6b Nutritional Peculiarities of Cats Flashcards
What are the amounts of energy substrates for cats?
protein > fat > carbs
Do cats have a carb requirement?
no
Do cats have a fiber requirement?
yes, for GI health
How do the taste receptors differ in a cat?
- Tas1r2 unexpressed
- not attracted to carbs or sweeteners
How does pancreatic alpha-amylase activity differ in cats compared to dogs?
- only 5% of those in dogs
How does disaccharidase activity in cats compare to those in dogs?
- only 40% activity of those in dogs
Describe the expression of SGLT in cats.
- reduced expression along crypt-villus axis
- cats cannot increase expression of this transporter when sugar eaten
Describe hexokinase, glucokinase and fructokinase activity in cats. (convert glucose to glucose-6-phosphate)
- hexokinase activity in tissues normal
- glucokinase activity in liver minimal so cannot clear large amounts of glucose
- lack fructokinase (fructose excreted in urine)
Describe how cats blood glucose changes in a carb free diet.
- increases more than a carb diet
How do cats meet glucose requirements in a carb free diet?
- rely on gluconeogenesis to sustain blood glucose
- source of carbon skeleton: AA, propionate and glycerol
- some amino acids can enter the Krebs cycle
Why do cats have a high protein requirement for maintenance?
- not due to amino acid requirement
- due to high amino acid turnover (high activity of hepatic enzymes, urea cycle enzymes)
How high is the feline protein maintenance requirement compared to dogs?
- kitties 50% higher than puppies
- adult cat 2x higher than adult dog
How do cats control protein metabolism?
- they don’t
- are constantly metabolizing fixed amount of protein
- can’t decrease liver enzymes
- muscle wasting can occur quickly
How do cats control the urea cycle?
- cannot reduce enzymes in urea cycle so do not have nitrogen pool in the body
- highly efficient detoxification of nitrogen wastes
- contrast to omnivores
- non adaptive to dietary protein levels
What happens with regards to the urea cycle during fasting or reduced protein intake?
- urea cycle intermediates become depleted
- with protein meal, intermediates replenish
- key intermediate: ornithine
- dietary precursor: arginine
Why do cats have an arginine requirement?
- low activity of enzymes in small intestine to produce arginine from ornithine and citrulline
- pyrroline-5-carboxylate synthase
- ornithine aminotransferase
What happens with an arginine deficient meal is fed?
- ammonia cannot be converted to urea
- ammonia toxicity in less than an hour
- death within 2-5 hours
but this is rare
Why do cats have a taurine requirement?
- taurine is a beta-amino sulfonic AA
- important for bile acid conjugation
- essential for normal retinal, cardiac, neurologic, reproductive, immune and platelet function
- cat liver has limited capacity to synthesize taurine
- limited enzymes to convert methionine and cysteine to taurine
Why do cats need taurine for bile acid conjugation?
- cannot change to glycine conjugation
- enterohepatic circulation usually occurs
- but microbial degradation = beconjugation
- obligate taurine loss
Where can a cat get taurine?
- abundant in animal tissues, absent in plant
What effects does taurine deficiency have?
- feline central retinal degeneration
- reproductive failure and impaired fetal development
- feline dilated cardiomyopathy
- hearing loss and impaired immune function also reported
What is the first limiting AA in cat diets formulated with natural ingredients?
methionine
Cysteine can provide how much of sulfur AAs?
about half
- but low in vegetable based diets and must be supplemented
Why do cats have a higher methionine/cysteine requirement than other species?
- cysteine synthesis
- limited taurine synthesis
- high rate of methionine catabolism
- hair synthesis
What effects does a tyrosine deficient diet have?
- redder hair coat
- needed for melanin synthesis
What is the main form of stored energy in cats?
- triglycerides
- major fat depots
Why do cats have an arachidonic acid requirement?
- high ability to digest and use fat
- cannot synthesizer arachidonic acid from linoleic acid
- low hepatic delta6 desaturase
- only in fats from animal tissues
Why do cats require niacin?
- high activity of picolinic carboxylase
- cannot convert tryptophan to niacin because of competing path
What happens with niacin deficiency?
- Pellegra (4 Ds)
- diarrhea, dermatitis, dementia and death
Describe pyridoxine requirement in cats.
- vitamin B6
- 4x higher than dogs
- high pyridoxine turnover
Describe vitamin A requirement in cats.
- needed for growth, development, immune system, vision
- cats cannot convert b-carotene to vitamin A
- required preformed vitamin A (animal tissue)
Describe vitamin D requirement in cats.
- needed for calcium absorption, muscle contraction, blood clotting, nerve conductance, phosphorous homeostasis
- have insufficient 7-dehydrocholesterol in their skin so cannot meet metabolic need for vitamin D photosynthesis
Describe water requirement in cats.
- ancestral adaptation to desert environment
- survive on less water than dogs
- compensate low water intake by highly concentrated urine
- risk of crystalluria or urolithiasis
- Feline lower urinary tract disease complex (FLUTD)
What is the effect of feeding method on urinary pH in cats?
- if meal fed, greater alkaline peak 3-6 hours after feeding
- greater risk for FLUTD
