Obligate vs Super Carnivores

[jojodancer]

I'm starting a new thread since hijacking other threads drives me bonkers! (I can never find what I'm looking for)

OK, so I thought I had read in a Bob Church article that ferrets are obligate carnivores - they don't have a caecum. Felines are one step (maybe a 1/2 step below them) because they have a caecum, but it is small. Since they have that caecum, they are able to digest some plant matters. Canines, on the other hand, have a larger caecum, so they are farther down the carnivore/herbivore scale and are considered omniverous carnivores.

I read through my Diet 101 series and can't find that reference.

Giuli mentioned a Dr Susan Brown article from 2006. Is that where it is from? I specifically recall mentioning the sizes of caecums and that ferrets are more meat-only than felines due to the caecum size....

Can anyone help me? This is going to drive me nuts!

[jojodancer]

OK - I think I found it. From Bob Church's Diet 101 Series. Part 13, Sunday, May 31, 1998

Doesn't say anything about feline caecum size though... I'm going to have to keep looking.
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What happens when a carnivore eats prey? Is it the same as when an omnivore
or a herbivore eats something? The ferret is a primary carnivore, which is
an animal that includes very little or no plant material in their natural
diet. Non-primary carnivores, sometimes referred to as secondary carnivores,
do not equal the omnivorian degree of plants included in their diet, but
still eat far more plants than primary carnivores. Diets are actually a
continuum rather than a scale with stops. Imagine primary carnivores
blending into secondary carnivores, which blend into omnivores, which blend
into secondary herbivores, which blend into primary herbivores. Many
zoologists would classify a bobcat as a primary carnivore, a coyote as a
secondary carnivore, a black bear as an omnivore, a rat as a secondary
herbivore, and a deer as a primary herbivore.

Mammalian primary carnivores exhibit general modifications to their
digestive systems that include cutting--rather than grinding--teeth, a
rather large and simple stomach, shorter intestines, a reduced or absent
caecum, and rapid food transit times. The stomach is large in proportion to
its body to hold a lot of food; important when you might only eat once a day
(if lucky), or when you have to eat fast. Its construction is rather simple
when compared to the herbivore stomach. The caecum (helps digest plant
foods) is an extension of the large intestine, forms a blind pouch and is
found at the small intestine-large intestine junction. In primary
herbivores the caecum can be extremely long, even longer than the large
bowel; in primary carnivores, the caecum is small or absent. Ferrets no
longer have a caecum and the junction of the small intestine to the large
intestine cannot be seen with the naked eye. So even though ferrets are
domesticated, they are still physiologically pretty much of a primary
carnivore. That means animal eater.

Digestion starts in the mouth when the teeth cut or grind the food, mixing
it to various degrees with salivary juices, which is mostly water and some
enzymes. Not all mammals have the same mix of enzymes in their salivary
juices; carnivores tend to lack some which convert starches into sugars.
This is evolutionary streamlining; if you primarily eat meat products with
high protein and fat contents, why produce an enzyme for starches which are
primarily found in plants? Herbivores grind food for a long time, mixing it
well with lots of enzyme-laced saliva; many primary herbivores will either
eat their "green" feces to gain extra nutrients, or cud chew to help break
them down. Carnivores simply cut the meat and bone into chunks small enough
to swallow and gulp it down "unchewed." In primary carnivores, the grinding
molars are extremely reduced or absent; in ferrets, the grinders are a
fourth or smaller than the cutting tooth.

Once the food gets to the stomach, herbivores tend to keep it there a while,
and they can have large, complex, or multiple stomachs to help break down
the plant materials so the intestinal bacteria can convert the cellulose
into sugars. Carnivores lack such complexity in the stomachs, and normally
the stomachs empty rapidly because the extraction of nutrients from meat
products is rather simple compared to the extraction of nutrients from plant
materials.

The digestive enzymes also reflect the diet of the mammal, and are geared
towards digesting meat products in carnivores. Herbivore mammals tend to
specialize in digestive enzymes that specialize in breaking down starches
into sugars. Carnivores tend to lose the ability to break complex starches
and sugars soon after weaning, which is why lactose-tolerant babies become
lactose-intolerant adults (there is some evidence that drinking milk as an
infant and continuing through adulthood helps maintain lactose tolerance in
many species). They are also better at converting proteins into energy than
most herbivores, with fewer negative side effects, notably ketone related
acidosis.

There are many other differences (pick up a copy of Hyman's Comparative
Vertebrate Anatomy), but the point is a mammal takes millions of years to
evolve, and during that time the digestive system becomes fine-tuned to a
particular type of diet. The bottom line is herbivores are not omnivores,
and are definitely not primary carnivores. It is a mistake to assume
animals from one category can subsist on the foods from another category and
remain healthy. Try and imagine what would happen to a horse fed a
carnivore diet. Even if you could get the horse to eat it, could you keep
it healthy? What would the long term effects of such a diet be on the
bowel physiology? Yes, domestic herbivores, such as cattle and sheep, can
be growth-stimulated by the inclusion of animal byproducts into their meal.
Its also true most herbivores will consume the occasional small animal or
chew a bone, but these instances are about as frequent as the times a
primary carnivore consumes plants. You cannot convince anyone that horses
will live better, fuller, happier lives subsisting on the diet of a lion.
Why convince people what primary carnivores will be better off eating an
omnivorian or herbivorian diet? Primary carnivores, even domesticated ones,
do best when subsisting on a diet nearest to the evolutionary natural diet
possible. The same goes for all animals.

Why do ferrets eat carrots and potatoes? Well, its not natural, that's for
sure. Heck, potatoes are a New World plant and weren't even around for
European polecats to dig up. I suspect the ferrets are either conditioned
to think of them as food, perhaps from trying them as a youngster, or
because some smell associated with them is similar to part of the kibble
smell. New Zealand feral ferrets and European polecats share a common
characteristic in that both go past the carrots and potatoes for the real
meat. You can write this down and believe it: ferrets are primary
carnivores that evolved eating animals and they have a digestive system
that reflects that basic fact.

[Forum Administrator]

Email me and I will send you Dr. Browns lecture in its entirety. I dont think it mentions the feline caecum though. Oh boy this is going to drive us ALL nuts!