Do minke whales (Balaenoptera acutorostrata) digest wax esters?

Area of Science:

• Marine Mammal Physiology
• Nutritional Ecology
• Biochemistry

Background:

• Mammals typically digest wax esters with less than 50% efficiency.
• Minke whales consume krill, a diet rich in wax esters.
• Investigating digestive capabilities in marine mammals is crucial for understanding their energy assimilation.

Purpose of the Study:

• To determine if minke whales (Balaenoptera acutorostrata) efficiently digest wax esters from their krill diet.
• To quantify the dry-matter digestibility of wax esters (DMDwax) in minke whales.
• To compare minke whale wax ester digestion efficiency with the general mammalian pattern.

Main Methods:

• Analysis of forestomach and colon contents from minke whales fed on krill (Thysanoessa inermis).
• Measurement of dry mass, energy density, lipid content, and major lipid classes, including wax esters.
• Calculation of DMDwax by comparing wax ester concentrations in diet and feces, and in vitro dry-matter disappearance estimates.

Main Results:

• Wax esters constituted 21% of the krill diet's energy and 47% of total lipids.
• Energy density decreased by 50% from forestomach to colon.
• Calculated dry-matter digestibility of wax esters (DMDwax) was 94.1% (SD 2.8%).

Conclusions:

• Minke whales exhibit exceptionally high efficiency in digesting wax esters, exceeding 94%.
• The presence of fatty alcohols in feces indicates successful hydrolysis and absorption of wax ester components.
• Minke whales are highly efficient at absorbing energy from wax esters, representing an exception to the general mammalian pattern.