Effects of encapsulated Lavandula angustifolia essential oil in alginate hydrogel capsules as feed additives to enhance the performance and health of broiler chickens and its in vitro antibacterial activity against multidrug-resistant Escherichia coli strains.

The study aimed to evaluate the in vivo effects of the addition of lavender essential oil (LEO) immobilized in alginate hydrogel administered during the first period of rearing on production performance, selected blood parameters, gut microflora, and jejunum morphology in broiler chickens, as well as to assess its in vitro antibacterial activity against clinical Escherichia coli strains with varying drug resistance isolated from 1-day-old chicks. The experiment was conducted on a commercial farm using 300 unsexed Ross 308 broilers. One-day-old chicks were assigned to three experimental groups of 100 birds each, with five replicates of 20 birds per group. In the control group (CON), the chicks received feed without essential oil supplementation throughout the rearing period. In the experimental groups hydrogel (H) and hydrogel with LEO (HE), 2 % (w/w; relative to the other feed components) of alginate hydrogel capsules were added to the starter feed mixture (days 1-10). During the experiment, body weight (BW), feed intake (FI), water intake (WI), and mortality of the chicks were recorded. At the end of the starter feed period (day 10), blood and jejunum samples were collected from the chicks for analysis of selected biochemical, microbiological, and morphological parameters. The results demonstrated that supplementation with hydrogel containing immobilized LEO positively affected the feed conversion ratio (FCR) (P < 0.05), while no differences were observed between the groups in FI, mortality, or blood biochemical parameters (P > 0.05). It was shown that supplementation with hydrogel capsules containing immobilized LEO reduced the counts of E. coli and coliforms in intestinal samples (P < 0.05). No differences were observed in the counts of lactic acid bacteria (P > 0.05), and no relevant morphological changes were detected in the liver or jejunum. LEO was effective in inhibiting the growth of all E. coli strains, with minimal inhibitory concentration (MIC) values ranging from 1.0 to 4.0 % (v/v).