VETN 211B: Digestion and Absorption

Why would reproductive status affect energy requirements?

Decrease in hormones and activity levels

What does increased fat lead to?

Increased palatability - meaning they want to eat more

What are voluntary oral intake factors?

• Number of animals being fed together

• Smell of food

• Frequency of meals

What are examples stress affecting thermogenesis?

• Change in temps

• Emotional stress :(

• Alterations in food intake

What is voluntary muscular activity affected by?

Duration and intensity

RER accounts for what kind of energy?

Obtaining, digesting, and absorbing nutrients

What is something that is hydrolyzed to glycerol, free fatty acids, and are some monoglycerides and diglycerides?

Fats

Negative energy balance is when…

Caloric intake is less than energy expenditure

What is broken down to simple sugars - glucose, galactose, and fructose?

Carbs

Voluntary muscular activity accounts for how much total energy expenditure?

30%

Where does absorption of water and electrolytes take place in?

Colon - where waste turns into solid poop

What are lipase, amylase, and peptidase?

They are enzymes that break up proteins, carbs, and fats in the small intestines

What is manual digestion?

Physical mastication, mixing and movement of food through the GI tract

What are the two types of digestion?

1. Mechanical - chewing

2. Chemical - enzymes

What are some factors that can affect RER?

• Sex

• Reproductive status

• Thyroid and autonomic nervous system tunfciont

What is positive energy balance?

Caloric intake is greater than energy expenditure

What taste do dogs prefer?

Sweet tastes

What is the degree of body heat production based on?

Meal size and nutrient composition

What does increased meal frequency lead to?

Increase energy loss through dietary thermogenesis

What does the liver break down?

Amino acids, glycogen, and fats

What is chemical digestion?

Splitting the chemical bones of complex nutrients through enzymes (enzymatically catalyzed hydrolysis)

What is digestion?

Breakdown of large, complex molecules of many nutrients into their simples, most soluble forms so that they can be absorbed

What are the two types or methods of digestion?

1. Mechanical - chewing

2. Chemical - via enzymes

Where does the GI tract begin and end?

Mouth → Anus

What’s in between?

Mouth/Teeth → Esophagus → Stomach → SI → LI → Colon → Rectum → Anus

What is the function of the mouth?

• Bring food into the body, chew the food, mix food with saliva

What is the function of saliva?

Lubricant to help chewing and swallowing - is secreted in response to sight and smell of food (just like me fr)

What is the difference between teeth of cats and dogs?

Cats are carnivores = canines are sharper to cut through meat

Dogs are omnivores = canines are not as sharp

What kind of flavor do dogs like?

Sweet tastes

What kind of flavor do cats like?

Bitter tastes

What muscle is located in the esophagus?

Cardiac sphincter muscle - allows food to enter the stomach and prevent reflux back into esophagus

Which animal has a bigger reservoir in the stomach?

Dogs do - bc they eat freely vs cats who might only eat twice a day (reservoir is not as big)

What is in the stomach that helps digest proteins?

Hydrochloric acid

What else does the stomach do to help lubricate food and protect the lining of the stomach?

It produces mucus

What helps control the rate of chyme entering the small intestines?

Pyloric sphincter

What structures are located in the small intestine?

• Duodenum

• Jejunum

• Ileum

What is the purpose of the small intestines?

Chemical digestion of proteins, carbs, and fats via enzymes

Mainly digestion and absorption

What is produced in the gallbladder?

Bile salts

What do bile salts do?

Emulsify fats → Lymphatics → blood (yadda yadda)

What does the liver do?

Helps further digestion of amino acids, sugars (glycogen), and fats

What are the parts of the large intestine?

• Ileocecal valve, cecum, ascending, transverse, and descending colon, rectum, and anus

What does the ileocecocolic valve do?

Where material enters the large intestine from the small intestine

What is the function of the cecum in cats and dogs?

Nothing

What is the function of the cecum in rabbits/horses/herbivores?

Digestion → fermentation (rumination) all that jazz from ap likely

What structure do rabbits/horses/herbivores have that cats and dogs don’t?

Cecum

What is the function of the colon?

Absorption of water and electrolytes back to the body - prevents dehydration in the body and helps feces pass (makes poop solid)

What organism helps fermentation of insoluble fibers in the colon?

Bacteria

What is the function of the rectum?

Stores feces

What is the function of the anus?

End of the digestive tract that waste material is expelled

What should energy expenditure (how much they use) equal to?

Energy intake (how much they eat) - it should be balanced with each other

What is positive energy balance?

Caloric intake > energy expenditure

What does positive energy balance lead to in different stages of life?

