Correct Option
The correct option is (a).
Explanation
Antibiotics are chemical substances produced by microbes (or synthesized) that inhibit the growth of or kill other microorganisms. While primarily used in human medicine, their application extends significantly to veterinary science, animal husbandry, and agriculture for disease control and growth promotion.
Statement-wise Analysis
- Statement 1 is Correct: Antibiotics are frequently mixed with the feed of livestock and poultry. This practice is undertaken to treat sick animals, prevent microbial infections (prophylaxis) in crowded conditions, and serve as growth promoters to enhance feed efficiency.
- Statement 2 is Incorrect: Antibiotics are effective against bacterial plant pathogens. Compounds such as streptomycin and oxytetracycline are used in agriculture to control specific bacterial diseases in plants, such as fire blight in apples and pears, or citrus canker. Therefore, the claim that they are ineffective against any plant disease is factually wrong.
- Statement 3 is Incorrect: The unnecessary or indiscriminate use of antibiotics does not enhance the population of beneficial bacteria. Instead, it often destroys the beneficial microbial flora (microbiome) present in the body, leading to dysbiosis. Additionally, such misuse exerts selection pressure that favors the survival and proliferation of antibiotic-resistant bacteria.
Key Takeaway: Antibiotics are utilized in animal husbandry for disease prevention and growth promotion, and in agriculture to treat bacterial plant diseases. However, their misuse destroys beneficial flora and contributes to antimicrobial resistance.