The present invention relates to the combination of organic acid salts with at least one active ingredient of plant origin, preferably essential oils, partially protected with vegetable fats and/or oils, which prevent these active ingredients from being digested by stomach enzymes during the digestive process. The sodium salts of short-chain acids, preferably salts of butyric, acid are preferred. The preferred essential oils are ginger, piperine, oregano, garlic, thymol, carvacrol, cinnamaldehyde and/or any combinations thereof. The combination of organic acid salts and the essential oils protected with vegetable fats and/or oils, are used as powerful promoters or stimulants for animal growth, as organic bactericides against pathogenic bacteria present in said animals and as modulators of immune response thereof.