Feed additives

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Effects of thyme extracts on broilers

Antibiotics have been banned as a growth promoter. However, there are alternative feed additives that can improve broiler performance. Thyme oil is an important antibiotic alternative - let's have a look at the effects on broilers.

The use of antibiotics in poultry feed has demonstrated beneficial effects with regard to improved performance and morbidity in broiler chickens. However, the occurrence of antibiotic residues in products and the development of antibiotic-resistant bacteria has resulted in the ban of its use as growth promoter. Alternative feed additives in animal rations may also improve broiler performance.

Thyme oil - important antibiotic alternative

Essential oils, organic acids, and phytogenic compounds such as thyme oil are important antibiotic alternatives. Essential oils consist of several active compounds, with some of them comprising more than 60 individual components that can inhibit the growth of certain microorganisms, as Salmonella spp and other pathogens.

The chemical composition of essential oils is variable. The primary components are the major active ingredients, whereas the secondary components act synergistically to increase the total effectiveness.

It has been reported that dietary thyme (major components thymol and carvacrol) had a different effect on weight gain and body mass when used as an herb or oil; there is limited evidence whether its inclusion as a solid herb material would have a growth-promoting effect in live birds. The effects of dietary thyme-oil-extract fortification on immune functions of male broiler chicks were therefore determined. In a 42 day feeding trial the effect of dietary thyme-oil extract supplementation on immune functions of male broiler chicks were assessed by feeding graded levels (50, 100, 200, or 400 ppm).

Negative-control diet with no feed-additive supplementation and 2 positive-control groups supplemented with virginiamycin or zinc bacitracin were included. Diet modifications had no significant effect on blood leukocyte subpopulations and heterophil-to-lymphocyte ratio, dietary supplementation with thyme-oil extract, especially at the level of 100 ppm, improved immunological responses of broiler chicks.

Fahimeh Alipour, Ahmad Hassanabadi, Abolghasem Golian, and Hassan Nassiri-Moghaddam, Poultry Science.

Roel Mulder

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