As I understand we humans cannot live on a diet of protein alone and I’m assuming that carnivores such as Lions, Tigers, wolves etc are just the same.
So where do these animals get the other foodstuffs from to enable to live?
Carnivores are taking in blood, fat, bone and meat, along with various organs–a lot more than just “protein” if by “protein” you mean amino acids.
Is your question around trace elements or the need for veggies? Your mom was exaggerating a little when she said you had to eat your veggies. They are good for you, but not absolutely necessary. NB carnivores tend not to live particularly long lives, although on this Board someone will come along shortly and correct me with some exception or another, I’m sure.
Plus, not all “carnivores” are exclusively meat-eaters – though the main part of their diet may come from meat, many will not turn up their noses at plant materials that present themselves (e.g., house cats eating grass).
I asked a similar question some time ago on here - as to how animals aren’t constantly malnourished with their monotonous diets. Turned out that the animals in question can synthesise all the right vitamins and things from their samey food intake - although only humans and guinea pigs have lost the ability to synthesise Vitamin C, so need to take it in their diet.
Moral: never take your guinea pig on a long sea voyage.
I believe many carnivores will also eat the contents of the digestive tract, so they are getting some semi-digested carbohydrates as well.
Regards,
Shodan
Eating a liver is like eating a giant multivitamin. Eating bones is like a hot injection of calcium. Unlike modern human dining, animals tend to eat organs as well as meat. Toss in natural synthesis of vitamins and Mr. Carnivore is doing alright.
House cats eat grass as an emetic not as a food.
You’re mostly right–most primates cannot synthesize their own vitamin C, so humans aren’t really special.
Not just humans but all primates have lost the ability to synthesize vitamin C.
Different animals have different nutritional needs. A cow can get everything it needs to live simply by eating grass because its digestive system is organized differently than the human digestive system.
You don’t need to injest carbs. Your body can metabolize Protiens to get the needed glucose. You do need a small amount of fat.
Here’s what you need (in rough order):
A source of energy (Fats, protiens, carbs)
Protiens, well balanced (which meat does)
Fiber (pretty much veg sources only)
Essential fatty acids (EFA) and fats. (Meat has these)
minerals. (Meat is a good source)
vitamins. (In raw or rare fresh meat you can get pretty much any vitamin, vit C has to be watched)
trace nutrients. (phytos, anti-oxidants, etc, mostly in bright and dark colored veggies)
And fiber is the one thing that even total carnivores like cats eat grass for.
As has been said, carnivores tend to eat organ meats etc, also, not just muscle tissue.
DrDeth
My understanding is that cats only eat grass as an emetic, to make them sick in order to get rid of fur balls.
I may be wrong of course, if I am, someone will put me right
If I’m right, where do carnivores get their fibre from?
Many of the questions asked in the OP are answered in this thread about cats as carnivores, going on simulaneously. 
That is indeed one use of grass. But if you have had cats and allow them access to cat grass, you will see cat scat with grass in it in the litter box. Cats and other carnivores also get grass, ect when they consume the stomach contents.
Here’s an article about cats & grass which shows coughing up fur balls to the the secondary benefit.
http://www.pet-food-zone.com/cat_eating_grass.htm
Well I’ll be jiggered:smack:
I’ve had cats for many years, matter of fact my last one died just a few days ago.
I never knew they ate grass for anything other than coughing up fur balls
They just don’t need the same amount of fiber that humans need. A healthy diet for a human would kill a cow or a horse. We need fiber because our digestive systems evolved to deal with a diet that has a moderate amount of fiber, and if our digestive systems don’t get what they evolved to deal with they don’t work well. A cow’s digestive system presupposes massive amounts of cellulose, if they don’t get it they will die. A cat’s digestive system evolved to deal with almost no fiber, so they don’t need it to stay healthy.
Moving away from mammals, there’s a bit in The Life of Birds in which David Attenborough remarks that meat is so packed with nutritional goodness that a single successful kill will sustain (some raptor or another) for a full day of flying around and doing bird stuff. This was in marked contrast to the herbivore birds who’d spend all day trying to locate enough seeds, berries, etc.
So I guess you just need the system to extract all the meaty goodness. I’m fairly sure raptors don’t supplement their diet with fruits & nuts.
If you really want a specialized digestive system in a mammal, consider the vampire bat, which lives on blood. I doubt that very many other animals could get away with that diet.
ETA:
At least not warm-blooded vertebrate animals. Plenty of worms, etc, do OK that way.
Have you seen a vampire bat?
I just Googled, jebus they are ugly buggers for sure
To add something here- for those of you with an indoor only cat(s)*, please make sure he has a little grass to graze on. Specialized “kitty-grass” from the pet store is OK, but a tad over-priced, you can just buy the same sized tub of wheat-grass at your grocery store. Or grow your own, using oat seeds.
- and of course, in general, most cats should be indoor only in todays world. ymmv.
Conversely, nominal herbivores get some measure of protein from insects and other small animal life (like ground nesting birds) that they consume while grazing.