How to formulate winter rations to reduce acidosis and lameness

• Latest genetics deliver big benefits

• Balance rations to optimise maize

• Paying attention to ration structure

Getting the most out of high energy maize is increasingly important for dairy farmers looking to make optimum use of home-grown feeds.

Significant improvements in the digestibility and reliability of high energy maize si-lage mean milk producers must pay more attention to they feed it – if they are to avoid complications with potential acidosis and laminitis.

“Plant genetics and knowledge have improved significantly in recent years, says Grainseed’s  Neil Groom.

“Wth many growers now able to produce consistent, high quality crops that when included in total mixed ration (TMR) feed regimes can really boost milk production and quality.

“In particular, the wider use of earlier varieties able to finish fully, even in more marginal areas of the country, have meant most maize growers can achieve starch levels of more than 30% with a corresponding rise in MEs to over 11.0mj/kg DM.

“While this is great news for producers looking to get more from home-grown re-sources, it does mean they have to understand the effects of such high energy maize in the rumen and take steps to avoid any potential issues.”

Avoiding these starts well before feeding, with the choice of a maize variety that will definitely finish in a particular location and is well suited to the system in which it is to be used, he says.

“Producers shouldn’t be afraid of producing high energy maize – energy drives both yield and solids – so choose a variety that’s going to give you maximum starch yields with the heat units you have available.

“D-value is an increasingly important consideration, with varieties like Bonnie able to combine an 11.9mj/kg DM ME with a cell wall digestibility of over 60%. That’s providing a lot of very accessible energy which has to be factored into ration plan-ning.

“Acidosis, the precursor to lameness-inducing laminitis, occurs when dairy cows digest too much energy, too quickly, so the first question to ask is whether other constituents in the ration, such as compound feeds or wholecrop, can be reduced.”

Balanced rations key

Dairy farmers should also be prepared to use chopped straw or rumen buffers to moderate rumen pH, where appropriate, he says.

“Rations need to be balanced at all times and you need to get into the habit of test-ing all your forages at least once a month as feed values do change as the winter progresses.

“Acids produced in the fermentation process continue to soften the maize grain in the clamp making more starch available as time goes on, which is why maize al-ways feeds better after Christmas than before.”

Independent feed advisor Martin Attwell agrees, adding dairy farmers can feed high levels of maize energy without complications provided some simple rules are fol-lowed.

“Producers must monitor changes in their forage through the feeding period and adjust rations accordingly to account for the extra starch availability to the rumen and small intestine as material matures in the clamp.

“If different varieties have been clamped separately, making sure an analysis is done before feeding and allowing 10 days change over from old to new season maize is also important.

“Fresh cows are particularly at risk as we tend to feed them a high energy diet, in terms of both starch and sugar content, to ensure they don’t dip into a negative en-ergy balance.

“Rumen pH can quickly drop to 5.5 or less in such circumstances and this can not only decrease the rumen bug population, but in turn reduces digestion rates and thus decreases dry matter intake.

“Even before laminitis becomes an issue, acidosis and sub clinical acidosis lead to inefficient rumen function, reduced butterfat’s, loose dungs and poor utilisation of diet.”

Ration structure critical

The overall structure of the ration is of critical importance when looking at how to minimise the threat of acidosis, he points out.

“With the increase in grass silage in rations from multi-cut systems and the tenden-cy to chop maize shorter, we are inevitably heading towards reduced structural fibre levels in high producing cow diets with an increase in rumen flowrates resulting.

“When assessing a TMR ration it is, therefore, important to look at balancing the structural fibre contained within it and considering the proportion of neutral deter-gent fibre (NDF). This should ideally be 34% or over.

“Aiming to slow the passage of rations with poor structure through the rumen by adding fibre from chopped haylage, good quality straw or similar, can be very bene-ficial.”