Profitably reduce calcium and phosphorus in broilers with Hy-D® and enzymes

Modern poultry production faces a unique set of challenges and opportunities. With advancements in genetics, broilers are growing faster, depositing more muscle mass, and reaching market weight at an earlier age. However, this accelerated growth demands precise nutritional support, particularly in the areas of calcium (Ca) and phosphorus (P) nutrition, which are essential for bone development, metabolic function, and overall health.

Historically, nutritionists relied on total calcium values and fixed Ca:P ratios in feed formulations. But current research shows that this approach falls short in meeting the nuanced requirements of the modern broiler. A re-evaluation of mineral strategies—integrating digestible calcium, enhanced vitamin D metabolism, and advanced enzyme technologies—is necessary to unlock performance gains, ensure skeletal health, and reduce costs and environmental impact.

The complexity of calcium utilization

Calcium is a central component of skeletal tissue and plays a role in nerve conduction, muscle contraction, and enzyme regulation. However, its bioavailability is affected by numerous factors:

• Source of calcium: Most commercial diets use limestone due to cost-efficiency. Yet, limestone varies greatly in particle size, solubility, and digestibility, depending on its origin and processing.
• Digestive pH: High calcium levels can raise the pH in the proventriculus and gizzard, reducing protease activity and forming insoluble complexes with other minerals such as phosphorus and iron. This tamponing effect not only decreases mineral availability but also disrupts gut microbiota.
• Endogenous regulation: Calcium homeostasis involves hormonal regulators like parathyroid hormone (PTH), calcitonin, and active vitamin D (1,25-(OH)₂D₃). These govern absorption, resorption, and deposition of calcium, adding metabolic complexity to nutritional decisions.

The variability of limestone quality was clearly demonstrated in Brazilian studies where over 25 samples showed significant differences in calcium content, solubility, and particle size—factors that failed to correlate strongly with digestibility. This underscores the importance of characterizing the specific limestone source used in formulation, rather than relying on standard tables or assumptions.

Phosphorus: the hidden challenge

Phosphorus is a vital component of bone and cellular metabolism, but in typical plant-based diets, much of it is bound in phytate. Without phytase, this bound phosphorus is poorly available, leading to suboptimal utilization and high excretion rates.

The advent of phytase enzymes revolutionized phosphorus nutrition, significantly improving P availability and reducing environmental phosphorus load. But calcium can interfere with phytase efficacy, especially in high-Ca environments where insoluble calcium-phytate complexes form. Therefore, optimizing phosphorus usage is inextricably linked to calcium management and enzyme supplementation.

From total to digestible calcium

A major shift in poultry nutrition is the move from total to digestible calcium. Unlike total calcium, digestible Ca accounts for the actual amount that can be absorbed and used by the bird. This shift aligns with how phosphorus has long been treated in diet formulation.

Digestible Ca formulation requires:

• Accurate assessment of limestone solubility under gastrointestinal conditions,
• Understanding age-specific requirements, as younger birds have limited HCl production and a more sensitive balance of mineral absorption,
• Consideration of interactions with vitamin D and other dietary components like phytase and fiber.

Formulating digestible Ca can help avoid excess mineral inclusion, reduce formulation costs, and improve nutrient utilization.

Vitamin D and the role of 25-OH-D₃ (Hy-D®)

Vitamin D is essential for calcium and phosphorus absorption. In broilers, it exists in several forms:

1. Vitamin D₃ (cholecalciferol): Traditionally added to premixes.
2. 25-hydroxycholecalciferol (25-OH-D₃), commercially known as Hy-D®: A more bioavailable form that bypasses hepatic conversion.

Hy-D® is particularly beneficial in intensive production systems, where birds are raised without sunlight and rely solely on dietary sources of vitamin D. Studies have shown that 25-OH-D₃ is:

• More efficiently absorbed, as it binds with greater affinity to intestinal receptors,
• More rapidly converted to its active form 1-25-oh-D3 in the kidneys,
• In the presence of phytase, it synergistically enhances calcium and phosphorus utilization, bone strength, and growth performance (Figure 1)

The Hy-D® improvement factor: practical application

Based on the information above, the Hy-D Improvement Factor was formulated. The Hy-D® Improvement Factor is a practical concept designed to quantify the extent to which dietary calcium and phosphorus levels can be reduced when Hy-D® is used in combination with phytase. This approach was evaluated in three independent trials involving over 1,200 Cobb broilers, assessing performance outcomes across varying levels of mineral and phytase supplementation.

Key outcomes:

• Improved feed conversion ratio (FCR) by 2–5%,
• Increased bone ash and tibia strength,
• Higher circulating levels of 25-OH-D₃, indicating improved vitamin D status,
• Positive effect even under reduced dietary Ca and P levels.

Regression analysis from these trials enabled the quantification of nutrient equivalencies provided by Hy-D®:

• Available Phosphorus equivalency: 0.08%
• Total Calcium equivalency: 0.16–0.20%

These equivalencies allow nutritionists to confidently reduce mineral levels in the diet while maintaining or improving animal health.

Economic and environmental impacts

A simulation of broiler starter, grower and finisher diets using Hy-D®improvement factor revealed that:

Economic:

• EUR 2/ton average feed cost savings, depending on formulation phase,
• Reduced reliance on high-inclusion mineral ingredients, freeing up formulation space.

Environmental:

• Up to 9% reduction in mineral-related environmental footprint, due to lower excretion of undigested phosphorus and calcium.

These benefits align with sustainability goals, offering producers a path to reduce input waste and environmental impact while improving ROI.

Conclusion: a paradigm shift in mineral nutrition

Optimizing calcium and phosphorus nutrition in broilers is no longer a question of "more is better." With deeper understanding of digestible calcium, the synergistic effect of phytase and Hy-D®, and the use of data-driven formulation tools like the Hy-D® Improvement Factor, poultry nutritionists can:

• Enhance skeletal strength and reduce deformities,
• Improve feed efficiency and growth,
• Reduce feed costs and environmental load.

In an industry where margins are narrow and pressures are high, such innovations offer a clear path to precision, profitability, and progress in broiler nutrition.