DCP diets; effects were less pronounced in TCP diets.
  • Despite improvements in AIAAD and potential reductions in frictional heat, growth performance (0–21 d LWG) did not show a clear improvement; FCR worsened modestly in DCP + AZM versus DCP − AZM, while TCP + AZM tended to improve FCR relative to DCP + AZM.
• Practical applications and recommendations:
  • AZM can be used to reduce pellet mill energy consumption and potentially decrease reliance on IPS, with some improvements in amino acid digestibility under certain IPS conditions.
  • The benefits on growth performance may require longer grow-out periods to manifest; additional work is needed to confirm long-term effects and economic viability.
• Future research directions:
  • Explore longer grow-out periods (e.g., >42 days) to determine if AIAAD improvements translate into improved performance.
  • Investigate mechanisms of AZM interaction with intestinal microflora, toxins, and protein conformational changes under different moisture/temperature regimes during pelleting.
  • Refine AZM dosage and IPS combinations to maximize pellet quality and energy efficiency without compromising growth.

Ethical, Philosophical, or Practical Implications

• Ethical considerations:
  • All animal work conducted under approved institutional guidelines; welfare monitoring and humane endpoints implied by the study design.
• Practical considerations for industry:
  • AZM may offer a practical route to reduce energy consumption in pelleting and lessen dependence on IPS costs, particularly in TCP-dominated formulations.
  • The disentangling of digestibility improvements from growth performance requires careful cost-benefit analysis for producers.
• Environmental and safety considerations:
  • Reduction in IPS usage could align with environmental and sustainability goals by lowering phosphate excretion if digestibility and utilization improve.

Key Numerical References and Formulas (LaTeX)

• Digestibility formula used for AIAAD:
  ext{AIAAD}( ext{%}) = igg[1 - igg(rac{TDi}{TDO}igg)igg(rac{NO}{Ni}igg)igg] imes 100
  where
• $TDi$ = TiO2 in diet (g/kg DM)
• $TDO$ = TiO2 in ileal digesta (g/kg DM)
• $Ni$ = concentration of nitrogen or amino acid in diet (g/kg DM)
• $NO$ = concentration of nitrogen or amino acid in ileal digesta (g/kg DM)
• Growth performance metric:
  $ext{FCR} = \frac{ ext{Feed intake (kg)}}{ ext{Live weight gain (kg)}}$

Key Takeaways by Topic

• Pellet production and energy use:
  • TCP increases production rate and reduces motor load vs DCP, likely due to die-scouring properties.
  • AZM inclusion reduces motor load modestly, possibly via lubrication and die-surface coating effects.
• Pellet quality and temperature:
  • AZM enhances pellet durability of DCP diets but not TCP diets; AZM with TCP increases hot pellet temperature modestly.
• Amino acid digestibility and growth:
  • AZM improves cysteine AIAAD in DCP diets; possible trends for lysine, isoleucine, valine in DCP diets.
  • No significant improvement in 21-d LWG; some improvement in FCR with TCP + AZM vs DCP + AZM, but overall short-term growth not clearly enhanced.
• Practical takeaway for industry:
  • AZM can be used to reduce energy usage and manage die wear, with variable effects on digestibility and short-term growth; longer trials are needed to confirm production and economic benefits.

References and Related Works (selected from transcript)

• Boltz, T. P. et al. 2021. The effect of a dacitic tuff breccia (Azomite™) on pellet production rate and pellet quality (JAPR).
• Wamsley, K. G. S. et al. 2012. Inorganic feed phosphate effects on feed quality and manufacturing efficiency.
• Tillman, N. S. et al. 2020. Influence of AZM on pellet production rate and pellet quality.
• Pirzado, S. A. et al. 2020, 2021. Effects of AZM on growth performance and digestibility in broilers.
• Tan, C. G. et al. 2014. AZM supplementation effects in shrimp diets.
• Loar, R. E. II et al. 2014. Conditioning temperature and mixer-added fat on broiler performance and digestibility.
• Lamp, A. E. et al. 2015; 2020. Inorganic phosphate type and mineral digestibility in broilers.
• Boroojeni, F. G. et al. 2016. Effects of hydrothermal processing on nutrient availability and digestion in poultry.