How to Calculate Metabolizable Energy and Crude Protein in Livestock Feed (Complete Guide)

Table of Contents

1. What metabolizable energy and crude protein actually mean
2. Why these two numbers matter so much
3. How ME is measured differently across species
4. Nutrient requirements by species and production stage
5. Nutrient values of common feed ingredients
6. How to calculate metabolizable energy in a feed formula
7. How to calculate percentage crude protein in a feed formula
8. Worked example — step by step
9. How to adjust your formula once you have the numbers
10. Common calculation errors and how to avoid them
11. Key takeaways
12. FAQ

Introduction

Calculating metabolizable energy and crude protein in livestock feed is the foundation of every effective feed formula. These two numbers determine whether your animals grow at the rate you are planning for, produce at the level you are expecting, and stay healthy throughout the production cycle.

Get both numbers right and your feed does exactly what you need it to do. Get them wrong and you spend the same money on feed while your animals underperform and you often will not know why until it is too late in the cycle to correct it.

This guide teaches you exactly how to calculate both metabolizable energy (ME) and percentage crude protein (%CP) from scratch, using a real worked example with common feed ingredients. No complicated maths. No laboratory required. Clear, step-by-step calculations you can apply to any feed formula you create; for poultry, pigs, ruminants, or fish.

1. What Metabolizable Energy and Crude Protein Actually Mean

Metabolizable Energy (ME) is the amount of energy in a feed that an animal can actually use for body maintenance, growth, and production. It is measured in kilocalories per kilogram (kcal/kg) or megajoules per kilogram (MJ/kg).

Think of it like this: if you fill a car with fuel, not all of it powers the engine. Some energy is lost as heat and exhaust fumes. ME is the equivalent of the fuel that actually moves the car — after subtracting what is lost.

More precisely, ME is calculated from gross energy (the total energy in the feed) by subtracting energy lost in faeces, urine, and fermentation gases during digestion. What remains is the energy the animal’s body can actually put to work.

Crude Protein (%CP) is the total protein content of a feed ingredient or formula, expressed as a percentage of total weight.

It is called “crude” because it is not measured directly. Instead, it is estimated from the nitrogen content of the ingredient. The calculation is: %CP = % Nitrogen × 6.25. This formula works because most proteins contain approximately 16% nitrogen, and 100 ÷ 16 = 6.25. This conversion factor is a scientific standard used globally in animal nutrition.

It is important to understand that crude protein is a measure of total nitrogen; it does not tell you the quality or digestibility of that protein. Two ingredients can have the same %CP but very different amino acid profiles and digestibility levels. This is why amino acid supplementation (methionine, lysine) is important in feed formulation alongside total %CP.

2. Why These Two Numbers Matter So Much

Every livestock species at every production stage has a defined requirement for ME and %CP. These requirements are established by agricultural research institutions and published in nutrient requirement tables used by nutritionists worldwide.

If your formula’s ME is too low, your animals will eat more feed trying to meet their energy needs; directly increasing your feed cost per kg of production. If ME is too high, animals may reduce feed intake and miss their protein and other nutrient targets.

If %CP is too low, growth slows, egg production drops, milk yield falls, and immune function weakens. If %CP is significantly too high, the excess protein is excreted as nitrogen; wasting money on expensive protein ingredients and increasing environmental nitrogen load from your farm.

Knowing how to calculate both numbers lets you check every formula you create before you produce it in bulk and correct problems on paper before they cost you money in the field.

3. How ME Is Measured Differently Across Species

This is the single most common source of error in feed formulation. ME values in ingredient tables are species-specific, and using the wrong species’ values will give you incorrect results.

Poultry (birds): ME for poultry is called Apparent Metabolizable Energy (AME) or Nitrogen-Corrected Apparent Metabolizable Energy (AMEn). Poultry have short digestive tracts and pass feed quickly, which means they extract less energy from high-fibre ingredients than pigs or ruminants do.

Pigs: ME for pigs is typically higher than for poultry for the same ingredient, because pigs digest fibre better than birds. Pig ME is sometimes expressed as Digestible Energy (DE) in older reference tables — DE is slightly higher than ME because it does not subtract urine losses. When formulating pig feed, use ME values specifically measured in pigs.

Ruminants (cattle, goats, sheep): Ruminant ME is fundamentally different. In ruminants, feed is first fermented in the rumen. Volatile fatty acids absorbed from the rumen provide the major source of metabolizable energy to the animal. Microbial protein produced during rumen fermentation also supplies much of the animal’s protein needs. This is why ruminant ME and protein systems are more complex than those for pigs and poultry; and why ruminant nutritionists often work with metabolizable protein (MP) rather than crude protein alone.

