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The importance of maize in a diet

Advice from our specialist Advice from our specialist24-2-2020
Afbeelding: Maize Cob 2

Maize is an excellent source of energy, starch and fibre for inclusion in the rations of ruminant livestock. By feeding a proportion of forage maize in the ration, feed intake and milk/meat production will increase.

For the best returns growers should select maize varieties based on maximizing both dry matter yields and the nutritional feeding qualities: starch and digestible fibre.

Maize growing costs are relatively fixed, leaving little scope to reduce establishment or harvesting costs. 

Maize is also ideal for the utilisation of organic manures such as slurry and farm yard manure, further reducing input costs.

Maize silage feed characteristics

  • High energy, high starch
  • Digestible cell wall material (fibre)
  • Livestock adapt easily to it in rations
  • Palatable
  • Consistent feed value
  • Low protein content so should be fed with reasonably high protein feeds

The total energy yield of a crop and the relative proportions of energy from each source will vary depending on the variety grown, the quality of the standing crop and the stage of maturity at harvest.


The key energy sources in maize are digestible fibre and starch. Maize starch supplies a combination of:

  • Rumen fermentable energy – which fuel the microbial population
  • Rumen bypass starch – which is converted to glucose which is absorbed and utilised by the animal

The proportions of each are determined by the genetic make up of the plant, the stage of maturity and the level of grain processing at harvest.

Cereals, for example wheat contain ‘simpler’ starch which is largely rumen available and can cause rapid pH drops as a result of fast fermentation. Maize starch therefore is a ‘safer’ source to feed since fermentation rates in the rumen are slower and not all the starch will be degraded. This reduces the rate and quantity of volatile fatty acid production and decreases the risk of rumen acidosis. 


Maize silage rarely contains above 9% crude protein. The fermentable starch and fibre sources in maize silage require a supply of rumen degradable protein in order to provide the microbial population of the rumen with a balanced fuel stock. Protein supplementation is key to unlocking the feeding potential of maize. 

Underfeeding protein can severely limit the productivity of maize based diets as rumen function will be restricted. This will lead to slow starch degradation and increased faecal starch losses. Rapemeal, soyabean meal, high clover silage make ideal complements to maize silage. These provide a readily available source of nitrogen which the rumen microbes will use to produce microbial protein. This is used for maintenance, milk protein synthesis and muscle development. 


Maize silage will typically have a neutral detergent fibre content (NDF) of between 40 and 50%. However, the harvesting process has a major impact on the level of effective fibre.

  • Short chop material (<20mm) will have insufficient effective structural fibre to maintain rumen health.
  • Longer chop (>25mm) will have a positive impact on rumination time and rumen function.

The optimum chop length will vary according to target feeding rates, characteristics of other forages and level of concentrate feeding.