Animal Foods and Nutrition Lecture Flashcards

Fundamental Principles of Animal Nutrition and Feed Intake

• Nutritional Balance: An animal's diet must provide the correct amount and balance of all essential nutrients. To be effective, ingredients must be digestible, absorbable, and utilizable by the species in question.

• Ruminant Feeding Philosophy: In ruminants, feed is designed primarily for the rumen microorganisms and secondarily for the animal. Ruminants cannot benefit from feed that their microorganisms do not consume.

• Universal Feeding Requirement: Regardless of the species (microorganism, ruminant, or nonruminant), nutrition is only gained if the animal actually eats the food.

• Feed Intake Dynamics: Caretakers must select foods that satisfy dietary requirements while anticipating the animal's natural selection processes. This is categorized under two main headings:     * Palatability: A measure of how well an animal likes a specific food. Influencing factors include odor, temperature, texture (mouth feel), the presence/concentration of specific nutrients, and habit.     * Acceptability: Indicates whether an animal will ingest enough food to meet its total caloric requirements. Diets must be palatable enough to ensure this level of intake.

• Appetite Factors:     * True Appetite: The biological nutritional need of the animal.     * Learned Appetite: Previous experiences that may lead to feed aversion.

• Physical Form of Feed: The size of food particles affects acceptability, specifically in ruminants. They select for particle size and require a certain size to trigger rumination (regurgitating and chewing the cud). If processing reduces particle size too much, ruminants may stop ruminating, and acceptability is lost.

• Balanced Diet Construction: Designed based on an animal's age, sex, species, and physical condition. It must balance nutrients relative to the caloric density ($\text{energy concentration}$). Once an animal consumes enough to meet its caloric requirements, it should automatically receive the necessary amounts of other nutrients.

Essential Nutrients: Sources and Biological Quality

• The Six Essential Nutrients: Water, proteins, lipids, carbohydrates, vitamins, and minerals.

• Protein Quality:     * Higher quality proteins contain more essential amino acids. Quality is best determined by comparing amino acid content to the actual requirements for growth, reproduction, and maintenance.     * Analysis Limitations: Crude protein is measured by nitrogen levels. This analysis fails to distinguish between protein nitrogen and non-protein nitrogen ($\text{NPN}$), such as urea ($\text{the chief compound of urine}$).     * Urea Utilization: Ruminants can utilize urea, but carnivores cannot.     * Health Implications of Protein:         * Excessive levels can cause kidney issues in dogs and cats.         * Cattle fed excess urea may suffer from ammonia toxicity.         * Pigs on high-protein diets often eat less and gain weight more slowly.     * Recommended Protein Sources: High-quality animal proteins are generally superior to plant products. Examples include meat, fish meal ($55\text{--}60$ protein content of dried matter), powdered whole eggs, and lactose-free casein (with $2$ methionine added).

• Carbohydrate Sources:     * Should be high-quality starch rather than simple sugars.     * Starches must be heat-treated to prevent intestinal distress.     * Fiber: In carnivores, fiber must be minimal as it lowers digestibility and causes water retention in feces.

• Lipid Sources:     * Provide essential fatty acids but are prone to becoming rancid and oxidizing.     * Sources: Poultry fat, pork fat, suet, plant oils (coconut, palm, sunflower, soybean, corn), and purified fish oils.

Vitamin and Mineral Sources and Feed Additives

• Micronutrient Sources: Mostly provided via commercially manufactured supplements. Minerals like calcium phosphate and calcium carbonate must be readily assimilated. Brewer’s yeast is a primary source for B vitamins.

• Feed Additives Defined: While vitamins/minerals are often called additives, the term technically refers to non-nutrient substances like antibiotics, hormones, or growth-stimulating agents used to increase efficiency and lower costs.

