Phytase Supplementation in Poultry: Unlocking Phosphorus Availability

Phytase is one of the few feed additives that saves money and reduces environmental impact at the same time. I don’t say that lightly. Most feed additives are a cost, with the hope of a return. Phytase is different it directly reduces the need for expensive inorganic phosphorus.

The Phytate Problem

About 60-70% of the phosphorus in plant-based feed ingredients is bound as phytate (phytic acid). Phytate phosphorus is largely unavailable to poultry because chickens don’t produce enough phytase enzyme in their digestive tract.

A typical corn-soy diet contains 0.25-0.30% total phosphorus, but only 0.10-0.12% is available. The rest passes through the bird and ends up in the litter. That wasted phosphorus is an economic loss and a runoff issue.

Phytate also binds other minerals (calcium, zinc, iron) and can reduce their availability. And it has been shown to reduce protein digestibility by forming complexes with amino acids.

What Phytase Does

Phytase is an enzyme that breaks down phytate, releasing the phosphorus for absorption. Adding 500 FTU (phytase units) per kg of feed typically releases 0.10-0.12% of phytate phosphorus, making it available to the bird.

In practical terms, adding 500 FTU/kg of phytase allows me to reduce dicalcium phosphate in the feed by about 1.0-1.5%. At current prices, that saves $1.50-3.00 per ton of feed. The phytase itself costs about $0.50-0.80 per ton of feed. Net saving: $1.00-2.20 per ton.

Types of Phytase

There are three main phytase types:

Bacterial phytase (E. coli derived) is the most common type used in poultry feed. It has high activity at the low pH of the proventriculus and gizzard, which is where most phytate degradation should occur. Most commercial products contain 2,500-5,000 FTU/g.

Fungal phytase (from Aspergillus niger) has a broader pH range but is less active at low pH. It’s still used in some applications but has been largely replaced by bacterial phytase in poultry.

Yeast phytase is a newer option that’s gaining interest. It’s less heat-stable than bacterial phytase but has some advantages in liquid application.

The key specification to check is heat stability. Some phytase products survive pelleting at 80°C, and others lose 50%+ activity. I pay close attention to the manufacturer’s heat stability data.

Optimizing Phytase Response

The matrix value how much phosphorus phytase replaces varies with several factors:

Calcium level. High calcium inhibits phytase activity. I keep calcium at 0.65-0.75% in broiler grower feeds when using phytase. Above 0.85% calcium, phytase effectiveness drops significantly. The calcium to available phosphorus ratio should be 2.0-2.2:1.

Vitamin D3. Adequate vitamin D3 (3,000-4,000 IU/kg) improves the response to phytase by enhancing phosphorus absorption in the gut.

Particle size. Fine grinding of the feed reduces phytase effectiveness because phytase has less time to work on smaller particles. A moderate particle size (coarse grind) gives the enzyme more time to hydrolyze phytate.

Superdosing Phytase

There’s growing interest in “superdosing” phytase at 1,500-3,000 FTU/kg. This goes beyond phosphorus release and has been shown to:

• Improve amino acid digestibility by 3-5%
• Increase calcium and zinc availability
• Reduce the anti-nutritional effects of phytate
• Improve growth performance independently of phosphorus

I’ve tested superdosing in three commercial trials. The results are inconsistent. Two trials showed 1-2 point FCR improvement. One showed no response. The cost of superdosing adds $1.50-2.00 per ton, and the breakeven is about 2 points of FCR improvement.

For now, I use standard dosing (500 FTU/kg) in all formulations because the economics are clear. I only superdose for antibiotic-free or high-value programs where every performance advantage matters.

Practical Application

When adding phytase to a formulation, I:

1. Reduce available phosphorus by 0.10-0.12% (for 500 FTU/kg)
2. Reduce calcium by 0.08-0.10% (to maintain Ca:avP ratio)
3. Adjust the calcium:phosphorus ratio to 2.0-2.2:1
4. Increase vitamin D3 by 500 IU/kg to support the higher phosphorus absorption

I also add 5-10% overage of phytase activity to account for storage losses and mixing variability. A premix containing 500,000 FTU of phytase per kg, added at 1 kg per ton of feed, delivers 500 FTU/kg plus about 50 FTU/kg overage.

Carbon Footprint

Phytase is genuinely good for the environment. Each ton of feed with phytase uses about 5-7 kg less dicalcium phosphate. Dicalcium phosphate production is energy-intensive, requiring mining, processing, and transportation of phosphate rock. The carbon footprint of a ton of broiler feed drops by roughly 5-8 kg CO2 equivalent when phytase replaces dicalcium phosphate.

For a feed mill producing 200,000 tons annually, that’s a reduction of 1,000-1,600 metric tons of CO2 per year. Not bad for an additive that also saves money.