Lecture 4

Question 1

Importance of Evaluating Feedstuffs

Answer 1

Quantity of nutrients
Quality of nutrients
How nutrients are utilized by the animal

Question 2

Factors Affecting Nutrient Utilization

Answer 2

Species
Age
Physiological state
Type of GIT (Gastrointestinal Tract)
Plane of nutrition
Physical form of nutrient
Presence of disease/parasites
Overall balance of nutrients

Question 3

Methods of Evaluate Nutrient Utilization

Answer 3

Growth/Feeding Trials
Digestion Trials
Balance Trials

Question 4

Growth/Feeding Trials:

Answer 4

-Determines ability to promote weight gain/efficiency
-Parameters measured: Feed intake, absolute weight gain, feed efficiency

Question 5

Digestion Trials:

Answer 5

-Determines proportion of nutrients absorbed
-Calculates apparent digestibility

Question 6

Balance Trials:

Answer 6

Determines nutrient utilization after absorption

Question 7

Definition of Growth

Answer 7

-Increase in body weight
-Body tissues grow in order: Bone -> Muscle -> Fat
-Nutrient requirements change during growth
-Expressed as absolute or relative weight gain

Question 8

Growth/Feeding Trials - Design

Answer 8

-Animals fed test and basal diets
-Parameters measured: Feed intake, weight gain, feed efficiency
-Paired feeding to account for intake variations

Question 9

Advantages of Growth Trials

Answer 9

-Obtain data at reasonable cost
-Maintain animals under typical conditions
-Easily obtained measurements
-Reflect biological responses

Question 10

Disadvantages of Growth Trials

Answer 10

-Growth response varies among animals
-Body weight gain may not reflect composition
-Accurate weight gain measurement challenging in ruminants

Question 11

Digestion Trials - Conventional Method

Answer 11

-Feed known composition diet
-Adaptation period (5-10 days)
-Collection period (5-10 days)
-Calculate apparent digestibility

Question 12

Indicator Methods for Digestion Trials

Answer 12

-Use non-absorbed indicators
-Internal (lignin, silica) or external (chromic oxide) indicators
-Water-soluble markers for GIT fluid flow

Question 13

Apparent vs. True Digestibility

Answer 13

-Apparent digestibility includes endogenous secretions
-True digestibility excludes endogenous sources
-Important for determining protein digestibility

Question 14

Endogenous Nitrogen Excretion

Answer 14

-Estimate methods: nitrogen-free diet, regression analysis, digestible nitrogen
-Important to determine true digestibility of protein

Question 15

Balance Trials

Answer 15

-Determine nutrient utilization post-GIT absorption
-Most accurate for nutrient requirements
-Net retention (positive balance) or net excretion (negative balance) indicates nutrient status

Question 16

Use of Purified Diets

Answer 16

-Allows changing a single nutrient without affecting others
-Graded levels determine nutrient requirements

Question 17

Rumen Digestion Methods

Answer 17

-In vitro methods: Batch cultures, continuous fermenters
-Nylon bag technique for feed evaluation
-Surgical techniques: Fistulation, cannulation in rumen, stomach, duodenum, ileum, cecum
-Catheters in arteries and veins for sampling and infusion