1. Feed additive containing: eugenol in an amount of 30% to 45%, cinnamaldehyde in an amount of 30% to 45% and an extract of a plant selected from the following group: leeks (Allium ampeloprasum), onions (Allium sulfur L. ), cultivated garlic (Allium sativum L.), shallots (Allium ascalonicum), spring onions (Allium fistulosum L.), chives (Allium schoenoprasum) in an amount from 10% to 40%, the rest of the content in the amount, supplementing up to 100%, may include other compounds, in particular, organosulfur compounds. 2. A feed additive according to claim 1, wherein said plant belonging to the genus Allium is cultivated garlic (Allium sativum L.). A feed additive according to any one of claims 1 or 2, containing from 15% to 35% garlic extract. 4. A feed additive according to claim 3, containing from 24% to 26% garlic extract. A feed additive according to any one of claims 1 or 2, in which said plant extract contains at least one compound having the following general chemical formula F: R-SO-S-R ', where R and R' are identical alkyl groups or different, and "a" is equal to 1 or 2.6. The feed additive according to claim 5, wherein the groups R and R 'in the general chemical formula F are alkyl groups containing from one to five carbon atoms. A feed additive according to claim 6, wherein the groups R and R 'in the general chemical formula F are propyl groups. A feed additive according to claim 5, wherein the R and R 'groups are identical. Feed additive according to claim 5, in which in the general chemical formula F "a" is equal to 1 or 2.10. A feed additive according to claim 5, wherein the compound with the general chemical formula F is dipropyl thiosulfinate. A feed additive according to claim 5, comprising a mixture of dipropyl thiosulfinate and dipropyl thiosulfonate. Feed additive containing: 30% to 45% eugenol, 30% to 45% cinnamaldehyde and 10% to 40%1. Кормовая добавка, содержащая:эвгенол в количестве от 30% до 45%,коричный альдегид в количестве от 30% до 45%
