ANSC315 exam 1

Animal Nutrition Study Guide

Unit Conversions and Dimensional Analysis

Key Concepts:

• Dry Matter (DM): The weight of a feedstuff after all moisture has been removed.

• As Fed (AF) Basis: The nutrient content of a feedstuff in its natural state, including moisture.

• Dry Matter Basis: The nutrient content of a feedstuff expressed as a percentage of the dry matter.

• Basis: Refers to what the denominator of a percentage is.

• Percent (%): Means "per 100 parts".

• Dimensional Analysis: A method of problem-solving that focuses on the units of measurement to ensure calculations are set up correctly and the final answer has the desired units. This involves multiplying or dividing by conversion factors to cancel out unwanted units.

Review Questions:

1. What is the fundamental principle of unit conversion when trying to obtain a desired unit?

2. Explain the difference between nutrient percentages expressed on an "as fed" basis versus a "dry matter" basis. Why is this distinction important in animal nutrition?

3. If a feed has 90% dry matter, explain how you would convert a nutrient percentage expressed on a dry matter basis to an as-fed basis.

4. Define "basis" in the context of nutrient conversions and provide an example illustrating its importance.

5. In dimensional analysis, how do you ensure that the units cancel out correctly to arrive at the desired unit for the answer?

Protein Supplements and Amino Acid Requirements

Key Concepts:

• Essential Amino Acids: Amino acids that cannot be synthesized by the animal in sufficient quantities and must be supplied in the diet.

• Nonessential Amino Acids: Amino acids that can be synthesized by the animal. Note that "nonessential" does not mean they are not needed.

• Crude Protein (CP): An estimate of the total protein content of a feed, calculated by multiplying the nitrogen content by a factor (usually 6.25).

• Non-Protein Nitrogen (NPN): Nitrogen-containing compounds that are not true proteins, such as urea. Ruminants can utilize some NPN with the help of rumen microbes.

• Limiting Amino Acid: The essential amino acid present in the lowest quantity relative to the animal's requirement, thus limiting protein synthesis.

• Rumen Degradable Protein (RDP): Protein that is broken down by microbes in the rumen.

• Rumen Undegraded Protein (RUP) (Escape Protein): Protein that passes through the rumen without being significantly degraded and is digested in the small intestine.

• Metabolizable Protein (MP): The true protein available to the animal for metabolic processes, consisting of microbial protein and RUP digested and absorbed in the small intestine.

Review Questions:

1. Distinguish between essential and nonessential amino acids. Give two examples of each.

2. Explain why non-protein nitrogen (NPN) is primarily utilized by ruminant animals and how it is converted into a usable form.

3. What is a limiting amino acid, and why is it important to consider when formulating diets for non-ruminants like poultry and swine?

4. Describe the fate of dietary protein in ruminants, explaining the roles of RDP and RUP.

5. Define metabolizable protein (MP) and briefly outline its significance in meeting the protein needs of ruminants.

Forages and Feed Quality

Key Concepts:

• Dry Matter Intake (DMI): The amount of dry feed consumed by an animal, usually expressed as a percentage of body weight or in kilograms per day.

• Neutral Detergent Fiber (NDF): Represents the total fiber content of a feed, including cellulose, hemicellulose, and lignin. NDF is negatively correlated with voluntary intake.

• Acid Detergent Fiber (ADF): Represents the less digestible fiber components, primarily cellulose and lignin. ADF is negatively correlated with digestibility.

• Relative Feed Value (RFV): An index used primarily for legume forages (like alfalfa) to estimate their quality based on digestibility (estimated from ADF) and intake potential (estimated from NDF).

• Relative Forage Quality (RFQ): A more comprehensive index that predicts forage quality based on NDF digestibility and intake potential. It is applicable to a wider range of forages.

• Total Digestible Nutrients (TDN): A measure of the total digestible energy content of a feed.

• Non-Fiber Carbohydrates (NFC): Readily digestible carbohydrates in feed, calculated as: 100 - (NDF + CP + EE + Ash).

• Bloat: A condition in ruminants characterized by the excessive accumulation of gas in the rumen, often associated with certain types of forages or rapid fermentation.

