Date Full Report Received


Date Abstract Report Received



Primary Investigator:
This project specifically evaluated the impact of ultra-high doses of phytase on production parameters of late finishing pigs and further evaluated whether the response to phytase was dependent on amino acid concentrations in the diet. Past research efforts have demonstrated positive effects of phytase supplementation at approximately 1,500 to 3,000 FTU/kg, but higher inclusion levels have not been adequately tested in commercial production environments. The cost of phytase has decreased substantially; therefore, inclusion of ultra-high levels of phytase (beyond those required for P release) becomes economically feasible. In the first experiment with 1,762 pigs (starting body weight of 84.3 kg), we demonstrated that mega-dosing of phytase at 4,500 and 6,750 FTU/kg decreased feed intake without improving feed efficiency compared to the control diet which contained a standard super-dosing concentration of phytase of 2,250 FTU/kg of feed. The floor space in the present study was 7.1 ft2/pig and the pig density was 36.9 lbs/ft2 prior to the first marketing (at day 35 of the study), which was expected to provide significant stress and erode feed efficiency. However, ultra-dosing of phytase did not impact feed efficiency, but could save a moderate amount of feed due to reduced feed intake. In the second experiment with 594 pigs (mean initial body weight of 29.5 kg) we evaluated the impact of phytase in pigs fed adequate levels of amino acids and pigs fed diets with reduced levels of amino acids (reduced by 15%). Pigs fed diets with reduced amino acid concentrations had lower daily gain only during the first grower stager. Reduced amino acid supply increased feed intake and feed:gain ratio. Supplementation of phytase at 3,000 and 6,000 FTU/kg of feed slightly decreased feed intake, although not significantly, and improved feed efficiency during the first grower stage only. For the overall period until market, phytase supplementation in control pigs had no effect on feed efficiency, but improved feed efficiency in pigs fed 6,000 FTU/kg of phytase in the reduced amino acid diet. Results indicate that mega-dosing phytase had relatively small effects on growth performance, largely unrelated to dietary amino acid concentration, but slightly reduced feed intake which could save feed costs

Key Findings:
• Supplementation of phytase appeared to slightly reduce feed intake without impacting daily gain, which could save on feed cost.
• If ultra-high levels of phytase liberate energy from dietary ingredients, then a decrease in feed intake would be expected, based on the premise that pigs eat to meet a constant energy need.
• Supplementation of phytase at ultra-dosing levels was expected to have a greater impact on growth performance than when supplemented to diets with control levels of amino acids, which tended to be the case for overall feed efficiency.

Contact: Eric van Heugten
North Carolina State University
Raleigh, NC 27695-7621
Phone: (919) 513 1116
E-mail: Eric_vanHeugten@ncsu.edu