Research being carried out at the University of Illinois and funded by AB Vista will significantly improve the accuracy of calcium provision in growing pigs by generating much-needed standardised or true total tract digestibility (STTD or TTTD) values for calcium across a range of common feed ingredients.

Dr Carrie Walk, AB Vista's Senior Research Manager, explained: "The aim is to achieve the same level of precision for calcium when formulating diets as is possible for phosphorus.

"We formulate using digestibility values for the majority of the important – and expensive – nutrients in the diet, such as phosphorus and amino acids but that data is currently not available for calcium in growing pigs."

The study will determine digestibility values both with and without the addition of a phytase, since any reduction in phytate-calcium binding through phytase use will increase calcium availability, leading to potential oversupply.

Dr Walk added: "Although considered a relatively inexpensive nutrient, the implications of calcium oversupply are significant. Even marginally high levels of dietary calcium have been shown to increase gastric pH and reduce the digestibility of two of the most expensive nutrients, protein and phosphorus."

The initial phase of the project, which is being led by the University's Professor Hans Stein, used canola meal as the primary source of calcium. The trials generated calcium endogenous loss values of 0.160g per kg dry matter intake (DMI) and 0.189g per kg DMI for untreated and phytase-treated diets, respectively. The corresponding average calcium TTTD values for canola meal of 46.6 per cent and 70.3 per cent, respectively.

Professor Stein explained: "Unless these endogenous losses are taken into account by using TTTD values during diet formulation, calcium digestibility will be under-estimated and subsequently over-supplied."

Caroline Gonzalez-Vega is a PhD candidate in Dr Stein's laboratory who has conducted much of the work on calcium digestibility.

She said: "The research has also demonstrated that TTTD values for calcium are not affected by the calcium level in the diet, indicating that the resulting figures would be additive in diet formulation calculations.

"The long term goal is to establish the requirement for digestible calcium for all groups of pigs. By doing so, we will be able to formulate diets in the future based on the requirement for both digestible phosphorus and digestible calcium."

The next phase of the research is to establish calcium TTTD values for a wide range of commonly used plant- and animal-based feed ingredients.

January 2015