Impact of antimicrobials with or without the addition of phytase on phosphorus digestibility and utilization in swine and broiler chickens

McCormick, Katherine. M. S., Purdue University, May 2014. Impact of antimicrobials with or without the addition of phytase on phosphorus digestibility and utilization in swine and broiler chickens. Major Professor: Dr. Olayiwola Adeola. Three studies were conducted for this thesis. In study 1, effects of antimicrobials on nutrient digestibility and retention of 18 to 20-kg pigs was investigated. The study used a randomized complete block design (RCBD) with 4 treatments and 6 replicate pigs in individual metabolism crates per treatment. The four treatments consisted of, negative control (NC) devoid of antimicrobials with 0.41% total P and 0.71% Ca, NC with 55 mg/kg carbadox (Mecadox 10, Phibro Animal Health), 44 mg/kg tylosin (Tylan 40, Elanco Animal Health), and 11 mg/kg virginiamycin (Stafac 20, Phibro Animal Health). A 5-d total collection period with chromic oxide used as an initiation and termination marker for feces followed a 5-d adaptation period. Supplementation with carbadox increased (P < 0.05) energy (E) digestibility and retention relative to pigs fed the NC diet. Overall, supplementation of an antimicrobial did not significantly influence DM, P, and Ca utilization; however, specific antimicrobial supplementation influenced N digestibility and E utilization.