Final answer:
The use of antimicrobial drugs at a lower dosage in animals for purposes other than treating sickness is referred to as subtherapeutic. This practice is associated with risks such as the development of antimicrobial resistance.
Step-by-step explanation:
The use of antimicrobial drugs at a lower dosage than would be used for sick animals is referred to as subtherapeutic. This approach is typically used for purposes such as growth promotion in livestock or prophylaxis to prevent the onset of disease. However, it's important to understand that subtherapeutic use of antibiotics in animals can lead to the development of antimicrobial resistance, making treatment of disease with antibiotics in humans and animals more difficult. It is crucial that antimicrobial drugs are used responsibly to limit the spread of resistant bacteria.
Selective toxicity is a key property of effective antimicrobial drugs, as these should kill or inhibit the growth of pathogens without harming the host. Narrow-spectrum antimicrobial drugs are often preferred as they target specific pathogens and help prevent the development of resistance as well as superinfection. Chemotherapy refers broadly to any use of drugs to treat disease, whether it's cancer or infections caused by microorganisms.