Evaluation of alternative antimicrobial strategies in high-performance pigs for managing endemic Mycoplasma hyopneumoniae populations

This study evaluated pig production performance in herds with M. hyopneumoniae by replacing in-feed antimicrobials with the herbal extract carvacrol during nursery and finishing phases. A total of 324 piglets were allocated across three treatments: ATM-Free (without antimicrobial); HE (carvacrol); and ATM (antimicrobial). They were housed in the nursery from 21 to 63 days of age (doa), then transferred to finishing and slaughtered at 175 doa. Piglets were weighed and feed consumption was measured at 21, 28, 35, 42, 49, 56, and 63 doa in the nursery and at 75, 98, 107, 128, 135, 152, 161, and 174 doa in the finishing phase. Lung macroscopic lesions were evaluated at slaughter. Body weight (BW), average daily weight gain (ADG), and mortality/removal rate at nursery end did not differ between the HE and ATM treatments. However, feed-to-gain (F/G) was slightly worse in HE compared to ATM at nursery. The HE and ATM-Free treatments did not differ in ADG and BW, but HE was better than ATM-Free in F/G at nursery. Lung lesions score tended to be higher in ATM-Free compared to the ATM treatment. However, the frequency of lungs with a low lesion score did not differ among treatments. Removing antimicrobials from feed for pig populations endemic to M. hyopneumoniae reduces production performance during nursery and finishing phases and tends to cause larger affected lung areas suggestive of pneumonia at slaughter. Carvacrol can be an alternative to antimicrobials without relevant impacts on performance, except for the removal rate in the finishing phase.