Getting the feeding balance right for cows

Approximately 70 per cent of cows' energy requirements and 80 per cent of cows' protein requirements can be met by the nutrients that rumen bacteria produce. As efficient as this can be, there is still a requirement for nutrients that bypass the rumen. This can affect performance but it can also be influenced by the season.

How can we determine when more bypass protein is needed? A cow's requirement for bypass protein increases as her milk yield increases. This is because the rumen has a limit of how much microbial protein it can produce. Generally, this can be seen in early lactation cows failing to achieve the expected peak yield.

To achieve this level of bypass protein, we can fall into feeding a high level of overall crude protein (both rumen available and bypass protein) which can be expensive, detrimental to the environment and may encourage a loss of body condition in early lactation cows.

So to avoid this, feeding lower levels of rumen degradable protein and therefore overall crude protein but feeding a higher percentage of bypass protein can help achieve higher milk yields while not experiencing some of the detrimental effects of feeding too higher crude protein.

This is very much the case when grazing cows. A cow's rumen protein is easily met with fresh grass (depending on grass intakes of course) but bypass protein is often still needed to meet performance requirements.

What about bypass energy? In a similar scenario to protein, there is a requirement for rumen energy in the form of carbohydrates which is used by rumen bacteria. However, if we over-feed carbohydrates, ruminal acidosis becomes a risk and this can limit the amount of rumen energy we can supply.

This can limit both animal performance and health since energy is often the first limiting factor to production.

Therefore by protecting carbohydrates so they bypass the rumen and get utilised in the hind gut, cows can consume the energy they need without putting added pressure on rumen health.

To achieve a higher bypass protein level, soya bean meal is the common ingredient used. While this is an excellent form of both rumen and rumen bypass protein, soya is expensive and its use is often questioned by retailers due to its sustainability and environmental impact. Therefore protected rapeseed meal such as UltraPro R can be used which at approximately 70 per cent bypass exceeds soya’s 40 per cent level. This can be a viable alternative to both soya bean meal but also regular rumen degradable protein sources.

From an energy perspective, maize grain can be fed as an alternative to wheat and barley as maize contains more bypass starch and is, therefore, healthier to the rumen.

However, maize grain has variable availability and can be expensive, which highlights a protected wheat such as Ultra Starch W as a viable alternative. Ultra Starch W supplies 30 per cent more starch to the hind gut than regular wheat, which enables more digestible energy to be utilised by the cow while reducing the pressure on rumen health.

Adam Clay is NWF Head of Technical.