• Cool Season Grasses: Grasses that grow best in cooler temperatures (e.g., fescue, rye).

• Warm Season Grasses: Grasses that grow best in warmer temperatures (e.g., Bermuda grass).

Review Questions:

1. How does the Neutral Detergent Fiber (NDF) content of a forage influence voluntary dry matter intake in cattle? Explain the general rule of thumb.

2. Describe the components that make up Acid Detergent Fiber (ADF). How does ADF relate to forage digestibility?

3. What is Relative Feed Value (RFV), and for what type of forage is it primarily designed? What two factors does it take into account?

4. Explain how Relative Forage Quality (RFQ) differs from RFV, and why is RFQ considered a more comprehensive measure of forage quality?

5. Briefly describe the condition of bloat in ruminants and mention one factor related to forages that can contribute to this issue.

Particle Size Analysis

Key Concepts:

• Penn State Forage Particle Separator: A tool used to measure the distribution of particle sizes in forages and Total Mixed Rations (TMRs). It typically consists of multiple sieves with different pore sizes and a bottom pan.

• Total Mixed Ration (TMR): A nutritionally balanced mixture of all feed ingredients (forages, concentrates, supplements) formulated to meet the animal's requirements.

• Feed Sorting: The selective consumption of certain feed components over others by animals, often leading to an imbalanced nutrient intake compared to the formulated ration.

• Cumulative Percentage Undersized: The percentage of feed particles that are smaller than a given sieve size.

• Lognormal Paper: A type of graph paper recommended for plotting particle size results as feed particle size distribution typically does not follow a normal distribution.

Review Questions:

1. Describe the purpose of using the Penn State Forage Particle Separator in livestock feeding management. What information does it provide?

2. Explain why it is recommended to measure Total Mixed Ration (TMR) particle size fresh from the feed bunk before the animals consume it.

3. What does the term "feed sorting" refer to, and how can particle size of the ration influence this behavior in dairy cows?

4. Explain how to calculate the cumulative percentage undersized for a particular sieve in the Penn State Particle Separator. What does this value represent?

5. Why is lognormal paper recommended for graphing particle size data obtained from the Penn State Particle Separator?

Nutrient Intake Calculations

Key Concepts:

• Nutrient Intake: The quantity of a specific nutrient consumed by an animal over a period of time.

• Concentration of Nutrient ([Nutrient]): The amount of a nutrient present in a given quantity of feed, often expressed as a percentage, parts per million (ppm), or amount per unit weight (e.g., Mcal/kg, g/lb).

• Food Intake: The amount of feed consumed by an animal, typically measured in units of weight (e.g., kg, lb, g) or volume (e.g., L) per day.

• Dimensional Analysis: Crucial for ensuring that units cancel out correctly when calculating nutrient intake.

Review Questions:

1. State the basic formula for calculating nutrient intake. Make sure to specify the units for each component of the formula.

2. Provide an example of a nutrient intake calculation, clearly showing how the units cancel out to arrive at the correct unit for the nutrient intake.

3. Why is it important to pay close attention to the units of food intake and nutrient concentration when performing nutrient intake calculations?

4. Describe a scenario where you would need to convert the units of food intake or nutrient concentration before applying the basic nutrient intake formula.

5. Explain how dimensional analysis helps ensure the accuracy of nutrient intake calculations.

Feed Naming, Regulation, and Factors Affecting Feed Intake

Key Concepts:

• Common Feed Name: Informal names for feed ingredients that can vary by region or country.

• Legal Definition (Feed Tag): Standardized and regulated names and descriptions of feed ingredients required on feed labels.

• International Feed Name: A more uniform and systematic naming system for feedstuffs.

• Adulterated Feed: Feed that contains harmful or illegal substances.

• Misbranded Feed: Feed that is labeled falsely or misleadingly.

• Generally Recognized As Safe (GRAS): Feed ingredients that are considered safe for their intended use under normal circumstances.

• Palatability: The relative attractiveness of a feed to an animal, influencing its consumption.

• Appetite Regulation Center: Areas in the brain (hypothalamus) that control hunger and satiety.

• Short-Term Intake Regulation: Mechanisms that control the initiation and cessation of individual meals (e.g., glucostatic, chemostatic, distension).

