Ruminant Nutrition - Final Exam

What are at least 2 biological advantages that the ruminant gastrointestinal tract provides compared to the non-ruminant digestive system?

• They can eat “junk” like dead grass and still gain nutrients, pregastric fermentation allows breakdown of cellulose

• Avoid predators because they can eat a lot at once and later hide to digest

Provide at least 4 defining characteristics of ruminant animals

1. ungulate

2. only have lower incisors

3. obligate herbivores

4. multi-compartmented stomach

What are the 5 sacs of the rumen and what biological advantage do they provide compared to if the rumen was a single continuous compartment?

• dorsal sac

• dorsal blind sac

• cranial

• ventral blind sac

• ventral sac

  • Each sac contracts at a different time, allowing for the mixing of feedstuffs and better digestibility

What are 2 factors that influence digestion of feed in ruminants?

• rate of passage

• rate of fermentation

What are 2 examples of fermentation end products that are not directly useful to ruminant animals?

Methane & Carbon Dioxide

Ruminant species have different grazing strategies and differences in grazing strategies are often related to body size. Why?

Since different types of ruminants are different sizes, their rumen is proportional to their body size and the amount of food they can eat.

What are the 3 different grazing strategies utilized by ruminant species and describe how they differ from each other.

• Browsers - eat nuts, leaves, seeds, and berries; rumen is mostly used for detoxification; goats

• Intermediate Feeders - are able to eat diets of both browsers & grazers + twigs; giraffes

• Grazers - typically have a grass & forage based died; cattle

List 3 short-chain fatty acids produced in the rumen that account for almost all organic acids produced from ruminal fermentation.

Acetate, Propionate, Butyrate

The detergent fiber system commonly results in measures material insoluble in a neutral detergent and material insoluble in an acidic detergent. Which material or fiber most closely reflects all of the fiber components found in plants?

Neutral Detergent Fiber (NDF)

The detergent fiber system commonly results in measures material insoluble in a neutral detergent and material insoluble in an acidic detergent. What is the primary difference between the material insoluble acidic and neutral detergent?

removal of hemicellulose

If ruminant have no specific requirement for carbohydrates, then why do we feed ruminants carbohydrates?

Carbohydrates are a cheap, easily accessible energy source. The rumen microbes can break down the B-linkage in some feedstuffs that humans cannot.

Provide 4 examples of ways that VFA production can be manipulated.

1. add ionophores

2. add buffers to diet

3. changing grain to forage ratio

4. further process feedstuff (heat treat, grinding, etc.)

What is the primary difference between starch and cellulose?

Cellulose is a structural carbohydrate and has a B-linkage. Starch is a non-structural carbohydrate and has a-linkage.

Which volatile or short-chain fatty acid produced by the rumen accounts for at least 50% of ruminal short-chain fatty acids?

Acetate

Why is grater amounts of lactic acid production in the rumen a concern?

It can cause acidosis in the rumen and abscesses in the liver leading to a sick or dead animal.

Why is greater proportional of production of propionate commonly associated with improvements in feed efficiency in ruminants?

Propionate is easily converted into glucose because propionate has 3 carbons and glucose has 6. It is easy to put two propionates together to make a glucose, therefore improving feed efficiency.

What is the primary structural heteropolysaccharide that closely associates with lignin?

Hemicellulose

Which type of starch is less soluble? Why?

Amylose is less soluble because it is linear. Amylopectin is branched and can draw more water in and around its branches.

What is physically effective NDF?

Fiber that is effective in the rumen, also known as “scratch factor”. Feeds need to be greater than or equal to 1.2 mm to be considered physically effected and can get up to 5-6 mm.

Why is physically effective NDF related to ruminal pH?

The smaller the physically effective NDF particle size, the lower (more acidic) rumen pH becomes. If acid load is too high, microbes will begin to die.

What is an example of a negative associative effect when feeding ruminants? Provide and explanation of why this negative associative effect would occur.

An example of feedstuffs that can cause negative associative effect is corn and hay. The fiber in these feedstuffs is not easily digestible, making them stay in the rumen longer.

What happens to amino acids provided in excess of needs for protein synthesis?

The amino acids will be broken down into NH3 and a carbon skeleton. The NH3 will bind to urea and be excreted as urine/uric acid. The carbon skeleton is then recycled to form other amino acids, oxidized into ATP, or synthesized into glucose by gluconeogenesis.

