Effects of a blend of essential oils on broiler performance and intestinal morphology during coccidial vaccine exposure

A 2 × 2 factorial experiment (8 pens/treatment, 26 birds/pen) was conducted with 2 doses of a coccidial vaccine [1× or 5× (Paracox-5, Schering-Plough Animal Health, Uxbridge, UK)], administered at 1 d of age) with or without supplementation (125 g/1,000 kg) with a phytogenic feed additive containing a blend of essential oils from oregano, anise, and citrus peel [Biomin P.E.P. 125 poultry (Biomin GmbH, Herzogenburg, Austria); EO]. Within each pen, 13 birds received the coccidial vaccine, whereas the remainder were naturally exposed through the recycling of oocysts in the litter. In pens of birds receiving the higher (5×) dosage of coccidial vaccine, the BW of broilers decreased by up to 2.7% (P</it> = 0.08), but feed-to-gain ratio (FCR) and mortality at 27 d of age (P</it> > 0.05) were not affected. Between d 14 and 27 within pens of birds receiving the 1× dosage of coccidial vaccine, those that were fed EO had a 5.6% increase in BW gain (P</it> < 0.05). Supplementation with EO did not affect feed intake or FCR (P</it> > 0.05). Birds naturally exposed in pens receiving the higher (5×) dosage of coccidial vaccine had an 11% reduction in ileal crypt depth (P</it> < 0.05) and a 19% quicker enterocyte turnover rate (P</it> = 0.086), but there was no effect on ileal villus length or number of goblet cells (P</it> > 0.05). In naturally exposed birds with pen-mates given the 1× dosage of coccidial vaccine, birds fed EO had 12% longer villi than did unsupplemented birds (P</it> < 0.05), with 30% more goblet cells and 23% more goblet cells/10 µm of villus length (P</it> < 0.05). In conclusion, the dosage of coccidial vaccine had an impact on BW, intestinal turnover rate, and crypt depth, whereas dietary supplementation with the EO additive increased villus length and goblet cell density, which may have created an improved barrier against pathogens during a mild coccidial exposure.