• FDA Approval Requirements for Additives:     1. Research must establish safety.     2. Carcinogenic substances (cancers in humans or animals) are never considered safe.     3. No residues are allowed in animal tissues.     4. Proven effectiveness for the intended use.     5. Established levels of use and tolerances.     6. Labels must include precautions and withdrawal statements.     7. Practical analysis methods for residues must exist.

• FDA Classifications:     * GRAS (Generally Recognized as Safe): Additives with a long history of safe use.     * Controlled Agents: Substances regulated for specific quantities/uses.

• Additive Classifications: Anti-caking agents, chemical preservatives, emulsifying agents, sequestrants, stabilizers, general-purpose additives, spices/seasonings, flavors, color additives, therapeutic agents, hormones, and growth-stimulating substances.

Functional Types of Additives and Growth Stimulants

• Chemical Preservatives: Retard spoilage and nutrient loss (specifically Vitamin A and carotene). They prevent rancidity, which would otherwise make the food unpalatable.

• Flavoring Agents: Enhance acceptability, particularly crucial for dog and cat foods.

• Color Additives: Used exclusively in pet foods to appeal to owners; dogs and cats cannot distinguish these colors. Common colorings include organic food dyes and iron oxide.

• Therapeutic Agents: Include antibiotics, arsenicals, antimycotics, antiprotozoals, anthelmintics, hormones, and pesticides.

• Antibiotics as Growth Stimulants: Used since 1949 to increase production. They are most effective during rapid growth periods or when diets are marginal in protein, minerals, or B vitamins.     * Mechanism: They may reduce competition between bacteria, decrease toxins like ammonia (resulting in a thinner gut wall that absorbs nutrients better), or spare nutrients.

• Hormonal Compounds:     * Thyroid-active materials: Create a mild hyperthyroid state to stimulate growth, milk secretion, and wool production.     * Goitrogens: Occur naturally in some forages; they depress growth but can increase the rate of fattening.     * Synthetic Hormones: Estrogens, androgens, and progestogens are used to stimulate growth and fattening in meat animals, primarily as implants in ruminants.     * Stilbestrol: A feed additive that boosted gain and decreased feed requirements.

• Specialty Additives:     * Copper Sulfate: Boosts growth response in pigs similar to antibiotics.     * Arsenic Compounds: Fed to poultry to kill protozoan parasites (causing blackhead in turkeys or coccidiosis in chickens) and stimulate growth.     * Enzymes/Cultures: Added to high-barley rations (often via live yeast) to boost growth. Rumen cultures have shown no demonstrable advantage.

Regulatory Controversy and Safety

• Antibiotic Resistance: Concerns exist regarding the development of antibiotic-resistant organisms. European countries have banned routine use; the US continues usage as the FDA finds no direct link to human disease yet.

• Hormone Concerns: The practice of implanting estrogen pellets in poultry was stopped due to residues in meat. Public concern remains high despite some scientists noting that natural foods like soybeans contain higher hormone levels than treated meat.

• Veterinary Feed Directive (VFD): Since 2017, all medically important antibiotics for use in food animal species require a VFD or prescription to ensure veterinary oversight.

Estimating Energy Requirements and formula

• Caloric Density Formula:     $\text{Caloric density} = \text{energy provided by each nutrient} \times \text{the amount of that nutrient in the food}$

• Metabolic Availability: Benefit is based on energy remaining after digestion and absorption. A dense food that is hard to digest is a poor energy source.

• Environmental Influences:     * Extreme Cold: Increases caloric requirements (e.g., sled dogs). Animals need either more volume or higher caloric density.     * Extreme Heat: Increases density needs because the body expends calories to stay cool, while the heat simultaneously suppresses appetite.

Feed Manufacturing and Forage Classification

• Feed Types:     * Concentrates: Low fiber, high energy. Used for monogastric species and nonruminant herbivores.     * Forages (Roughage): High fiber, low energy.

