Can we completely exclude inorganic phosphorus in broiler diets with higher doses of phytase?
The global market price of inorganic phosphorus has increased significantly due to regional and international supply chain disruptions with outbreak of COVID-19. Therefore, it is timely to revisit dietary strategies to reduce use of inorganic phosphorus in feed formulation to minimise the economic impact of increasing phosphorus prices. A large volume of scientific publication has demonstrated that addition of inorganic phosphorus can be significantly reduced via use of very high doses of phytase with application of recommended matrix. However, so far, commercial practice in application of phosphorus matrix with supplementation of phytase has been extremely conservative, particularly in Asia-Pacific region. Some of the rationales for such a conservative phosphorus matrix includes (1) variation in phytate-P content in feed ingredients; (2) use of book value phytate-P content rather than using measured phytate-P content; (3) doubt in the phosphorus matrix provided by enzyme suppliers; and (4) potential loss of enzyme activity in the final feed due to scale errors, and/or excess heat treatment during the pelleting process. One of the frequently asked questions from Asia-Pacific nutritionists is that with a high dose of phytase can they completely exclude inorganic phosphorus in diets for broilers without compromising performance and leg problems. With the current market price of inorganic phosphorus, feed millers can save a significant amount of money if the full potential phosphorus matrix is applied with an efficient phytase. In this issue, a recently accepted paper will be discussed in light of abovementioned issues, which was conducted by one of the large broiler integrators in South East Asia. The title is "Effect of graded levels of an enhanced E. Coli phytase with step-wise reduction of supplemental inorganic phosphate on growth performance of broilers fed corn-soy diet" authored by Poernama et al. (2020. Brazilian Journal of Poultry Science, In Press).
Figure 1. Inclusion of MCP (kg/MT feed) in each phase diet (left) and total MCP use from starter to finisher (right) in corn-soy based experimental diets with gradual application of enhanced E. coli phytase with full avP matrix (Quantum Blue, AB Vista; re-drawn from Poernama et al., 2020).
Figure 2. Body weight gain (left) and feed conversion ratio (right) in broilers fed corn-soy based experimental diets with gradual application of enhanced E. coli phytase (Quantum Blue, AB Vista) and avP matrix. ^denotes significantly lower, while *denotes significantly higher than PC (re-drawn from Poernama et al., 2020).
An important matter to be considered when phytase superdosing is implemented as a dietary strategy to reduce inclusion of inorganic phosphorus is that commercial phytases in the market have a significant difference in their ability to hydrolyse phytate phosphorus. As can be seen in Figure 3, the efficiency of phytase to hydrolyse phytate phosphorus becomes even more important when a superdosing strategy is applied.
Figure 3. Available phosphorus (avP) release with increasing dose of different phytase (From matrix published by commercial companies).
With increasing inorganic phosphorus prices, nutritionists could consider increasing the use of meat and bone meal (MBM) as a source of phosphorus, rather than applying full avP matrix; however, such an approach should be undertaken with careful consideration of the variability in Ca and digestible amino acid contents of MBM. For example, MBM contains around 10% Ca with +/- 20% variation which depends on the ingredients used during the particular batch of the rendering process. If a nutritionist were to increase the use of MBM from 3% to 6% in a diet, the Ca content in the diet could vary by +/- 0.12% (6% MBM at 10% Ca = 0.6% Ca; +/- 20% variation = 0.12%). What this means is a broiler starter diet formulated to 0.9% Ca can contain up to 1.02% Ca, which is a risk factor that could reduce growth rate and feed efficiency and also the efficacy of phytase.
In conclusion, the results provide an answer for the question whether inorganic phosphorus supplementation can completely be excluded with superdosing of an efficient phytase. It is demonstrated that significant reduction or even complete exclusion of inorganic phosphorus in the diets for broilers with supplementation of 1000 – 1500 FTU Quantum Blue with full avP matrix application supported optimal growth performance of broilers. Considering increasing market price of inorganic phosphorus, a significant opportunity exists for feed millers and integrators to reduce diet cost and also to reduce phosphorus pollution from animal production by adapting superdosing of an efficient phytase as a dietary strategy. AB Vista provides NIR service for instant measurement of phytate phosphorus content in ingredients and final feed and also provide onsite phytase test kit to provide confidence in use of avP matrix and to minimise the risk of lower than target phytase activity in final feed.