Effects of Benzoic Acid and Thymol on Growth Performance and Gut Characteristics of Weaned Piglets

A total of 144 weaned crossed pigs were used in a 42-d trial to explore the effects of different concentrations/combinations of benzoic acid and thymol on growth performance and gut characteristics in weaned pigs. Pigs were randomly allotted to 4 dietary treatments: i) control (C), basal diet, ii) C+1,000 mg/kg benzoic acid+100 mg/kg thymol (BT1), iii) C+1,000 mg/kg benzoic acid+200 mg/kg thymol (BT2) and, iv) C+2,000 mg/kg benzoic acid+100 mg/kg thymol (BT3). Relative to the control, pigs fed diet BT3 had lower diarrhoea score during the overall period (p<0.10) and improved feed to gain ratio between days 1 to 14 (p<0.05), which was accompanied by improved apparent total tract digestibility of ether extract, Ca and crude ash (p<0.05), and larger lipase, lactase and sucrose activities in the jejunum (p<0.05) at d 14 and d 42. Similarly, relative to the control, pigs fed diet BT3 had higher counts for Lactobacillus spp in digesta of ileum at d 14 (p<0.05), and pigs fed diets BT1, BT2, or BT3 also had higher counts of Bacillus spp in digesta of caecum at d 14 (p<0.05), and lower concentration of ammonia nitrogen in digesta of caecum at d 14 and d 42 (p<0.05). Finally, pigs fed diet BT3 had higher concentration of butyric acid in digesta of caecum at d 42 (p<0.05), and a larger villus height:crypt depth ratio in jejunum and ileum at d 14 (p<0.05) than pigs fed the control diet. In conclusion, piglets fed diet supplementation with different concentrations/combinations of benzoic acid and thymol could improve feed efficiency and diarrhoea, and improve gut microfloral composition. The combination of 2,000 mg/kg benzoic acid+100 mg/kg thymol produced better effects than other treatments in most measurements.