Phytase, High‐Available‐Phosphorus Corn, and Storage Effects on Phosphorus Levels in Pig Excreta

Abstract

Phosphorus-based land application limits for manure have increased the importance of optimizing diet P management and accurately characterizing the bioavailability of manure P. We examined the effects of pig (Sus scrofa) diets formulated with high-available-P corn and phytase on P levels in excreta and slurry stored for 30, 60, 90, 120, and 150 d. Twenty-four pigs (approximately 14 kg each) were fed one of four low-P diets: (i) normal corn, no phytase (control); (ii) normal corn with 600 phytase units kg(-1) (PHY); (iii) high-available-P corn, no phytase (HAP); and (iv) high-available-P corn with 600 phytase units kg(-1) (HAP + PHY). Fresh fecal and stored slurry dry matter (DM) was analyzed for total phosphorus (TP), dissolved molybdate-reactive phosphorus (DRP), dissolved organic phosphorus (DOP), acid-soluble reactive phosphorus (ASRP), acid-soluble organic phosphorus (ASOP), and phytate phosphorus (PAP). The PHY, HAP, and HAP + PHY diets significantly (alpha = 0.05) decreased fecal TP 19, 17, and 40%, respectively, compared with the control. Dissolved reactive P was 36% lower in the HAP + PHY diet compared with the other diets. Relative fractions (percent of TP) of DRP, DOP, ASOP, and PAP in slurry generally decreased with storage time up to 150 d, with the largest decreases occurring within 60 to 90 d. Diet-induced differences in relative fractions of DRP, DOP, ASRP, and PAP were significant when averaged across storage times, simulating a mixed-age slurry. Relative fractions of DRP in simulated mixed-age slurries were higher in HAP and HAP + PHY diets, indicating that diet may affect P losses under certain P-based application scenarios.

Phosphorus utilization and characterization of excreta from swine fed diets containing a variety of cereal grains balanced for total phosphorus1

“…Therefore, manures that have a greater proportion of phytate P will have decreased WSP concentrations and WSP:TP. Examination of the available literature reveals a similar trend in swine feces (Baxter et al, 2003;Leytem and Thacker, 2008), broiler litter (Maguire et al, 2004;Toor et al, 2005), and manure from laying hens (Leytem et al, 2006).…”

Response to dietary phosphorus deficiency is affected by genetic background in growing pigs1

“…Although dietary P is essential for the growth, development, and maintenance of both muscular and skeletal tissues, increased public and governmental concerns over the environmental effect of excess P in the excreta of pigs has driven research to minimize the environmental effect of swine production (Baxter et al, 2003;Sutton and Richert, 2004). These concerns have led to research focused on more accurately defining the P requirements of pigs, as well as developing and evaluating technologies that could minimize P excretion from pig production (Cromwell et al, 1995;Spencer et al, 2000;Veum et al, 2001;Jendza et al, 2005).…”

Environmental implications of inositol phosphates in animal manures.

“…However, during storage of manure from the normal diet for 150 days, myo-inositol hexakisphosphate as a percentage of total phosphorus decreased from 15.5°/0 to 8.5%, which was attributed to microbial degradation. For the phytase-amended diet the decrease in myo-inositol hexakisphosphate during storage was only between 9.1% and 9.8%, indicating hydrolysis by the added phytase prior to excretion (Baxter et al, 2003). Therefore, after 150 days of storage, there was no significant difference in myo-inositol hexakisphosphate concentrations in swine manures from the two diets.…”

“…It would be expected that manures from diets that included phytase would have less myoinositol hexakisphosphate than equivalent diets without phytase. This was the case in a study of manures from swine fed diets with and without phytase (Baxter et al, 2003). Concentrations of myo-inositol hexakisphosphate in fresh swine manure were decreased by 2.0-3.9 g P/kg by adding phytase to the feed.…”