Antibiotics in Agriculture

Antibiotics not only help us to recover from nasty illnesses but are important in the agricultural industry for increasing output and preventing disease. However, the negative implications surrounding the overuse of antibiotics in agriculture are much the same as in humans. You might have heard of the increased use of antibiotics giving a higher likelihood of microorganisms developing antibiotic resistance. This antibiotic resistance in agriculture can endanger livestock and humans. Today we shall be looking at some examples of antibiotics in agriculture, their uses, and the impacts of the overuse of antibiotics on farms.

Antibiotics in Agriculture Meaning

Agricultural workers depend on the output and efficiency of their farms to make a living. They need their livestock to be healthy and grow quickly. Therefore, farmers will apply antibiotics to their livestock to prevent the spread of disease, improve feed efficiency, and improve growth rates. In many countries, there are not strict enough laws and legislations to control antibiotic use, and many common agricultural antibiotics can be bought over the counter. It is for this reason that antibiotic-resistant bacteria are becoming prevalent in agriculture and resulting in an increased dependency on more antibiotics to prevent the spread of new strains.

Antibiotics in Agriculture Examples and Types

Let's now have a look at some of the most common antibiotics used in agriculture, which are creating the opportunity for rising antibiotic-resistant bacteria population:

• β- lactams: almost half of the antibiotics sold over the counter are β-lactams (including many penicillin derivatives). These molecules inhibit the growth of peptidoglycan in pathogens (a key component of bacterial cell walls), which results in cell death (bactericidal).
• Tetracyclines: the most commonly used group of antibiotics in agriculture, tetracyclines are cheap antibiotics that promote growth in poultry and swine when applied in sub-therapeutic doses.
• Sulphonamides: sulphonamides are used in humans to treat urinary tract infections (UTIs). In agriculture, they are applied therapeutically to poultry to control a wide range of diseases.
• Aminoglycosides: these antibiotics prevent the spread of disease by inhibiting protein synthesis within the cell (bacteriostatic)
• Macrolides: macrolides are used to counteract a range of bacterial infections such as pneumonia and tonsilitis. They bind irreversibly to 50S ribosomes inhibiting any protein synthesis (bacteriostatic).

Now that we know what antibiotics are, and why they are needed in agriculture, let's explore some of their uses:

• Prevention of disease: the most important use of antibiotics in agriculture (and in human health) is to stop the spread of disease. Livestock are normally kept in confined spaces where high temperatures and close contact allows disease to spread rapidly. Even if just one animal catches the disease, the infection could spread throughout the farm and between different animals.

• Improve growth rates: certain antibiotics can improve growth rates in livestock. Applying antibiotics to livestock in low dosages can cause them to grow larger and faster. However, these low-levels of antibiotics are perfect conditions for rising resistant bacteria populations,

• Feed conversion efficiency: similarly, the application of antibiotics to livestock at sub-therapeutic doses has been proved to improve feed conversion efficiency. This means that digestion rates increase and the ratio of food product to fat/useless material increases.

Sustainable Agriculture

Sustainable agriculture aims to reduce the need for agrochemicals (fertilisers, pesticides, antibiotics). When considering antibiotics, they are required when diseases are common, or when livestock are not growing large or fast enough.

Intensive agriculture involves the entirety of a farmer's livestock being cramped into confined spaces (warehouses) where they can barely move. The conditions in these warehouses are poor, with close contact and high temperatures (many individuals in the same place moving around) resulting in disease spreading easily and quickly. These high temperatures will also raise the metabolic rate of the livestock, meaning that their feed conversion efficiency will decrease.

Sustainable agriculture refers to the livestock being reared in pastures, where they have access to nutritious grass and legumes that are inedible to humans. This type of farming removes the need for radical land changes and improves the biodiversity of the surrounding ecosystem, which further protects livestock from disease. Developing relationships between livestock and crops is important in improving the productivity of agroecosystems.

Antibiotics in Agriculture Impacts

Let's have a look at some of the impacts of the overuse of antibiotics in agriculture:

• Antibiotic-resistant bacteria: the major impact of the overuse of antibiotics on farms. Intensive agriculture provides the conditions for the rapid transmission of disease across a farm, and then sub-therapeutic antibiotic application (for increased growth rates and feed efficiency) provides the conditions for resistant bacterial strains to rise.

• Costs: although antibiotic application is intended to reduce costs (from the loss of livestock and produce to disease, and speed up the growing process), the prevalence of resistant strains requires more antibiotics to be synthesised and more antibiotics to buy.

• Slurry: the mismanagement of slurry can lead to the contamination of waterways. This can spread dangerous resistant bacteria to humans if this water is treated to be used as drinking water.

• Contamination of produce: if antibiotic-resistant bacteria are not noticed in livestock before they are slaughtered, there is the possibility of these bacteria being present in produce and being passed on to humans.

• Global trade: agriculture is a worldwide industry. Therefore. the trade of livestock between countries and continents increases the risk of novel resistant pathogens being spread.

• Agricultural workers: those working on farms will be in close contact with infected individuals so will be at high risk of becoming infected with zoonotic diseases.