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?

First, 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

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 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.

Glycerides are powerful alternatives

It is suggested that monolaurin, one of the most studied glycerides, can replace frequently used AGPs in pig and poultry farming. Based on the results of the Brazilian study of Fortuoso and colleagues (2019) monolaurin in the diet of broilers showed potent antimicrobial effects and a growth promoting capacity. A better overall intestinal health allows young broilers to efficient absorb nutrients and to achieve a higher end weight. Also, its potent anti-inflammatory action is expected to play a significant role. Researchers expect monolaurin to reduce the release of macrophages producing pro-inflammatory cytokines. These cytokines cause tissues damage when produced in excess and increase the energy expenditure, causing a lower feed efficiency in farm animals.

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