Botanicals and bacterial resistance

Botanicals and bacterial resistance: a nutritional approach in animal production

Antibiotic resistance represents a major challenge to public and animal health on a global scale.

The World Health Organisation asserts that the indiscriminate use of antibiotics in animal production contributes significantly to the development of resistant bacteria, which can be transmitted to humans through the food chain and the environment (Marshall & Levy, 2011).

This challenge has prompted the search for sustainable alternatives, including botanicals, which are plant-derived compounds with antimicrobial, antioxidant and microbiome-modulating properties..

In this article, an analysis will be conducted of botanicals as a strategy to combat antimicrobial resistance. The focus of this analysis will be on the mechanisms of action of botanicals, their impact on reducing antibiotic use and their specific applications in poultry, swine and ruminants.

Botanicals: mechanisms of action

Botanicals are defined as compounds comprising plant and spice extracts, which are characterized by a high content of polycyclic rings. These bioactive compounds encompass a diverse array of structures and molecular compositions, including polyphenols, flavonoids and terpenes. 

1) Direct antimicrobial activity

Compounds such as carvacrol and thymol, which are present in oregano and thyme, have been shown to have the capacity to alter the bacterial cell membrane, thereby compromising its structural and physiological integrity (Lobiuc et al., 2023).

In addition, phenolic compounds have been demonstrated to be capable of hindering enzymatic activity and altering DNA structure, a process which can prevent cell replication and multiplication.

Consequently, the antimicrobial action of these compounds serves to reduce the harmful bacterial load in the gastrointestinal tract, thereby controlling the population of pathogenic microorganisms such as Escherichia coli and Clostridium perfringens (Lobiuc, A. et al, 2023).

2) Modulation of saprophytic microbiota

The utilization of botanicals has been demonstrated to promote a healthy balance in the intestinal and respiratory microbiota. This is achieved by stimulating the multiplication of beneficial bacteria such as Lactobacillus spp. and Bifidobacterium spp., while inhibiting the growth of pathogenic microorganisms.

This optimization of digestive processes, improved nutrient absorption, and enhanced systemic immunity consequently leads to an improvement in production parameters (Windisch et al., 2008).

3) Antioxidant and anti-inflammatory potential

Polyphenols and flavonoids have been shown to neutralize free radicals, thereby protecting cells from oxidative stress that occurs in situations of high production loads (Hashemi & Davoodi, 2012). This process has been demonstrated to reduce systemic inflammation and improve overall animal health.

4) Stimulation of the immune system

It has been posited that certain botanicals have the capacity to enhance the immune response by stimulating the activity of macrophages and cytokines (communication molecules between white line defense cells), thereby enhancing the body’s ability to resist bacterial and viral infections, even before they can occur (Greathead, 2003).

Impact on antibiotic reduction

Numerous studies show the capacity of botanicals to substitute for, and in some cases fully supplant, the use of antibiotic growth promoters. The European Union has prohibited the use of antibiotics as growth promoters since 2006, and subsequently followed by the United States.

Furthermore, studies have shown that botanicals can mitigate the necessity for antimicrobial treatments in complex health scenarios, such as disease outbreaks. The underlying reasons for this phenomenon are multifaceted. 

» Disease prevention: in monogastric animals, the inclusion of botanicals in the daily diet has been shown to decrease the incidence of diarrhea and other clinical signs by modulating the gut microbiota, improving the anatomical structure of intestinal tissue and reducing the growth of pathogenic bacteria (Zeng et al., 2015). In addition, they have been demonstrated to strengthen the immune system and possess antioxidant potential.

» Improved production efficiency: these compounds may improve daily weight gain and feed conversion by optimizing digestive processes, so another consequence of their use is a noticeable improvement (Khan et al., 2012).

» The reduction of zoonotic pathogens is an area of significant research. In poultry, the use of botanicals has been shown to be effective against Salmonella enteritidis and Campylobacter jejuni (Almeida et al., 2012). These microorganisms have been found to be reduced in the food chain, and their passage to the final consumer has been prevented. 

