Essential Concepts in Animal Nutrition and Feed Analysis

Posted on Sep 28, 2025 in Human Nutrition and Dietetics

Proximate Analysis and Feed Composition

Components of Proximate Principles

The Proximate Analysis system divides feed components into six categories:

  • Moisture: Water and other volatile compounds.
  • Ash: Minerals (inorganic matter).
  • Crude Fiber (CF): Cellulose, hemicellulose, and lignin.
  • Nitrogen-Free Extract (NFE): Starch and sugars (highly digestible carbohydrates).
  • Ether Extract (EE): Lipids (fats and oils).
  • Crude Protein (CP): Calculated from nitrogen content (N x 6.25).

Analytical Methods

  • The Kjeldahl method used in proximate analysis directly measures nitrogen.
  • Acid Detergent Fiber (ADF) measures cellulose and lignin, but excludes hemicellulose.

Sample Calculation (NFE)

If a 100g feed sample contains 10g water, 10g ash, 20g CP, 20g EE, and 10g CF, the amount of NFE is 30g (100g total – 70g known components).

Characteristics of Common Feedstuffs

Carbohydrates and Energy Sources

  • The organic matter of roots consists mainly of sucrose.
  • Storage Carbohydrates: Starch and sugar; the main source of highly digestible energy for monogastrics.
  • Structural Carbohydrates: Major source of energy for fore/hindgut fermenters; includes soluble and insoluble fiber, digested only by gastrointestinal tract (GIT) microbiota.
  • Molasses and beet pulp are examples used to increase energy content in feeds.

Protein Sources

  • Oilseed cakes and legumes (e.g., peas and beans) generally contain high protein content.
  • Non-Protein Nitrogenous (NPN) Sources: Used in ruminant diets, including ammonia salts, urea, and poultry waste.
  • Animal Proteins: Good sources of Ca, P, Se, and Fe.
  • Concerns with Animal Proteins: Potential for Salmonella contamination, high ash content, and sometimes poor palatability.
  • Protein supplements may be necessary for ruminants when they are being fed low-quality forage.

Lipids (Fats)

  • Fats added to animal feed do all of the following EXCEPT: increase digestibility of fiber in ruminants.
  • Characteristics of lipids as an energy source EXCEPT: high crude fiber content (Lipids are low in fiber).

Roughages and By-products

  • Plant food sources tend to be low in protein, high in carbohydrates, and high in lipids.
  • A roughage with high fiber content but low protein and calcium content is Bluegrass.
  • Ruminants should not be fed concentrates free access.
  • Concerns with Non-Legumes/Grass Forages: Nitrate poisoning, mycotoxicosis, and grass sickness.
  • Concerns with Cereal By-products: Protein deficient in lysine/methionine, presence of phytic acid, low palatability, and deficiency in Vitamins D, A, and Riboflavin.

Roots and Tubers

  • All of the following are examples of roots EXCEPT potatoes (Potatoes are tubers).
  • All of the following are examples of tubers EXCEPT beet molasses (Molasses is a liquid by-product).
  • Statement: Potato starch is not digestible for monogastrics when fed raw – TRUE.
  • Concerns with Roots/Tubers: Low in protein, potential tainting of milk, molasses is a laxative, potato starch is not digestible for monogastrics when fed raw, poor source of minerals, and presence of cyanogens.

Energy Utilization and Metabolism

Defining Energy Terms

  • Metabolizable Energy (ME): Digestible energy minus energy lost through urine and gasses.
  • Basal Metabolic Rate (BMR): The amount of energy an animal’s body needs to survive when it is resting.
  • Energy is an essential nutrient: FALSE (Energy is supplied by essential nutrients).

Heat Increment (HI)

Heat Increment (HI) is energy lost as heat during metabolic processes. Sources of HI include:

  • Fermentation (e.g., heat of fermentation, given off by chemical reactions of digestive tract bacteria).
  • Digestion and absorption.
  • Product formation.
  • Waste excretion.

Heat increment includes energy lost EXCEPT energy used for tissue growth.

Maintenance Energy

Maintenance energy is required for all processes EXCEPT growth.

The three main processes contributing to total energy expenditure are:

  1. Basal Metabolic Rate (BMR).
  2. Physical activity.
  3. Production (e.g., milk, eggs, wool).

The efficiency of energy utilization for wool and mohair production is generally high: FALSE.

