Applied Digestive Physiology Of Ruminants A11,12,13

Question 1

What CH can be found in plant feedstuff?

Answer 1

1. Non-structural CH
   - plant cell components
   - highly soluble
   - readily fermentable
   - sugar, starch
2. Structural CH
   - plant cell wall components
   - low solubility
   - fermantable (slow)
   - pectin, hemicellulose, cellulose

Also lignin: non-soluble, non-fermentable

Question 2

Ruminal degradation of CH

Answer 2

Bacteria produce different enzymes (cellulase, cellobiase, amylase, maltase) that will degrade dietary CH to smaller molecules (hexanes, pentanes).
These smaller molecules will be absorbed by microbes and there they are gonna anaerobically fermented into pyruvate.
Pyruvate production releases ATP that is gonna be used by microbes.
After that pyruvate -> volatile fatty acids (acetic/butyric/propionic)

Question 3

Ruminal degradation of CH

Answer 3

• Bacteria produce different enzymes (cellulase, cellobiase, amylase, maltase) that will degrade dietary CH to smaller molecules (hexanes, pentanes)
• These smaller molecules will be absorbed by microbes and there they are gonna anaerobically fermented into pyruvate.
• Pyruvate production releases ATP that is gonna be used by microbes.
• After that pyruvate -> volatile fatty acids (acetic/butyric/propionic)

Question 4

VFAs, their production and proportion

Answer 4

• 5-7kg produced per day
• acetic : propionic : butyric = 60-70 : 20-30 : 10-15% (feedstuff can influence, chewing movements!. More forage -> more chewing movements -> more saliva -> more alkaline pH -> cellulotic bacteria will be dominant -> more acetate)
  (If more concentrates are fed -> less chewing movements -> less saliva -> lower ruminal pH -> amylitic bacteria proliferate -> increase of propionic acid)

Question 5

What is normal rumen pH?

Answer 5

6,2 - 6,8

Question 6

VFAs as energy supply

Answer 6

• can be supply of 70-80% of daily energy demand
• can be rapidly absorbed
• acetate —> milk fat and body fat production
• propionate —> GNG
• butyrate —> ketone bodies (mainly beta-hydroxybutyrate)
• in early stages of acetate and butyrate fermentation, CO2 is produces that can be later converted to methane and eliminated by belching
• methane production inhibits the bioutilisation of dietary energy because methane is rich in energy but this energy can’t be utilised by the animal

Question 7

What’s special about production of propionic acid?

Answer 7

Can be 2 routes:
- direct reduction route: pyruvate -> lactate -> 2 propionic + acetate
- random route: 2 propionic acids

Propionic acid will get into liver and enter gluconeogenesis

Question 8

Crude protein, true protein, NPN, RDP, UDP, MP, MPE + FOM, MPN - meanings

Answer 8

Crude protein - all nitrogen containing substances
True protein - nitrogen containing substances built from AAs
NPN - non protein nitrogen - e.g. urea
RDP - rumen degradable protein
UDP - undegradable proein (by-pass protein)
MP - metabolisable protein -
MPE + FOM -
MPN -

Question 9

Answer 9

1. RDP is degraded by microbial enzymes (protease, peptidase)—> AAs —> ammonia (NH3). In case of NPN —> ammonia
2. Microbes can utilise ammonia and/or AAs for microbial protein synthesis
3. MP = microbial protein + UDP in the small intestine, and will be digested by host’s enzymes

Question 10

Why is RDP/UDP ratio important?

Answer 10

It can influence fertility.

If proportion of UDP is too high —> rumen fermentation is limited —> VFAs production is reduced —> energy supply is insufficient —> to maintain order ion cow must mobilise more body reserves

=> max UDP content is 40% of total dietary proteins

Question 11

Which feeds are excellent UDP sources?

Answer 11

1. heat treated full-fat soybean
2. heat treated extracted soybean meal
3. hot pressed rapeseed meal
4. maize gluten meal
5. DDGS - (distillers dried grains with solubles ?)

Question 12

What types of lipids are found in plant feedstuff?

Answer 12

• simple lipids: triglycerides
  Found in grains and seeds. Rich in mono and polyunsaturated FAs
  E.g in maize, oats, soybean, oilseeds
• composed lipids: galactolipids, phospholipids
  Galactolipids are mainly in found in photosynthetic tissues, phospholipids in plant cell membranes
  Forages! 2-4% of DM content

Question 13

Degradation of lipids in the rumen. Steps.

Answer 13

1. Hydrolysis
2. Biohydrogenation

Question 14

Degradation of lipids in the rumen. Hydrolysis

Answer 14

1. By microbial lipase —> glycerol + FAs (+ galactose in case of composed lipids)
2. Glycerol and galactose are rapidly fermented by bacteria into propionic acid (C3) that will enter gluconeogenesis (GNG) to produce blood glucose

Question 15

Degradation of lipids in the rumen. Biohydrogenation

Answer 15

Dietary lipids are rich in unsaturated fatty acids that are toxic for microbes
So saturated long chain fatty acids (LCFAs) are gonna be formed to protect microbes.
Linolenic acid (18:3), linoleic acid (18:2) -> oleic acid (18:1) -> stearic acid (18:0)

Question 16

Synthesis of lipids in the rumen

Answer 16

Anaerobic fat synthesis by microbes. Mostly С18 and C16 = 2:1
Small amount monounsaturated fat acids is synthesised as well (15-20%)

Question 17

Dietary fat supplementation in dairy cows. When? Why? What? How much?

Answer 17

When: high (peak) milk production
Why: excess amount of concentrates must be given -> pH of rumen declines -> ruminal acidosis
To decrease amount of concentrates in total mix ratio, fat supplementation is given !!
What and how much: only plant oils
Usually in total mix ration lipids are 2-4% of DM (~0,5kg)
Total fat content in the rumen should never be more than 7-8% of DM, otherwise microbial fermentation will be abnormal -> decreased milk fat content
Rumen protected fats: e.g. palm fatty acid powder

Question 18

Examples of rumen protected fats

Answer 18

• hydrogenated rapeseed
• hydrogenated full fat soy been