Animal Energetics Flashcards
The Maintenance State
- When body weight and body energy content is constant, an animal is said to be in the maintenance state 2. In the maintenance state, the energy of food available to an animal is completely utilized. 3. All of metabolizable energy (ME) from a diet ultimately is released as heat ME Intake = heat production of the animal (kcal/day)
Define Maintenance Energy Requirement (MER)
The amount of metabolizable energy (ME) needed to sustain the maintenance state
MER is the sum of what four general categories of activity?
- Heat increment 2. Basal metabolism 3. Physical activity 4. Body temperature regulation
Define MER - heat increment
Energy used in digestion, assimilation, and metabolism of food.
The heat increment in ruminant compared to simple stomached animals is large, greater than 30% of MER. Nutritional consequences of this are that ….
- Feeding is advantageous for survival in very cold temperatures. 2. Feeding is hindrance in very warm temperatures because the added body heat reduces food intake and production dependent on food intake.
Define MER - Basal metabolism
- The largest component of MER is in basal metabolism. 2. Basal metabolism is mostly processes of cellular maintenance.
The energy need (or use) of basal metabolism is called the….
basal metabolic rate (BMR)
Basal metabolic rate (BMR) is determined from heat production under a strict, defined set of conditions:
- Post-adsoprtive state 2. Awake 3. At rest 4. Thermoneutral environment
BMR is dependent on what?
The body weight (mass) of the animal
A commonly used approximation of BMR is also called what?
“Resting energy requirement (RER) or “resting energy expenditure”
BER equation is used to estimate RER; what are two equations to find RER?
- RER (~BMR) = 70 x Mkg.75 (kcal/day)
- RER = 30 x Mkg + 70 (kcal/day)
- linear transformation of RER equation for DOGS between 2 and 45 kg
MER - Physical Activity
Energy of physical activity energy is variable in animals at the maintenance state
Ex - foraging versus bunker-fed steer; activity of dogs etc. - has to do with normal activity, light work, moderiate work and heavy work
MER - Body Temperature Regulation
- Energy expended in processes is improtant to thermal regulation
- Cold environment - shivering and non-shivering thermogenesis
- Hot environment - panting, gular fluttering, and sweating
- Varies with enviornemntal temperature, humidity, wind
- MER increases with decreasing temperatures - has to do with body temperature regulation
MER estimation using body weight for adult dogs:
MERdogs = RER x activity factor (kcal/day)
RER = 70 x Mkg.75 (kcal/day)
*activity factor decreases for neutered adults and for inactive/obese dogs
MER estimation using body weight for cats
MERcats = RER x activity factor (kcal/day)
RER = 70 x Mkg.75 (kcal/day)
Adult mammals for which activity factor is unknown, MER is about…
twice RER
MER mammals = RER x 2 (kcal/day)
RER = 70 x Mkg.75
List two methods of determination of MER
- Change in body weight
- Calorimetry
Methods of determination of MER - Change in Body Weight
MER is taken as the metabolizable energy intake that supports maintenance of a body weight stable condition.
Adventages - requires only weighing and feeding animals
Limitations - many animals are needed, outcome will vary with body size and composition, hydration and gut fill bias body weight measurements
Methods of determination of MER - Calorimetry
- Method assumes energy released as heat is equivalent to the energy requirements of maintenance
- Direct calorimetry (rare) - heat energy can be measured directly, by placing an animal in an enclosed chamber
- Indirect calorimetry (common) - breath oxygen consumed, breath carbon dioxide expired, and ratio of CO2 to O2 (aka respiratory quotient RQ) are determined
Growth is more energetically demanding than maintenance because….
- Some energy is deposited in body tissue.
- Some energy is expended in synthesis of the body tissue
Energy required for growth is partitioned between ….
- Support of the maintenance state
- Expansion of the tissue mass
Daily energy requirement (DER) for growth…
DERgrowth = MER + energy expended in synthesis of new tissue + energy deposited in new tissue
- NOTE: estimating daily energy requirement for growth requires frequent re-estimation. Hence, after an initial estimate is given, instruction on adjustment of the feeding according to body condition must be given!
Energy requirement in gestation for dogs:
Energy need does not substantially increase above MER until the last third of gestation when body weight substantially increases
Energy requirement in gestation for cats:
Energy intake increases linearly during gestation
Energy Requirement for Lactation
- The energy requirement for lactation is the most demanding of physiological states
- The energy requirement of lactation increases with increasing litter size
Estimating the energy requirements of lactation vs gestation
Pregnancy: use a multiplier of MER depending on gestational stage
Lactation: use a multiplier of MER depending on litter size
The energy requirement of illness or injury
- The energy requirement in illeness and injury is often lower than MER
- The energy requirement in most illness and injury states should be initially assumed to be no more than RER
- Patients justifiably may be fed above RER in very severe injury
- The increase in energy requirement even in severe injury is not greater than osberved in pregnancy, lactation, or growth
- The increase in energy requirement in severe injury is only as great as MER!!!
- Overfeeding of patients can be worse than underfeeding
