Harvesting maize too early: what does it actually cost?

Due to the varying weather conditions this growing season, the maize is ripe later on average in the Netherlands this year. The advice is obvious to always let maize ripen, but what is the reason for this? What can be the losses if harvesting earlier? We have briefly explained a few things for you and listed the global (loss) costs.

Everyone knows the importance of a healthy diet with sufficient nutrients. The fact that our food is also tasty is important for the appetite. Last year we saw many people who lost their smell and taste because of corona. As a result, the food tasted lousy and the healthy appetite was also lost. This is no different for ruminants. For example, with unripe maize, the risk of sap loss is greater and the pH will often be lower. Ruminants like this less, which means that the intake is also lower. Mold in the silage can also affect the appetite of your ruminants.

When do we speak of too early harvest?
Harvesting too early means a dry matter content of 32% or less. With that maize, a part of the yield is lost due to a lower dry matter yield and a lower starch content on average. This results in a lower feed value of the maize, which is at the expense of milk production. WUR feed trials have shown that the utilization of highly productive cows is higher with a ds content of 36% instead of 30%. The starch content is higher and the resistant starch content that is not broken down in the rumen but only in the intestine is higher. This gives a better utilization, which results in a higher milk production.

When is it too late and what is the ideal time for maize harvest?
We speak of a late harvest with a ds content of around 40% or higher. We have seen this happen regularly in the past three years. The corn is then too dry. This makes it more difficult to compact the pit properly. More air remains in the silage and storage is worse. The risk of overheating and mold formation is then a lot greater. This also results in a loss of feed value and a lower intake by the cows. Overripe maize also contains fewer sugars, which are the breeding ground for the lactic acid bacteria that are necessary for proper preservation of the maize silage. Both cases will therefore cost money. The ideal time to harvest the maize is when the dry matter content is between 35% and 38%.

And what does it cost to harvest too early?
From the graphs below it can be read what harvesting too early (approximately 28% DM) costs compared to harvesting at an ideal dry matter percentage (approximately 36% DM):

• about 40 grams of starch/kg ds
• 2 points digestibility
• About 10 to 15 VEM per kg ds

A calculation: what can harvesting too early cost?
With the current high raw material and compound feed prices, the importance of harvesting at the right time, if conditions permit, has become even more important! After all, having to correct the silage can entail considerable extra costs for extra concentrates. 

An example if we look at a lower VEM due to harvesting too early:

• a cow eats 21 kg of maize per day = 7 kg of dry matter from maize
• 300 lactation days = 2.100 kg dry matter from maize
• +/- 1 VEM is needed for 460 liter of milk

A silage with 36% dry matter and 960 VEM = 2.100 x 960/460 = 4.382 liters of milk

A silage with 30% dry matter and 945 VEM = 2.100 x 940/460 = 4.314 liters of milk

Result:
15 VEM less/kg DM = 68 liters less milk =
+/-  € 24 less/cow/lactation
(at a milk price 1 liter of milk = € 0,35)