Effects of two feeding periods of tiamulin fed in combination with chlortetracycline for control and treatment of swine respiratory and enteric disease and subsequent growth performance of growing-finishing pigs

The objective of this study was to evaluate the effects of two dietary feeding periods of tiamulin in combination with chlortetracycline for the control and treatment of swine respiratory and enteric disease and subsequent growth performance. The study used 1,151 commercial crossbred barrows and gilts in a randomized complete block design. Pigs were housed in single-sex groups of 25 at a floor space of 0.69 m²/pig. There were two dietary treatments: 1) nonmedicated controls and 2) 39 mg/kg tiamulin + 441 mg/kg chlortetracycline (<b>TIACTC</b>) fed from days 7 to 20 and again days 49 to 62. There were 23 pens per treatment group. Daily observations were made throughout the study, including the number of pigs in each pen coughing, with diarrhea, or showing signs of lameness as well as the number of pigs in each pen requiring individual therapy treatment for each symptom. Pigs were weighed as a group on days 0 (for allocation purposes), 7, 21, 49, 61, 89 (start of marketing), and at time of slaughter. Within pen, animals were selected by visual appraisal and sent for slaughter over 4 wk to a commercial slaughter facility where HCW was collected and used to calculate carcass yield. There was no difference (<i>P</i> > 0.05) between treatments for the incidence of morbidity or mortality. Pigs fed TIACTC tended to have less coughing observations (<i>P</i> = 0.10) and less diarrhea observations (<i>P</i> = 0.08) during the study period, and had less observations of lameness (<i>P</i> < 0.001) and required less treatments than nonmedicated controls (<i>P</i> < 0.001). For the overall study period, pigs fed TIACTC had greater (<i>P</i> < 0.05) total BW gain (43.3 kg greater/pen) and greater (<i>P</i> < 0.05) ADG and ADFI than controls. There was no effect (<i>P</i> > 0.05) of treatment on G:F. Overall, pigs fed TIACTC weighed 1.3 kg heavier (<i>P</i> < 0.05) at the start of marketing and completed the study with an overall BW advantage of 1.6 kg (<i>P</i> < 0.05) compared to controls. The difference between treatments for live BW increased with marketing group (1.0 kg in marketing group 1 and 3.3 kg in marketing group 4). Pigs fed TIACTC had greater (<i>P</i> < 0.05) HCW (1.0 kg) than controls; however, there was no difference (<i>P</i> > 0.05) between treatments for carcass yield. The results of this study suggest that feeding TIACTC was successful at controlling respiratory and enteric disease and, consequently, improved growth performance and carcass weight of grow-finish pigs.