Carnivore biochemistry

CARNIVORE BIOCHEMISTRYBVM I: 2014/2015

By Saphan

Feeding habits of order carnivora

Overview

Cats are amazing creatures, unique & interesting in almost every way imaginable.

What separates cats from dogs has been ingrained into their genetics & biochemistry throughout their evolution.

This is particularly true in their nutritional Biochemistry.

Overview cont’d

However, vets consider cats and dogs to be similar for anesthesia protocols, clinical dizzs & Rxs.

Cats are strict carnivores unlike dogs.

A nutritional carnivore is an animal that can thrive throughout its life cycle without any carbohydrate in the diet.

Comparative physiology

Digestive system is similar to that of humans.

No enzyme in the saliva, its role is to lubricate food.

In the stomach, pH is very Low due to high conc. of Hcl- kills bacteria & other microbes & facilitates protein digestion.

Comparative physiology cont’d

Colon harbors microbes that produce vit B6, 12, biotin, Vit K and folic acid.

However, they are not absorbed through the colon wall.

So, are they of any importance????

Special nutrient requirements of cats

Proteins Cats are metabolically adapted to

preferentially use protein and fat as energy.

This is attributed to low km values of hepatic enzymes that remove amino groups & those involved in fat metabolism.

The gluconeogenic pathway is well adapted to utilization of carbon skeletons for glucose production.

Special nutrient requirements of cats cont’d

Taurine Cats require taurine in significantly large

amounts because: High physiological demand as they only use

taurine to form bile salts. Production of taurine from its precursor

cysteine is limited due to the decreased activity of cysteinesulfinic acid decarboxylase.

Additionally, some of the cysteine is shunted toward synthesis of felinine.

Biosynthesis of Bile salts

Special nutrient requirements of cats Cont’d

Arginine Cats are unable to synthesize sufficient

amounts of ornithine or citrulline for conversion to arginine.

Additionally, cats use a lot of arginine in the urea cycle, as this cycle is not down-regulated during periods of protein shortage.

Special nutrient requirements of cats Cont’d

Methionine & Cysteine

They are gluconeogenic substrates only in cats.

In addition, Cysteine is used for production of felinine in cats- territorial marker. This is particularly true in sexually intact cats.

Special nutrient requirements of cats Cont’d

Tyrosine Used in large amounts in hair production in

form of melanin.

This is particularly true in black cats.

Also the rate at which hair is lost in cats is exceptional.

Special nutrient requirements of cats Cont’d

Carbohydrates Cats require low intake of CHOs because they

lack salivary amylase, an enzyme responsible for initiating CHO digestion.

They also have low activities of intestinal and pancreatic amylases & reduced activities of disaccharidases in small intestines.

However, cats utilize simple sugars.

Special nutrient requirements of cats Cont’d

Carbohydrates cont’d

Cats’ hepatic glucokinase has minimal function and its activity is not adaptive.

Cats also have minimal activity of hepatic glycogen synthetase.

Special nutrient requirements of cats Cont’d

Fats They provide most of the fuel for energy.

Linoleic, linolenic, arachidonic acid, & some eicosotrienoic are essential fats.

Specifically, cats lack adequate hepatic- 6- desaturase activity and other hepatic desaturases required for the synthesis of arachidonic acid, eicosapentaenoic acid and decosahexaenoic acid.

Special nutrient requirements of cats Cont’d

Vitamins Pyridoxine- an essential cofactor in all transamination &

deamination reactions that are constantly active in cats.

Niacin- high physiological demands due to a higher rate of breakdown of vitamin precursors such as Tryptophan.

Vit A- cats can’t convert beta carotene to retinal because they lack intestinal beta carotene dioxygenase.

Vit D- cats have insufficient 7-hydrocholesterol in their skin to meet the vit D requirements.

Summary-Nutritional uniqueness of cats

Greater requirement of taurine, arginine, cysteine, methionine, tyrosine.

Need for dietary supply of linoleic acid, perhaps arachidonic acid.

Cannot make vitamin A from beta carotene.

Cannot make enough niacin/nicotinic acid.

Need more pyridoxine for the greater rates of amino acid metabolism