Ch 2 - Nutrient Requirements Flashcards
Nutrient Requirement
The minimum amount of a nutrient necessary to meet an animal’s minimum needs for maintenance, growth, reproduction, lactation, or work
This implies there is some minimum that will meet the needs of a population, which is NOT true
DRI
Dietary Reference intakes
EAR
Estimated Average Requirement
meets the requirement of half the healthy individuals in a particular life stage and gender group
Need to know the requirement
EAR is 50% overfed 50% underfed
RDA
Recommended Dietary Allowance
Meets the nutrient requirement of nearly all (98%) healthy individuals in a particular life stage
Must know the requirement ad the variance around the requirement
AI
Adequate intake
middle of flat part of graph
UL
Tolerable upper limit
high end of flat part
Factors affecting nutrient requirements
Physiological state - maintenance, reproduction, growth, lactation.
Climate
Sex and feed restriction effects on protein and fat deposition
Males deposit more protein and less fat.
As animals mature, rate of protein deposition declines, rate of fat deposition increases
Effect of ambient temperature on energy requirements
too far below thermalneutral zone, need more mcal
How are nutrient requirements determined
Performance and health responses to nutrient:
breakpoint analysis, saturation kinetics, economic returns
factorial approach - nutrient output/nutrient utlization
Evaluation of Breakpoint Analysis
3 week growth study with chicks, evaluated does response to choline
Performance Responses
nutritionally optimum versus economically optimum
marginal rate of return
The factorial approach
Requirements are the sum of the needs for various physiological functions
Maintenance Requirements
State at which there is neither gain nor loss of nutrients by the body - amounts of a nutrient needed to achieve an equilibrium state
Feed intake and feed efficiency
increased feed intake dilutes the proportion of feed used for maintenance
