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Feed Testing

The quality of a feed can be highly variable and is influenced by a range of management and seasonal factors.

The only way to know the absolute nutritional value of your home-grown or bought-in feed is to feed test a sample of the feed. This knowledge allows the best use of the feed and if any additional supplements are required. The information from a feed test can help indicate how much an animal is likely to consume and how this will affect her growth or milk production. The results also help determine the dry matter of the ration and if there is any opportunity to use alternative, less costly fodder.

WHEN SUBMITTING FEED SAMPLES FOR ANALYSIS IT IS IMPORTANT THAT THE SAMPLES ARE:

  • Representative of the feed the herd will consume.
  • Processed according to the laboratory’s requirements.

Other measures of silage quality include pH or acidity and ammonia-nitrogen. A low pH indicates good anaerobic fermentation: the target range is pH 3.5 to 4.5. An ammonia-nitrogen content of less than 10% also indicates good fermentation. Higher levels of ammonia-nitrogen can reduce cow intakes.

Core samples of your hay or silage can be obtained and tested for nutritional value.  It is ideal to also weigh a representative proportion of round or square bales to enable optimal interpretation of the feed test results. Call the clinic today to discuss core sampling, feed testing and weighing of bales.

An example of high quality silage able to support good milk production:

An example of high quality silage able to support good milk production:

  • Crude protein: 16%
  • Dry matter digestibility: 70%
  • Metabolisable energy: 10 MJ ME/kg DM
  • NDF: 50%.

    Interpreting a feed test result

    description

    1. Sample
    2. Moisture
    3. Dry Matter (DM)
    4. Crude Protein
    5. Neutral Detergent Fibre (NDF)
    6. Acid Detergent Fibre (ADF)
    7. Dry Matter Digestibility (DMD)
    8. Metabolise Energy (ME)

      interpretation

      1. Gives details of the sample sent to the lab.
      2. Measures the weight before and after drying to give moisture percentage.
      3. The percentage of the residual feed after removing the water content. Examples include:
      • Concentrate feeds: ~90% DM
      • Hay: ~85-90% DM
      • Pit silage: ~30-35% DM (Less than this may result in poor fermentation)
      • Baled silage: ~35-45% (Less than this may result in very heavy bales with poor fermentation. More than 45% DM will result in inadequate fermentation due to poor compaction).

      4. Gives an estimate of the protein content in a sample. In good silage, there should only be a small difference in the quality of the silage compared to the original pasture.

      5. Measures the amount of fibre which consists of various components (hemicellulose, cellulose, and lignin). The amount of NDF is negatively associated with the cow’s dry matter intake ie the higher the NDF the less a cow can eat. High quality silage will have an NDF of 50% or less.

      6. Another measure of fibre in the diet, usually concentrates. ADF consists of cellulose and lignin.

      7. Measures the amount of a feed removed after passing through the cow’s digestive system. The higher the digestibility the better the feed quality.

      8. Estimates the amount of energy in a feed available to the animal to perform normal physiological functions. The higher the ME the better the quality of feed. ME is estimated from digestibilty. For high levels of production, the energy content of the diet should be above 11 MJ ME/kg dry matter.

          Feed testing arms you with the knowledge to get the most out of your feed. Talk to your dairy vet about arranging a feed test.