Insight Focus

Protein is an integral part of any ruminant cow’s diet. Understanding its makeup, absorption and utilisation enables nutritionists to formulate balanced, cost-effective rations. This improves cow performance while reducing environmental impact and financial waste.

In our last article we discussed the importance of energy throughout the production cycle of the ruminant cow. However, protein is an equally critical component of her feeding regime.

Essential for metabolic activity and general health, protein provides the basis of cow health and performance.

Protein and the Ruminant Cow

Protein is a group of compounds, known as amino acids, which form chains, or peptides, linked by peptide bonds, which in turn make up proteins. These proteins are the building blocks for any animal.

Amino acids contain the elements:

  • Carbon ‘C’
  • Hydrogen ‘H’
  • Oxygen ‘O’
  • Nitrogen ‘N’

Protein has an average of 16% nitrogen, which is used to calculate the basis of ‘crude protein’ (CP) in any feed, thus calculated:

EITHER %CP = %N × (100/16)

OR %CP = %N × 6.25

As discussed in our article on understanding livestock nutrition, cows have the ability to produce their own amino acids within the rumen.

Thus, a proportion of the cow’s supply of amino acids originates from the rumen as ‘rumen degradable protein’ (RDP). These amino acids can be re-formed into improved quality ‘microbial protein’ (MCP), subsequently digested in the small intestine.

The remaining protein requirement originates directly from the diet as ‘undegradable protein’ (UDP), which passes through the rumen and is digested in the small intestine.

The physical and chemical characteristics of different proteins are due to the varying proportions of amino acids contained within them.

There are two types of amino acids:

  • Ten ‘essential’ amino acids, which must be supplied in a cow’s feed
  • Ten ‘non-essential’ amino acids, which can be produced by the cow in her rumen

Ration Formulation for Protein

A nutritionist is interested in the amino acids that make up the CP within a feed, as they influence its availability and efficiency of use by the cow.

Major sources of protein in dairy cow feeds include:

  • Various oilseed meals, including soybean meal (often referred to as hi-pro soya)
  • Legumes
  • Distillers’ dried grains (DDGs)
  • Forages and silage
  • Compound feeds

Protein is critical for both the health and productivity of the cow.

Assessing the protein composition and its utilisation enables nutritionists to create cost-effective, balanced feeding regimes. These regimes are tailored to optimise cow performance while reducing financial waste in nitrogen excretion, which in turn aids sustainability and benefits the environment.