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Making the most of your maize

Sector News Sector News23-2-2018

While the overall nutritional quality of maize harvested in 2017 is similar to 2016, the higher fermentable levels of starch recorded in crops means it is important farmers are aware of the nutritional opportunities and challenges that the silage poses and its potential impact on rumen health and cow performance. 

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Maize quality

Now is the time to assess your maize silage stocks. Analyse the quality of your maize silage and predict how this silage will complement the use of current concentrates, forages and even grazed grass.

  2016 2017
Dry Matter (%) 30.7 33.3
ME (MJ/kg DM) 11.4 11.3
Starch (% DM) 31.0 30.0
Feed2Milk value    
MELK ('/kg DM) 1072 1053
RFC (g/kg DM) 135 156
DUS (g/kg DM) n/a 103
AI (g/kg DM) n/a 84

Headline analysis on 2017 season maize silage (source ForFarmers)

MELK - More Energy for the Lactating Cow

RFC - Rapidly Fermentable Carbohydrate

DUS - Digestible Undegradable Starch

AI - Acidosis Index

Once the quality of your maize silage has been established, it is important to gauge how long your supplies will last and what your approach will be to fill any identified shortfall. 

Understanding starch

Starch is an important source of energy in maize silage and when broken down in the rumen, can have a significant impact on improving milk yield and glucose potential. When maize is clamped its feeding characteristics, especially starch degradability, start to transform. The longer that the maize is sealed in a clamp the greater the fermentation rate, starch degradability and the reduction in the levels of by-pass starch (DUS). 

With higher levels of fermentable starch recorded in maize this year, there is the potential for higher energy availability from silage and higher milk yield potential. There is also an increased risk of acidosis (AI) caused by this more fermentable material. This risk becomes higher later in the season when maize has been exposed to fermentation acids for a longer period (see table below). 

Maize silage - nutrient value change over time

  October January February March April
Starch 29.4 29.4 29.4 29.4 29.4
DUS 103 88 84 80 76
RFC 148 156 159 163 166
AI 84 91 94 96 99

Managing starch

It is important to limit the inclusion of other starch rich feeds when using high starch maize silage and carry out regular ration analysis to ensure that a herd's diet is balanced. 

Too much starch in a cow's diet can reduce milk yield and stage of lactation will impact this. Excess starch in late lactation cows will increase body condition. Excess starch in early lactation cows could result in acidosis. 

The increased risk of acidosis caused by more fermentable maize silage also needs to be managed and the use of a live yeast or rumen buffer should be considered to maintain rumen health in more challenging circumstances. 

The use of digestible fibre sources, soya hulls or sugar beet pulp (non molassed) as concentrates can also be a useful tool to help improve overall rumen health. When more starch is needed in the ration consider the use of maize meal and/or caustic treated wheat as a rumen friendly alternative. 

The feeding characteristics of maize change over time in the clamp. Below is a box which highlights the issues surrounding an earlier or later feed out. 

Feeding maize silage early in the season
Unlikely to feed as well as expected
Produces higher levels of bypass starch
May require more rapidly fermentable carbohydrate to maximise milk yield potential


Feeding maize silage later in the season
More higher rapidly fermentable carbohydrates (starch)
Produces lower levels of bypass starch
Must be rationed carefully as there is a greater risk of acidosis from more fermentable starch

For more information on managing maize in the diet, please contact your ForFarmers Account Manager, or ask to speak to one of our Forage Specialists.