Feed analyses 2 Flashcards
Define ‘gross energy’
Measure of heat of combustion of feed via bomb calorimeter
Most feeds GE ~ 18MJ/kgDM
Define ‘digestible energy’
GE of feed - GE of faeces
Define ‘metabolisable energy’
GE of feed - (GE faeces + GE urine + GE gas)
ie GE of feed - waste products
Define ‘net energy’
ME - heat increment (energy stored by animal)
Define ‘heat increment’
Energy lost as heat (general metabolism of cell maintenance/growth/prod. (main) & microbial fermentation) measured by calorimeter (directly) or resp. exchange (indirectly)
Describe process of direct calorimetry
Airtight, insulated container - evaporative losses measured as change in air moisture & sensible heat loss thru wall
Heat production measured at 2 levels of intake
Describe process of indirect calorimetry
Resp. exchange
Resp. quotient (RQ)
Protein oxidised estimate via urinary nitrogen
Brouwer equation
What is the ‘respiratory quotient’? What does it calculate?
Ratio of CO2 produced & O2 consumed - calculates fat & CHO oxidised
Technique for measuring non-structural carbohydrates (NSC)?
Sugars - colorimetrically after digestion
Starch - after hydrolysis & polarimetric analysis
Technique(s) for measuring minerals?
Atomic absorption spectroscopy
Flame emission spectroscopy
Technique for measuring AAs, FAs, vitamins?
Chromatographic separation after proteins, fats hydrolysed or extracted
What is ADIN?
Acid-detergent insoluble nitrogen - measures unavailable nitrogen of animals
What is NIRS?
Near Infrared Reflectance Spectroscopy - measures feed parameters
Requires large calibration set for known data
Fast, cheap, non-destructive
