Cymraeg

Feeds and Feeding
Session 4 - Measures of Feed Components and Quality

This resource is suitable to support Level 2 Agriculture courses.

Introduction to Dry Matter

As feeds vary so much in water content they are compared on a dry matter basis.

  • At a dry matter content of 25%, 10kg of fresh silage would contain 7.5kg of water.
  • At a dry matter content of 86%, 10kg of wheat would only contain 1.4 kg of water.
    • Image with text '10kg Wheat' which shows 1.4kg water and 8.6kg dry matter, and an image with text '10kg Silage' which shows 2.5kg dry matter and 7.5kg water

    Fresh Versus Dry Analysis

    It is important not to confuse fresh and dry matter analyses.

  • Rations calculated on a dry matter basis must be converted to fresh weight to know how much actual feed to give to livestock.
    • image of cow lying down

    Calculation

    If feed quantities are converted from dry matter to fresh weight the answer must be larger than the amount started with.

    Example: if a ration has 1 Kg of dry matter of a 25 % dry matter silage the fresh weight needed could be worked out like this:

  • Quantity of silage dry matter (Kg) % dry matter percentage of the silage X 100 = Fresh weight of feed
  • 1 Kg of silage % 25 X 100 = 4kg of fresh silage
    • graphic showing Kg / Kg x 100 = %

    Calculation

    To calculate the amount of dry matter in a given amount of fresh feed, the formula below can be used:

  • Fresh weight of feed (Kg) X Dry matter percentage = Dry matter of the feed in Kg

    • Example: How much dry matter is there in 8 kg of 25% dry matter silage?

    graphic with text 'Kg x % = KG'

    Answer

    8 kg of silage X 25 dry matter = 2kg of dry matter in the silage 100

    Voluntary Feed Intake - VFI

    It is possible to estimate the amount of dry matter that livestock can consume; this figure is used as the basis for ration calculations.

  • Voluntary food intake (or appetite) for dry matter will be approximately 2-3 % of the animals liveweight.
    • graphic of cow with text '2-3%'

    What influences VFI?

    It is influenced by:

  • How quickly the food is digested and moved through the gut.
  • The level of productivity of the animal.
  • The palatability of the food.
  • The stage of pregnancy.
    • graphic of cow with cycle around it - with text 'Pregnancy > Digestion > Productivity > Palatability >'

    Monogastric Versus Ruminant Animals

    If the ration has a low dry matter content (wet), this may limit the amount of dry matter that can be eaten.

  • Single stomached animals are unable to digest fibre.
  • Ruminants can digest fibre through the action of rumen microbes, however it is a relatively slow process compared to the digestion of other carbohydrates such as starch.
  • Fibre is needed in ruminant rations to stimulate them to chew the cud.
    • image of cows in field

    D Value and Digestibility

    D-value is the percentage of the digestible organic matter in the dry matter of a feed.

  • Weight of digestible organic matter in the feed (kg) X 100 = D-value Weight of dry matter (kg)
  • The higher the D-value the more digestible the feed.
  • For example young grass will contain less fibre than grass that has gone to seed, so it will be more digestible and have a higher D-value.
    • image of grass

    Energy in Feeds

    Often feeds are compared according to the amount of energy they contain in the dry matter.

  • The units used to measure energy are megajoule (MJ).
    • graphic with text: 'MJ - Megajoule - One Million Joules'

    ME - Metabolizable Energy

    There are different measures of energy; for example gross energy is all of the energy in the feed, (this can be measured by burning the feed), however, not all of the energy is available to the animal.

  • Metabolisable energy (ME) gives an indication of the amount of useful energy content in the feed. ME is generally used to compare the energy value of livestock feeds.
    • A diagram showing Gross Energy. Gross Energy splits in two - Faecal Energy and Digestible Energy. Off Digestible Energy is Urine Energy, Methane Energy and Metabolisable Energy. Off Metabolisable Energy is Heat Increment (Used for Maintenance) and Net Energy (Used for Production)
    same graphic as previous page

    Maintenance and Production

    Feed for maintenance (a maintenance ration) is the food needed by an animal to stay alive without any change in condition.

  • This will vary according to the size of the animal. The food is use for essential body functions such as breathing.
  • Food for production is the extra feed that is needed by animals to do things other than stay alive and maintain their condition.
    • graphic with images of pig and sheep inside it

    Categories of Production

    There are several categories of production:

  • Growth – for young animals to increase in size and produce bone, muscle, fat and other tissues.
  • Reproduction – for the growth of the lambs/calves inside the ewes/cows and the production of sperm.
  • Lactation – to produce milk and udder tissue.
  • Wool – to produce the fleece.
  • Work – some animals will need additional feed because of a high level of activity e.g. sheepdogs.
    • Graphic with text: 'Growth, Reproduction, Lactation, Wool, Work' in a numbered list

    Energy Requirements

    Energy requirements can be calculated and rationing tables are available to indicate the amount of energy needed for maintenance and production in different sizes and types of livestock.

  • If animals receive less energy than they require they will lose condition; if animals have a ration that provides more energy than they use they can store the energy as fat.
    • Graphic of a pile of rationing tables
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