The impact of dietary calcium content on phosphorus absorption and retention in growing pigs is enhanced by dietary microbial phytase supplementation
2023
Hu, Y.X. | Hendriks, W.H. | Van Baal, J. | Resink, J.W. | Rodehutscord, M. | Van Krimpen, M.M. | Bikker, P.
Sixty growing male pigs were used to test the hypothesis that high dietary Ca content reduces P absorption to a greater extent in microbial phytase-supplemented diets via reducing inositol phosphate (IP) degradation and enhancing P precipitation. Pigs were equally allotted over diets with three Ca contents 2.0, 5.8 and 9.6 g/kg with or without microbial phytase (0 vs. 500 FTU/kg) in a 2×3 factorial arrangement. Faeces and urine were collected at the end of the 21-day experimental period. Subsequently, pigs were euthanized and digesta quantitatively collected from different gastrointestinal tract (GIT) segments. Increasing dietary Ca content reduced apparent P digestibility in all GIT segments posterior to the stomach (P<0.001), with greater effect in phytase-supplemented diets in the distal small intestine (P interaction=0.007) and total tract (P interaction=0.023). Nonetheless, increasing dietary Ca to 5.8 g/kg enhanced P retention, but only in phytase supplemented diets. Ileal IP6 degradation increased with phytase (P<0.001) but decreased with increasing dietary Ca content (P=0.014). Proportion of IP esters in total IP (ΣIP) indicated that IP6/ΣIP was increased while IP4/ΣIP and IP3/ΣIP were reduced with increasing dietary Ca content, also with a greater impact in phytase-supplemented diets (P interaction=0.025, 0.018 and 0.009, respectively). In all GIT segments, P solubility was increased with phytase (P<0.001) and tended to be reduced with dietary Ca content (P<0.096). Measurements in GIT segments showed that increasing dietary Ca content reduced intestinal apparent P digestibility via reducing IP degradation and enhancing P precipitation, with a greater impact in phytase-supplemented diets due to reduced IP degradation.
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