Botanicals are already being used worldwide to minimise the use of synthetic chemotherapy. Examples of the use of botanicals in current production systems include:

Poultry production

The health of the gastrointestinal tract and respiratory system are of critical importance in the context of meat and egg production. The poultry population is subject to constant health challenges due to their rapid growth rate, high population density and high susceptibility to climatic parameters such as temperature and humidity. 

Oregano, thyme and cloves contain active compounds such as carvacrol and thymol that stimulate the secretion of digestive enzymes and improve the absorption of nutrients present in the diet (Hashemi & Davoodi, 2012). 

In intensive poultry production systems, there is a prevalence of diseases such as coccidiosis, a parasitic infection caused by Eimeria spp., and necrotic enteritis, a bacterial infection caused by Clostridium perfringens. 

In this regard, the use of oregano and thyme has been shown to significantly reduce the incidence of these pathologies by inhibiting the multiplication and growth of both the parasite and the harmful bacteria (Walsh et al., 2012).

Reducing oxidative stress and improving meat quality

Antioxidant molecules present in plants have been shown to reduce oxidative stress, thus protecting muscle cells and improving muscle fat infiltration and resistance to rancidity (Hashemi & Davoodi, 2012). Consequently, this results in a significant increase in the shelf life of the product designed for the final consumer.

A study by Zeng et al. in 2015 demonstrated that the incorporation of botanicals in broiler diets resulted in enhanced feed conversion efficiency by up to 5% and a reduction in the prevalence of diarrhea by 30% (Zeng et al., 2015).

Swine production

In the context of pig production, botanicals are predominantly employed to prevent digestive diseases and enhance nutrient absorption, particularly during critical stages such as weaning.

During weaning, piglets experience significant alterations in their diet and gut microbiota, rendering them vulnerable to infections. 

The addition of certain components of cinnamon, cloves and garlic to pig diets has been demonstrated to enhance the composition of the microbiome by promoting the proliferation of saprophytic bacteria such as Lactobacillus spp. and concomitantly reducing Escherichia coli (Zeng et al., 2015).

» Concurrently, the absorption of nutrients such as iron and zinc is optimized, with the latter being micronutrients that are essential for both body development and the control of diarrhea. 

In later stages, such as fattening and finishing, botanicals have been shown to be effective against the incidence of porcine ileitis (the causative agent of which is the bacterium Lawsonia intracellularis).

⇒ The antimicrobial and anti-inflammatory properties of botanicals have been demonstrated to play a pivotal role in preventing the onset of the disease in susceptible farms, while concurrently reducing the severity of the disease by significantly decreasing the utilization of antibiotics (Krause et al., 2018).

Environmental impact

An additional environmental benefit is the utilization of botanicals to curtail the production of volatile compounds, such as ammonia, thereby markedly diminishing environmental contamination by bad odors in the environments of pig farms (Windisch et al., 2008).

Ruminants

In both meat and dairy ruminants, botanicals represent a significant novel approach to optimizing rumen fermentation, enhancing metabolic health and reducing environmental impact.

Garlic and anise extracts have been demonstrated to function as modulators of the rumen microbiome, enhancing the ratio of volatile fatty acids (acetic, propionic and butyric) and curtailing ammonia production (Patra & Saxena, 2009).

In dairy cows, polyphenols present in milk thistle and rosemary have some hepatic protective capacity, reducing the risk of hepatic steatosis and improving metabolic efficiency during lactation (Hashemi & Davoodi, 2012).

Reduction of methane emissions

Research has demonstrated the antimicrobial properties of botanicals on methanogenic archaea, the microorganisms responsible for methane production in the rumen.

This has been shown to enhance the energy efficiency of animals, thereby contributing to environmental sustainability by reducing greenhouse gas emissions. (Patra & Saxena, 2009). 

Summing up…

They are effective in poultry, pigs and ruminants, adapting to the health and production challenges of each species.