Feed additives and their relationship with antibiotics


The use of preventive antibiotics has now been banned in many countries. However, in the search for effective alternatives, we must first return to the mode of action of antibiotics. How can we use this knowledge to maintain growth performance and health of our animals?


BY R&D FRAMELCO B.V F


irst, let us take a closer look at antibiotics used for growth promotion (AGPs). Understanding how AGPs function is likely to deliver critical information towards the development of alternatives. Current


evidence has led to two primary hypotheses: a bacteria- centric mode of action and a host-centric mode of action.


Bacteria-centric mode of action AGPs, inhibit or kill bacteria by disturbing essential cell processes, like inhibiting the synthesis of bacterial cell wall and proteins, damaging the outer cell membrane, inhibiting of nucleic acid synthesis, and interfering in the bacterial metabolism. By killing pathogens, AGPs modulate the


intestinal microbiota, thereby altering the competition for nutrients. As more nutrients and energy become available for the host, growth and feed efficiency are improved. In addition, colonisation of pathogenic bacteria in the gut is prevented, which significantly reduces the risk of infections.


Host-centric mode of action AGPs reduce inflammation and seem suppress an over- reaction of the animal’s innate immune system. As such a reaction is very costly in terms of energy, any reduction of immunological stress, allows more resources to be used for processes such as growth.


The downside of AGPs Being a therapeutic drug, AGPs control diseases to a certain extent. But at the same time, they mask sub-clinical diseases and dampen signs of infections. This may cause infections to spread unseen. Although the use of AGPs has enabled farms to improve production and productivity in intensive production systems, concerns about residues and cross- resistance of pathogenic bacterial strains in people have risen, causing a complete ban of AGPs in the EU in 2006. Other countries will follow. Figure 1 shows the most used AGPs. A preference for bambermycins and bacitracin is seen.


Figure 1 - Number of countries reporting use of AGPs in 2018. Bambermycins


(i.e., Flavomycin) Bacitracin


Tylosin


Avilamycin Enramycin


Virginiamycin Colistin


Lincomycin


Oxytetracycline Tiamulin


0 2


7 7


4 4 6 8 10 Number of countries 16 12 14 16 18 12 10 10 9


Most used AGP’s


13 16


17


▶ ANTIBIOTIC REDUCTION | DECEMBER 2021


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