ruminant digestion

What animals are examples of ruminants?

Cattle, sheep, goats, bison, moose, reindeer, giraffe, antelope, etc.

What is a defining feature of a true ruminant’s stomach?

A four-chambered fore-stomach: rumen, reticulum, omasum, abomasum

Why do ruminants chew their cud?

To reduce particle size, increase saliva, and improve digestion efficiency

What enzyme do mammals lack that microbes provide for fiber digestion?

Cellulase

What is the role of saliva in ruminants?

Buffers pH (7.0–8.0), adds moisture, helps with chewing and rumination

What regulates saliva composition in ruminants?

Hormones: aldosterone (adrenal cortex), renin (kidney)

What is the function of the reticulum?

Traps foreign objects, initiates rumination and eructation; no enzymes/mucus

What is the main role of the rumen?

Large fermentation vat for microbial digestion of fiber

What structures increase surface area in the rumen?

Papillae

What gases are produced by microbes and released by eructation?

CO₂ and CH₄ (methane)

What happens if a cow can’t eructate?

Bloat, which can cause death due to pressure on the diaphragm

What is the function of the omasum?

Regulates flow of digesta, absorbs buffer salts, reduces particle size

What makes the abomasum different from the other chambers?

It’s the true stomach – secretes HCl, pepsin, and mucus

What breaks down microbial cells in the abomasum?

Lysozyme (in mucus)

What are the 3 bacterial niches in the rumen?

• Starch fermenters

• Cellulose digesters

• Sugar fermenters

What do rumen protozoa do?

Prey on bacteria, engulf starch, aid in nitrogen recycling

How hot does the rumen get from fermentation?

Around 103°F, which helps in cold stress but is a liability in heat

How much methane energy is lost during fermentation?

5–10% of gross energy; higher with forages than grains

How is a neonatal ruminant different?

• Born with sterile rumen

• Esophageal groove directs milk past rumen to omasum

Describe protein digestion in the rumen.

• Bacteria break proteins into peptides/ammonia

• Use them to build microbial protein

• Microbial protein is digested later in abomasum/SI