• Forage Storage and Dry Matter (DM) Content:     * Hay: Grass cut green and dried. $1\text{ pound} = 90$ DM.     * Haylage: Harvested wet, wilted, and fermented in a silo. $1\text{ pound} = 45$ DM ($2\text{ lbs haylage} \rightleftharpoons 1\text{ lb hay}$).     * Silage: Green forage fermented directly without wilting. $1\text{ pound} = 30$ DM ($3\text{ lbs silage} \rightleftharpoons 1\text{ lb hay}$).     * Direct Cut (Green Chop): Cut and fed immediately. $1\text{ pound} = 22.5$ DM ($4\text{ lbs green chop} \rightleftharpoons 1\text{ lb hay}$).

• Grain Processing Methods:     * Grinding: Hammer mill crushing.     * Rolling/Crimping: Crushing between rollers (crimping uses corrugated rollers).     * Pelleting: Condensed grain; results in fiber loss.

• Pet Food Manufacturing:     * Kibbles: Baked on sheets and broken.     * Meals: Mixed dry ingredients.     * Expanded Foods (Extrusion): Cooked in an extruder at high temperatures and forced through a die. This increases carbohydrate digestibility and achieves sterilization. Can be coated with fat/vitamins.     * Soft-moist Foods: Processed at lower temperatures using acids to lower pH and retard spoilage.     * Canned Foods: $75$ water (vs $9$ in dry food). Cooked in the can for sterility. Higher fat content on a DM basis. Contains ration-type (soy, cereals, tissues) or gourmet-type (muscle, by-products, TVP).

• Textured Vegetable Protein (TVP): Extruded soy flour with added coloring to look like meat.

Diet Formulation and Balancing Procedures

• Ration Balancing Requirements: Knowledge of daily nutrient needs (by species, weight, and state) and nutrient concentrations in specific feeds.

• Formulation Steps:     1. Determine nutritional needs for maintenance and production.     2. Select the least expensive ingredients (considering palatability and transportation).     3. Balance for energy.     4. Ensure protein, minerals, and vitamins are present.     5. Formulate supplements for any deficiencies (via free-choice blocks, molasses licks, or preformulated mixes).     6. Ensure the form (cubes vs loose hay) fits the facility equipment (mangers or bunks).

Government Regulations and Labeling

• Federal Agencies:     * FDA: Regulates interstate commerce, clears drugs/additives, and prohibits adulterated/misbranded food via the Food, Drug, and Cosmetic Act.     * Federal Trade Commission (FTC): Regulates advertising (TV, print, radio) to prevent false claims.     * USDA: Performs voluntary inspections and regulates meat ingredient levels.

• Adulterated Food Definition: Food that is filthy, contains diseased animal parts, is packed in unsanitary conditions, or contains poisonous substances.

• Fair Packaging and Labeling Act: Requires product identity and net weight on the lower third of the principal display panel, along with company address and ingredient list (by predominance).

• State Regulations:     * AAFCO (Association of American Feed Control Officials): Developed the Uniform State Feed Bill.     * Requirements: Manufacturers must guarantee minimum crude protein/fat and maximum fiber/moisture.

• Guaranteed Analysis:     * Uses the Proximate Analysis Method (approximate percentages because many nutrients cannot be precisely measured).     * Does not indicate quality, only quantity.     * Example of Misleading Data: A dog food listing $30$ crude fiber may include cellulose, which dogs cannot digest, meaning it provides negligible energy despite the high percentage.

Supplementation and Specialty Feeds

• Supplementation Risks: Adding nutrients to an already balanced diet can cause toxicity or secondary deficiencies. Supplements (energy, protein, vitamins) should only be used to correct specific conditions (e.g., calcium deficiency).

• Specialty Feeds: Targeted foods for growth, maintenance, work, or disease. Often sold via veterinarians to ensure proper usage.

• Case Study (Doggie Lite): A weight-reduction diet failed because it was unpalatable. The "new and improved" version increased fat for taste but also increased caloric density, defeating its purpose for weight loss.