Effect of carvacrol on fermentation characteristics in the ileum of piglets during the process of weaning

Twelve landrace piglets selected from four different sows were fitted with an ileal T-shaped cannula at an age of 17 to 18 days (d-10; BW 6.13 ± 0.46 kg). After surgery, the animals were placed back with the sows. Ten days later (d0) the animals were weaned, placed on metabolic cages and assigned to one of the two dietary treatments, a control diet vs. a control diet with carvacrol. Carvacrol, a component naturally present in oregano and thyme, is known for its antimicrobial properties (Hammer et al., 1999; Manzanilla et al., 2004; Michiels et al., 2007). The current study aimed to assess the effect of carvacrol on the microbial activity in the distal ileum of piglets during weaning. Ileum chyme samples were collected at 11.30 h and 16.30 h at d-3, d1 to d7, d10, d14 and d15 relative to weaning and analyzed for fermentation end-products, volatile fatty acids (VFA) and ammonia (NH3). Morning versus afternoon sampling showed no differences in VFA (P = 0.353), but NH3 and branched-chain VFA proportions (BCP) were increased in the morning samples compared to afternoon samples (P = 0.053 and P = 0.033 respectively). Both dietary treatments showed a strong decline in VFA between pre-weaning (d-2) and the first day post-weaning (d1; P ≤ 0.008), followed by a general increase in concentrations through d7 post-weaning. At d10 and especially at d13 a strong decrease in VFA was observed (P ≤ 0.026). Ammonia concentrations follow a similar pattern through the period of weaning, with highest concentrations observed at pre-weaning (d-2; P < 0.0001). The BCP showed a general decrease from pre-weaning to post-weaning. Our observations suggest that addition of carvacrol seemed to alter the pattern of fermentation during weaning, although weaning itself seemed to be the major factor as effects did not differ significantly from the control.