Question 1

What is cost per MJ and why does it matter?

Accepted Answer

Cost per MJ (megajoule) of metabolisable energy tells you how much you are paying for each unit of energy in a feed, adjusted for its dry matter content. A feed might appear cheap per tonne but if it is wet (low DM%) or low energy, the true cost per unit of energy can be much higher than a seemingly more expensive dry, high-energy alternative. This is the most important metric for comparing energy feeds like cereals, maize and co-products.

Question 2

What is cost per kg of crude protein?

Accepted Answer

Cost per kg of crude protein compares feeds on their ability to deliver protein, adjusted for DM content and price. High-protein feeds like soya bean meal (50–52% CP) are expensive per tonne but can be cheaper per kg of actual protein than lower-protein alternatives at similar prices. This metric is most useful when comparing protein supplements — rapeseed meal, soya, distillers grains — rather than energy feeds.

Question 3

Why do I need to enter the price per tonne of fresh weight?

Accepted Answer

Feed prices are always quoted per tonne of fresh weight as delivered — not per tonne of dry matter. This calculator converts your fresh weight price to a dry matter basis using the DM% for each feed, then calculates the cost per MJ of ME and cost per kg of CP. This corrects for the fact that a wet feed like pressed sugar beet pulp (20% DM) at £30/t is actually much more expensive per unit of nutrition than it appears.

Question 4

How do I use this to make a buying decision?

Accepted Answer

Add all the feeds you have prices for and sort by cost per MJ for energy feeds, or cost per kg CP for protein feeds. The cheapest feed per unit of nutrition is the best value — but do not compare energy feeds against protein feeds using the same metric. Energy feeds (cereals, maize) have low CP and high ME; protein supplements (soya, rapeseed) have high CP but are bought for protein, not energy. Use the ME rank for energy decisions and the CP rank for protein decisions.

Question 5

Why is the cost per kg CP very high for some feeds?

Accepted Answer

Feeds with low CP% — like cereals (barley 12%, wheat 13%) or silages — will show a very high cost per kg of crude protein because there is very little protein in them. These feeds are not bought for protein; they are bought for energy. The cost per kg CP figure for a cereal is meaningless — focus on cost per MJ for energy feeds and cost per kg CP only for feeds with CP above about 20%.

Feed Cost Comparator

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