• Long-Term Intake Regulation: Mechanisms that control feed intake over longer periods (e.g., lipostatic).

• Physical Fill: The limitation of feed intake due to the physical volume of feed in the digestive tract.

• Physiological Regulation: The control of feed intake based on the animal's energy or nutrient requirements.

Review Questions:

1. Explain the difference between a common feed name and a legal definition on a feed tag. Why is standardization important in feed naming?

2. Briefly describe what constitutes an adulterated feed and a misbranded feed according to feed law.

3. What factors related to the feed itself can affect its palatability and, consequently, an animal's desire to consume it?

4. Distinguish between short-term and long-term mechanisms of feed intake regulation. Give an example of each.

5. Explain the concepts of physical fill and physiological regulation of feed intake. How does the energy density of a diet influence whether intake is primarily controlled by physical or physiological mechanisms?

Feed Analysis: Proximate Analysis and Detergent Fiber System

Key Concepts:

• Proximate Analysis (Weende System): A traditional method of feed analysis that separates feed into six fractions: Dry Matter (DM), Ash, Crude Protein (CP), Crude Fat (Ether Extract, EE), Crude Fiber (CF), and Nitrogen-Free Extract (NFE).

• Dry Matter (DM) Determination: Measuring the weight of the feed after removing all moisture.

• Ash Determination: Measuring the mineral content of the feed by burning off the organic matter.

• Crude Protein (CP) Determination (Kjeldahl Method): Estimating protein content based on nitrogen content.

• Ether Extract (EE) Determination: Measuring the fat content of the feed by extraction with ether.

• Crude Fiber (CF) Determination: Measuring the less digestible structural carbohydrates after sequential boiling in acid and alkali.

• Nitrogen-Free Extract (NFE) Determination: Calculated by difference and represents the more digestible carbohydrates.

• Detergent Fiber System (Van Soest): A more advanced system that fractionates fiber into Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF), providing a better understanding of fiber digestibility and intake potential.

• Neutral Detergent Fiber (NDF): Represents hemicellulose, cellulose, and lignin.

• Acid Detergent Fiber (ADF): Represents cellulose and lignin.

• Near-Infrared Reflectance Spectroscopy (NIRS): A rapid analytical technique that uses the near-infrared spectrum to predict the nutrient composition of feeds.

Review Questions:

1. List the six fractions determined by proximate analysis and briefly describe what each fraction represents.

2. Explain the basic principle behind the Kjeldahl method for crude protein determination.

3. What are some of the limitations of the Crude Fiber (CF) and Nitrogen-Free Extract (NFE) fractions in providing an accurate assessment of feed carbohydrates?

4. Describe the key differences between the detergent fiber system (NDF and ADF) and the crude fiber method for analyzing feed fiber. Why is the detergent fiber system considered more informative for animal nutrition?

5. Briefly explain the principle of Near-Infrared Reflectance Spectroscopy (NIRS) and what makes it a useful tool for feed analysis.

Cereal Grains and Energy Feeds

Key Concepts:

• Cereal Grains: Seeds of cultivated grasses, such as corn, wheat, barley, oats, and sorghum, that are primary sources of energy in animal feeds.

• Bushel: A unit of volume commonly used for cereal grains, but actual weight varies by grain type.

• Test Weight: The weight of a specific volume of grain, used as an indicator of quality.

• Endosperm: The starchy part of the grain kernel that is the primary source of energy.

• Germ: The embryo of the grain kernel, rich in oils, vitamins, and minerals.

• Bran: The outer layers of the grain kernel, higher in fiber.

• Processing of Grains: Methods such as grinding, rolling, or steam-flaking used to improve the digestibility of cereal grains for livestock.

• Mycotoxins: Toxic compounds produced by molds that can contaminate cereal grains.

• Fats and Oils: Highly concentrated sources of energy in animal diets.

• Iodine Number: A measure of the degree of unsaturation of fats and oils.

• Biohydrogenation: The process in the rumen where unsaturated fatty acids are converted to more saturated fatty acids by microbes.

• Molasses: A byproduct of sugar production, used in animal feeds as an energy source, palatability enhancer, and pellet binder.

