Just so happens we have your answer.....Cud is a portion of food that returns from a ruminant's stomach in the mouth to be chewed for the second time. More accurately, it is a bolus of semi-degraded food regurgitated from the reticulorumen of a ruminant. Cud is produced during the physical digestive process of rumination. The idiomatic expression chewing one's cud means meditating or pondering; similar expressions such as "he chewed that over for a bit", or "chew on that!" likely have the same derivation.
Explanation...... The alimentary canal of ruminants, such as cattle, goats, sheep, alpacas and antelope, is unable to produce the enzymes required to break down the cellulose and hemicellulose of plant matter. Accordingly, these animals have developed a symbiotic relationship with a wide range of microbes, which largely reside in the reticulorumen, and which are able to synthesize the requisite enzymes. The reticulorumen thus hosts a microbial fermentation which yields products (mainly volatile fatty acids and microbial protein), which the ruminant is able to digest and absorb. This allows digestion of less edible plants.
Hope that helped Heifer Holly.
Oh. MY. GaWH!!!!!!! This was a gooder.