138 Effects of Antibiotics and Low Crude Protein Diets on Growth Performance, Carcass Characteristics, and Disease Incidence of Growing Pigs

Abstract

Abstract This study investigated the effect of antibiotics and low crude protein (CP) diets on growth performance, carcass characteristics, and disease incidence of growing pigs. Barrows (n = 180; 59-d-old; 18.5 ± 2.5 kg BW; AGPIC 800 × TN70) were distributed in a randomized complete block design, in a 2 × 2 factorial arrangement, nine replicates, and five pigs per pen. The factors were CP (18.5% or 13.0%) and antibiotics (none or 100 mg/kg tiamulin + 506 mg/kg oxytetracycline). Medicated diets were fed for 14 days. After that, all pigs were fed their respective CP diets for an additional 14 days (Post-medication period). Diets were formulated according to the NRC, (2012). Growth performance, backfat thickness, loin muscle area (ultrasound; Aloka SSD 500V), and disease incidence (couch and diarrhea) were evaluated. Data were analyzed using the Mixed procedure in SAS 9.4. For the first 14 days, pigs with antibiotics had improved (P < 0.05) BW, ADG, ADFI, and G:F compared with those without antibiotics. Pigs with 18.5% CP had greater (P < 0.05) BW, ADG, and G:F, whereas decreased (P < 0.05) ADFI compared with those with 13.0% CP. There was no interaction (P > 0.05) between CP and antibiotics for growth performance and carcass variables. Reduced (P < 0.05) cough and diarrhea incidence were observed in pigs fed antibiotics diets compared with those without antibiotics. Pigs fed 13.0% CP diets presented with less (P < 0.05) diarrhea incidence only when fed without antibiotics. During post-medication period, there was no carryover effect (P > 0.05) of antibiotics on growth performance, whereas pigs fed the 18.5% CP diets had greater (P < 0.05) BW, ADG, and G:F than those with 13.0% CP. Overall, G:F was improved (P < 0.05) by the use of antibiotics and the 18.5% CP diets improved (P < 0.05) ADG and G:F compared with 13.0% CP. Antibiotics did not have carryover effects (P > 0.05) on cough and diarrhea incidence whereas, pigs with 13.0% CP diets had less (P < 0.05) diarrhea incidence than those with 18.5% CP. Pigs fed 18.5% CP diets had improved (P < 0.05) loin muscle area compared with the 13% CP, whereas treatments did not influence the backfat thickness (P > 0.05). In conclusion, the reduction of dietary CP from 18.5% to 13.0% reduces the growth performance and loin muscle area of growing pigs, although it was effective to reduced diarrhea incidence. Antibiotics improved growth performance and reduced cough and diarrhea incidence. However, overall, only G:F was improved by the use of antibiotics.