I have had a fascination for penguins since I worked with them between 1988-1990. So I enjoyed reading this:
From the New Scientist print edition e-zine, with some comments addded;
Original title - "How penguin dads keep fish for chicks".
"MALE king penguins have a unique way of putting the digestive process in their stomachs on hold. By producing less stomach acid and all but immobilising their guts, the birds can preserve fish in their bellies for up to three weeks to provide an emergency meal for hatching chicks." Smaller penguin species may be unable to do this - hours or days at most.
"Males take the last turn in incubating their eggs. Foraging females usually return to feed the chicks, but are often delayed (sometimes over 9 days), leaving the task to males who may have eaten their last meal weeks earlier. Yvon Le Mahon and his team at the National Centre for Scientific Research in Strasbourg, France, had previously shown that male penguin guts secrete antibacterial chemicals that preserve food. But that didn't explain why the food is not digested."
"To find out, the researchers inserted gastric probes into the bellies of 15 male penguins (Aptenodytes patagonica) on Possession
Island in the southern Indian Ocean. The stomach temperatures of all the birds remained constant They are incubating eggs after all. But pH levels in the gut were much higher than the optimum level at which digestive enzymes work.
That suggests that the birds suppress the amount of acid in their stomach to limit the digestion process. Most of the birds also significantly reduced their gut movements, helping keep their stomach contents intact."
Food protein quantity and quality is preserved since proteinases are inactivated. However, lipases may be active as some pancreatic enzymes from the duodenum may reflux into the stomach, apparently a feature of avian digestion. The researchers did detect a decrease in total lipid content.
For more, read their article at J. Exp. Biol., 207: 2715-2724. Access available for NUS accounts.