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Interpretive Summary: Increased microbial phytase increased phytate destruction, plasma inositol, and feed efficiency of weanling pigs, but reduced dietary calcium and phosphorus did not affect gastric pH or fecal score and reduced growth performance and bone ash   

By: Dr. Emily Taylor

Due to stress during the post-weaning period, morbidity and mortality can be significantly increased. These stressors can be environmental, nutritional, physiological, and immunological changes. Therefore, the objectives of the current study were to evaluate if reducing dietary Ca and P would reduce gastric pH and diarrhea in weanling pigs, as well as establishing any adverse effects on pig growth performance due to low Ca and P. Authors hypothesize that any adverse effects from reduced Ca and P may be mitigated by the addition of phytase in the diets. Two phases consisted of eight corn-soybean meal-based diets containing two control diets with 100 or 50% of the Ca and P requirement, and six in which 500, 2,000, or 16,000 units of phytase/kg feed were added. 

During phase 1, the reduction in Ca and P did not reduce gastric pH or fecal score; however, pigs ed the 50% diets had reduced average daily gain (ADG) and average daily feed intake (AFI). In both the 50% and 100& requirement diets, phytase above 500 FTU increased gain:feed ratio (G:F) and tended to reduce gastric pH. Data averaged from all phases was shown to reduce ADG, ADFI, concentrations of inositol phosphate esters (IP) in the colon, and bone ash in pigs fed 50% diets. Phytase did not affect bone ash or most blood metabolites; although, concentrations of IP in the colon decreased and plasma inositol increased with the addition of phytase. Moreover, pigs fed 100% diets saw a linear increase in G:F and plasma inositol as phytase level increased, with IP in the colon linearly decreased. 

In conclusion, reducing Ca and P in diets for weanling pigs did not influence gastric pH or fecal score but compromised growth performance and bone ash. The inclusion of high doses of phytase in the diets formulated to be adequate in Ca and P improved pigs' growth performance. The authors suggest this was likely a result of phytate degradation and increased inositol release and absorption.

This article is available in the Journal of Animal Science.