Chapter 9 Rumen Acidosis

Question 1

What’s the dilemma that is with feeding forages to high producing dairy cows?

Answer 1

They require increasing amounts of energy >30 Mcal/day
Feeding only forages cannot meet this energy requirement.
Concentrates are used to increase the energy density of the diet.
But theres a limit to how much grain can be fed due to rumen acidosis.

Question 2

Propionate does it use carbon?

Answer 2

No, 3C

Question 3

Does acetate use carbon?

Answer 3

Yes 1 carbon , so its (2C)

Question 4

How does rumen acidosis occur?

Answer 4

1)Animals gorge on feed (large fluctuations in feed intake)
2)Fed too much concentrates
4)”empty” rumen
5)Heat stress *panting
6)In frequent feeding

Question 5

In lactose synthesis, what two disaccharides are used?

Answer 5

Glucose + galactose, primary (CHO) in milk

Question 6

What’s the lactose precursor?

Answer 6

Glucose

Question 7

How much does it take of glucose to make 1kg of milk?

Answer 7

72g

Question 8

What is the primary determinant of milk yield?

Answer 8

Lactose- Have the cow make lactose and then the more money you make.
Synthesis of lactose depends upon animals glucose status

Question 9

Whats the precursor to glucose?

Answer 9

Propionate

Question 10

Whats glucose made from?

Answer 10

Propionate

Question 11

What is lactose made from?

Answer 11

Glucose

Question 12

What is milk yield determined by?

Answer 12

The amount of synthesized lactose

Question 13

What decreases the rumen pH?

Answer 13

-Eating and ruminating times are reduced, therefore decreased saliva production
-Rate and extent of acid production is greater
-Forages exert some buffering capacity (difficult to induce acidosis when the rumen is full of fibre
-More complete fermentation

Question 14

Why do total VFA’s go up as you go from high forage to high conc diet?

Answer 14

VFA’S = acids. The pH rate of concentrates

Question 15

Whats the monosaccharides in lactose?

Answer 15

gluocse and galactose

Question 16

Precursor for lactose?

Answer 16

Galactose, VFA= (Propionate) makes more lactose, so we feed them a high concentrate diet if we want out animals to produce more lactose

Question 17

Why does fermentation of conc reduce the pH

Answer 17

Glycolysis from glucose to pyruvate more hydrogen is being produced, you have more VFA’s being made , the rate in which there made= increased. Both of these drag the pH down. pH kills the bugs if they get too low.

Question 18

explain what ruminations role is in rumen acidosis?

Answer 18

Concentrations (already a small particle, cow doesn’t have to spend energy making it smaller) less incentive for the cow to ruminate, to bring a cud back up to the mouth to chewing. Chewing = saliva production, saliva contains buffers(bicarbonate + phosphate) gets swallowed and goes back into rumen and the pH goes up. but if eating high con there isn’t a lot of chewing so less saliva production.

Question 19

On a high forage diet to high concentrate diet

Answer 19

They produce more VFA’s and its quicker. high forage diet favours bacteria that makes acetic.
high concentrate diet favours bacteria that makes propionate

Question 20

Rumen acidosis and the consequences

Answer 20

Rapidly fermented grain fed to cattle, acidosis(low rumen pH), gut lesions, Bacteria population increase, rumen wall abscesses inflammation and tissue death, bacteria travel to liver via blood, liver abscesses.

Question 21

Whats the dietary allowance of starch? and whats the type of grain and how do we store it? Whats important to know about processing starch?

Answer 21

Early April on forage diet- grass can contain high sugar levels may be carful animals don’t get rumen acidosis. 25-35% of DM as starch.
Type of grain-Barley or wheat (more more fermentable then processed corn) type of grain matters.
Storage- High moisture corn (much more fermentable than dry corn)
Biggest contributor about how digestible something is : How its processed:
* Degradability/fermentability increases with fineness of grind (surface area)
* Starch in steam flake corn is rapidly fermented that not steam flaked
* Starch in rolled corn silage degrades faster than if ”unrolled”

Question 22

What does rumen acidosis increase the production of? whats the pK of it?

Answer 22

-Lactic acid, its not absorbed from rumen as well as VFA’s
-Lactic acid = strong acid. pK: Lactic acid 3.08

Question 23

Whats the pK of Acetic, propionate, butyrate:

Answer 23

4.75-4.81

Question 24

What is the process of rumen acidosis :

Answer 24

Digestion in rumen goes down with acidosis. Non digestible feeds leave rumen undigested. Pancreatic amylase isnt being made in duodenum of ruminant because its not ment to make it to there. Now starch is arriving at illicial secal junction and then the same process that happens with people lactose intolerance happens with animals.