Review Questions:

1. List five common cereal grains used in animal feeds and briefly describe a key nutritional characteristic of each.

2. Why is it often necessary to process cereal grains before feeding them to livestock? Provide an example of a processing method and its benefit.

3. What are mycotoxins, and why are they a concern in cereal grain-based animal feeds? Give an example of a mycotoxin.

4. Explain why fats and oils have a higher energy density compared to carbohydrates. What are some practical reasons for including fats in animal diets?

5. Describe the process of biohydrogenation in the rumen and how it affects the fatty acid composition of the animal's tissues, particularly in ruminants fed unsaturated fats.

Nutrient Requirements and Dietary Reference Intakes

Key Concepts:

• Nutrient Requirement: The minimum amount of a nutrient necessary to meet an animal's needs for maintenance, growth, reproduction, lactation, or work, and to optimize health.

• Dietary Reference Intakes (DRIs): A set of nutrient-based reference values used for planning and assessing diets for healthy individuals (in humans). Includes terms like EAR, RDA, AI, and UL.

• Estimated Average Requirement (EAR): The daily nutrient intake level estimated to meet the requirement of half the healthy individuals in a particular population.

• Recommended Dietary Allowance (RDA): The average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (97-98 percent) healthy individuals in a particular life stage and gender group.

• Additive Approach to Nutrient Requirements: Determining total nutrient needs by summing the requirements for different physiological functions (e.g., maintenance + growth + lactation). Common in ruminants and horses.

• Maintenance Requirements: The nutrients needed to support basic life functions without any production.

• Production Requirements: The additional nutrients needed for specific outputs like growth, milk, eggs, or work.

• Utilization Efficiency: The proportion of a dietary nutrient that is effectively used for its intended purpose in the animal.

Review Questions:

1. Define the term "nutrient requirement" in the context of animal nutrition. Why is it important to recognize that requirements can vary?

2. Briefly explain the difference between the Estimated Average Requirement (EAR) and the Recommended Dietary Allowance (RDA) as they relate to nutrient intake levels.

3. Describe the "additive approach" to determining nutrient requirements. For which types of animals is this approach commonly used?

4. What are maintenance nutrient requirements, and what physiological processes do they primarily support?

5. Explain the concept of utilization efficiency in the context of nutrient requirements. Provide an example of a factor that can affect the utilization efficiency of a nutrient.

Quiz

Instructions: Answer the following questions in 2-3 sentences each.

1. A feedstuff is analyzed to be 90% dry matter. If it contains 20% crude protein on a dry matter basis, what is the crude protein percentage on an as-fed basis? Explain your calculation.

2. Why are essential amino acids crucial in the diets of monogastric animals like swine and poultry? Provide one example of a limiting amino acid in corn-based diets for these species.

3. Explain the relationship between Neutral Detergent Fiber (NDF) content in forages and voluntary feed intake in ruminants. What component of NDF is least digestible?

4. What is the primary purpose of using the Penn State Forage Particle Separator to analyze Total Mixed Rations (TMRs)? How can the results help in managing dairy cattle?

5. A dog consumes 500 grams of a dog food that contains 22% crude protein. Calculate the daily crude protein intake in grams. Show your calculation.

6. Why is the legal definition of a feed ingredient on a feed tag important for both animal producers and feed manufacturers?

7. Briefly describe the Kjeldahl method used in proximate analysis to determine the crude protein content of a feed sample. What element is measured as an indicator of protein?

8. Cereal grains like corn are primarily used as energy sources in animal feeds. Which part of the grain kernel is the main source of this energy?

9. What is the key difference between maintenance and production nutrient requirements in animals? Give an example of a production requirement.

10. Explain the role of rumen microbes in utilizing non-protein nitrogen (NPN) sources in the diet of ruminant animals. What end product is beneficial to the animal?

Quiz Answer Key

1. The crude protein percentage on an as-fed basis would be lower. Calculation: 20% CP (DM basis) x 90% DM = 18% CP (as fed). This is because the as-fed weight includes water, which dilutes the concentration of nutrients.

