Although the EU banned the use of antibiotics as animal growth promoters in 2006, the transition to antibiotic-free production systems has been far from easy.

Despite the time that has elapsed, the livestock sector continues to face major challenges to maintain productivity, health and animal welfare without resorting to these drugs.

In this context, the search for effective alternatives remains a strategic priority to mitigate the development of resistance and move towards more sustainable production models.

To achieve this objective, it is necessary to implement a set of integrated strategies that include the reinforcement of biosecurity, the mitigating production stress and environmental, and the development of innovative nutritional solutions aimed at boosting immunity and optimising the productive performance of the animals.

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What is antibiotic resistance and why is it a threat?

La antibiotic resistance is a process by which bacteria and other micro-organisms acquire the ability to survive and multiply in the presence of previously effective antibiotics. This is one of the greatest threats to animal health, food safety, livestock productivity and public health.

• Drug treatments become less effective, as resistant bacteria hinder the cure of common diseases such as mastitis, pneumonia or infectious diarrhoea, increasing mortality, veterinary costs and the use of complementary medicines.
• Reduced productivity and profitability, because when antibiotics fail, sick animals have lower weight gain, reduced meat, milk or egg production and require more days of fattening. In addition, when antibiotics are used for therapeutic purposes, mandatory withdrawal times before slaughter or harvesting limit marketing, affecting production efficiency and farm margins.
• They compromise food safety and public health, as resistant bacteria can be transmitted to humans through food, direct contact or the environment, posing a global risk.

 

Biosafety and stress management: first pillar to reduce antibiotic use

Reducing the use of antibiotics in animal husbandry starts with disease prevention through appropriate biosecurity and stress management practices. Both aspects form the basis of a sustainable production system by strengthening the animals' natural defences, reducing the incidence of infections and minimising the need for drug treatments.

Biosecurity is the first pillar in disease prevention and reduction of antibiotic use in animal production. Its effective implementation requires strict control of visitor and vehicle access, the establishment of quarantine protocols for replacement animals, and the application of rigorous cleaning and disinfection procedures in all facilities.

It is also essential to ensure the sanitary quality of water through appropriate treatments, to establish integrated pest management programmes, and to ensure a unidirectional flow of people and materials to minimise the risk of cross-transmission.

Finally, the separation of animals by age and stage of production helps to reduce exposure to pathogens and to improve the overall health status of the farm.

On the other hand, stress reduction is essential to maintain the health, welfare and productive performance of animals, and it is essential to control the various stressors that can affect them.

• Environmental stressl, associated with inadequate temperature conditions (overheating), overcrowding, poor ventilation or excessive humidity in the premises.
• Physiological stress, The main reason for this is the presence of disease, injury or dietary restrictions that compromise the metabolic balance and immune response.
• Behavioural stress, caused by excessive noise, intense handling, isolation or lack of stimulation that alters the natural behaviour of the animals.
• Social stress, linked to early separation of offspring, competition for food or space and hierarchical instability within the group.

 

Functional nutrition and antibiotic reduction: the role of organosulphur compounds in livestock farming.

Today, animal nutrition represents a fundamental tool for improving animal health and productivity, especially in the context of reducing the use of antibiotics.

Among the main alternatives are the probiotics, prebiotics, organic acids and phytogenic compounds, which contribute to balancing the gut microbiome, strengthening the immune system and improving digestive efficiency.

Within these strategies, the use of phytogenic compounds has gained considerable scientific and technological interest, offering a wide range of possibilities to promote animal health in a natural and sustainable way, minimising the need for conventional antimicrobial treatments.

In particular, the compounds organosulphurates (OSCs) derived from alliaceous plants such as garlic (Allium sativum) and onion (Allium cepa) are an outstanding example of phytogenic ingredients with high functional potential. These secondary metabolites have been shown to possess multiple beneficial properties, among which the following stand out:

• Antiparasitic effects, which help to reduce the load of intestinal pathogens and improve the health status of the animal.
• Broad spectrum antimicrobial activity, effective against bacteria, fungi and some pathogenic viruses.
• Modulating capacity of the intestinal microbiome and the immune response, promoting a healthy microbial balance and a better response to infectious agents.

 

Scientific evidence on the use of organosulphur compounds in animal production

There is extensive scientific literature supporting the use of OSCs in different livestock species. Numerous studies in vivo have shown that these compounds contribute to balance the gut microbiota and strengthen the immune response, resulting in improved health status and production performance in various animal species.

• Pigs: In weaned piglets, supplementation with CSOs has shown a beneficial modulation of the gut microbiome, characterised by an increase in lactic acid bacteria (LAB) and a reduction of potentially pathogenic microorganisms, resulting in a significant decrease in post-weaning diarrhoea episodes. These positive effects on gut microbial stability correlate with higher average daily gain, improved feed efficiency and lower feed conversion ratio, which are key factors in optimising animal performance at this critical stage of development.

Similarly, in fattening pigs, the inclusion of OSC-rich extracts in the diet has been shown to improve nutrient utilisation and promote better conversion of feed to body mass, while maintaining a healthy gastrointestinal tract.

In addition, a reduction in oxidative and metabolic stress indicators has been observed, as well as improved faecal consistency, reflecting a stabilising effect on gut physiology and overall diet digestibility.

• Poultry farming: In laying hens, supplementation is correlated with increased egg number and size, as well as a decrease in intestinal enteropathogens and an increase in beneficial populations of Lactobacillus and Bifidobacterium. In broilers, the inclusion of CSOs in the diet improves feed conversion and weight gain, even under health challenges such as infection by Eimeria acervulina, by reducing oocyst excretion and enhancing the specific immune response.
• Ruminants: Likewise, in small ruminants such as fattening lambs, supplementation of water or feed with OSC-rich extracts has shown positive effects on weight gain, ammonium reduction and stabilisation of ruminal pH, results comparable to those obtained with conventional additives such as monensin.
• Other species: In aquaculture, dietary supplementation with sulphur compounds from alliaceae has been shown to improve innate immune response and reduce mortality against bacterial pathogens such as Aeromonas o Vibrio. At rabbits and horses, These extracts have shown antioxidant effects and improvements in productivity and intestinal stability in situations of stress or dietary changes, as well as a increased repellency to ectoparasites, thus contributing to the welfare and general health of the animals.

 

Conclusions

Ultimately, the available evidence indicates that organosulphur compounds (OSCs) of plant origin constitute a promising tool in an integrated approach to animal management and nutrition, oriented to preventing infections and maintaining intestinal health.

Their incorporation, together with other good biosecurity, management and nutritional practices, has proven to be an efficient, cost-effective and sustainable solution to improve animal welfare and optimise farm productivity.