PSIV-13 Evaluation of Floor Space Restriction and Hyper-Dosing of Phytase on Growth Performance, Carcass Characteristics and Serum Chemistry of Late Finishing Pigs

Abstract

Abstract This study was conducted to evaluate the impact of strategically applied hyper-dosing of phytase on growth performance, carcass characteristics and serum chemistry profile of late finishing pigs housed under space-restricted conditions. A total of 375 finishing pigs (94.63 ± 0.61 kg) were randomly assigned to 48 pens, with 7 to 8 pigs per pen equally balanced for gilts and barrows. Two phytase supplementation doses (control of 2,500 FTU/kg or hyper-dose of 5,000 FTU/kg) and two space allocation dimensions (adequate with 0.85 m2/pig or restricted with 0.66 m2/pig) were combined to create 4 treatments in a 2 x 2 factorial arrangement. Pigs were fed a finishing diet formulated to contain 0.68% standardized ileal digestible (SID) lysine, 0.55% Ca, and 0.24% available P and phytase was given equal matrix values for Ca, P, SID amino acids, and net energy for both supplementation levels. Analyzed dietary phytase concentrations were 2,970 and 6,560 FTU/kg for the 2,500 and 5,000 FTU/kg treatments, respectively. The 3 heaviest pigs per pen (2 barrows and 1 gilt) were marketed on d 28 and the remaining pigs were marketed on d 42. No interactions; P > 0.10) were observed between floor space allowance and phytase supplementation. Pig body weight was determined weekly and was reduced (P < 0.008) by restriction of space on week 3 (116.7 vs. 118.4 kg), and 4 (time of first marketing; 123.6 vs. 125.4 kg) and tended to be reduced (P < 0.08) on week 5 (125.5 vs. 127.8 kg), and 6 (second marketing; 133.0 vs. 135.3 kg). Body weight considering all pigs marketed (d 28 and d 42) was reduced (P = 0.009; 133.9 vs. 135.4) by space restriction. Space restriction reduced ADG during week 1, 3, the first marketing period, and for all pigs marketed (P < 0.05). Similarly, ADFI was reduced in space restricted pigs for all periods (P ≤ 0.001), but gain:feed was not impacted (P > 0.08). Back fat depth and loin eye area measured using ultrasound was not impacted by space restriction. Hyper-dosing with phytase did not impact (P > 0.06) growth performance or carcass characteristics, regardless of space allowance. Space restriction and phytase supplementation did not impact serum chemistry except for increased serum total protein and decreased urea N (P < 0.05) due to space restriction and decreased aspartate transaminase with hyper-dosing phytase. Results indicate that restricted floor space allowance reduced growth rate, feed intake and body weight of late finishing pigs and that hyper-dosing phytase was not an effective strategy in improving growth performance regardless of space allowance.