Term
| What determines the requirements for DIP and UIP in a diet? |
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Definition
| the requirements of the animal's microbes |
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Term
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Definition
portion of CP that can be degraded in the rumen
degradable true protein & non-protein N |
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Term
True or False
B vitamins contain N |
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Definition
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Term
| What are cyanogenic glycosides? Why are they a concern? |
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Definition
| phytotoxins found in plants that are degraded by rumen microbes, can release cyanide |
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Term
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Definition
| everything that is not a protein/peptide/AA |
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Term
| What factors affect extent of protein degradation in the rumen? |
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Definition
-chemical nature
-microbial access
-rate of passage (time spent in rumen)
-intake
-particle size
-rumen pH (low ph = less degradation)
-heat treatment
-feed processing |
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Term
| Why is urea so high in CP (281% of DM)? |
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Definition
| because it is 40% N, and 6.25 X .40 X 100 = 281 |
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Term
| Why does DIP of different meals (soybean, canola, blood meal etc) vary? |
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Definition
| due to heat processing which can reduce digestibility |
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Term
| Why do you not want to feed too much DDGS? Why do we feed it? |
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Definition
feed it bc it is good source of energy and protein
dont want to include in excess because it is high in fat, and will result in high N & P excretion in feces |
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Term
True or False
rumen microbes can synthesize all EAAs so feeding only DDGS, which are limiting in lysine, is not a concern |
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Definition
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Term
| How can rumen protein degradability be measured in vivo? In situ? In vitro? NIRS? |
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Definition
-rumen & duodenal cannulas
-daran bags incubated in rumen
-feed samples incubated with protease enzymes
-near infrared spectroscopy |
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Term
| What happens to DIP when it is digested? |
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Definition
NPN broken down to NH3, MCP is synthesized
true protein broken down to AA, small peptides, NH3, used for MCP synthesis |
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Term
| What are some sources of N for microbes? |
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Definition
DIP (protein and NPN)
recycled urea N obtained from crossing rumen wall, or saliva
endogenous sources |
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Term
| When is MCP synthesis maximized in terms of available N? |
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Definition
| if you have 2-5mg NH3-N for every 100ml of rumen fluid |
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Term
| How does pH affect MCP synthesis? |
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Definition
| too low = less degradation of DIP = less MCP synthesizes |
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Term
| How does eNDF affect MCP synthesis? |
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Definition
| more eNDF = more chewing & saliva production = more buffers = higher pH |
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Term
| How can you calculate how much MCP is produced? |
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Definition
13% X TDN
(13g MCP for every 100g TDN)
Only 7.5% if forage is low quality |
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Term
| How do microbes produce proteins? |
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Definition
they ferment an energy source, reducing it to its carbon skeleton, then attach an NH3 molecule
then assemble the AAs into peptides |
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Term
| Why do low quality forages have a slower rate of passage? |
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Definition
| they are high in NDF, so more rumination is required to reduce particle size enough that they can clear the RR |
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Term
| How can you estimate protein synthesis experimentally? |
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Definition
| Use microbial markers, isotopes etc to compare what goes in vs what comes out |
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Term
| What do cell wall-digesting microbes require as a N source? |
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Definition
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Term
| What do cell content-digesting microbes require as a N source? |
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Definition
| NH3, some AA and peptides |
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Term
| What are some sources of dietary NPN? |
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Definition
| nucleic acids, nitrates, amides, amines, urea, NH3 |
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Term
| Why is haylage/silage higher in NPN than other feedstuffs? |
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Definition
| because microorganisms in the ensilaging process ferment the CHO, and proteins are broken down to NPN in the process |
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Term
| Why would you add ammonia to a feed? |
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Definition
| provides more N for microorganisms |
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Term
| What is the advantage to feeding biuret over urea? In what situation would feeding urea be preferred? |
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Definition
urea is converted to NH3 almost immediately by microbes, only useful if they have a C skeleton ready to form an AA
biuret is converted to NH3 more slowly, can be used more effectively
if your diet is very high in cell contents, rather than cell wall CHO, then the urea NH3 can be used quickly |
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Term
| If your diet is already high in DIP, would you feed NPN? |
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Definition
| no, no reason to because DIP can be converted to NPN easily |
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Term
| Hoes does energy content of the diet affect NPN utilization? |
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Definition
| higher energy density= more C skeletons provided and energy available to attach NH3 to form AA |
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Term
| Why would you want to increase feeding frequency to maximize NPN utilization? |
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Definition
more frequent feedings = more ability for microbes to use the urea in the diet, more C skeletons available for MCP synthesis
*not practical from a labour standpoint |
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Term
| When would you use urea in a diet? |
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Definition
when the combined price of corn/barley/wheat and urea is less than the price of SBM
(feeding SBM is ideal but expensive) |
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Term
| Is an adaptation period required for feeding urea in the diet? |
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Definition
yes, it can decrease feed intake for 3-4 weeks. Less palatable
Can cause ammonia toxicity if fed in excess |
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