Monogastric species and polygastric species?

Question

Please discuss the differences and similarities between monogastric species and polygastric (ruminant) species; include why you think these differences developed and how animals have adjust to specific food types.

Answer 1

Monogastric just means that an animal has a one compartment stomach, like humans.  Our stomachs have distinct regions, the small cardiac region (non glandular portion), body, fundus and pyloric region (all glandular- produce pepsin, mucin and HCl).  All of the domestic species have these regions, they are just arranged differently.  Polygastric does not mean that ruminants have four different discrete stomachs, just four compartments.  The reticulum, rumen and omasum are all non-glandular, like one giant expanded cardiac region in the human stomach.  The abomasum is the glandular stomach.  Hind-gut fermenters like horses have an extremely developed cecum, but have a stomach similar to a monogastric (pigs, dogs, cats).  In ruminants (cow, sheep, goat, deer), the chambers all have a function.  The reticulum evolved as a particle strainer, so that flow into the rumen could be regulated.  Large blades of grass or heavy objects like rocks would sink into the reticulum so they could be expelled back into the esophagus for further chewing (the cud).  The rumen is a giant bacteria vat used for breaking down cellulose, a cow's diet.  ~75% of the food nutrients (through bacterial VFA formation) are absorbed through the wall of the rumen, something that does not happen in a monogastric.  The omasum has many plies that essentially strain all the water out of the ingesta before it passes to the abomasum, where protein digestion in all species occurs.  The rest of the GI tract is similar to a monogastric, with a few minor anatomic differences.  As a consequence of their anatomy, cows can get a lot out of what they eat, but suffer when fed poor quality ingredients (it just takes too long to process).  Horses do not break down their food as much (fermentation is in the colon, much further down the line relative to absorption which occurs in the jejunum) and can't absorb much of what they eat.  Hence, the difference in cow and horse p**p (soup vs. pellets).  So they make up for this by eating...all...the...time (with no gallbladder and continuous drip of bile).  Horses can eat c**p and essentially survive a diet that would starve a ruminant.  Monogastrics eat plants and meat, which requires enzymes to digest, necessitating a greater glandular portion of their stomach.

Answer 2

Sounds like you're taking Animal Science. WCC by chance? I'm stuck too. I guess that's the bad part of taking an online class. I even tried to Wikipedia it and found nothing. Good luck.