2. Essential amino acids cannot be synthesized in sufficient amounts by monogastric animals and must be provided in the diet for proper protein synthesis and growth. Lysine is often a limiting amino acid in corn-based diets for swine and poultry.

3. Higher NDF content in forages generally leads to lower voluntary feed intake due to physical fill in the rumen. Lignin is the least digestible component of NDF.

4. The primary purpose is to measure the distribution of particle sizes in the TMR, which affects rumen function, chewing, and the potential for feed sorting. This helps ensure the cows consume a balanced ration and prevents metabolic issues.

5. Daily crude protein intake: 500 g feed x (22 g protein / 100 g feed) = 110 grams of crude protein per day.

6. The legal definition provides a standardized description of the feed ingredient, ensuring consistency, preventing misrepresentation, and allowing producers to make informed decisions about feed quality and nutritional value.

7. The Kjeldahl method involves digesting the feed sample in acid, converting nitrogen to ammonium ions. The amount of nitrogen is then quantified, and crude protein is estimated by multiplying the nitrogen content by a factor (usually 6.25).

8. The endosperm of the cereal grain kernel is the primary source of energy, as it is rich in starch, a readily digestible carbohydrate.

9. Maintenance requirements are needed for basic bodily functions like respiration and circulation, while production requirements are the additional nutrients needed to support output such as growth, milk production, or reproduction. For example, the calcium required for milk production in a lactating dairy cow is a production requirement.

10. Rumen microbes possess enzymes that can break down NPN compounds like urea into ammonia. This ammonia can then be used by the microbes to synthesize microbial protein, which is later digested by the animal in the small intestine, providing a source of amino acids.

Essay Format Questions

1. Discuss the importance of understanding dry matter and its role in accurately formulating and evaluating animal diets. Explain how expressing nutrient content on different bases (as-fed vs. dry matter) can impact feeding management decisions.

2. Compare and contrast the Proximate Analysis system and the Detergent Fiber System for evaluating feed composition. Highlight the strengths and limitations of each system in predicting feed digestibility and nutritional value for livestock.

3. Explain the factors that influence voluntary feed intake in animals, considering both animal-related (physiological) and feed-related (physical and chemical) aspects. Discuss the interplay between short-term and long-term intake regulation mechanisms.

4. Describe the key considerations in meeting the protein requirements of ruminant animals versus non-ruminant animals. Discuss the concepts of rumen degradable protein (RDP), rumen undegraded protein (RUP), and essential amino acids in the context of diet formulation for these different digestive systems.

5. Evaluate the significance of forage quality in livestock nutrition. Discuss the use of indices like Relative Feed Value (RFV) and Relative Forage Quality (RFQ) in assessing forage feeding value and their importance in ration balancing for different classes of livestock.

Glossary of Key Terms

• Acid Detergent Fiber (ADF): The portion of plant fiber that is insoluble in acid detergent solution; primarily composed of cellulose and lignin, and inversely related to digestibility.

• Adulterated Feed: Feed that contains any poisonous or deleterious substance which may render it injurious to health.

• Amino Acid: An organic compound containing both an amino (-NH2) and a carboxyl (-COOH) group; the building blocks of proteins.

• As Fed (AF): The state in which a feed is normally offered to an animal, including its inherent moisture content.

• Ash: The inorganic residue remaining after the combustion of organic matter in a feed sample; represents the mineral content.

• Biohydrogenation: The process in the rumen by which microorganisms saturate unsaturated fatty acids, converting them to more saturated forms.

• Bloat: The excessive accumulation of gas in the rumen of ruminant animals, often causing distension of the abdomen.

• Bushel: A unit of volume commonly used for measuring grains; the weight of a bushel varies depending on the type of grain.

• Concentrate: A feed ingredient that is high in energy and/or protein and low in fiber; typically grains, oil meals, and byproduct feeds.

• Crude Fiber (CF): An estimate of the less digestible carbohydrate fraction of feed, determined by sequential boiling in dilute acid and alkali.

• Crude Fat (Ether Extract, EE): The portion of a feed sample soluble in ether, representing the fat or lipid content.

• Crude Protein (CP): An estimate of the total protein content of a feed, calculated by multiplying the nitrogen content by a factor (usually 6.25).

• Diet: The total of the feed regularly consumed by an animal.

