Better rumen function critical for milk solids and milk value

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Extracting the greatest possible milk value from home-grown forage will be one of the factors affecting feed costs and margins per litre this winter.

For many, that includes maximising butterfats, and the key to that is a well-functioning rumen.

Winter forage challenges

First cut grass silage analysis results released so far by Trouw Nutrition suggests that higher average fibre levels (NDF and lignin) compared to last year may be a challenge.

In many areas the grass grew early and fast this year, so was more mature than usual when cut. The result is a lower average fermentable energy (FME) content. Silage is also in plentiful supply, so as well as the potential challenge of maintaining ration energy levels – encouraging potential overreliance on rapidly fermentable starch feeds – there’s also a risk that many will rely too heavily on forage to save costs by cutting back on other feed ingredients.

Both scenarios pose a risk to the balance of nutrients needed to maintain good rumen function. Ensuring the ration is correctly balanced to support the rumen is therefore critical. Issues such as sub-acute ruminal acidosis (SARA) have been shown to result in milk losses of up to 2.7 kg/cow/day, as well as a drop-off in milk quality.

Stabilising rumen pH

Feeding strategies should look to target a balanced energy release in the rumen, which limits the dramatic rumen pH drop associated with SARA. It also needs to promote the production of milk fat pre-cursors to support butterfat production in the udder.

By providing as stable a rumen pH as possible and minimise the time spent below pH 5.8, which is when microbial activity and fibre digestion are compromised. This maximises production of the volatile fatty acid (VFA) acetate in the rumen, which is an important pre-cursor for milk fat production.

The overall diet must balance both the amount and rate of energy and protein release in the rumen, correctly matching the nutrient supply of concentrates to the nutrients contained within home-grown feeds. With grass silage FME levels potentially lower, additional energy feeds may be needed.

The addition of a rumen conditioner like Acid Buf or live yeast such as Vistacell can help reduce the rate and extent of any rumen pH drop. Research has shown that including Acid Buf in addition to a yeast such as Vistacell can produce gains exceeding those of using the yeast alone. The result was a substantial improvement in rumen pH, volatile fatty acid (VFA) production and butterfat yield, leading to a 3% advantage in fat-corrected milk (FCM) production (per kg of dry matter intake).