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Rumen GI- F&F > Rumen Characteristics > Flashcards

Rumen Characteristics Flashcards

1
Q

Normal rumen capacity

A

-Cattle: 100-225 L
-Sheep: 10-25L

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2
Q

Rumen fill detection

A

-detected by tension receptors
>volume of contents
>weight
**stimulate motility when moderate stretch, but when high levels of stretch such as in bloat, motility will be decreased

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3
Q

Rumen capacity in late pregnancy

A

-rumen capacity is decreased because fetus takes up space
>highest energy demand during this time
»Can result in negative energy balance (less room for intake and therefore less energy production) AND pregnancy toxemia

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4
Q

Stratification

A

-layers form based on particle density and size
>low density fiber raft on surface (inescapable), denser fall to the bottom
»fiber mat is ruminated and mastication occurs which decreases their size and allows them to enter the escapable middle pool that can exit through omasum

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5
Q

What does fermentation result in?

A

-gas retention, and allowing particles to float

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6
Q

Inescapable dense particle pool

A

-very dense particles at bottom of rumen
-ex. sand

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7
Q

Fiber mat purpose

A

-mechanical receptors on the rumen stimulated by the fiber mat will stimulate rumination

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8
Q

Rumination purpose

A
  • mastication (breaking down particle size)
  • saliva (buffering rumen)
    -eructation needs to occur as well to rid the rumen of the gas formed in fermentation
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9
Q

Fermentation Stratification

A

-active fermentation results in gas allowing particles to float
-the more that particles are broken down, the less gas present and the density decreases and particles sinks down
-the undegradable fraction remains (dense and small particle size)

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10
Q

Movement of escapable middle pool into the omasum

A

-opening is 2-4mm in cattle
-particles must be smaller than opening
-the more dense the particles, the faster the transit is because it will sink from raft to middle pool quicker

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11
Q

Stratification purpose

A

1.Flotation capacity
2.Water absorption capacity- osmolarity of the rumen and whether water comes in or not
3. buffer capacity

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12
Q

Normal osmolarity of the rumen

A

-hypoosmotic

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13
Q

Rumination and buffering

A

-Raft stimulates rumination. Rumination (bringing cud up) results in increase saliva production which increases buffering
>keeps rumen hypoosmotic

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14
Q

Rumen temperature

A

-38-39 degrees
-important that fluids needed for rumen lavage be heated up because otherwise it will kill the natural bacteria by dropping the temperature of the rumen

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15
Q

Rumen pH

A

-very important in maintaining a healthy rumen
-normal pH ~6-7 (less than 5.5 = acidosis)

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16
Q

How does rumen pH vary?

A

-diet
-feed processing
-feed intake
-time between meals

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17
Q

Ruminant diets

A

-high forage diet: pH 6.5-7.2
-high concentrate diet (high in starch): pH 4.9-6.0

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18
Q

Grain/concentrate diets

A

-high in starch
-rapidly fermentable by bacteria which results in VFA production which drops pH of rumen
>Rumination of lower forage diet/high concentration then decrease the stimulation of salivation/rumination for buffering (saliva pH 8.2)
-promotes growth of bacteria that produce lactic acid further decreasing pH and affecting osmolarity (bringing water into rumen)

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19
Q

Saliva production of different ruminant diet

A

High forage: 150L of saliva/day
High concentrate: 40L of saliva/day

20
Q

Adaptation to high concentrate (grain) diets

A

-would need to slowly introduce over time to transition gut microbiome
=step-up rations

21
Q

Feed processing

A

-chopping and grinding reduces particle size (increases SA)
-lowers the rumen pH (because increases fermentation rate and stimulates the rumen epithelial receptors less)
>less rubbing of fiber results in decreased chewing and rumination, salivation and buffering

22
Q

Feed intake

A

-going from maintenance to full intake (drops pH by 1 full unit)
>more substrate results in more fermentation

23
Q

Feed withdrawal

A

-including reduced/no intake during illness
-reintroduce feed in a controlled manner (do not allow to gorge)

24
Q

Rumen pH over time

A

-pH is lowest 3-4 hours after feeding from rapid fermentation of starch
-then increases until next feed
*more frequent meals result in less pH fluctuation (less likely to have acidosis)

