Superdosing phytase fed to mature boars improves semen concentration and reproductive efficiency

The purpose of this project was to evaluate the effects of superdosing phytase fed to boars on sperm production, semen quality, and serum mineral concentrations. Thirty boars (9 to 12 mo of age, PIC 280) were enrolled in the study and were fed 2.5 kg/d of a commercial corn-soybean meal diet containing 500 phytase units/kg modified Escherichia coli phytase to release 0.15% available phosphorus and 0.16% Ca. The boars were blocked by age and randomly assigned to receive 1 of 2 top-dresses at 0.5 kg/d: (1) control (corn only) or (2) superdosed (corn plus 5,000 phytase units/kg E. coli phytase to equate to 3,000 phytase units/kg in the overall diet). Semen was collected weekly from all 30 boars for 12 wk and motility, mobility, and morphology evaluated at the time of collection. Monthly semen samples were shipped to Purdue University for additional assessment of motility, morphology, viability, and DNA denaturation. Serum mineral concentrations were determined on wk 1, 6, and 12. The concentration of sperm in the ejaculate was greater in the superdosed boars (P = 0.03), resulting in a tendency for an additional 3 doses (2.8 billion cells/dose) extended per ejaculate (P = 0.10) from a 13% increase in semen output. Some significant variations in motility, mobility, and morphology were found, but all semen samples fresh and stored were considered acceptable at industry standards for use in breeding doses. Serum minerals were reduced in boars fed superdosed levels of phytase, possibly due to a shift of minerals being used for reproduction.