Nutritive Value Flashcards
What are the 2 main goals of ruminant nutrition?
- Improve the amount of nutrients extracted per unit feed and the efficiency of nutrient utilization
- Improve the efficiency of use of absorbed nutrients
What factors effect nutritive value of a feed? (3)
- Digestibility
- Feed consumption
- Energetic efficiency
What is digestibility?
the matter lost through the digestive tract for a given feedstuff
What is the difference between apparent and true digestibility?
Apparent: takes nutrients in feces as is
True: accounts for endogenous secretions
Given that 1000g of feed DM contained 25% of a nutrient and 170g of fecal DM contained 75% of that same nutrient, calculate total tract digestibility of that feed?
=127.5/250 =0.51% undigested
= 122.5/250 = 0.49% digested
What factors affects digestibility and how? (6)
- Lignin (decreases D)
- Preservation (if ensiled decrease D) (if alkali or acid treat, increase D)
- Particle size (smaller, increase D)
- Associative effects (depends)
- Feed intake
- Rate of passage (more time, more D)
Why is knowledge about an animals feed intake important?
- Intake directly influences production
- Forage utilization
- Need to know intake to formulate rations
- Intake changes are associated with metabolic disorders
What are some ways feed intake is expressed?
- DM basis
- % of body
- As a function of maintenance requirements
- Relative to a test feed
What factors affect feed intake and how?
- Gut fill (stretch receptors in rumen)
- Animal factors (size, age, health, etc)
3.Palatbility - Feed quality (ie. spoilage)
- Choices
- Ambient temperature
What is palatability?
free choice consumption when an animal is given more than 1 choice
What factors are affected by feed intake?
- Energy needs (less efficient digestion as they eat more)
- Growth of rumen bacteria
- Rate of passage (more = faster)
- Digestibility
- Gut fill
- Performance
