Efficacy of an herb and essential oil-based phytobiotic blend and its interaction with an antibiotic on intestinal health, growth performance, and carcass characteristics in growing pigs.

Antibiotics were commonly added to pig diets to promote growth of pigs but are now restricted or no longer allowed worldwide due to concerns about antimicrobial resistance. However, because removing antibiotics from pig diets may compromise growth performance, researchers have actively explored alternative solutions. Phytobiotics, which are plant-derived compounds, are considered a potential alternative to antibiotics in pig diets. Therefore, the objective was to evaluate the effects of an herb and essential oil-based phytobiotic blend (HEP) on intestinal health, growth performance, and carcass characteristics in growing pigs fed diets with or without an antibiotic. A total of 96 pigs including 48 barrows and 48 gilts (initial weight = 41.5 ± 2.7 kg) were allotted to 4 dietary treatments based on a 2 × 2 factorial arrangements with the factors of antibiotic (0 or 0.05%) and HEP (0 or 0.05%). Pigs were fed the diets for 42 d and body weight and feed disappearance were recorded every 7 d. Blood samples were collected from each pig on d 37 to obtain plasma. On d 42, a pig with the median weight in each pen was euthanized to assess carcass characteristics and collect samples of tissue and mucosa from the duodenum and jejunum. The MIXED procedure of SAS was used to analyze data on intestinal health, growth performance, and carcass characteristics. The fixed effects were sex, antibiotic, HEP, and interaction between antibiotic and HEP, whereas initial body weight was a random effect. The supplementation of the HEP tended to decrease (P = 0.096) tumor necrosis factor-α in the jejunal mucosa. The supplementation of the HEP tended to increase villus height in the jejunum in pigs fed the diet without the antibiotic, whereas it had no effect on villus height in pigs fed the diet with the antibiotic (interaction; P = 0.061). The supplementation of the antibiotic increased (P < 0.05) average daily gain during the overall period. The supplementation of the HEP tended to decrease (P = 0.071) average daily feed intake, whereas it tended to increase (P = 0.087) gain:feed during the overall period. The supplementation of the antibiotic increased (P < 0.05) hot carcass weight, cold carcass weight, and loin color, and tended to decrease (P = 0.092) 48-h drip loss. In conclusion, supplementing antibiotic to the diets for growing pigs increased the weight gain resulting in increased hot and cold carcass weight, whereas supplementing the HEP increased the gain:feed of pigs without affecting the weight gain, which may be attributed to reduced inflammation in the jejunum. These results suggest that the HEP can be a potential alternative to the antibiotic, but the ways in which the antibiotic and HEP improve growth performance may differ.