What to study for the exam

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Hindgut/forgut fermenters

- foregut: sloth, kangaroo
- colon: horse, elephant
- caecal: rabbit, guinea pig
- sort of an enlarged stomach -> colon or caecum where fermentation takes place by microbes
- they also do have digestion by their own enzymes    

Difference between digestion, absorption and utilization

- digestion is the breakdown of macromolecules and modification of the physical form of the feed
- absorption is the uptake of nutrients by the epithelial cells of the gut and intestinal walls. Happens passively, actively or via pinocytosis
- utilization is the efficiency with which the absorbed nutriets are used in processes within the animal

Factors that affect the digestibility of a diet

- animal factors
  • different species
  • amount and composition of enzymes excreted by the pancreas
  • composition of the microbial population
- feed factors
  • levels of feeding: more feed menas higher passage rate
  • digestibility of a diet is closely related to its chemical composition: dietary fibra has the greatest influence
  • interactions between dietary compounds
- NAFs
  • factors depressing the digestion or utilisation of proteins
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Factors depressing the digestion of carbohydrates

- alfa-amylase inhibitor:
  • it impairs the working of alfa-amylase, the starch digestibility
  • more starch will get into the large intestine where it will be degraded by the microbes
  • volatide fatty acids will be formed instead of monosacharides
  • cramps
- Tannins

Factors affecting absorption of minerals

- phytic acid
  • contains phosphorus so it can bind different minerals like Ca, Fe and Mg
  • Thus is reduces the availability of these nutrients
  • this may improve amino acid and energy digestibility in pigs and poultry
  • increases the body retention of N, Ca and P
- oxalic acid:
  • it binds with divalent cations as Ca and Mg
  • reducing their availability

Factors altering the immunesystem

- antigenic proteins
  • macromolecular proteins that are capable of inducing a hormonal immune repsonse when ingested by animals
  • cause gut wall damage and may also cause chronic hypersensitivy
  • chemical and enzymatic treatment

What are the effects of drying forages on the feeding value?

- conserving (especially for ruminants who are indoors during winter and cant graze)
- sundrying takes a while and nutrients may be lost. Also risky with unpredictable weather
- harvesting always happens in a later stage of growth so nutritional value of hay is way lower than young and fresh grass (good for horses)
- moisture content is lower so there will be less bacterial growth and mould   

Concentrate feedstuff cereal grains

- all starchy vegetable seeds like barley, maize, wheat and oats
- rich in cabrohydrates -> good energy source
- low in protein, low in lysine and methionine (= essential AA for monogastric and non-ruminant herbivores)
- low in some minerals and vitamins
- low in fat
- variation among cerals is small
- most of the phosphorus is bound to phytate -> this inhibits protein and mineral absorption      

Concentrate feedstuff pulses or legume seeds

- pea, common bean, soybean and peanut
- rich in starch/carbohydrates, but lower than cereal grains
- high in protein (higher than cereals) and lysine but low in methionine
oil content is negligible expect for soybean and peanut
- high in P but low in Ca
- most contain NAFs: protein-inhibitors (soybean) and lectins (which is bad)

Concentrate feedstuffs (oilseeds)

- reserve energy is stored as oil like sunflower seed, rapeseed and linseed
- rich in protein
- rich in oil
- high in P, but low in Ca

Coccidiostats and histomonostats additives

- prevention of sub-clinical coccidiosis (parasites)

Other factors that predict the value of a feedstuff

- palatability
  • taste, smell and texture determine voluntary feed intake -> has to be attractive for animals. Poultry doesn't have very developed taste and smell buds so they select on texture (grinding in crop)
  • cell wall material stimulates intestinal peristalitc (fibres)
- NAFs

  • protease inhibitors -> processed by heating
  • lectins -> processed by heating
  • tannins -> processed by dehulling or breeding/biotechnology
  • phytic acid -> use of enzymes
  • anitgenic proteins -> chemical and enzymatic treatment

Concepts of protein evaluations in ruminants

- microbial protein
  • Can be estimated from the ratio between the duodenal flow of microbial marker and the concentration of the marker in isolated bacteria
  • or by measuring the amount of organic matter fermented in the rumen
- digestible protein
  • mobile nylon bag technique
  • the composition of absorbed amino acids in ruminants is rather constant because of the microbial protein supply is constant
- by-pass protein
  • To assess which proteins escape from microbial degradation the nylon bag technique is used

Formula to calculate ME on the basis of digestible nutrients in diets or feedstuffs

ME = 14.7 * DCP + 32.8 * DEE + 17.2 * Dstarch + 14.8 Dsugar

Why to choose for ME, DE or NE in an energy evaluation system

Monogastrics:
- DE is not used for poultry because faeces and urine cant be collected seperately. So impossible to measure.
- DE system does not into acount the proportion of different nutrients
- ME is a better measurement for especially protein but still the efficiently of utilisation of digested nutrient for different purposes is ignored
- ME is mostly used for poultry
- NE values are difficult to determine in vivo but are used
- For pigs -> DE, ME and NE systems are used.

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