If growing or pregnant → lean body tissue (going to assume muscle)

If an adult → stored as fat (bc they don’t need it anymore)

What is negative energy balance?

Caloric intake < energy expenditure

What does negative energy balance lead to?

Weight loss → decrease in fat and lean body tissue (muscle?) can occur

What does daily energy requirement depend on?

The amount of energy the body uses each day

Ex: A working dog will need more energy/food compared to a lazy dog that only goes on a walk 2x a week

What are the 4 common measurements of energy?

1. BER - basal energy requirement

2. RER - resting energy requirement

3. MER - metabolizable energy requirement

4. DER - daily energy requirement

What is BER?

Energy required for a normal animal in a thermo neutral environment - for an awake, resting but fasting animal (no food)

What is RER?

Energy requirement for a normal animal at rest in a thermo neutral environment, awake but not fasted animal

What accounts for RER?

Energy used for digestion, absorption, metabolism of nutrients, and recovery from physical activity

• ~60-75% of total daily intake

What are factors affecting RER?

• Sex and reproductive status*

• Thyroid and autonomic nervous system function, body composition, body surface area, nutritional status

What is MER?

Energy required for a moderately active adult animal in a thermo neutral environment

• Amount of energy required to maintain an animal at its current weight and body composition

What does MER account for?

• Obtaining, digesting, and absorbing nutrients

• Spontaneous activity

What is DER?

Energy required for average daily activity of an animal, which can be dependent on lifestyle and activity

What does DER account for, or what is included in it?

• Work

• Gestation and lactation

• Growth

• Maintaining a normal body temp

• Surviving basically

What is voluntary muscular activity also called?

Exercise → most variable area of energy expenditure (how animals use their energy)

Ex: Working dogs vs. once a month walk

How much of total energy expenditures does exercise use?

~30%

As weight increases, what can amount of energy used do?

It increases - bc ain’t no one want a super fat dog amirite

When taking reproductive status into account, what happens to RER?

RER decreases in fixed animals

By how much do you have to decrease amount of food after neutering an animal?

~25% immediately after neutering - or else you’ll overfeed them and they’ll turn fat

Why do neutered animals have lowered RER?

Changes in:

• Body composition - they have less muscle (lean body tissue)

• Decrease in activity levels

• Decrease in hormones

What is body heat production? AKA dietary thermogenesis

Energy associated with ingestion, digestion, absorption, and metabolism of food

How much of total DER (daily energy requirement) does body heat production take up?

~10-15%

What type of nutrient creates the most heat?

Protein

What type of nutrient creates the least heat?

Fat

What is the degree of heat production based on?

• Meal size - the bigger the meal = the more heat created

• Nutrient comp. - carbs vs. proteins vs. fats

What can the body do in response to any environmental changes?

It adapts - there is a change in RER if the room gets hot or neutral temp.

What does the body being adaptive when it comes to environmental stress lead to? (idk how to word this)

Allows body to maintain energy balance despite changes in caloric intake by being less efficient in energy use - kind of like a thermostat

What is voluntary oral intake of food regulated by?

• Internal physiologic controls - eating

What are the physical signs of internal physiologic control (of voluntary oral intake)?

Stomach contractions when its empty (rumbly tummy) and stomach distention (big tummy) when full

What are external cues to voluntary oral intake of food?

• Diet palatability

• Food composition

• Food texture

• Timing and environment of meals

What kind of food do both cats and dogs prefer?

Warmed up meals (rather than cold bc they’re bougie like us smh)

When timing meals, what kind of signs will animals show?

Behavioral - cats will yell at you or act super nice to get food

Physical - they’ll wait at their food dispenser until it goes off

What should you do when there are multiple dogs in your house and you’re feeding them?

Don’t feed them together unless there’s a physical barrier → or else they will eat each other’s food and get fat (they might also fight over food just like me fr)

What is the main thing for cats when feeding them?

They need to be able to smell the food or else they won’t eat it (bc they’re sassy like that)

What does increased meal frequency lead to?

Increase in energy loss through dietary thermogenesis (produce body heat)

Because cats are so special, what do they need more of?

They need higher/more proteins

What do cats NEED need?

Taurine

What else are cats deficient in? (other than taurine)

Vitamin A, niacin (Vitamin B3), arachidonic acid

Why do cats have such a strict/unique metabolic requirements?

They always have a high number of enzymes to catabolize proteins → Therefore, they cannot adjust their protein metabolism (it’s fixed and they deal with it)

Where do cats get all of their necessary nutrients?

Animal tissue (MEAT)

What are cats when it comes to their diet?

Obligate carnivores → They need meat, they cannot go with being a vegan cat (they will probably die)