Fish: Fish have lower energy requirements per unit of body weight than land animals, but they require a higher protein-to-energy ratio in their feed. ME values for fish feed are measured differently again and should come from aquaculture-specific reference tables.

The practical rule: always confirm that the ME values you are using in your calculations come from a table measured for the same species you are feeding.

4. Nutrient Requirements by Species and Production Stage

Use these verified reference ranges as your targets before you begin formulating. These are based on established nutritional guidelines from agricultural research institutions:

Poultry

Type / Stage	Crude Protein (%CP)	ME (kcal/kg)
Broiler starter (0 to 14 days)	22% to 23%	3,000 to 3,100
Broiler grower (15 to 28 days)	20% to 21%	3,050 to 3,150
Broiler finisher (29+ days)	18% to 19%	3,100 to 3,200
Layer pullet (0 to 18 weeks)	17% to 18%	2,750 to 2,850
Laying hen (18+ weeks)	16% to 18%	2,650 to 2,800

Pigs

Stage	Crude Protein (%CP)	ME (kcal/kg)
Piglet / starter (up to 25 kg)	20% to 22%	3,200 to 3,400
Grower (25 to 60 kg)	16% to 18%	3,100 to 3,300
Finisher (60 kg to market)	14% to 16%	3,100 to 3,300
Breeding sow (gestation)	12% to 14%	2,900 to 3,100
Lactating sow	16% to 18%	3,100 to 3,300

Ruminants (cattle, goats, sheep)

Animal / Stage	Crude Protein (%CP)	ME (MJ/kg DM)
Beef cattle (growing, 200 to 400 kg)	12% to 14%	10.0 to 11.5
Dairy cow (lactating)	16% to 18%	11.5 to 12.5
Dairy cow (dry, non-lactating)	12% to 14%	9.5 to 10.5
Goat (growing)	14% to 16%	9.5 to 11.0
Sheep (growing)	14% to 16%	9.5 to 11.0

Note on ruminant ME units: Ruminant ME is commonly expressed in megajoules per kilogram of dry matter (MJ/kg DM) rather than kcal/kg. To convert: 1 MJ = 239 kcal. So 11.0 MJ/kg = approximately 2,629 kcal/kg.

5. Nutrient Values of Common Feed Ingredients

To calculate ME and %CP in your feed, you need verified nutrient values for each ingredient. The values below are based on established feed ingredient composition tables from FAO and peer-reviewed research. Always note which species the ME value was measured for.

Feed Ingredient	Crude Protein (%CP)	ME for Poultry (kcal/kg)	Notes
Maize (yellow corn)	8.0% to 9.0%	3,300 to 3,381	Primary energy source in most poultry and pig feeds. Values vary by variety and moisture content.
Soybean meal (44% CP, solvent-extracted)	44% to 46%	2,230 to 2,440	Most widely used protein source globally. ME varies with bird age.
Soybean meal (48% CP, de-hulled)	47% to 49%	2,440 to 2,620	Higher protein and slightly higher energy than standard soybean meal.
Fish meal (65% CP)	60% to 72%	2,820 to 3,000	Highest-quality protein source. ME varies with fat content and processing method.
Wheat offal (wheat bran)	14% to 16%	1,300 to 1,600	High fibre reduces energy availability. Useful bulking ingredient at controlled rates.
Groundnut cake (peanut meal)	40% to 45%	2,100 to 2,400	Good protein source. Must be aflatoxin-free. Values vary with oil extraction method.
Palm kernel cake (PKC)	14% to 18%	1,400 to 1,700	Widely available in West Africa. High fibre limits inclusion rate for poultry.
Palm oil	0%	7,700 to 8,000	Pure energy source. No protein contribution. Used to increase ME of low-energy formulas.
Blood meal	75% to 85%	2,000 to 2,500	Very high protein but low digestibility in some forms. Use at low inclusion rates only.
Di-calcium phosphate (DCP)	0%	0	Mineral source only. No energy or protein contribution.
Limestone / oyster shell	0%	0	Calcium source only. No energy or protein contribution.
Salt	0%	0	Mineral source only.
Vitamin-mineral premix	0% to 2%	0 to minimal	Micronutrient source. No significant ME or CP contribution at standard inclusion rates.

Important note on ingredient variability: These are standard reference ranges. Actual nutrient content can vary depending on variety, origin, processing method, and moisture content. For high-volume commercial production, laboratory analysis of your specific ingredients gives you the most accurate values for formulation.