Nutritional Needs Based on Life Stage

Maintenance Requirements

Maintenance nutritional requirements are largely driven by body weight.

General nutrient levels in a maintenance diet:

  • High in CHO (Carbohydrates), Fat, and Water.
  • Low in Protein, Vitamins, and Minerals.

Growth and Weight Management

  • Energy required by a growing animal is supported by providing high levels of carbohydrates and lipids.
  • General nutrient levels in a growth diet: Very high protein, CHO, and fat; high vitamins and minerals.
  • To adjust an underweight animal’s daily feed allowance to promote weight gain, you should increase daily feed allowance, specifically increasing energy and protein.

Pregnancy and Gestation

  • The highest level of nutrients is needed during the last 3 months of gestation.
  • Energy requirements for pregnancy include all of the following EXCEPT: energy needed to account for the efficiency of egg production.
  • Specific energy requirements for pregnancy include: Maintenance, Conceptus growth, Reproductive organ development, Inefficiency of energy utilization, and Fluid production.

Lactation

  • In which stage of lactation would animal milk have the greatest amount of Dry Matter (DM)? The beginning stage.
  • General nutrient levels in a lactation diet: High protein, Ca, P, Vitamin A, B complex, CHO, and fat.
  • Example: If “Fluffy the cat gave birth,” the highest nutritional demands would fall on Fluffy (the lactating mother).

Essential Nutrients and Supplements

Vitamins and Minerals

  • The main criteria for assessing the adequacy of vitamins are growth rate and freedom from signs of deficiency.
  • Carnivores in captivity have a higher requirement for the B complex vitamins.
  • Cats require Vitamin B3 (Niacin) supplementation due to their inability to convert tryptophan to niacin efficiently.
  • Four essential minerals that must be supplied in the diet are: Calcium (Ca), Sodium (Na), Potassium (K), and Magnesium (Mg).

Fatty Acid Deficiency

Symptoms of Arachidonic Acid deficiency include:

  • Poor growth.
  • Hair loss and rough hair coat.
  • Poor immunity.
  • Slow healing and skin lesions.

Feed Additives and Supplements

  • Examples of energy supplements in feedstuffs include cereal by-products, molasses, beet pulp, and surplus fats.
  • Feed additives are used for five main reasons: improving quality, digestibility, nutrition (indirectly), aesthetics, and performance.
  • A common misconception is that feed additives are primarily for supplying additional nutrients; however, their main role is often enhancing utilization or preservation.

Principles of Ration Formulation

Optimizing Feed Intake and Efficiency

  • A Balanced Ration provides the proper level of nutrients by including the necessary amounts of appropriate feedstuffs.
  • To allow for higher feed consumption and the provision of higher energy density, one must typically feed ingredients that are lower in moisture and lower in fiber.
  • A long-standing theory in animal nutrition suggests that when energy demands are high, dietary energy density should be increased.
  • When formulating a diet for an animal, meeting specific nutritional requirements is essential: TRUE.

Importance of Knowing Nutrient Content

It is important to know the nutrient content of feedstuffs to:

  1. Optimize nutrition for health and performance.
  2. Address under- or over-performance issues.
  3. Reduce food production costs.

Energy Restriction and Longevity

  • Energy intake relates to utilization: Dietary energy intake dictates energy expenditure by the body. Obesity can decrease the quality and length of life.
  • The only nutritional modification consistently shown to increase lifespan is dietary energy restriction.

Specialized Exotic Animal Feeding

Goals for Feeding Exotic Animals

The four primary goals for feeding exotic animals in captivity are:

  1. Promote health and longevity.
  2. Support production (e.g., breeding).
  3. Provide environmental enrichment and aid in animal training.
  4. Achieve the least cost formulation possible while meeting needs.

Key Questions for Diet Formulation

When formulating a diet for an exotic animal, key questions include:

  • What species is it?
  • What is its digestive anatomy?
  • What is its feeding history?
  • What does it naturally eat?
  • What model species can be used for comparison?

Regulatory Aspects of Zoo Management

Three regulatory aspects governing zoo activities often involve:

  1. Passing application and inspection processes.
  2. Establishing and meeting standards for health and welfare.
  3. Managing fundraising, zoo staffing, and involvement in global conservation efforts.