Notes on Livestock Feeding and Feed Evaluation

Feeds for Livestock

Classification of Livestock Feeds

  • Roughages:

    • Feed with over 18% crude fiber.
    • Low energy content (less than 60% Total Digestive Nutrients (TDN)).

  • Concentrates:

    • High energy content (greater than 60% TDN).
    • Low crude fiber (less than 18%).
    • Includes energy feeds, animal protein feeds, and plant protein feeds.

  • Supplements:

    • Feedstuff mixed with primary grain/roughage to provide complete nutrition.
    • Includes amino acid, mineral, and vitamin supplements.

  • Feed Additives:

    • Non-nutritive substances added to feed for specific purposes.
    • Examples: enzymes, probiotics, prebiotics, acidifiers.
    • Purpose: to improve performance and feed efficiency.

Common Roughages

  • Grasses:

    • Roughly 6-10% crude protein.
    • Calcium content around 0.9%.
    • Examples:
    • Guinea grass: trichomes at nodes.
    • Para grass: trichomes throughout the culm.
    • Napier grass: rough leaves.
    • Star grass: has root nodes.
    • Alabang X: features trichomes at nodes.

  • Legumes and Other Forages:

    • Crude protein content of 10.5% or more, calcium content exceeding 0.9%.
    • Examples include Ipil-ipil, Centrosema, Madre de Cacao, and Madre de Agua.

Common Concentrates

  • Energy Feeds:

    • Variable nutrient amounts with high energy content.
    • Sources: cereal grains, milling by-products, processed tubers, fats and oils.
    • Examples: ground corn, feed wheat, sorghum grains (hegari, Kafir, milo), and rice bran.

  • Animal Protein Feeds:

    • Derived from by-products of meat processing, dairy, or marine industries.
    • Characteristics: > 47% crude protein, > 1.0% calcium, > 1.5% phosphorus, < 2.5% crude fiber.
    • Examples include tankage and fishmeal.

  • Plant Protein Feeds:

    • By-products of oil extraction from seeds.
    • Characteristics: 14-47% crude protein, < 1.0% calcium, < 1.5% phosphorus, 2.5% crude fiber.
    • Examples: soybean meal, full-fat soybean, and copra meal.

Common Feed Supplements

  • Synthetic Amino Acids:

    • Feedstuff rich in one or more pure amino acids to address deficiencies.
    • Produced through bacterial fermentation.
    • Common types: DL-methionine, L-lysine, L-threonine.

  • Mineral Supplements:

    • Rich in inorganic elements such as:
    • Limestone (calcium).
    • Monocalcium phosphate (phosphorus).
    • Salt (sodium and chlorine).
    • Mineral premix (trace minerals).

  • Vitamin Supplements:

    • A mix of various vitamins to enhance diet.

Common Feed Additives

  • Enzymes:

    • Protein molecules (e.g., phytase) that catalyze biochemical reactions.

  • Antioxidants:

    • Protect polyunsaturated fatty acids from destruction via peroxidation.

Definitions

  • Crude Fiber:

    • Insoluble carbohydrate made of cellulose, hemicellulose, and lignin.

  • TDN (Total Digestible Nutrients):

    • Relative energy value of feed, calculated as the sum of digestible protein, fiber, fat, and nitrogen-free extract.

  • Soilage:

    • Fresh herbage cut and fed to animals during confinement.

  • Silage:

    • Fermented forage stored anaerobically in a silo, made from green/dry chops with 60-65% moisture.

  • Hay:

    • Dried forage/roughage used for animal feeding, typically with 18-34% crude fiber and 40-60% TDN.

  • Crop Residues:

    • Parts of plants left in the field post-harvest.

Methods of Feed Evaluation and Quality Control

Physical Evaluation
  • Assess feed visually for:
    • Color, odor, texture, taste, dampness, foreign materials (mold, insects).
Feed Microscopy
  • Examines feeds under a stereomicroscope to determine purity and check for adulterants (cheap, non-nutritive substances added to increase weight).
  • Common adulterants: fine sand, sawdust, corn cobs, rice hulls.
Chemical Evaluation
  • Measures nutrients using the proximate analysis (Weende method):
    • Moisture: Weigh before and after drying at 105°C overnight.
    • Ether Extract: Determine fat by boiling in ether and measuring the residue.
    • Crude Fiber: Measure poorly utilized carbohydrates by boiling in weak acidic and alkaline solutions and assessing loss during ignition.
    • Crude Protein: Total nitrogen content multiplied by 6.25 (Kjeldahl method).
    • Ash: Measures inorganic content by burning in a furnace, with the remainder representing mineral content.
    • Nitrogen-Free Extract (NFE): Represents undetermined portion and digestible carbohydrates.
Expressing Feed Nutrient Values
  • Nutrient values typically expressed on an "as fed" basis; comparisons often made on a "dry matter" basis.
Microbial Evaluation
  • Tests for harmful bacteria (e.g., Salmonella) and mycotoxins (e.g., Aflatoxin) that can adversely affect animal health and performance.

Feed Formulation for Farm Animals

Trial and Error Method
  1. Determine vital nutrients needed.
  2. List nutrient requirements of animals.
  3. Create an arbitrary feed ration totaling 100%.
  4. Calculate nutrients contributed by each feed component using a feed composition table.
  5. Adjust as necessary based on differences in calculated and desired nutrient content.
Pearson Square Method
  • Use for feed formulation considering two ingredients:
  1. Draw a square; place the desired protein percentage in the center.
  2. Position feed ingredients at opposite corners.
  3. Calculate the difference in protein contents and account accordingly to derive proportions needed for the desired nutrient level.