In feed formulations, approximately 60-75% of phytate-P comes from the protein sources while the remainder comes from the cereal source (Table 1).
The determination of P matrix values for phytase enzymes are usually estimated using corn/soy diets. Therefore, if soybean meal is replaced with an alternative protein source like sunflower seed or rapeseed meal, and corn is replaced by wheat and barley, does this have an impact on the P matrix values of OptiPhos®?
A recent research trial carried out at Wageningen University investigated the effect of OptiPhos® at single, double or triple dose on the degradation of phytate-P from different protein sources and cereals using an in vitro digestibility model, mimicking the function of the stomach/gizzard and the small intestine. The results are shown in Table 2.
* Total P release by phytase at a certain FTU minus total P release in control diet
** Improvement in P release / total phytate-P in feed material
All doses were significantly different compared to the control (p < 0.05)
The trial concluded that:
- Adding a single dose of OptiPhos® to the diet significantly increased the amount of total P release (mg/g feed material), demonstrating that OptiPhos® is already a very powerful phytase even when included at a single dose.
- Of the three protein sources, the improvement (%) in phytate-P degradation was highest for sunflower seed meal (86%) and rapeseed meal (70%) compared to soybean meal (59%) with a triple dose of OptiPhos®.
- Of the three cereals, phytate-P breakdown was highest in corn (76%) with a triple dose of OptiPhos®.
Based on this data, OptiPhos® will release:
- 0.10 - 0.15 g/kg more P from a corn/soy diet compared to a wheat/soy diet.
- 0.25 - 0.30 g/kg more P when 5% sunflower seed meal or rapeseed meal is incorporated in the feed to replace soybean meal.
- 0.40 - 0.50 g/kg more P when 10% sunflower seed meal or rapeseed meal is incorporated in the feed to replace soybean meal.
Conclusion
- The P matrix values of OptiPhos® calculated using corn/soy diets may be higher when using alternative protein sources (with higher phytate-P levels) in feed formulations.
- They phytate-P levels in sunflower seed and rapeseed meal are not only higher than in soybean meal, but the phytate-P is more easily degradable by OptiPhos®, leading to more P release.
