• Lipid Peroxidation in Aquafeeds:
• Aquafeeds are exceptionally rich in marine lipids containing long-chain polyunsaturated fatty acids (EPA, DHA) that are highly susceptible to free radical autoxidation, resulting in toxic hydroperoxides, aldehydes, rancidity, and nutritional loss.
• Role of Synthetic Antioxidants:
• Butylated Hydroxyanisole (BHA) and Butylated Hydroxytoluene (BHT) (as well as Ethoxyquin) are phenolic free-radical scavengers added to feeds (typically at $\le 150-200\text{ mg/kg}$) to intercept peroxide radicals, breaking the propagation chain of lipid peroxidation.
• nalysis:
• (Butylated hydroxyanisole): Correct synthetic antioxidant.
• Options 1, 2, 4: Solvents, sweeteners, or organic acids without free-radical scavenging properties.

Correct option: (3) Butylated hydroxyanisole

• Fungal Contamination and Mycotoxins:
• During storage in warm and humid tropical climates, finished aquafeeds and feed raw materials are vulnerable to mold growth (e.g., Aspergillus flavus, Penicillium, Fusarium), which produce lethal mycotoxins (aflatoxin $B_1$, ochratoxin, zearalenone).
• Propionic Acid and Propionates:
• Propionic acid (and its calcium/sodium salts) is the most widely utilized and effective antifungal agent (mold inhibitor) in compound feed manufacturing.
• It readily penetrates mold cell walls in un-ionized form, disassociates intracellularly to lower pH, disrupts cellular proton gradients, and inhibits metabolic enzymes.
• nalysis:
• (Propionic Acid): Correct.
• Options 1, 2, 4: Inorganic salts and strong mineral acids not used as safe organic mold inhibitors.

Correct option: (3) Propionic Acid