• Digestibility: The proportion of a nutrient in a feed that is absorbed by the animal's digestive tract.

• Dimensional Analysis: A problem-solving method that uses the units of measurement to guide calculations and ensure the correct units for the answer.

• Dry Matter (DM): The weight of a feedstuff after all moisture has been removed.

• Dry Matter Intake (DMI): The amount of dry feed consumed by an animal over a specific period.

• Essential Amino Acid: An amino acid that cannot be synthesized by the animal in sufficient amounts and must be supplied in the diet.

• Feed Sorting: The behavior of animals selectively consuming certain components of a mixed feed, leading to an actual intake that differs from the formulated ration.

• Forage: Plant material that is fed to herbivorous animals; typically high in fiber and lower in energy than concentrates (e.g., grasses, legumes, hay, silage).

• Generally Recognized As Safe (GRAS): Feed ingredients that experts consider safe for their intended use under the conditions of their intended use.

• Limiting Amino Acid: The essential amino acid present in the diet in the lowest quantity relative to the animal's requirement for that amino acid.

• Maintenance Requirement: The amount of nutrients needed to support basal metabolic functions in an animal that is not growing, lactating, or performing work.

• Metabolizable Protein (MP): The true protein available to the animal for metabolism after digestion and absorption in the small intestine.

• Misbranded Feed: Feed whose labeling is false or misleading in any particular way.

• Molasses: A viscous byproduct of sugar production, often used in animal feeds as an energy source and palatability enhancer.

• Mycotoxin: A toxic secondary metabolite produced by fungi (molds) that can contaminate feedstuffs.

• Near-Infrared Reflectance Spectroscopy (NIRS): An analytical technique that uses the near-infrared region of the electromagnetic spectrum to determine the composition of a substance.

• Neutral Detergent Fiber (NDF): The portion of plant fiber that is insoluble in neutral detergent solution; includes hemicellulose, cellulose, and lignin, and is negatively correlated with voluntary intake.

• Nonessential Amino Acid: An amino acid that can be synthesized by the animal in sufficient quantities.

• Non-Fiber Carbohydrates (NFC): Readily digestible carbohydrates in feed, typically calculated as 100% minus the sum of NDF, crude protein, ether extract, and ash.

• Non-Protein Nitrogen (NPN): Nitrogen-containing compounds that are not true proteins, such as urea.

• Nutrient Requirement: The minimum amount of a specific nutrient needed by an animal to support a particular physiological state (e.g., maintenance, growth, lactation).

• Palatability: The sensory characteristics of a feed that stimulate a selective appetite in an animal.

• Particle Size Separator: A device with a series of sieves of different mesh sizes used to determine the distribution of particle sizes in feedstuffs.

• Percent (%): Parts per hundred.

• Physiological Regulation (of Intake): Control of feed intake based on the animal's metabolic needs for energy and nutrients.

• Physical Fill (Regulation of Intake): Limitation of feed intake due to the bulk or volume of feed in the digestive tract.

• Proximate Analysis (Weende System): A chemical procedure for partitioning feedstuffs into six fractions: dry matter, ash, crude protein, ether extract, crude fiber, and nitrogen-free extract.

• Ration: The total amount of feed provided to an animal over a 24-hour period.

• Relative Feed Value (RFV): An index used to rank forages based on their estimated digestibility and intake potential, primarily used for legumes.

• Relative Forage Quality (RFQ): A more comprehensive index than RFV, used to rank forages based on NDF digestibility and intake potential, applicable to a wider range of forages.

• Rumen Degradable Protein (RDP): Dietary protein that is broken down by microorganisms in the rumen.

• Rumen Undegraded Protein (RUP) (Escape Protein): Dietary protein that escapes microbial degradation in the rumen and passes to the small intestine for digestion.

• Total Digestible Nutrients (TDN): A measure of the approximate total digestible energy content of a feedstuff.

• Total Mixed Ration (TMR): A nutritionally balanced mixture of all feed ingredients (forages, concentrates, supplements) formulated to be fed to livestock.

• Utilization Efficiency: The proportion of an ingested nutrient that is absorbed and used for its intended metabolic purpose by the animal.