40 Questions
Apparent digestibility coefficients for mineral elements are always satisfactory.
False
Why are true digestibility coefficients difficult to determine?
Because components in faeces arising from the feed and from the animal are indistinguishable from one another
What do apparent digestibility coefficients represent?
The net result of the ingestion of food
True digestibility coefficients provide a more accurate measure of nutrient absorption by accounting for ____________________ losses.
endogenous
Which of the following mineral elements has high endogenous secretions?
All of the above
True digestibility coefficients are easier to measure than apparent digestibility coefficients.
False
Match the following types of digestibility coefficients with their characteristics:
True digestibility = Provides a more accurate measure of nutrient absorption by accounting for endogenous losses. Apparent digestibility = Easier to measure and satisfactory for most organic nutrients.
Why are apparent digestibility coefficients unsatisfactory for some mineral elements?
Because of high endogenous secretions, leading to potentially misleading results.
What are the three components of energy systems?
Energy requirements, energy value of foods, and efficiency of energy utilization
Animals tend to show a discrete response to changes in energy supply.
False
What is the main limiting nutrient in animal nutrition?
Energy
The balance between nutrient requirements and nutrient supply is made separately for each ______________________.
nutrient
What are the two essential steps in the scientific rationing of animals?
Calculation of animal nutrient requirements and selection of foods
Energy systems are used to formulate diets to support specified levels of animal performance.
True
Carbohydrates are the main ______________________ compounds.
energy-yielding
Match the terms with their descriptions:
Energy requirements = The amount of energy needed by the animal Energy value of foods = The amount of energy provided by the food Efficiency of energy utilization = The ability of the animal to use the energy from the food
What is the efficiency of Metabolisable Energy (ME) utilization based on?
Metabolisability (qm)
The efficiency factor (k) for different productive processes depends on the animal's age.
False
What is the purpose of the efficiency factors (k) in calculating animal ME requirements?
To account for different productive processes (e.g. maintenance, lactation, and growth)
For low-quality foods, kg is only _______% of km.
34
What is the relationship between metabolisability (qm) and ME concentration of the diet?
qm increases with decreasing ME concentration
Match the following diets with their corresponding efficiency factors (k):
Low-quality foods (qm = 0.4) = High-quality foods (qm = 0.7) Options: 1. kg is 34% of km = 2. kg is 74% of km
The Blaxter system is used to calculate animal ME requirements using efficiency factors (k).
True
Who developed the series of equations to predict the efficiencies of ME utilisation (k)?
McDonald et al. (2022)
What is the Gross Protein Value (GPV) of a test protein calculated as?
Ratio of extra liveweight gain per unit of supplementary test protein to extra liveweight gain per unit of supplementary casein
The GPV is a measure of protein quality for ruminant animals.
False
What is the purpose of adding casein to the basal diet in the GPV calculation?
To provide a standard protein for comparison
The GPV is calculated as A/B, where A is the _______________ gain per unit of supplementary test protein and B is the _______________ gain per unit of supplementary casein.
extra liveweight; extra liveweight
What is the unit of measurement for the variables A and B in the GPV calculation?
Grams
The GPV is a measure of protein quality that takes into account the animal's maintenance requirements.
False
Match the following components with their roles in the GPV calculation:
Basal diet = Provides a standard diet for comparison Test protein = Provides a protein to be evaluated Casein = Provides a standard protein for comparison
What is the significance of the GPV value?
It represents the protein's ability to promote growth in monogastric animals
What is the formula for Metabolisable Protein (MP)?
MP = 0.6375 x MCP + DUP
The true digestibility of microbial crude protein (MCP) is 0.75.
True
What is UDP in the context of protein digestion?
Undegradable protein in rumen, but digestible in the intestine
DMTP is calculated as 0.75 x 0.85 x __________.
MCP
Match the following protein components with their descriptions:
DMTP = Contribution of microbial protein to truly absorbed amino acids DUP = Undegradable protein in rumen, but digestible in the intestine MCP = Microbial crude protein UDP = Undegradable protein in rumen
What is the assumption about the digestible fraction of UDP?
It has a true digestibility of 0.9.
What is the formula for calculating DMTP?
DMTP = 0.75 x 0.85 x MCP
The proportion of microbial crude protein (MCP) present as true protein is assumed to be 0.65.
False
Study Notes
Digestibility Trials
- True digestibility coefficients are difficult to determine due to the challenge of distinguishing between feed-derived and endogenous components in feces.
- Apparent digestibility coefficients are satisfactory for most organic nutrients, but can be inaccurate for mineral elements with high endogenous secretions.
True Digestibility vs. Apparent Digestibility
- True digestibility: provides a more accurate measure of nutrient absorption by accounting for endogenous losses, but is difficult to determine.
- Apparent digestibility: easier to measure, satisfactory for most organic nutrients, represents the net effect of food ingestion on digestion and absorption, but can be inaccurate for mineral elements.
Energy Systems
- Energy systems consist of three components: energy requirements of the animal, energy value of foods, and information on the efficiency of energy utilization.
- Energy systems are used to formulate diets to support specified levels of animal production or to predict performance from given levels of energy supply.
Scientific Rationing of Animals
- Two essential steps: calculation of animal nutrient requirements and selection of foods to supply these requirements.
- The balance between nutrient requirements and nutrient supply is made separately for each nutrient, with energy usually being the main limiting nutrient.
Blaxter System
- Animal ME requirements are calculated using efficiency factors (k) for different productive processes, which depend on the ME concentration of the diet (ME/DE).
- The efficiency of ME utilization (k) is based on the metabolisability (qm) of the diet.
Measures of Protein Quality
- Gross protein value (GPV) is calculated as the extra liveweight gain per unit of supplementary test protein stated as a proportion of the extra liveweight gain per unit of supplementary casein.
- Metabolisable protein (MP) has two components: digestible microbial true protein (DMTP) and digestible undegradable protein (DUP).
Metabolisable Protein (MP)
- DMTP is calculated as 0.6375 x MCP, where MCP is the microbial crude protein.
- DUP is calculated as 0.9 (UDP - ADIN x 6.25), where UDP is the undegradable protein in rumen, but digestible in the intestine, and ADIN is indigestible.
This quiz covers the concept of digestibility trials, including true and apparent digestibility coefficients, and their applications in animal nutrition.
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