Energy metabolism

energy metabolism

how your body turns the food we eat into energy to keep us alive and active

Energy sources (kcal/g)

• Carbohydrates 4

• Protein 4 

• Lipids 9

carbohydrates

quick energy, first to fuel your body during excersize, fastest energy source, stored as glycogen/ glucose

protein

back up fuel, muscle repair, amino acids

lipids

long term energy, stored as body fat, slower to use but gives us a lot of energy, fatty acids

What is energy?

the capability to do work

work

force x distance

chemical energy

potential energy in food (calories)

Calorie (cal)

• amount of heat required to increase the temperature of one gram of water by one degree Celsius

Joule

• standard unit for energy (work); energy required to displace 1 newton, 1 meter

  • One calorie= 4.184 joules

Bomb Calorimeter

a tool scientsts use to measure how many calories are in food/ how much energy the food gives. Step 1: food sample goes into small container Step 2: bomb is filled with oxygen and placed in a tank of water Step 3: the food is set on fire Step 4: the food burns completely releasing heat Step 5: the heat warms up the water around it Step 6: scientists measure how much the water temperature rises Step 7: from that they calculate how much calories (energy) was in the food

Energy Expenditure 

• Expressed as units of energy per amount of time 

  • Watt= 1 J/sec 

  • Horsepower= 746 J/sec 

First law of thermodynamics 

Energy can neither be created nor destroyed 

positive energy balance

eating more than you’re burning (gain weight)

negative energy balance

burning more than you’re eating (lose weight)

gross energy

total energy in the food you ate

amount of heat liberated when a feed sample is completely burned into carbon dioxide and water

digestible energy

the energy that is left over (after some is lost in feces) and absorbed in your body

DE = gross energy (total) - Fecal energy (amount lost in poop)

metabolizable energy

energy your body can use for metabolism after digestion, gas, and urine loss

ME = DE - Urinary energy - gaseous energy

net energy

the energy your body actually uses for production purposes after all losses are taken into account

NE = ME - heat increment

energy maintenance

energy required to maintain constant body weight

Goal: metabolize energy intake = energy expenditure

maintenance energy expenditure

resting energy expenditure, heat increment, physical activity, thermoregulation

resting energy expenditure - % contribution to energy expenditure

50-80

heat increment - % contribution to energy expenditure

10-15

physical activity - % contribution to energy expenditure

10-40

thermoregulation - % contribution to energy expenditure

variable

metabolic consequences of energy imbalance

weight gain or loss

reduced fertility

decreased productivity

compromised immune system

behavioral changes

increased mortality

management strategies of consequences of energy imbalance

optimize feed intake

provide energy- dense feeds

body condition scoring

proper feeding management

transition period management

early detection and treatment

disorders associated with energy intake

obesity

fatty liver disease

ketosis

pregnancy toxemia

equine metabolic syndrome

obesity

associated with excess energy intake

commonly seen in companion animals and horses

leads to reduced mobility, increased risk of disease, shortened lifespan

equine metabolic syndrome

disorder associated with insulin dysregulation

characterized by regional fat deposition & reduced ability to lose weight

commonly seen in ponies, donkeys, arabians and mustangs

increases the risk for laminitis

treated through diet and exercise management

fatty liver disease

when excess fat gets stored in the liver cells, making the liver less effective at its jobs

can happen from overfeeding, inactivity, sudden weight loss, or diseases

• Energy demands exceed intake 

• Fat stores are mobilized 

• Excessive NEFA accumulation in liver 

* Most often seen in high producing dairy cows

ketosis

cause: insufficient carbs in diet causing body to break down fat for energy leading to high ketone levels

• Body metabolizes large amounts of fat for energy

• Due to a lack of available glucose 

• Results in a buildup of ketone bodies in the blood 

* Most often seen in high producing dairy cows 

can cause weight loss and muscle wasting, fatigue and lethargy, or organ damage or death if untreated

pregnancy toxemia

• AKA: Pregnancy disease, lambing sickness and twin- lamb/kid disease

• Caused by low blood sugar (glucose) 

• Onset often triggered by stress 

  • Nutritional 

  • Inclement weather

• Most prevalent in ewes/ does carrying multiples; over- or underweight ewes/does 

• babies are growing fast and need a lot of energy. if the mother doesn’t eat enough, the body will break down fat to get energy. the fat turns into ketones which can build up and become toxic hense “toxemia”