Ruminant Nutrition

What factors highlight the importance of ruminant livestock to the human food chain?

Ruminant takes energy that is in too complex to digest and make it usable to humans.

Name each of the major digestive organs of ruminants.

Rumen, Reticulum, Omasum, Abomasum

What is the primary function of the Reticulum?

Open to the rumen, function similar to the rumen, honeycomb like tissue that retains course particles

What is the primary function of the rumen?

Muscular folds which aid mixing and movement of ingests

Microbes ferment materials not directly usable by the host animal

Absorptions occurs via diffusion ( VFA, water, NH3, urea) and active transport (Na, Cl)

What is the primary function of the omasum?

Function is somewhat unclear.

May be a biological filter: prevents passage of large particles, concentrates digesta, absorbs water, some VFAs, Na, K and other nutrients

What is the primary function of the abomasum?

Enzymatic and hydrolytic digestion

Comparable to monogastric stomachs

What is the gut wall like in the omasum?

Contains many folds (laminate) of tissue

What is the gut wall like in the abomasum?

Cardiac (entry) and pyloric (exit) sphincters control digesta movement

What is the gut wall like in the reticulum?

Honey-comb like tissue that retains coarse particles

What is the gut wall like in the rumen?

Finger-like projections covering the walls of the reticulum and rumen (Ruminal Papillae)

Increase surface area for greater nutrient absorption

Number, size, and morphology affected by nutritional conditions

Most responsive to butyric acid

What is Eructation?

Cow burps

Ruminal contractions force gas (CH4, CO2) to the roof of the reticulum

Relaxation of the lower esophageal sphincter allows gases into esophagus

Why is eructation necessary?

A lot of gas is produced from microbial fermentation in the rumen

What is rumination?

Regurgitating and rechewing previously ingested material

Why is rumination necessary?

Reduces particle size without rumination digestion would be inefficient and rate of passage would be very slow

Why is surface area important in the digestive process?

The increase in surface area allows for digestion to occur faster

How does the ruminant digestive tract change between birth and adulthood?

Calves have the reticulum groove so colostrum can pass directly to the abomasum.

Groove will eventually close as calf gets older so material will be forced to go through the reticulum and rumen.

How does the rumen digestive develop throughout time?

Ruminal epithelium of a newborn is relatively undeveloped

Diet of newborn has huge impact on Ruminal development

Butyrate will stimulate papillary development (feeding grain)

What is Mutualism?

Describes organisms that benefit from living in close association with other organisms ( both benefit)

Ruminants and microbes

What is commensalism?

An association between two organisms in which one benfints and the other is neither benefiting or being harmed

What is parasitism?

Relationship between two organisms in which one benefits at the expense of the other

What features of the rumen make it an ideal microbial habitat?

Water and Salvia provide an aqueous environment

Rumen maintains constant temperature (39C) and the optimal pH rang (6-7)

Continuous provision of substrate (food)

Ruminal contractions mix substrates and bring them into contact with organisms

End products of fermentation are removed by adsorption, eructation, and passage

No major host defense mechanisms inhibit microbes

What are the major microbes in the rumen?

Bacteria, Protozoa, Fungi

What do Structural Carbohydrate Fermenters (Bacteria) ferment?

Major components of the cell wall

Major substrates- cellulose and hemicellulose

What is the major end product of Structural Carbohydrate Fermenters (bacteria)?

Acetate, Hydrogen (H2), Carbon dioxide (CO2)

What are major substrates for Nonstructural Carbohydrate Fermemters?

Starch, sugars, pectin

What are the major end-products for Nonstructural Carbohydrate Fermenters?

Propionate, butyrate, Hydrogen (H2), Carbon Dioxide (CO2), lactate

What are the major substrate of Proteolytic/ Ammonia-producing bacteria?

Protein

What are the major end-products for Proteolytic/ Ammonia-producing bacteria?

NH3

What are the major substrates of Lipolytic Bacteria?

Hydrolyze Triglycerides

What are the major end-products of Lipolytic Bacteria?

glycerol and free fatty acids; hydrogenate unsaturated fatty acids

What are the major substrates for Intermediate Acid- Utilizing Bacteria?

Ferment end-products produced by other bacteria

What is the major end-product of Intermediate Acid- Utilizing Bacteria?

notably lactate

What is the major substrate of methanogens (archaea)?