6. How to Calculate Metabolizable Energy in a Feed Formula

The calculation is straightforward. For each ingredient in your formula:

1. Convert the ingredient quantity to a percentage of the total formula
2. Multiply that percentage (as a decimal) by the ME value of that ingredient
3. Add up all the ME contributions from every ingredient
4. The total is the ME of your finished feed

The formula:

ME of feed = Σ (Ingredient percentage ÷ 100) × ME of ingredient

Where Σ means “sum of all.”

7. How to Calculate Percentage Crude Protein in a Feed Formula

The calculation works exactly the same way as ME:

1. Convert each ingredient to a percentage of the total formula
2. Multiply that percentage (as a decimal) by the %CP of that ingredient
3. Add up all the CP contributions
4. The total is the %CP of your finished feed

The formula:

%CP of feed = Σ (Ingredient percentage ÷ 100) × %CP of ingredient

8. Worked Example — Step by Step

Here is a complete worked example using a sample chick starter formula. This is the same approach used by professional nutritionists — shown clearly so anyone can follow it.

The formula (100 kg total batch):

Ingredient	Quantity (kg)	% of Formula	ME (kcal/kg)	%CP
Maize	50	50%	3,350	8.5%
Soybean meal (44% CP)	30	30%	2,230	44%
Wheat offal	15	15%	1,400	15%
Palm oil	2	2%	7,700	0%
Bone meal	1.5	1.5%	0	0%
Oyster shell	0.5	0.5%	0	0%
Salt	0.3	0.3%	0	0%
Premix	0.3	0.3%	0	0%
Methionine	0.2	0.2%	0	0%
Lysine	0.2	0.2%	0	0%
Total	100	100%

Step 1: Calculate ME contribution from each ingredient

Ingredient	% ÷ 100	ME of ingredient	ME contribution
Maize	0.50	3,350	0.50 × 3,350 = 1,675 kcal/kg
Soybean meal	0.30	2,230	0.30 × 2,230 = 669 kcal/kg
Wheat offal	0.15	1,400	0.15 × 1,400 = 210 kcal/kg
Palm oil	0.02	7,700	0.02 × 7,700 = 154 kcal/kg
All others	0.03	0	0

Total ME = 1,675 + 669 + 210 + 154 = 2,708 kcal/kg

Step 2: Calculate %CP contribution from each ingredient

Ingredient	% ÷ 100	%CP of ingredient	CP contribution
Maize	0.50	8.5%	0.50 × 8.5 = 4.25%
Soybean meal	0.30	44%	0.30 × 44 = 13.2%
Wheat offal	0.15	15%	0.15 × 15 = 2.25%
Palm oil	0.02	0%	0
All others	0.03	0%	0

Total %CP = 4.25 + 13.2 + 2.25 = 19.7%

What do these results tell us?

• ME = 2,708 kcal/kg — Below the 3,000 kcal/kg target for a broiler starter. The energy is too low.
• %CP = 19.7% — Below the 22% to 23% target for a broiler starter. The protein is too low.

Both numbers are below target. The formula needs adjustment before use. See Section 9 for exactly how to do that.

9. How to Adjust Your Formula Once You Have the Numbers

If ME is too low:

• Increase maize percentage — the main energy ingredient
• Add or increase palm oil or another fat source. Fats provide approximately 2.25 times more energy per gram than carbohydrates — even a 2% increase in palm oil adds significant ME to the formula
• Reduce high-fibre, low-energy ingredients like wheat offal

If %CP is too low:

• Increase soybean meal percentage
• Add or increase fish meal — at 60% to 72% CP, even a 2% to 3% increase makes a meaningful difference
• Reduce maize or wheat offal to make room for more protein ingredients

If ME is too high:

• Reduce maize or fat sources
• Increase wheat offal or other fibre sources

If %CP is too high:

• Increase maize and reduce protein sources
• This matters for finisher feeds where excess protein wastes money and increases nitrogen excretion from your farm

The adjustment rule: Every time you change one ingredient’s percentage, you must change another ingredient’s percentage in the opposite direction so the total always stays at 100%. Recalculate ME and %CP after every adjustment until both targets are met.

Adjusting the example formula to meet broiler starter targets:

• Increase maize from 50 kg to 53 kg (+3 kg)
• Increase soybean meal from 30 kg to 34 kg (+4 kg)
• Reduce wheat offal from 15 kg to 10 kg (−5 kg)
• Add fish meal at 2 kg
• Keep all micro ingredients the same

Recalculate after each change. Keep adjusting until both ME and %CP meet your targets.

