What are the three key functions of sebum in horse skin?

• A. Lubrication for joints, digestion, and respiration.
• B. Waterproofing, skin and hair moisturizing, and immune defense against harmful microbes.
• C. Hair coloring, scent, and shine.
• D. Cooling and sweating assistance.

Answer: (B)

Sebum acts as a protective coating on the horse’s skin and coat, produced by the sebaceous glands. The three key roles it plays are waterproofing the skin and hair, moisturizing the skin and coat, and helping defend the skin against microbes.

Waterproofing creates a hydrophobic layer that reduces water loss from the skin and helps the coat repel water, which keeps the horse drier and helps the hair stay resilient. Moisturizing comes from the oily lipid content enveloping the skin and hairs, keeping the skin supple and the coat smooth so it doesn’t crack or become brittle. Immune defense is aided by the antimicrobial properties of certain sebum components and by maintaining the skin’s barrier, making it harder for harmful microbes to invade.

Other options mix in functions that aren’t driven by sebum—the joints’ lubrication, digestion, respiration, or cooling primarily involve other systems, and while sebum can influence shine and scent, its main, defining roles are the three described above.