Ration balance vital when maize quality not so good
By FW reporters
VARIABLE quality maize silage means close attention to energy and protein balance is vital to help ensure best performance from winter rations.
CEDARs Richard Phipps says many producers have poorer quality maize silage this year due to bad weather and choosing later maturing varieties.
In the north, SACs Dave Roberts says variation in quality is likely to be more marked as some crops have not yet been harvested. "Maize silage is likely to be low in starch, and kernels may also be very hard, so where corn crackers were not used, grains may pass straight through animals."
He recommends that once clamped, maize silage is analysed. "Ensure it is analysed appropriately as maize silage and not against grass silage figures, as this could give misleading ME figures."
According to Dr Phipps, producers, particularly in marginal areas, who have moved away from early maturing varieties may have harvested immature crops, meaning lower starch content.
"The difference between maize cut at 23-25% and 30-35% dry matter is silage with 15% and 30% starch content," he says.
Independent nutritionist Gordon Newman says a high starch maize silage cut at 35% DM should have an ME of 11.5 and protein of 9.7%. But he warns that where this years crops have achieved similar quality, have them re-analysed; the analysis could be wrong and, therefore, misleading.
Increasing level of maize up to a maximum of 75% of the forage part of the ration is one way to counter lower quality, says Dr Phipps
But Dr Roberts says that knowing the exact analysis will help ensure the balance is right at feeding out. "Low starch is likely to be the greatest concern, which means that the concentrate portion of the ration must contain a higher proportion of starch to help improve milk protein levels."
Where maize silage quality is low, Mr Newman suggests boosting energy by supplementing maize like-for-like with wheat on a dry matter basis. In dry matter terms, wheat is cheaper than maize, but should be rolled before feeding.
Another alternative is to feed caustic-treated wheat: "I know of one farm feeding 7kg of caustic-treated wheat and 2kg straight wheat plus maize silage to 9000kg yielding cows giving 50kg milk a day. But be aware that too much caustic wheat can lead to acidosis." Balancing rations with a quality protein is essential, says Mr Newman. Shop around for cheap options: "Soya at £120/t is more expensive than rape at £70/t for a similar level of protein."
Even with limited and poor quality maize silage, producers can increase milk output. Milk Development Council-funded trials at CEDAR showed that feeding low quality maize – compared with grass silage – achieved a higher DM intake of 1.7kg a head a day, 1.4kg rise in milk yield and 0.18% increase in milk protein.
But producers concerned about limited maize silage stocks will be better off feeding it in early lactation to boost milk quickly and help redress body energy levels, Mr Newman says.
"Where there are limited stocks, consider buying-in surplus maize silage later in the season. It reclamps with little spoilage and is a common practise in Europe," adds Mr Newman.
But a lack of essential minerals may be a concern with low quality maize silage, warn specialists. Dr Phipps is concerned that frost-damaged crops will be low in phosphorous, which may require extra minerals to be fed.
Mr Newman says producers feeding maize to dry cows at up to 40% of forage intake – in part to reduce energy deficit post-calving – should offer magnesium chloride to avoid milk fever. *