Interpretive Summary: Effects of different antibiotic feeding programs on morbidity and mortality and growth performance of nursery pigs housed in a wean-to-finish facility
By: Jackie Walling
Antibiotics in swine production have been thought to boost immune function and growth performance while decreasing disease rate in nursery pigs sensitive to stressors. A recent article published in the January 2019 Issue of Translational Animal Science evaluated the incidence of morbidity, mortality, and growth performance on nursery pigs in a wean-to-finish facility undergoing two different antibiotic feeding programs.
The antibiotic regimen evaluated consisted of two phases with three experimental groups. The control for both phases always consisted of unmedicated pigs. Phase 1 consisted of 14 days of TIACTC (39mg/kg tiamulin + 441 mg/kg chlortetracycline) as Group 1 and Group 2 received 14 days of CAROTC (28mg/kg carbadox + 441mg/kg oxytetracycline). Phase 2, the same pigs given TIACTC then received 21 days of TIA (39mg/kg tiamulin) and CAROTC pigs received 21 days of CAR (55mg/kg carbadox). Both TIACTC and CAROTC are thought to increase growth performance compared to untreated pigs. TIACTC has also been shown to reduce morbidity and mortality.
This was a 35-day study utilizing 2250 crossbred pigs with body weights 6.7 to 25.5kg. Pigs were split using a randomized complete block design and were housed in groups of 25 single-sex pens. “Pen” was the experimental unit. Weights and feed intake were collected on day 0, 14, and 35 to calculate growth parameters.
Results for growth performance in Phase 1 showed TIACTC and CAROTC had greater average daily gain (ADG), average daily feed intake (ADFI), and BW compared to controls, but no significant difference between the two treatment groups. Gain:Feed (G:F) ratio improved the most for TIACTC and the least for CAROTC. In Phase 2, TIA and CAR had greater BW and ADFI than controls, but ADG was greater for CAR by 3.1% compared to TIA. Little information has been reported on TIA and CAR alone, but CAR is thought to have therapeutic and growth performance effects when administered at 55mg. TIA is only thought to have a therapeutic effect at 38mg providing possible explanation as to why CAR seemed more effective in growth parameters. G:F did not differ among treatments groups or the control.
Morbidity and mortality incidences along with G:F did not differ significantly among groups while growth parameters remained higher for pigs given antibiotics. Though mortality and morbidity were assessed, effective antibiotic use should be gaged from growth performance parameters first which serve as indicators for illness. The results from this study showed pigs on antibiotics had better growth performance results which is supported by realms of previous studies using these antibiotics.
Overall, antibiotic treatment groups had limited differences between themselves, but had improved performance over controls. Some results regarding the degree of improvement were on the lower side of previous comparative studies, but housing arrangement may have influenced results. Controls and treatment groups were housed next to each other potentially manipulating pathogen exposure. Surrounding control pigs with antibiotic protected pigs may have reduced pathogen exposure for controls while lower performance effects observed in antibiotics in treatment groups may have been from increased pathogen exposure from unmedicated pigs. Differing study designs as well as changing dosages of TIACTC, CAROTC, TIA, and CAR could provide additional information on antibiotic use.
For the full article, visit Translation Animal Science.