Digestibility of phosphorus in high protein corn co-products fed to growing pigs

New sources of high protein corn co-products have been recently developed and may be included in diets fed to pigs. Phytase is often employed during fermentation in the bioethanol process to improve the efficiency of fermentation. However, the use of phytase during fermentation may impact the nature of phosphorus (P) in any post fermentation products, which could subsequently alter the levels of phytate-bound and non-phytate P. As a consequence, this may influence digestibility and concentration of digestible P in any feed product derived from fermentation. Therefore, an experiment was conducted to determine the standardized total tract digestibility (STTD) of P in high protein corn fermented products and in the residual distillers dried grains and solubles (DDGS) produced from a fermentation with or without the use of phytase. It is also the objective of this experiment to test the hypothesis that inclusion of phytase during the fermentation process increases P digestibility in corn co-products.

 

Experimental design

Three sources of high protein corn fermented products (i.e., CFP, ET-Ultra High Pro, and ET-Ultra High Pro+) and two sources of Post-MSC DDGS were procured. Two sources of high protein corn fermented products (i.e., ET-Ultra High Pro and ET-Ultra High Pro+) and one source of Post-MSC DDGS (i.e., ET-Post-MSC DDGS) were treated with microbial phytase during the fermentation process, whereas phytase treatment was not performed for the two other corn co-products. Five diets were formulated by mixing each source of corn co-product with sucrose and cornstarch, and corn co-product was the only source of P in these diets. Five additional diets were also formulated similarly to the previous two diets with the exception that 500 units of phytase/kg were added to these diets. Eighty pigs (14.38 ± 1.50 kg) were used and allotted to ten diets with eight replicate pigs per diet. Pigs were housed individually in metabolism crates. The initial 5 days were considered the adaptation period to diets, and fecal samples were collected for 4 days following the adaptation period. Diets, ingredients, and fecal samples were analyzed for P to calculate for apparent total tract digestibility (ATTD) and standardized total tract digestibility (ATTD) of P in each diet.

 

Results

A reduction in concentration of phytate-bound P and a subsequent increase in concentration of myo-inositol was observed in corn co-products that were treated with phytase during the fermentation process (Table 1). Inclusion of 500 FTU/kg of phytase in CFP and Post-MSC DDGS diets reduced the concentration of P in feces; however, phytase did not affect the concentration of P in feces by pigs fed diets containing the enzyme-treated corn co-products (interaction, P < 0.01; Table 2). Likewise, P output was reduced in pigs fed the CFP diet upon phytase supplementation; however, P output was not influenced by phytase supplementation in pigs fed diets with the other corn co-products (interaction, P < 0.05). Due to increased P intake, P absorption was greater (P < 0.01) in pigs fed the diet containing CFP and Post-MSC DDGS compared with that of pigs fed diets with other corn co-products regardless of phytase supplementation. Absorption of P also increased (P < 0.05) when diets were supplemented with phytase. The ATTD and STTD of P in the CFP and Post-MSC DDGS diets increased upon phytase supplementation; however, phytase supplementation did not influence the ATTD and STTD of P in diets containing the enzyme-treated corn co-products (interaction, P < 0.05).

 

Key points

  • Concentration of phytate-bound P was less and myo-inositol concentration was greater in enzyme-treated corn co-products compared with corn co-products without enzyme treatment.
  • The ATTD and STTD of P in corn-co products that were treated with phytase during the fermentation process were greater compared with CFP and Post-MSC DDGS (without enzyme treatment).
  • Dietary supplementation of phytase increased the ATTD and STTD of P in CFP and Post-MSC DDGS.
  • Phytase did not influence P digestibility in enzyme-treated corn co-products, which likely indicates that phytase treatment during the fermentation process is sufficient to maximize P utilization.

 

Table 1. Analyzed nutrient composition of ingredients

1ET = enzyme-treated.

2Calculated as 28.2% of phytic acid.

3Calculated as total P – phytate bound P.

 

Table 2. Effects of microbial phytase on P balance, apparent total tract digestibility (ATTD), and standardized total tract digestibility (STTD) of P in three sources of high protein corn fermented products and two sources of Post-MSC DDGS fed to growing pigs1

1Data are least squares means of 7 to 8 observations per treatment.

2EPL = endogenous P loss. This value was estimated to be at 190 mg/kg DMI (dry matter intake). The daily basal EPL (mg/d) for each diet was calculated by multiplying the EPL (mg/kg DMI) by the daily DMI of each diet (Almeida and Stein, 2010).

3Values for STTD were calculated by correcting values for ATTD for the basal endogenous loss of P (NRC, 2012).

4FTU = phytase units.

a-eMeans within a row lacking a common letter are different (P < 0.05).

 

 

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