lecture quiz 5: proteins

Question 1

diet for swine

Answer 1

corn & soybean

Question 2

ideal protein

Answer 2

diet w/ AA profile that 100% matches animal requirements

Question 3

synthetic AA use

Answer 3

to balance nutrient profile

Question 4

protein quality

Answer 4

• depends on composition of AA & digestibility of protein
  
  • how close to AA requirement profile (closer = better)
• biological value (BV) = measure of proportion of protein absorbed from a food used in protein synthesis → >70% considered high-quality
• very important for non-ruminants
• ruminants can produce high-quality protein from low-quality sources
  
  • can use NPN to make microbial proteins
  • microbial proteins = good source of EAA
  • quality not important, quantity is
  • exceptions for high-performing animals (e.g. dairy cows) ➞ can benefit from supplementation
  • hind-gut fermenters also produce microbial enzymes but occurs past absorptive stage (in cecum/colon) so ends up in feces
    
    • horses participate in coprophagy: eat feces & can get microbial proteins & survive if needed

Question 5

biological value

Answer 5

measure of proportion of absorbed protein from a food used in protein synthesis

• 100% = all aa absorbed are used in protein synthesis
• BV > 70% considered high quality protein
• egg protein has highest BV of all natural sources (~94%) → needs to turn into a being so needs all the proteins necessary
• other animal-based proteins BV = 60-80%
  
  • animal-based protein always higher value but more expensive
• plant-based proteins BV ~40-65%
  
  • usually missing at least 1 EAA (except soybean → has best protein quality among plant sources)
  • can mix diff plant sources in right proportion to make good combination & not miss any EAA
    
    • a mix of indiv ingredients w/ low BV can have high-quality protein
• applies to all species

Question 6

true protein

Answer 6

composed only of AA

Question 7

non-protein nitrogen (NPN)

Answer 7

compounds that are not true protein in nature (not made of AA) but contain N

• nucleic acids have N but very small source
• e.g. urea, B vitamins
• ruminants can use NPN (humans cannot)

Question 8

crude protein (CP)

Answer 8

= true protein + NPN

• based on N content
• NPN = small proportion of diet
• CP% = %N x 6.25
  
  • 6.25 from assumption that most proteins contain 16%N
  • CP% = N% in feed/16% or N% x (100/16) = N% x 6.25
• does not tell you how much true protein vs NPN