Written by John Swire
While initial results for maize silage are encouraging, dairy farmers are being warned that later harvested crops will need careful monitoring.
Reporting the results from over 870 samples received so far at their laboratory in Ashbourne, Dr Liz Homer, Ruminant Technical Development Manager with Trouw Nutrition GB says that for early harvested crops, feed value is comparable with the 2018 season.
“On average, crops are well-fermented but over 10% of samples received had to be discarded due to incomplete fermentation, probably reflecting a need to get maize into diets quickly,” she explains.
“At 32.6% dry matter, 11.6MJME/kgDM and 31.2% starch early crops have analysed close to last year. Starch degradability is also similar to 2018 and bypass starch levels are good.
“On average early maize silage appears to be very fermentable with high levels of total and rapidly fermentable carbohydrate. However, this results in an increased acid load which coupled with a low fibre index, a result of lower NDF, may affect rumen health unless diets are carefully balanced.”
Overall, Dr Homer believes early maize should complement this year’s grass silages well. The high level of fermentable carbohydrates and glucogenic energy will balance the high NDF and lignin values in grass silage, but she warns that the total diet will need careful balancing.
“It will be about feeding the right supplements rather than what is cheap. Cereals, for example, may need to be trimmed back despite being good value as there will already be a good supply of fermentable carbohydrates from the maize. Many diets will also require a supply of bypass protein.”
While the news is encouraging for farmers who were able to get maize harvested before the weather broke, Dr Homer says the protracted harvest could have implications for feed quality in later harvested crops.
She says late harvested crops should have higher starch content but will also have higher levels of both NDF and lignin which will affect how the crops will feed, so regular analysis throughout the winter will be essential.
“It is possible that later crops will be less fermentable due to the higher fibre content, and so diets based on later maize may require more fermentable carbohydrates in the concentrate portion. It is worth mentioning that starch will however be higher so will contribute to fermentable energy.
“If late maize has a high NDF and lignin content and is fed with grass silage with a similar profile we could see issues with rumen throughput as cow’s struggle to digest the forages, so maintaining rumen balance and effective digestion will be essential.
“The key message is to know what you have got in your clamp and balance the diet accordingly. As maize starch fermentability increases with time in the clamp, it will be important to get clamps analysed regularly and to fine tune the diet to maintain optimum rumen health,” Dr Homer concludes.
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