Crude protein in diets fed to ruminants consist of true protein and non-protein nitrogen. Which source of nitrogen found in dietary crude protein can contribute to RDP and RUP

True Protein

What is the primary goal when providing RDP to ruminants?

The primary goal when feeding RDP is providing protein to rumen microbes so they can synthesize microbial crude proteins.

Illustrate ruminal fermentation of carbohydrates. Clearly identify the different fractions of carbohydrates on the chart.

*Refer to question 7 on Quiz 4

What is metabolizable protein?

Metabolizable protein is the protein that is digested or the protein that is available for synthesis of other proteins; MP =dRUP + dMCP

Why is diet net energy almost always more limiting to performance in ruminants compared to metabolizable protein supplies?

Metabolizable protein is less limiting because protein is not entirely needed in the ruminant diet, as the microbes are able to synthesize all the proteins needed by the ruminant.

Name 2 separate strategies used to improve the amino acid profile of diets fed to ruminants.

• feeding complementary amino acids

• feeding synthetic amino acids

How does net protein differ from metabolizable protein?

Net proteins can be synthesized into other proteins in the body and metabolizable proteins are those that are readily digested.

What is the goal of protein and carbohydrate synchrony?

Protein and carbohydrates to be fermented at the same rate.

Why do diets that provide synchronous amounts of rumenally degradable protein and fermentable carbohydrates often fail to provide real benefits?

This doesn’t allow for proper nitrogen recycling

Why is metabolizable protein not usually the most limiting nutrient for production in cattle?

Metabolizable protein isn’t limiting because the microbes can make the protein needed by the ruminant each day as microbial crude protein.

What role does the liver play in nitrogen use by ruminants?

The liver detoxifies ammonia and neutralizes it, the using the nitrogen in urea recycling.

Illustrate ruminal fermentation of protein. Clearly identify the different fractions of protein on the chart.

*Refer to question 7 on Quiz 5

What are 3 factors that can influence rate of protein disappearance in the rment

• rumen pH

• intrinsic factors in feed

• particle size

How much metabolizable protein is provided from rumenally degradable protein?

~64%

How does the efficiency of protein use for growth in ruminants compare to the efficiency of protein used for growth in many non-ruminants?

Ruminants are less efficient than non-ruminants

• non-ruminants: 50-65%

• ruminants: 30-40%

What are 4 ways in which ruminants lose water from their body?

• sweat

• urine

• feces

• respiration

What is the primary measure of water quality when determining suitability of a water source for ruminants?

total solids dissolved

What are 4 factors that influence water intake?

• availability

• dry matter intake

• age/size

• weather/temperature

What is the primary concern related to water harness when evaluating water sources for rumiannts?

Integrity of the pipes/water lines

What is the primary role of vitamins and minerals in total mixed rations fed to cattle?

Makes money for people who sell the feed/”special” mineral/vitamin mix.

Primary conduit for humans to make money.

What type of vitamins are synthesized by ruminal microbes?

Water soluble (B-vitamins & vitamin C)

What fat soluble vitamin is the costliest and can be associated with improved immune function?

Vitamin EH

How much linear space is required to allow a feedlot steer adequate access to water during times of heat stress?

1-3” of linear trough space

What vitamin K antagonist is commonly used in rodent poison?

Dicumerol

What dietary strategy is used to prevent milk fever in dairy cows?

Feeding a negative DCAD diet to dry cows

What vitamins are functionally not required by ruminants after they have developed pregastric fermentation?

Water soluble (B-vitamins & Vitamin C)

List at least 2 common ingredients used to add calcium to ruminant diets. Clearly identify which ingredient has a greater standard for calcium concentration.

• Limestone - higher calcium concentration

• Rock Chalk

What disease is commonly associated with large concentrations of dietary sulfur (>0.45% diet DM) in ruminant rations?

PEM (header/brainer cattle)

Grass tetany can be a problem among ruminants grazing lush legumes. Why?

Lush legumes are high in potassium which limits the amount of magnesium that can access the body for utilization and absorption.

Which micro-mineral commonly fed to cattle has a toxicity in sheep at levels similar to requirements for cattle?

copper

Which micro-mineral is important for proper thyroid function?

iodine

List 2 water soluble vitamins that have been reported to have benefits related to lipid synthesis and mobilization

choline & niacin

Zinc is an essential trace mineral fed to ruminants. What aspect of zinc absorption from the ruminant digestive tract makes it difficult to determine zinc requirements and largely prevents zinc toxicity?

The absorption of zinc is highly regulated by the rumen based on intake, excess being lost in feces.

