Effects of primary calcium source on phytase efficiency in weaned piglets

Area of Science:

• Animal Nutrition
• Swine Physiology
• Digestive Physiology

Background:

• Calcium formate is proposed as an alternative to limestone in piglet diets to potentially lower stomach pH and enhance nutrient utilization.
• Understanding the impact of calcium source on mineral digestibility and enzyme efficacy is crucial for optimizing piglet diets.
• Phytase supplementation is a common strategy to improve phosphorus availability, but its interaction with calcium sources needs investigation.

Purpose of the Study:

• To test the hypothesis that calcium formate, compared to limestone, lowers dietary buffering capacity, reduces stomach pH, and improves phytase efficiency in piglets.
• To evaluate the effects of different calcium sources and phytase levels on calcium and phosphorus digestibility, blood parameters, and bone mineralization in weaned piglets.

Main Methods:

• An 18-day experiment involving 60 weaned boars fed 10 diets in a 5x2 factorial arrangement (5 treatments x 2 calcium sources: limestone vs. calcium formate).
• Dietary treatments included a positive control and four negative controls supplemented with varying phytase levels (0-3000 FYT/kg).
• Measurements included stomach pH, apparent ileal and total tract digestibility (AID, ATTD) of Ca and P, serum mineral concentrations, plasma inositol, and bone ash.

Main Results:

• Calcium formate diets did not affect stomach pH but increased Ca digestibility (AID +5.7%, ATTD +3.6%) and decreased P digestibility (AID -3.2%, ATTD -2.4%) compared to limestone.
• Increasing phytase levels linearly improved Ca and P digestibility, but phytase efficiency was lower in diets containing calcium formate.
• Positive control and higher phytase levels increased serum P and P retention, while only the positive control increased bone ash.

Conclusions:

• Replacing limestone with calcium formate in piglet diets increases Ca digestibility but reduces P digestibility and phytase efficacy, likely due to insoluble Ca-P-phytate complex formation.
• The hypothesis that calcium formate lowers stomach pH was not supported by the results.
• These findings underscore the importance of considering calcium source and its digestibility when formulating piglet diets, especially when using phytase.