Impact of feeding blends of organic acids and herbal extracts on growth performance, gut microbiota and digestive function in newly weaned pigs

One hundred eighty newly weaned pigs were used to investigate effects of feeding organic acids and herbal extracts on growth performance, gut morphology and microbiota, and immune response in newly weaned pigs during a 4-wk period. There were five dietary treatments: control, Acid 1 (acetic, propionic, phosphoric and citric acid; 1.1% inclusion), Acid 2 (Acid 1 + 1.0% lactic acid), herbal extracts (0.75% inclusion; containing cinnamon, thyme and oregano extract), and antibiotic (110 ppm lincomycin). As compared to the control, pigs on antibiotic and Acid 2 showed higher (P < 0.05) ADG only during week 2 post-weaning, whereas pigs on herbal extract showed lower (P < 0.05) ADG only during week 3 post-weaning. Fecal coliform counts were lower (P < 0.08) in pigs on Acid 1 and 2 on day 4 post-weaning and in pigs on antibiotic and herbal extract on day 14 post-weaning. Fecal lactobacilli counts were lower (P < 0.05) in pigs on antibiotic on day 14 post-weaning. Based on PCR-DGGE, treatment influenced the composition of gut microbiota. The pH of the colon was lower (P < 0.05) in pigs on acid treatments and serum IgG was lower (P < 0.05) in pigs on antibiotic. Dietary treatment did not affect (P > 0.10) intestinal morphology. These results show that the inclusion of antibiotic in the diet reduced the proliferation of both potentially harmful coliform bacteria and potentially beneficial lactobacilli in the pig's gut, while herbal extract and organic acids appeared to reduce the proliferation of coliform bacteria. Blends of organic acids can serve as an alternative to in-feed antibiotics during the first few weeks post-weaning for pigs.