You’ve collected representative samples of feed and sent them for analysis. Interpreting the results and building a balanced ration is the next step. (see ‘Certificate of Analysis’ report example at bottom)
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Moisture and dry matter: Moisture represents the amount of water present in a feed sample. Dry matter is what remains after water is removed. Moisture content varies between chopped silage, bale silage, hay, greenfeed and grains. To compare nutrient content between different feeds, use the values provided in the dry column. Ruminant rations are balanced on a dry matter (DM) basis.
Protein: There are different analyses to fully determine protein quality. Crude protein is determined by nitrogen extraction and the value multiplied by 6.25. Crude protein is further broken down into soluble and non-soluble or undegradable protein. Soluble protein is available to the rumen microbes and is needed to maintain their populations. It is critical to meet soluble protein requirements so there are adequate numbers of microbes to digest fibre quickly and efficiently so feed intake is not reduced. Rumen undegradable or bypass protein is absorbed in the small intestine. Bypass protein supplies amino acids which increases milk fat content and muscle development in calves.
Protein availability can be reduced when it is bound to fibre fractions in forages. During silage fermentation or when hays or greenfeeds are baled with a high moisture content, heating can occur. The Maillard reaction starts when temperatures are above 35 C. This chemical reaction binds protein to acid detergent fibre (ADF) and neutral detergent fibre (NDF) which reduces protein availability. The higher the temperature and longer the duration, the more protein is tied up. These values are reported as ADF-CP and NDF-CP.
Some labs provide an acid detergent insoluble crude protein (ADICP) value which provides the amount of protein unavailable to the animal.
Here’s how to calculate the available protein:
- Crude protein in the forage is 11.13 per cent. ADF-CP is 1.92 per cent. Divide ADF-CP by crude protein (1.92/11.13) x 100 = 17.25 per cent.
- Subtract seven from the result. 17.25 – 7 = 10.25. Divide 10.25 by 100 and multiply by the crude protein. (10.25/100) = 0.1025 x 11.13 = 1.14 per cent. This is the amount of protein bound by the fibre.
- Available protein is 11.13 – 1.14 = 9.99 per cent. This is the value used when calculating the ration.
Acid detergent fibre (ADF) is an indicator of plant maturity. Straws have the highest ADF, and legumes at the bud stage have much lower levels. ADF can increase by one to two per cent per week depending on the forage. ADF is used to estimate a feed’s energy content. As ADF increases, energy content decreases. Optimum ADF content or maturity of a forage depends on animal type, stage of production and required performance.
Neutral detergent fibre (NDF) is mainly cell wall components such as hemicellulose (fermentable), cellulose (slowly fermentable) and lignin (largely unfermentable). Bacteria and microbes must digest these fibres so the forages can pass through the digestive system. If total NDF in the ration exceeds 60 per cent on a dry matter basis, feed intake will be reduced. Another rule of thumb is that animals will stop eating once they consume 1.2 per cent of NDF of body weight when consuming average- to good-quality forages. As forage quality decreases, intake also decreases. NDF content is highest in straws, and lower in grasses and annual cereal crops. In general, legumes have the lowest NDF content but lower digestibility because of the higher lignin content in the stems.
NDF digestibility estimates the volume of gas and volatile fatty acids produced during fermentation. This is directly related to the ability of the rumen microbes to digest the forages that are consumed. It helps to estimate available energy which affects animal performance. Digestibility declines as plants mature.
Energy content or estimates are provided in multiple forms: Total digestible nutrients (TDN), digestible energy (DE), metabolic energy (ME), net energy of maintenance (Nem), net energy of gain (Neg), and net energy of lactation (Nel). Nutritionists use differ- ent ration balancing programs and each one uses a specific energy system. The energy values are calculated by mathematical equations. Energy losses from methane and urine are calculated into ME values. Net energy values include losses from methane, urine and heat.
Macro and trace mineral content in feeds depends on many factors. Soil type, soil temperature, moisture early and throughout the growing season, application of manure or fertilizer, type of plants, and age of the stand all influence nutrient concentrations in the forages. Analysis for both macro and trace minerals is essential to balancing a ration.
There are many things to consider when building a ration. Using a ration balancing program or getting help from a qualified nutritionist is recommended. Not meeting the nutritional requirements of an animal throughout the year has both short-term and long-term consequences.
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Unpacking an oat silage feed report - Canadian Cattlemen
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