Rumen Acidosis

Why can't we feed only forages to dairy cows to meet their energy needs?

The rumen doesn't have the capacity to hold that amount of forages

Are we more concerned with forages or concentrates in regards to acidosis?

Concentrates (grain)

Do we want animals to eat smaller, more frequent meals or larger, less frequent meals?

Smaller, more frequent

What is the primary disaccharide in milk?

Lactose

What two monosaccharides make up lactose?

Glucose and Galactose

What monosaccharide is the precursor to lactose synthesis?

Glucose

Which of the three VFAs is most important for lactose/milk production?

Propionate

What is the pathway for milk synthesis?

1. Feed in

2. Bacteria ferment to VFAs

3. Propionate travels to the liver and is converted to glucose

4. Glucose bonds with galactose to form lactose

5. Lactose = milk

Why is it more efficient for fermentation with higher concentrate percentage?

Most carbon is contained is contained as propionate rather than belched out as methane or CO2

Why does VFA production go up as concentrate percentage increases?

The extent of fermentation and the rate of fermentation are both higher when we feed starch (grain)

Why does feeding more concentrates decrease rumen pH?

- VFAs are produced quicker than they are absorbed in the rumen

- Lactic acid produced quicker than it is absorbed

- Rumination and chewing time is reduced = less saliva = less buffer produced

Which components in ruminant saliva act as a buffer in the rumen?

Bicarbonate, sodium (Na), and potassium (K)

Which acid (not one of the VFAs) is also produced in the rumen and is more acidic?

Lactic Acid

What is the #1 clue of rumen acidosis?

Diarrhea

What side effect of rumen acidosis greatly decreases the price of a carcass?

Live abscesses

Does acute or subacute acidosis show visible signs of illness?

Acute rumen acidosis

Does acute or subacute acidosis occur more frequently?

Subacute rumen acidosis

What are mucin casts?

They are the shedding of the epithelium (mucous lining) of the small intestine

Why is lactose critical for milk production?

The mammary gland must secrete it out of the membrane to osmotically pull water out

If I feed my cow 10 lbs. of forage, how much should I expect to see in the feces?

3-4 lbs

If I feed my cow 10 lbs. of grain, how much should I expect to see in the feces?

Less than 1 lb.

Why is acetate a less efficient product of fermentation than propionic acid?

The animal loses more carbons because it produces more CO2 which the androgens change into CH4

Why do we see more diarrhea with higher concentrate diets?

The rate of fermentation increases, which quickly increases VFA production. The rumen cannot absorb the VFAs as quickly as they are produced. The high number of molecules pulls water into the large intestine.

As the pH value of the rumen increases, do amylolytic or cellulolytic flora increase?

Cellulolytic (forage digesting bugs)

When rumen pH gets too low, starch can escape the rumen and reach the small intestine. Why is this bad for the ruminant?

Has no pancreatic amylase to break down starch and no SGLT-1 transporter to absorb so it travels to the large intestine, ferments rapidly, and pulls water in; resulting in diarrhea

What does it mean if the rumen pH is chronically acidic?

It has been acidic for a long period of time (months or weeks)

T/F: Cattle are the only species that can experience laminitis (founder).

False, horses are another example

When are you most likely to see rumen acidosis in dairy cows?

A couple weeks after calving

Why does fine ground corn digest quicker than cracked corn?

It has more surface area!