lecture quiz 11: chemical & biological evaluation of feeds Flashcards
1
Q
specialized analytical chemical methods
A
- gross energy analysis
- AA analysis
- mineral analysis
- vitamin analysis
- fatty acid analysis
2
Q
bomb calorimetry
A
- first thing in diet formulation is balancing for energy
- gross energy (heat of combustion) measured by burning sample of feed in a bomb calorimeter & measuring heat produced
- calorie (cal) = basic unit of heat energy → amount of heat required to raise the temp of 1g of water 1ºC (use kcals for livestock)
3
Q
proximate analysis: ether extract (EE)
A
- supposed to represent the lipids (fats) in a feedstuff
- method: reflux sample w/ boiling ether (C₄H₁₀O) to remove the fat
- ether & hexane (C₆H₁₄) = organic solvent ∴ can dissolve fats/lipids (water = inorganic solvent)
- uses soxhlet extraction apparatus
- aka solvent extraction (as opposed to cold extraction that uses pressing/mechanical)
- calculation: %EE = (residue after evaporation of ether)/(sample weight) x 100
- implication of [EE]: ↑ EE% implies that feed has ↑energy
- limitations: crude fat contains true fat in addition to non-nutritive EE components (e.g. chlorophyll & other pigments) ∴ may overestimate fat content
- automated soxtec extraction system uses same mechanism (repeated boiling/condensing/washing → evaporate ether)
4
Q
proximate analysis: N-free extract
A
- supposed to determine non-structural carbohydrates → readily digestible carb portion (e.g. sugars & starch)
- not determined directly, determined by diff in calculation
- %NFE = 100 - (%H₂O + %CP + %EE + %CF + % ash)
- any errors in those calculations adds together to make big error in % NFE (accumulated errors)
- rarely used by nutritionists
5
Q
gross energy
A
- gross energy doesn’t give much direct value in evaluating feedstuffs
- don’t use gross energy to compare energy value of feedstuffs for animals
- used as starting point in feed energy evaluation systems
6
Q
near-infrared spectroscopy (NIRS)
A
- rapid & cost-effective alternatives to traditional wet chemistry analysis of feed samples (not as precise)
- NIR light is shone at sample & measures reflection (compares w/ internal library of feedstuffs)
- works well for forages → have good library
- good for dealing w/ indiv feedstuffs (not as accurate for TMR or mixed ration)
- not used in research
- estimates most likely values for moisture, DM, fat, protein, NDF, ADF, ash, & energy content, & some minerals
- disadvantages:
- only as accurate as database & calibration
- not accurate for mixed feeds or uncommon unique ingredients
7
Q
biological evaluation
A
- use of animals to measure utilization of nutrients from a given feedstuffs or diet
- all involve feeding
- common methods for biological evaluation of feeds:
- feeding trial determines palatability of feedstuffs & their effect on feed intake & animal performance (e.g. growth & weight gain, milk yield, egg production, etc.)
- digestion or metabolism trial
- feed energy evaluation systems
8
Q
feeding trials
A
- measure feed intake & output produced (e.g. weight gain, quantity of milk/eggs)
- used to measure efficiency of feed utilization
- beef, swine, fish, & poultry industries use feed efficiency (feed to gain ratio) as a bench mark for profitability
- feed to gain ratio (aka feed conversion ratio (FCR)) = feed consumption➗body weight gain
- lower # is better
- for every pound of weight gain animal consumed x amount of feed
9
Q
calorie (cal)
A
basic unit of heat energy → amount of heat required to raise the temp of 1g of water 1ºC
10
Q
gross energy in water
A
0kcal/g
11
Q
gross energy in minerals/ash
A
0 kcal/g
12
Q
gross energy in carbs
A
4.2 kcal/g
13
Q
gross energy in fats
A
9.45 kcal/g
14
Q
gross energy in protein
A
5.7 kcal/g
15
Q
implications of [EE]
A
↑ EE% implies that feed has ↑energy
