Ask A Scientist© Biology Archive

Author:      hignell
Text:        How long it takes for the digestive process to work in a 
ruminant?  With the various chambers and would digestion take longer than in 
other mammals?

Response #:  1 of 1
Author:      wizkid
Text:        A friend in animal nutrition is looking up an exact figure, but 
as he does, here are a few guidelines:  Time of digestion largely depends on 
the type of food an animal ingests:
  CARNIVORES:  short, uncomplicated digestive systems.  They eat very high on 
the food chain (other animals), which provide food stuff which is relatively 
easy to digest.  Hence, rapid digestion.
  OMNIVORES:  medium length, medium complex digestive systems.  We eat at all 
levels of the food chain, and so need a balanced system.  Medium time of 
digestion (roughly 2-10 hours per meal, depending on proportions of 
carbohydrates, fats, proteins).
  HERBIVORES:  (ruminants):  long, complex digestive systems.  They eat very 
low on the food chain (plants), and require more elaborate digestive 
capabilities (even help from microorganisms).  Hence, longer digestion.


Here is what Dr. Ingalls and his colleagues discovered from deer:  Time for 
passage of food from rumen:
     alfalfa dry matter:  15 hr
     trefoil:  15 hr
     timothy:  20 hr
     canary grass:  23 hr

(Ingalls JR, Thomas JW, Tesar MG, Carpenter DL.  Relations between ad libitum 
intake of several forage species and gut fill.  Journal of Animal Science.  
25(2):283-289.  That is a long time just to get past the first stage of 
digestion!  Another researcher, Dr. Church, discovered that many factors 
controlled the passage rate of food in ruminants:  physical nature of the 
food, particle size, digestibility, specific gravity, and amount eaten.  
Smaller particles passed through more quickly.  When the animal ate more food 
at one time, this also increased passage time.  Generally, passage rate 
through the entire digestive system took twenty-four to forty-eight hours.  
Also, remember that ruminants include a wide variety of animals, which differ 
widely in many ways.  They range from the diminutive mouse deer (rabbit-sized) 
to the middle-sized deer to the large-- sized cattle and giraffes.  Their 
digestive capabilities and diets are as varied, so digestive times vary, too.  
A good book discussing ruminant digestion and nutrition:  Wildlife Ecology, by 
Aaron N. Moen, Publisher:  W. H. Freeman & Co., 1973