10. Common Calculation Errors and How to Avoid Them

• Percentages not adding up to 100. Your formula must always total exactly 100 kg per 100 kg batch. If your percentages do not sum to 100, your ME and %CP calculations will be wrong.
• Using the wrong ME values for your species. Poultry AME values are different from pig ME or ruminant ME values for the same ingredient. Using pig values for poultry feed significantly overestimates the energy in your formula.
• Mixing wet-basis and dry-basis values. Nutrient values in tables are typically given on a dry matter (DM) basis or as-fed basis. Keep your values consistent throughout one calculation — mixing the two gives incorrect results.
• Forgetting that mineral and micro ingredients contribute zero ME and CP. DCP, limestone, salt, and vitamin premix contribute minerals and micronutrients only. Do not assign energy or protein values to these ingredients.
• Using outdated or unverified ingredient values. Ingredient nutrient values vary between sources, varieties, and processing methods. Use verified, current reference tables from FAO or your national agricultural research institute.
• Not recalculating after adjustments. Every change to your formula changes both ME and %CP. Recalculate both numbers after every single adjustment — not just after the final one.

11. Key Takeaways

• Metabolizable energy (ME) is the energy in a feed that an animal can actually use. Gross energy minus faecal, urine, and gas losses gives you ME.
• Percentage crude protein (%CP) is calculated from nitrogen content using the formula: %CP = % Nitrogen × 6.25.
• ME values are species-specific. Always use poultry ME values for poultry feed, pig ME values for pig feed, and ruminant ME values for cattle, goat, and sheep feed.
• To calculate ME or %CP of a feed formula: convert each ingredient to a decimal percentage of the total, multiply by that ingredient’s ME or %CP value, and sum all contributions.
• Your formula must total exactly 100% before any calculation is valid.
• If ME is too low, increase maize or fat. If %CP is too low, increase soybean meal or fish meal.
• Recalculate both ME and %CP after every formula adjustment, not just at the end.

For a complete guide to building a livestock feed formula from scratch, read our guide on how to formulate livestock feed to minimize cost.

To understand how mushroom-based supplements can complement your feed formulation, read our guide on how to use mushrooms in livestock feed. (Coming soon)

12. FAQ

What is the difference between ME and gross energy (GE) in livestock feed?

Gross energy is the total energy released when a feed ingredient is completely burned in a laboratory. Metabolizable energy is lower; it is the energy that remains after subtracting losses in faeces, urine, and gases during digestion. ME is what the animal actually has available to use, which is why it is the number that matters for feed formulation.

Why do ME values differ between poultry and pigs for the same ingredient?

Because different species digest and absorb nutrients differently. Pigs have a longer digestive tract and can extract more energy from fibrous ingredients than poultry, which have short digestive tracts and pass feed quickly. Using pig ME values for poultry feed will overestimate the energy your birds are actually receiving.

How is ME calculated for ruminants differently from poultry and pigs?

In ruminants, feed is first fermented in the rumen. Volatile fatty acids produced during fermentation are the main source of metabolizable energy absorbed by the animal. Ruminant nutritionists also work with metabolizable protein (MP) rather than crude protein alone, because microbial protein produced during rumen fermentation supplies much of the animal’s amino acid needs. This makes ruminant feed formulation more complex than poultry or pig formulation.

How do I get the ME and %CP values for ingredients I cannot find in standard tables?

Send a sample to a feed analysis laboratory. Most countries have accredited laboratories that can analyse feed ingredients for ME, %CP, moisture, fibre, calcium, phosphorus, and other nutrients. Your local agricultural extension office or veterinary service can direct you to the nearest facility.

My formula calculation gives a %CP of 19% but I need 23%. What do I do first?

Increase your protein sources. Soybean meal (44% CP) and fish meal (65% CP) are your primary options. Increasing soybean meal by 5 to 10 percentage points while reducing maize by the same amount will typically raise your %CP by 2 to 4 percentage points. Recalculate after each change until you reach your target.

Is it necessary to calculate both ME and %CP for every formula I make?

Yes, always. A feed that meets %CP targets but misses ME targets results in animals eating more than expected, which increases your feed cost. A feed that meets ME but misses %CP results in poor growth, reduced production, and weakened immunity. Both numbers must be verified for every formula before large-scale production.

Can I use the same ME and %CP targets for all my livestock?

No. Each species and production stage has different requirements. A broiler starter needs 22% to 23% CP and 3,000 kcal/kg ME. A laying hen needs 16% to 18% CP and 2,650 to 2,800 kcal/kg ME. A growing pig needs different targets again. Always formulate to the specific requirements of the species and stage you are feeding. Use the tables in Section 4 as your starting reference.

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