Question 25

Whats the problem with rumen acidosis (list them)

Answer 25

* Decreased feed intake * Reduced microbial growth * Reduced cellulose digestion * Diarrhea * Bloat (especially in growing ruminants) * Milk fat depression (usually 4 but now could be 3) * Laminitis * Liver abscess * Death

Question 26

Explain to me why rumen acidosis causes liver absesses***

Question 27

Acute ruminal acidoses

Answer 27

less that 5.0-5.2 pH

Question 28

Subacute ruminal acidosis (SARA)

Answer 28

less that 5.6 pH

Question 29

Whats acute acidosis

Answer 29

this is when its recognised by farmer and nutritionist * Most often recognized * Diet transition period * “Sudden Death Syndrome” * Liver Abscesses * Bloat * Reduced feed intake * Poor body condition and weight loss * Unexplained diarrhea * Temperature

Question 30

How would you recognises sub-acute acidosis

Answer 30

* Occurs more frequently * Difficult to observe or identify * Major response = Reduced feed intake! * Pen feeding conditions * Individual reductions in feed intake masked by pen average * Erratic feed intake patterns

Question 31

If pH is high healthy what happens?

Answer 31

- Good appetite - Good cellulose digestion - Good microbial growth.

Question 32

If pH is low what happens?

Answer 32

- Poor appetite - Little cellulose digestion - Poor microbial growth. if it gets lower than 5: Acute Rumen Acidosis - Deep physiological changes -May cause death

Question 33

Whats the rate of VFA's determined by?

Answer 33

* Total rate of production and concentration of VFA are directly related to intake of fermentable organic matter * Rates of production and concentrations of individual VFA are affected by forage:concentrate ratio

Question 34

What type of bacteria does high pH favour?

Answer 34

Celluloytic bacteria

Question 35

What type of bacteria does low pH favour?

Answer 35

Amyloyltic bacteria

Question 36

Why does rumen acidosis cause diarrhoea

Answer 36

Ph goes down , digestibility of soluble nutrients goes down , starch gets to small intestine , no pancreatic amylase, starch passed to large intestine and now its like rocket fuel. Acidosis in large intestine, damages the large intestine wall.

Question 37

Diarrhoea in Rumen and hind-gut fermenters:

Answer 37

Diarrhea: Nutrients that are not absorbed in rumen or small intestine, travel to large intestine and ferment Extensive fermentation in the hind gut Produces acids (VFAs) and other osmolites Increased osmolarity pulls water into large intestine Decreased pH damages gut wall Mucin secreted Mucin casts can be observed in feces Produces gas (CH4 and CO2) Gas bubbles in feces Similar to the consequences of highly digestible nutrients reaching the large intestine of a monogastric (e.g. lactose intolerance)

Question 38

Name the 3 problems with Acidosis:

Answer 38

-Laminitis (founder) If rumen pH is chronically acidic Epithelium releases metalloproteinases Cause tissue degradation If enter the blood stream causes inflammation of laminae above the hoof -Feedlot bloat Starch fermenting bacteria secrete polysaccharides Produce a foam Gas trapped in foam -Sudden death If large amounts of starch escape the rumen Overgrowth of Clostridium perfringens in the intestine Produce enterotoxin that might cause death

Question 39

When are animals at highest risk for rumen acidosis?

Answer 39

* Highest risk: – Last week before calving (if poorly managed transition diet) – The first few month after calving (high concentrate diet) – Heat Stress

Question 40

What are risk factors that aren't as high as the last one?

Answer 40

* Risk factors: – High concentrate diet (>55% diet DM) * Finely ground – High level of dry matter intake (i.e., high producing cows) – Lush Pasture (less salivation) and lots of soluble sugars – Method of feeding (TMR vs. separate ingredient) – Poor transition between dry cow diet and high producing cow diet (rumen papillae atrophy)

Question 41

What ferments quicker and slower in the rumen?

Answer 41

Quickest: Soluble Sugars Middle: Starches Slowest: Carbohydrates

Question 42

How do we manage acidosis:

Answer 42

1. Allow time for adjustment to diets with grain Gradually increase grain in the diet Program “step up” rations Limit intake until adjusted 2. Feed adequate roughage/forage 3. Manage feed consumption Prevent gorging of high starch feeds one of the main issues with heat stress “Read bunks” System for knowing when to change amount of feed offered 4. Feed ionophores

Question 43

In summary....

Answer 43

* Highly digestible grains are necessary to allow cows to reach genetic potential for milk yield – Therefore this will continue to be a problem as annual milk yield continues to increase * Increased digestibility and too much grain can cause acidosis * Prevention strategies – Be careful with how much grain contributes to DM – Effective fiber (stimulate chewing and saliva production) – Dietary HCO3 * Both concentrates and forages are essentially made up of repeating units of glucose * Microbes ferment these sugars into VFA * Processing of grains and forages alters their digestibility and fermentation pattern and * Waste products of fermentation are energy molecules for the ruminant animals * Gas production by microbes is a waste of money for the farmer