Evaluation of essential oils from natural extracts and medium chain fatty acids on piglets growth performance, salivary stress markers and gut health

This study evaluated the effect of adding an additive (Gastroherb Plus®) composed by essential oils from natural extracts (Oregano) and medium and short chain organic acids (MCFAs) to the diet of weaning piglets on growth performance, salivary stress markers and microbiota composition. At weaning, a total of 210 piglets (26 d, 7.66±1.09 kg) were allocated, according to their body weight, to two experimental treatments. Each treatment was replicated 7 times, with 15 piglets per pen forming the experimental unit. Piglets were assigned randomly into the control group (CTR) fed the basal diet and the treated group (T) fed the basal diet mixed with a dosage of Gastroherb Plus® corresponding to 1.5 kg/ton of complete feed. The body weight and feed consumption were taken at 0, 14 and 35 days. Performances parameters were analysed by means of ANOVA for repeated measures, accounting for the effect of the treatment, time, and their inter action. Cortisol, IgAs and antioxidant capacity were analysed were analysed considering the GLM procedure of SAS v.9.1. Saliva samples were taken at day 14, 21 and 35 of trial for cortisol and IgAs quantification using a competitive and a sandwich ELISA kit while total salivary antioxidant capacity was assessed with FRAP test. At the end of the trial, 7 animals per group were sacrificed and caecal content was sampled in order to perform microbiota evaluations. No significant differences were observed on BW, average daily gain, feed intake, and Feed convertion ratio, while increased fecal consistency was outlined in T compared to C. At day 21 no significant differences were noticed for cortisol in control (0.753±0.455 ng/mL) and treated animal (0.921±0.328 ng/mL). On the other hand, at day 35 d the treated group showed a significant decrease in salivary cortisol (0.672±0.308 ng/mL vs 1.289±0.645 ng/mL, p < 0.05). The levels of salivary IgAs and antioxidant capacity were not significative along the trial in control and treated animals. Sequencing the V3-V4 regions of the bacterial 16S rRNA gene produced a total of 2,815,715 reads. After bioinformatics processing, these yielded 741 OTUs with 336,691 total counts across all 14 samples. Firmicutes and Bacteroidetes were the most abundant phyla in both groups and a total of 12 differentially abundant genera (p-value <0.05) were identified in the treated group. In conclusion, the administration of Gastroherb Plus® positively affected salivary stress markers and gut health of weaned piglets.