Lecture 10 & 11 Energy Metabolism in Ruminants l and ll Flashcards

What is the primary site of digestion in non-ruminant animals?

The small intestine.

Which molecule serves as the major energy source for non-ruminants?

Glucose.

In ruminants, what is the primary site of digestion?

The rumen.

What is the major source of energy for ruminants?

Short Chain Fatty Acids (SCFA).

What process occurs in the hind gut of both ruminants and non-ruminants to produce SCFA?

Microbial fermentation.

Aside from feed protein, what is the other major source of protein for ruminants in the small intestine?

Microbial protein.

What is the approximate volume range of a rumen in a mature animal?

100 to 200 liters.

What type of oxygen environment is maintained within the rumen?

Anaerobic environment.

What is the approximate concentration of bacteria in the rumen per mL?

$\approx 10^{11}$ cells/mL.

What is the approximate concentration of protozoa in the rumen per mL?

$\approx 10^{4}$ cells/mL.

What is the approximate concentration of fungi in the rumen per mL?

Less than 10^3/mL.

Which enzyme is common to all rumen microbes (bacteria, protozoa, and fungi)?

Cellulase.

In the nutritional symbiosis of ruminants, what primary feed component does the animal provide to the microbes?

Cellulose.

Identify the two main nutritional products that microbes provide to the host ruminant.

SCFA (energy) and microbial protein.

List the two primary gases produced as byproducts of rumen fermentation.

CH_4 (methane) and CO_2 (carbon dioxide).

Which SCFA is categorized as lipogenic and contributes to milk fat and body fat?

Acetate.

Which SCFA is categorized as gluconeogenic and serves as the major glucose precursor?

Propionate.

What is the primary role of butyrate in the ruminant digestive tract?

Providing energy for the rumen epithelium.

Into what molecule is butyrate converted before it is used for energy?

beta-hydroxybutyrate.

How does increasing the proportion of grain in a diet affect acetate levels in the rumen?

It decreases the mol% of acetate.

How does increasing the proportion of grain in a diet affect propionate levels in the rumen?

It increases the mol% of propionate.

Which type of diet (high forage or high grain) favors milk fat synthesis?

High forage diets.

Which type of diet (high forage or high grain) favors glucose production?

High grain diets.

What is the underlying chemical cause of rumen acidosis?

Rapid starch fermentation leading to the accumulation of SCFA and lactic acid.

What is the typical rumen pH level during subclinical acidosis?

Approximately 5.5.

At what pH level is rumen acidosis classified as clinical?

pH less than 5.0.

Name one physical consequence of clinical acidosis on the rumen wall.

Papillae damage.

Which condition involving the hooves is an associated disorder of acidosis?

Laminitis.

What liver-related disorder can result from the consequences of rumen acidosis?

Liver abscesses.

How does increasing effective fiber help prevent rumen acidosis?

It reduces the rate of rapid starch fermentation and helps buffer the rumen.

What is the typical range for blood glucose in ruminants?

50 to 80 mg/dl.

What is the typical range for blood glucose in simple-stomached animals?

80 to 120 mg/dl.

Why do ruminants experience smaller fluctuations in blood glucose compared to non-ruminants?

Due to continuous SCFA production and gluconeogenesis.

True or False: Ruminants experience distinct absorptive and post-absorptive states regarding glucose.

False.

Name the primary precursor used for gluconeogenesis in ruminants.

Propionate.

List three secondary precursors (excluding propionate) used for gluconeogenesis in ruminants.

Amino acids, lactate, and glycerol.

In a lactating dairy cow, approximately what percentage of glucose supply is derived from gluconeogenesis?

75%.

In carbohydrate digestion kinetics, what does the term 'Rate' represent?

The speed of fermentation.

In carbohydrate digestion kinetics, what does the term 'Extent' represent?

Total digestibility.

Which microbial flora group is most active when the rumen pH is between 6.0 and 7.0?

Cellulolytic flora.

Which microbial flora group becomes more active as the rumen pH drops toward 5.5?

Amylolytic flora.

What acid begins to accumulate rapidly in the rumen as pH drops below 5.0?

Lactic acid.

Which feed additive can be used to stabilize rumen pH and prevent acidosis?

Buffers.

Which class of feed additives is mentioned as a strategy for preventing acidosis besides buffers?

Ionophores.

How does the steady flow of digesta in ruminants contribute to glucose homeostasis?

It provides a constant supply of precursors for gluconeogenesis.

What metabolic fate do SCFA products serve for the animal host?

They serve as the major source of metabolizable energy.

What nitrogenous compound is a common byproduct of rumen microbial fermentation?

NH_3 (ammonia).

Under a 100% forage diet (100:0 ratio), what is the typical mol% of acetate?

71.4 mol%.

Under a high grain diet (20:80 ratio), what is the typical mol% of propionate?

30.6 mol%.

How does the animal help maintain the pH of the rumen environment?

By providing a buffered environment (via rumination and saliva).

The condition of rumen wall thickening and scarring due to acidosis is known as _____.

Parakeratosis.

Why is propionate essential for high-producing dairy cows?

It is the primary precursor for the glucose needed for milk production.

What happens to microbial and epithelial function when rumen pH drops significantly?

Function becomes impaired.