H2 gas, primarily by directly reducing CO2 and CH4

What is the fermentative function of protozoa?

similar to bacteria, may contribute 40-60% of total VFA produced

What is the digestive role Ruminal Fungi play?

Colonize plant fragments

Huge role in fiber digestion

Can colonize lignified regions

What are the fermentation products of fungi?

acetate, formate, lactate, and Hydrogen (H2)

What does Lysis (Protozoa) do?

Releases nutrients for use by bacteria

Why is Lysis important?

used as a Nitrogen (N) source when protein is limited

What is Protozoa Predation?

Protozoa engulf both bacteria and intact feed particles; they can store starch in granules within their body

What influence does Predation have on fermentation?

may have a stabilizing influence on fermentation; affects substrate availability and fermentation rate

What is microbial cross-feeding?

end-products from some bacteria can be used by or, in some cases, are required for normal growth by other bacteria

Examples of Cross feeding.

Hydrogen removal by methanogens stimulates growth and fermentation by Hydrogen producing species

Adherent microbes

attached to feed and degrade insoluble polysaccharides, as well as the less-soluble proteins

Associated microbes

degrade oligopolymers of CHO and protein

Fluid

feed on monomers of soluble of CHO (glucose) and protein

Attached to epithelium

include facultative microbes that digest urea or protein from sloughed epithelial cells

Why is methanogenesis so important for ruminal fermentation?

Interspecies H+ transfer and H+ utilization by methanogens are the primary means of regenerating NAD+

What is absorbed during Ruminal Carbohydrate digestion?

VFA

What is eructated during Ruminal Carbohydrate digestion?

Methane (CH4) and Carbon dioxide (CO2)

What goes through as passage during Ruminal Carbohydrate digestion?

Microbial Cells

Lignin

Starch

Cellulose

Hemicellulose

What is absorbed during Ruminal protein digestion?

VFA and NH3

What goes through as passage during Ruminal protein digestion?

Microbial Cells and RUP

What happens to the recycled nitrogen during ruminal protein digestion?

it is returned to the rumen via saliva and cross the ruminal wall

What is absorbed during ruminal fat digestion?

VFA

What goes through as passage during ruminal fat digestion?

Saturated fatty acid, Microbial cell membrane, Waxes an dpigments

What is the relationship between extent of digestion and passage rate?

Slower the passage: less escape, more food digested

Faster the passage: more escape, less food digested

What is the relationship between intake and passage rate?

Intake increases the passage rate of both phases increases

How is urea synthesized and recycled?

Free ammonia from amino acids is converted into urea then goes back to the rumen??

What are the differences in ATP yield when glucose is directly oxidized (monogastric digestion) vs. fermented (ruminant digestion) to yield VFA?

Complete oxidation= there is a lot of energy lost in heat = CO2 + H2O +Heat

Fermentation= CO2 + H2O + VFA- preserves the energy value of the products of fermentation for use by the host

What is the ATP yield of glucose?

35

What is the ATP yield of Acetate?

20

What is the ATP yield of Propionate?

36

What is the ATP yield of Butyrate?

27

Why is accurate prediction of intake critical to successful animal management?

Intake drives the productive response (animals perform in direct proportion to the amount of nutrients that they consume

What are the limitations to accurate intake production from a mathematical standpoint?

most equations were based around diary-type diets and high-concentrate diets so high-forage diets are problematic

What are the limitations to accurate intake prediction from a biological standpoint?

Physical constraints-capacity and fell of the digestive tract

Metabolic constraints-Consume feed to satisfy demands for energy

Water content of feed

What are animal factors that influence feed intake?

Weight, Breed, Sex, Milk production, Pregnancy, Body Condition

What are diet factors that influence feed intake?

Chemical composition, DM content, Physical structure, Gut Fill

What are management factors that influence feed intake?

Feed processing, Feed additives, Anabolic agents, Supplementation, Stocking rate, Drinking water

What are environmental factors that influence feed intake?

Temperature, Humidity, Mud, Photoperiod, indirect effects on feed quality

Methods of Quantifying intake.

“Crate” or Metabolism studies, Growsafe, Pre- and Post- grazing forage clippings, Indirect markers (fecal output)

Why is choosing an appropriate predictive model so critical for intake?

Intake goes hand-in-hand with performance