What trace mineral has variable concentrations across different regions in the United States, when deficient can contribute to White Muscle Disease in calves, and is tightly regulated in cattle feed to prevent toxicity?

selenium

What are 4 factors that influence digestion according to the reactor theory of digestion? Circle (Highlight) those factors which positively influence digestion when all other factors remain the same.

• Reaction Rate

• Digesta Retention Time

• Concentration of Reactants

• Reactor Volume

Illustrate relationship of rate of appearance and time of an indigestible marker when fed to cattle. Clearly label the x- and y-axis. Clearly identify each separate area of marker pooling by labeling k1 and k2. Also, identify the transit time.

*Refer to question 4 on Quiz 8

What are 3 things that have to occur in order for a young ruminant to develop a functional rumen after birth?

• papillae development

• change in compartment size

• microbial inoculation

What factor has the greatest impact on papillae develop in young rumiannts?

fermentative end products

What factor in the reactor theory of digestion contributes to less digestion when all other factors are the same but contribute to greater digesta retention time?

reactor volume

What is the maximum allowable concentration of Se that can be legally added to catle rations on a dry matter basis?

0.3 mg/kg DM of selenium

What are the four stages involved in rumination?

• regurgitation

• remastication

• resalivation

• reduglition (reswallowing)

What is one of the principle hormones associated with hunger for daily intervals of feed intake and what organ or tissue type is predominately responsible for its production?

Ghrelin - secreted by the abomasum (stomach) to signal hunger

What is one of the principle hormones associated with satiety for daily intervals of feed intake and what organ or tissue type is predominately responsible for its production?

Leptin - secreted by adipocytes to signal satiety (fullness)

What is chemostatic regulation of intake?

• hormones

• plasma metabolites

• metabolic fuels

What is physical fill regulation of intake?

• digesta flow rate

  • reticulo-rumen distention

    feelings of fullness or satiety based on gut fill

Illustrate relationship of caloric intake and energy density of a diet fed to cattle. Clearly label the x- and y-axis. Identify the point where chemostatic control limits intake compared to physical fill.

*Refer to question 6 on Quiz 9

Generally, what metabolizable energy concentration in a feed or ration is associated with the chemostatic control point?

40-44 Mcal ME/kg of DM

It is difficult to determine when intake is limited by physical fill in ruminants; however, NDF is often used to estimate limits in physical fill. Intake of NDF at what percentage of body weight is typically thought to represent physical fill limits in ruminants?

1.2-1.3% NDF based on a percentage of body weight on a dry matter basis

Androgenic implants in beef cattle influence growth, in part, by increasing production of insulin-like growth factor-1. Insulin-like growth factor-1 reduces suppression of hepatic gluconeogenesis by insulin. Recalling what you know about the hepatic oxidation theory, what impacts would you expect implants to have on short-term feeding behavior in beef cattle? Explain why you would expect implants to influence short-term feeding behavior in that way.

Hepatic oxidation theory is on a meal-to-meal basis rather than daily intake. Androgenic implants could then be assumed that they will cause animals to have smaller more frequent meals.

What ionophore contributes to reductions in daily feed intake?

monensin

What drives predictions of dry matter intake when one assumes no environmental or outside influences?

The energy requirements of the animal and the energy content of the feed/forage.

Describe at least 4 factors that influences predictions of dry matter intake.

1. breed

2. body fat

3. environment

4. temperature

If adipose is associated with one of the predominate hormones of satiety then why do obese animals not always eat less amounts of food in a day than their non-obese counterparts?

Adipose doesn’t respond well to insulin, the body continues to produce insulin and a response never fully occurs, causing the animal to continue eating, getting more obese/continuing to be obese

Are predictions of daily dry matter intake increased, decreased or not affected by anabolic steroids? If so, then how much are predictions of dry matter intake influenced by anabolic steroids?

Increased dry matter intake by ~4%

What are 4 sources of protein loss in ruminants?

1. endogenous loses in feces (microbial & endothelial)

2. urine (urea)

3. hair

4. skin

Why is gain predominately predicted by energy intake?

As the body increases and has a decreasing proportional grade of protein and an increasing proportional rate of gain of fat that increases the total energy density of the body greater amount of fat which increases energy density of the next pound of gain

Using less than 2 words, what does equivalent empty body weight represent?

physiological maturity

When is amount of gain per amount of feed consumed lease efficient?

When the animal is older & physiologically mature as gain switches from protein to fat.

In what year were measures published for determination of EQSBW?

1984