25
Q

Results of abnormal pH

A

-effects on motility
-effects on microbes
-acute acidosis
-sub-acute ruminal acidosis (SARA)

26
Q

Abnormal pH effects on motility

A

-epithelial receptors detect low pH which sends inhibitory signals to gastric centers to slow motility

27
Q

Abnormal pH effects on microbes

A

-low pH favours starch digesters
>lactic acid (both D- and L- forms) producing bacteria (strep bovis, lactobacillus) increase in production resulting in acidosis

28
Q

Abnormal pH resulting in acute acidosis

A

-damage to rumen epithelium
-lactic acidosis (D-Lactic acid accumulates and is poorly cleared resulting in acidosis; L-isomer is cleared)

29
Q

Sub-acute ruminal acidosis (SARA)

A

-results in reduced efficiency, laminitis, and liver abscess (bacteria escape to the liver through portal vein)

30
Q

Acidosis Death spiral

A
  1. Rapidly fermentable carbohydrates (starch and sugars)
  2. Increase in VFA, lactic acid bacteria growth rates, and a decrease in pH and increase in lactase production
  3. Sub-acute ruminal acidosis- decrease in bacterial growth rates and enzymatic activities. Lactate production increases further.
  4. Acute ruminal acidosis- increase in D-lactate production, decrease in pH and death
31
Q

Testing Rumen pH

A

-When you have a low-producing dairy herd can suspect it could be SARA
1.stomach tube (risk of saliva contamination)
2.Sensor bolus- given orally and stays in the rumen (3-5 months) which records daily patterns

32
Q

Buffering

A

-acids constantly being produced during fermentation so need to be buffered through:
1.Saliva- contains large amounts of HCO3- and phosphate buffers
2.Carbonic anhydrases on rumen epithelium (converting CO2 and H2O into H+ and HCO3-). H+ is absorbed into blood, HCO3- stays in rumen as a buffer

33
Q

Saliva function

A

1.modifies the rumen pH through buffering
2.nutrients for microbes (nitrogen recycling)
3.anti-frothing properties (reduces Surface tension)
4.enzymes (pre-gastric esterase in calves to break down milk fat; no salivary amylase because not eating much starch feed)

34
Q

Saliva volume production

A

-more than 10% of body weight (100-200L/day)
-varies with diet and feed processing

35
Q

Composition of saliva

A

-NaHCO3
-Na2HPO4
-NaCl
-Nitrogen
-Urea

36
Q

3 major salivary glands

A

-parotid (serous)
-mandibular (mixed)
-sublingual
**many minor glands producing mucous)

37
Q

Rumen osmolarity

A

-normally ~280 mOsm/L (hypotonic than extravascular fluid, 300 mOsm/L)
>water will want to be absorbed out of rumen into circulation

38
Q

Rumen osmolarity after feeding

A

-increases because fermentation produces VFA resulting in more solutes
>brings water into rumen from circulation

39
Q

Acidosis and rumen osmolarity

A

-acidosis from increased VFA and lactic acid results in increased osmolarity
>water moves into rumen from blood
>splashing sound under auscultation because of added water to rumen
>dehydration

40
Q

Gas production

A

-product of microbial fermentation (anaerobic environment from no O2. Any O2 that does enter is used by facultative bacteria)
-maximum occurred ~2-4 hours after meal
-eliminated by eructation (secondary contractions)
-bloat can occur very quickly

41
Q

Cattle gas production

A

30-40 L/hour
400L/day

42
Q

Gas composition

A

-CO2 (65%)
-CH4 (25%)
-N2 (7%)
-O2 (0.5% but used up rapidly by facultative anaerobes)
-H2 (0.2%)
-H2S (0.01%)

43
Q

CO2 production

A

1.decarboxylation metabolism of acetate and butyrate
2.Carbonic anhydrase

44
Q

CH4 production

A

-Methanogens reduce CO2 and formic acid into CH4
-Energy is lost when CH4 is produced
>up to 16% of gross energy on high forage diet
>up to 8% on high concentrate diet (bit more efficient)

45
Q

Energy efficient VFAs

A

-propionate is the most energy efficient fermentation route because no need of CO2
-Acetate and butyrate produces CO2 resulting in methane

46
Q

Ionophores

A

-antibiotics that reduce CH4 production
-H2 is used to form propionate instead

Rumen GI- F&F (10 decks)

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