Effects of dose and formulation of carvacrol and thymol on bacteria and some functional traits of the gut in piglets after weaning

Abstract

Two trials were conducted to study the effects of dose and formulation of carvacrol and thymol on bacterial counts, metabolites and functional traits of the gut in weaned piglets. In the first experiment (Exp. I), 25 piglets (28 d, 6.59 ± 0.48 kg BW) were allocated to five dietary treatments: a control diet, or the same diet supplemented with either carvacrol or thymol at doses of 500 and 2000 mg kg⁻¹. In the second experiment (Exp. II), 35 piglets (28 d, 7.99 ± 0.73 kg BW) were assigned to seven dietary treatments: the same control diet as in Exp. I, or this diet supplemented with thymol in one of three formulations (on celite, on alphacel or microencapsulated) at doses of 500 and 2000 mg kg⁻¹. At 11/12 days post-weaning piglets were euthanised, and digesta from stomach, proximal and distal small intestine were sampled for bacteriological and biochemical analysis. Small intestinal tissue was sampled for histo-morphological determinations. In none of the experiments or sections of the gut was the number of bacteria lowered by the carvacrol or thymol supplementation. In Exp. I, the villus/crypt ratio at the distal small intestine for the experimental diets (1.30–1.32) was higher than for the control diet (1.24) (p < 0.05). Thymol fed animals in Exp. II had a lower number of intra-epithelial lymphocytes at the proximal (p < 0.05) and at the distal (p < 0.1) small intestine as compared to control animals. Mean concentration of the active ingredient in the stomach and proximal small intestine for the 2000 mg kg⁻¹ carvacrol diet was 521 and 5 mg kg⁻¹ fresh digesta, respectively, and for the 2000 mg kg⁻¹ thymol diets it ranged between 475 and 647 and between 13 and 24 mg kg⁻¹ fresh digesta, respectively. Cumulative absorption in the proximal small intestine was higher than 90% for all treatments and was not affected by formulation type. These data suggest that carvacrol and thymol can improve gut health, but evidence for clear antimicrobial effects towards the major culturable bacteria of the pig foregut is limited.

Keywords:

• carvacrol
• intestinal absorption
• intestinal microorganisms
• piglets
• thymol
• weaning

Acknowledgements

The authors wish to thank SODA Feed Ingredients (Monaco) for kindly providing the microencapsulated thymol. Part of this work was financially supported by the Institute for the Promotion of Innovation by Science and Technology in Flanders (IWT), Brussels, Belgium. The authors are also grateful to C. Vermander, A. Maes, E. Turtelboom, S. Coolsaet, S. Lescouhier and Y. De Bock for skilful technical support.