13: Ruminant Nutrition 1

What makes ruminants unique

Stomach anatomy

Rumen function

Fermentation of fiber

What side of the ruminant is taken up by the rumen

Basically all of the L side

Sacs of the rumen

• Cranial sac

• Dorsal sac

• Caudal sac

• Caudo-dorsal blind sac

• Caudo-ventral blind sac

Grooves of the rumen

• Longitudinal

• Dorsal coronary

• Ventral coronary

Pillars of the rumen

• Cranial

• Right accessory

• Right longitudinal

• Caudal

• Dorsal coronary

• Ventral coronary

Placement of retculum

Cranial side of stomach, between rumen and liver

Placement of omasum

Right cranio-ventral aspect

Placement of abomasum

Ventral aspect

Where is the ruminant’s thoracic anatomy relative to small animals

Pushed cranially because of rumen

What organs can be palpated rectally

• Kidneys

• Cecum

• Rumen dorsal sac

• Rumen caudo-dorsal blind sac

• Intestines (abnormal)

Feature in rumen that increases surface area

Papillae

When do rumen papillae develop

Months after birth

What stimulates development of rumen papillae

Nutritional stimulation (grains)

Defining structure of the reticulum

Honeycomb structure

Reticulum function

• Controls particle size

• Traps foreign materials

What can happen if something punctures the reticulum

Traumatic reticular peritonitis → carditis

Omasum structure

Firm sphere with many folds of mucosa

Omasum function

Absorption of VFAs and water

Abomasum function

Enzymatic digestion

Rumen pillar structure and function

Firm muscular tissue that partially separates the rumen to help with mixing

Reticular/esophageal groove structure

Muscular tube from esophagus straight to the reticulum

Reticular groove function

Takes milk straight to the abomasum

How is the reticular groove stimulated in neonates

Pharynx receptors

How is the reticular groove stimulated in adults

Drugs (not very effective)

Importance of rumen motility

Crucial for effective fermentation and digestion

Types of rumen motility

• Primary contractions

• Secondary contractions

Purpose and frequency of primary contractions

Mixing → every minute

Purpose and frequency of secondary contractions

Eructation → every minute or two

How are contractions evaluated for vitals

Auscultation

Rumination purpose

Physical breakdown of feed (especially cellulose) and incorporation of saliva (buffers!) into stomach

Why are ruminations an important vital sign

Decreased rumination can indicate sickness

Environment in rumen

Anaerobic with controlled pH and constant temperature

Purpose of analyzing rumen fluid

Can help with diagnosis and treatment

CHO digestion in ruminants

Starches and fibers are fermented by microbes into VFAs

How are VFAs absorbed

Through the rumen wall

When microbes digest cellulose, what are the microbial end products

Pyruvate and ATP

What do the microbes do with pyruvate

Turn it into more ATP, and VFAs are a byproduct

The metabolism of pyruvate produces what specific compounds

• Acetate

• Propionate

• Butyrate

• ATP

• Methane

Why do ruminants still need glucose

Nervous system is picky with energy source (it needs glucose)

2 carbon VFA used for FA synthesis

Acetate

3 carbon VFA used for glucose synthesis

Propionate

Purpose of butyrate

Converted to ketones

Why is the proportion of starch or fiber fed important in ruminants

Can affect microbial population, which can change the proportion of VFAs produced

VFAs produced from fiber fermentation

LOTS of acetate, some propionate, some butyrate

VFAs produced from starch fermentation

Acetate, more propionate than fiber, some butyrate

Primary component for regulating rumen pH

Bicarbonate in saliva

What process is crucial for regulating rumen pH

Rumination

The production of what VFA produces methane

Acetate

How is subclinical acidosis a production problem

Subclinical acidosis → kills off fiber digesters (methanogenic bacteria) → more starch digesters → lower acetate and higher propionate → less milk fat synthesis

Where is most protein digested in ruminants

In the rumen by microbes

What do the microbes use the protein for

MCP or VFAs

How do microbes process AA

Deaminates it into carbon skeleton (for synthesis of other things) and ammonia

Microbial uses of carbon skeletons

Synthesis of other things (like VFAs→ ATP)

T/F: all AA are deaminated by microbes

False, some can’t use preformed AA and instead need the building blocks

Building blocks that are provided to microbes for protein synthesis

NPN and glucose (starch → E)

Primary source of protein for the ruminant

Microbial protein

What happens if there is too much NPN and not enough energy

Microbes can’t synthesize MCP, and instead convert the NPN to VFAs, which leaves a lot of ammonia in the rumen

What happens if there is too much energy and not enough NPN

The energy is used for microbial maintenance instead of proliferation

How is ammonia recycled in the ruminant

Rumen wall → blood → liver → converted to urea → recycled in saliva for microbes or excreted by kidneys

What does the ruminant do with NPN

It doesn’t do anything with it

Crucial part of feeding NPN

Need to match it with enough of an easily digestible CHO

How do ruminants get vitamins

Mostly from microbes

How are vitamin supplements produced for ruminants

Chelated with an AA to bypass microbes

Why isn’t BUN a relevant measurement in ruminants

Even if there are problems with the kidney, the nitrogen will still get recycled efficiently

MUN use

Milk urea nitrogen; indicator of relative protein excess

Purpose of ionophores as a feed additive

Increases feed efficiency by shifting microbial population from G+ (fiber/acetate) to G- (starch/propionate), resulting in more glucose and more energy for growth