Warning over feeding new crop maize

Dr Kerensa Hawkey, Nutritionist and Technical Projects Manager 

Maize silage is an excellent source of energy, starch and fibre but when fed too early without adequate fermentation time it can affect rumen balance and digestion. 

Due to the quantities of maize silage fed last winter, with already tight-clamped stocks, it’s likely many farmers will be feeding new crop maize silage earlier than usual this year. This could cause a decrease in performance, a phenomenon known as ‘maize silage slump’. It’s the result of an abrupt change from old to new maize silage, often leading to a decrease in milk production, inability to reach production targets, decreased feed intakes or loose dung.

Factors which contribute to a slump include: 
• Lower starch degradability due to reduced fermentation time (see diagram) 
• High levels of fermentable sugars, which can contribute to Sub-Acute Ruminal Acidosis (SARA) 
• Variable dry matter and nutrient composition

Practical monitors include: 
• Milk yield and milk quality 
• Cudding activity - approximately 60 to 70% of cows should be cudding at any one time, with a cudding rate of about 60 to 70 chews per cud 
• Rumen fill - check the ‘hunger triangle’ on the left of the cow. If hollow or full, indicates if cows are being adequately fed 
• Dung scoring and sieving - dung consistency, too thick or thin, is commonly seen 
• Additional dung sieving could also highlight the presence of undigested fibre or grains and the presence of mucin casts or ‘slimy bits’ might indicate digestive imbalances

Practical strategies for reducing a slump include: 
• Allowing maize silage to ensile for as long as possible 
• Changing clamps gradually over a two-week period or introducing new crop maize slowly 
• Testing new maize silage for dry matter and nutrient content regularly 
• Reviewing rations for the total fermentable carbohydrate supply. 
• Additional sources may be required to balance energy within the rumen 
• Use X1-LIVE yeast to enhance digestibility and stabilise rumen pH when transitioning onto new crop maize 
• Consider Rumi-TOX as an insurance policy in case of a mycotoxin challenge 

As maize silage can represent a major part of the ration, understanding the degradation of maize silage is vital. Monitoring regularly and making gradual ration changes can help keep milk production steady, whilst managing silage clamp changes. 

  
For more information on feeding new crop maize please contact your local nutritionist or the Feed Enquiries Line on 01566 780261