Feed Conversion Efficiency

Balancing digestibility and profits

There is no doubt that every year farmers offer a greater variety of feed inputs, in ever increasing volumes, to maintain higher production expectations. Farmers also understand that continuous improvement of feed conversion efficiency is essential to enhancing operating profit. 

In order to run a profitable business, in a system with increased levels of supplementary feeding, rations should be well balanced to enable your cows to more efficiently convert kilograms of dry matter purchased, into kilograms of milk solids sold. 

Improving feed conversion efficiency

One thing commonly linked to improved feed conversion efficiency (FCE) is the amount of forage neutral detergent fibre (NDF) consumed relative to non-fibre carbohydrates (NFC) in rations. NFC is a calculation often used to help ascertain the amount of readily fermentable carbohydrates on offer within the rumen. In our dairy systems this is like a summary of the total sugars, starch and pectin content of a total ration. These more fermentable carbohydrates influence rumen volatile fatty acid content and levels of concentration, which have direct linkages to energy status and rumen pH.  

Rumen buffering

Most farmers understand that cows have their own rumen buffering mechanisms. The more a cow chews her feed (due to particle size and/or forage quality) and cud, the greater the flow of bicarbonate and phosphorus rich saliva into the rumen as a buffer. There is also a growing body of research work showing that the volume of ingested forage itself has a greater rumen buffering effect than the flow of saliva due to increased feed particle length in high production herds1.

pH and digestibility

Once rumen pH levels begin to fall below around 5.8, we have an unfavorable environment for fibre digesting bugs. As a result, forage fibre digestion and FCE decline. Conversely, rising pH levels have a positive effect on digestibility.  

In our pasture-based systems, we want the benefits associated with feeding supplements high in NFC, but we can’t afford to lose out on forage fibre digestibility. To gain the best possible FCE outcomes with increased supplementary feeding, particularly if this is via in-shed feed systems, balancing forage NDF:NFC will be one of your highest ration formulating priorities. Optimal milk solids yield in system 3 to 5 dairies are observed when forage NDF:NFC are kept within the range of 1.1 – 1.4:1. 

Balancing it out

For every 100 grams of NFC in the ration, we want our cows to be consuming 110 – 140 grams of forage NDF. (NDF from co-products such as PKE or DDG is not included.) When we maintain this ideal balance of nutrients for lactating dairy cows, we create a rumen environment that still favours fibre digestion, but also provides a great source of blood glucose precursors to stimulate milk production at the mammary gland.


  Impact of pH
  on Digestibility 2

     pH 5.6      

    pH 6.1     

Difference in




 + 15%




 + 30%




 + 36%


1 Allen, 1997 J. Dairy Sci. 80:1447    2 Wales at al. (2004)

For FREE advice on enhancing both feed conversion efficiency and profitability, talk to your local Ingham Dairy Nutrition Specialist

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