Effects of increasing concentrations of an Escherichia coli phytase on the apparent ileal digestibility of amino acids and the apparent total tract digestibility of energy and nutrients in corn-soybean meal diets fed to growing pigs1

Abstract

An experiment was conducted to test the hypothesis that inclusion of increasing concentrations of an Escherichia coli phytase to a corn-soybean meal (SBM) diet results in improved digestibility of DM, GE, CP, NDF, ADF, macrominerals, microminerals, and AA. Twenty-four growing barrows (initial BW: 37.0 ± 1.4 kg) were equipped with a T-cannula in the distal ileum and placed individually in metabolism crates, and allotted to a 2-period switch-back design with 6 diets and 4 replicate pigs per diet in each period. The positive control diet was a corn-SBM diet that contained limestone and dicalcium phosphate to meet the requirement for standardized total tract digestible (STTD) P and Ca (0.31% STTD P and 0.70% Ca). A negative control diet that was similar to the positive control diet, with the exception that no dicalcium phosphate was used, was also formulated, and this diet contained 0.16% STTD P and 0.43% Ca. Four additional diets were formulated by adding 500, 1,000, 2,000, or 4,000 units of microbial phytase (FTU) to the negative control diet. Each period lasted 14 d. Fecal and urine samples were collected from the feed provided from days 6 to 11 of each period following 5 d of adaptation to the diets. Ileal digesta were collected for 8 h on days 13 and 14. Results indicated that addition of the E. coli phytase to the negative control diet tended to quadratically improve the apparent ileal digestibility of Phe (P = 0.086) and Asp (P = 0.054), and linearly increased (P < 0.05) the apparent total tract digestibility (ATTD) of ADF, K, and Fe. Microbial phytase also quadratically increased (P < 0.05) the ATTD of NDF and Mg, and linearly and quadratically increased (P < 0.05) the ATTD and retention of Ca and P. However, no effects of the phytase on ATTD of GE or the concentration of DE were observed. In conclusion, the increased absorption of several minerals including Ca, P, K, Mg, and Fe that was observed as increasing concentrations of an E. coli phytase was added to a corn-SBM meal diet indicates that the dietary provision of these minerals may be reduced if phytase is fed.

Effects of microbial phytase on mucin synthesis, gastric protein hydrolysis, and degradation of phytate along the gastrointestinal tract of growing pigs1

“…The negative effect of phytase on the ATTD of GE that was observed in this experiment is in agreement with a recent meta-analysis for effects of microbial phytase on ATTD of GE (Torres-Pitarch et al, 2017). However, results of some studies also indicated that there was no effect of phytase on the ATTD of GE (Zeng et al, 2016;She et al, 2018), or that the ATTD of GE increased with supplementation of phytase to diets (Kiarie et al, 2016;Dersjant-Li et al, 2017). Thus, results of this and previous experiments indicate that the effect of microbial phytase on the AID and ATTD of GE is not consistent.…”

“…The observation that there was no effect of phytase on the AID of AA is in agreement with She et al (2018), who reported that inclusion of up to 4,000 FTU of an E. coli phytase to a corn-soybean meal-based diet had no impact on the AID of AA. Likewise, addition of up to 2,000 FTU of an E. coli phytase had no effect on the AID of the majority of AA (Liao et al, 2005;Velayudhan et al, 2015).…”

“…A quadratic effect of phytase on ATTD of Ca and P has been observed in some previous experiments (Almeida and Stein, 2012;Almeida et al, 2013;She et al, 2018). However, a linear increase in the ATTD of P has also been reported without an apparent breakpoint even if 20,000 FTU of phytase was added to the diet (Zeng et al, 2015).…”

“…Binding of protein to phytate may result in reduced AA digestibility and it is, therefore, possible that inclusion of exogenous phytase in diets increases AA digestibility, which has been demonstrated in broiler chickens (Cowieson et al, 2006;Yu et al, 2012). However, in pigs, effects of microbial phytase on digestibility of AA have not been consistent (Zeng et al, 2016;She et al, 2018). Phytate may increase mucin synthesis, and thereby increase endogenous losses of AA, which reduces calculated values for digestibility of AA.…”

Insoluble dietary fiber does not affect the ability of phytase to release phosphorus from phytate in the diet of nursery pigs1

“…(Madrid et al, 2013) and amino acid digestibility through the decrease of antinutritional effects of phytate and its derivates (Cowieson et al, 2017;Zouaoui et al, 2018). Zeng et al (2014) reported an increase in the apparent ileal digestibility of DM (using 1,000 to 20,000 FTU/kg), but Zeng et al (2016) using 0 to 20,000 FTU/ kg and She et al (2018) using 0 to 4,000 FTU/ kg, did not. However, these studies used much higher levels (super-dosed levels) of phytase than those used herein (0-327 FTU/kg), and investigated ileal as opposed to total tract digestibility, the focus of this study.…”