Calcium plays a significant role in phosphorus (P) utilization, which is important for broiler production performance. Therefore, optimizing available calcium levels, relative to phosphorus, can contribute to better diet results. Maximizing phytase performance begins with an optimized calcium matrix.
An animal’s calcium requirement is determined by an optimal calcium/ phosphorus ratio, which is defined by the poultry breeding company.
When creating a diet to maximize production profits, nutritionists have paid less attention to calcium (Ca), a cheap ingredient often extracted from limestone. The role of limestone in feed processing and formulation has traditionally been to serve as a carrier or filler material. Its role in phosphorus utilization has been greatly undervalued.
The link between Ca and P
The goal in feed formulation is often to meet an animal’s minimum requirement for available phosphorus using the break-point method, also called the requirement estimate, which aims to reduce phosphorus excretion. An animal’s calcium requirement is determined by an optimal calcium/ phosphorus ratio, which is defined by the poultry breeding company.
Maintaining the calcium/phosphorus (Ca/P) ratio demands a careful balancing act because there are complex molecular reactions involved. It is important to note that it is the ratio, not necessarily the calcium level itself, which has the potential to affect performance.
Too high a Ca/P ratio will lead to a decrease in performance. When phosphorus only meets the minimum requirement for growth, calcium will chelate with phytate in the small intestine making the phosphate from phytate inaccessible to the bird. The result could be a possible phosphorus deficiency and subsequent reduced digestibility and performance.
High levels of calcium will also increase the pH in the proventriculus and gizzard, which will also negatively impact digestion. Excess calcium will have less impact when phosphorus levels meet or exceed an animal’s minimal requirement.
However, the animal will excrete excess calcium through the urine, increasing the energy cost of maintaining the Ca/P balance.
Phytase is an enzyme commonly used in the diet to break down phytate, releasing digestible phosphorus. Ideally the phytase should be highly active in the upper gut at low pH, so it will break down the phytate quickly and before it can bind with calcium. It is possible to maintain a balance of phosphorus and calcium in the presence of phytase.
Calcium matrix
It is well known that calcium levels, as well as the particle size of the Ca source (a factor insolubility) can impact phytase efficacy. For example, in one study, adding just 0.5 per cent calcium from limestone reduced phosphorus digestibility by 63 per cent in the absence of phytase, by 26 per cent in a diet supplemented with a 3-phytase and by 41 per cent with a 6-phytase.
The impact of Calcium on phytase efficacy is directly related to phytase activity in the upper part of the gastrointestinal tract (GIT) where phytate is more soluble because of the low pH.
A phytase that is highly active at the low pH in the upper GIT will break down phytate more quickly and completely, thus less phytate remains to be bound by the excess Ca in the small intestine, which reduces the negative impact of excess calcium. In this way, availability of Ca is also increased by phytase.
For that reason, a defined calcium contribution number, or matrix value, would be desired in order to maintain proper Ca/P balance when phytase is used in the diet.
Without it, a calcium/ phosphorus imbalance may occur, thereby negatively impacting digestion and performance. As each phytase has a unique pH profile, calcium matrix values should be defined for each individual phytase.
Contact Jaguza Support