Feedlot cattle diets (click to download PDF file)

I. General comments

A. Objective: Grow cattle as fast and efficiently as possible.
B. Use the most economical feeds:

• High grain diets are definitely used more efficiently than high forage diets because they provide more energy above maintenance.
• High grain diets can cost more than high forage diets and still be more economical.
• Whether or not grain is fed to cattle is purely a matter of economics.

II. Energy

A. The major requirement is for nutrients to supply energy. Protein can be supplied in the form of NPN. Cost for other nutrients is relatively minor.

B. Well managed feedlot cattle are full-fed so, once the major ration ingredients are chosen, there is no need to balance for energy.

C. Energy systems.

1. California Net Energy System (CNES).

• An empirical prediction system based upon biological concepts.
• Not a biological system of equations.
• Requires NE maintenance (NEm) and NE gain (NEg) requirements of animals and contents of feeds.
• A prediction system based upon other energy units (TDN) could have been developed to work as well.

2. Use of CNES:

• Determine NEm requirement.
• Determine how much of the dry matter of a specific ration will be used to meet NEm requirement.
• Determine how much gain will be allowed by the NEg in the feed not used for maintenance.
• Example: 250 kg steer, 4.84 Mcal required for NEm
• Consumes 5 kg of a corn based diet containing 2.28 Mcal NEm or 1.48 Mcal NEg per kilogram
• How fast will the steer gain?
• Diet required for maintenance: 4.84 Mcal * 1 kg diet/2.28 Mcal = 2.12 kg diet
• NEg available for gain: (5-2.12) kg diet * 1.48 Mcal/kg diet = 4.26 Mcal NEg
• From a table, we can determine that a 250 kg steer will gain 1.15 kg per day if supplied with 4.26 Mcal NEg.
• CNES is difficult to use in balancing diets because it requires iteration (trial and error).

The only reasons it is necessary to use energy requirements and energy values of feeds are:

• For prediction of economics of feeding.
• For deciding upon the most economical source of energy.

III. Protein.

A. Crude protein (11.5% of diet DM).
B. Soluble protein.
C. Escaped protein.
D. Sources of protein:

SBM, CSM, LSM, good quality alfalfa, urea (281% CP)

IV. Calcium.

A. 0.6% of diet DM.
B. Sources:

• Limestone (36.5% Ca)
• Dicalcium phosphate (23.1% Ca, 18.6% P)
• Alfalfa (1.35% Ca)

V. Phosphorus.

A. 0.3% of diet DM.
B. Sources:

• Grains
• Dical
• Monosodium phosphate (23.5% P)

Ca:P ratio (1.1:1 to 4:1)

VI. Potassium

A. 0.6% of diet DM (possibly higher in diets for light, young cattle)
B. Sources:

• Forages
• KCl (50% K, needed for high grain diets)

VII. Salt (0.3% of diet)

VIII. Vitamin A.

A. 2000 IU/kg (1000 IU/lb) of diet DM
B. Sources:

• Green, leafy forages
• 400 IU A/mg B carotene

IX. Vitamins D and E.

X. Other factors:

• Selenium
• Buffers

Example:  Typical corn grain based diet for feedlot cattle.  (We'll use the substitution method):

Begin with 90 lb corn and 10 lb hay:

Protein

• 90 lb corn * 0.1 lb CP/1 lb corn DM = 0.9 lb CP
• 10 lb hay * 0.12 lb CP/1 lb hay DM = 0.12 lb CP
• Total CP in diet = 10.2 lb CP

CP shortage = 11.5 - 10.2 = 1.3 lb CP

Substitute SBM for corn:

• SBM contains 51.5% CP on DM basis so it adds (51.5-10) 0.415 lb of CP when it replaces 1 lb of corn
• 1.3 lb CP required * 1 lb SBM/.415 lb added CP = 3.13 lb SBM DM

Calcium

• 10 lb hay DM * 0.007 lb Ca/1 lb hay DM = 0.07 lb Ca
• (90-3.13) 86.87 lb corn DM * 0.0002 lb Ca/lb corn = 0.017 lb Ca
• 3.13 lb SBM * 0.0036 lb Ca/1 lb SBM = 0.011 lb Ca
• Total = 0.098 lb Ca

Ca shortage = 0.3 - 0.098 = 0.202 lb Ca

Substitute limestone for corn:

• Limestone contains 36.5% Ca or 36.48% more Ca than corn so:
• 0.202 lb Ca required * 1 lb limestone/.3648 lb Ca = 0.55 lb limestone

Phosphorus

• 10 lb hay DM * 0.003 lb P/1 lb hay DM = 0.03 lb P
•  (86.87-.55) 86.32 lb corn DM * 0.003 lb P/1 lb corn = 0.26 lb P
• 3.13 lb SBM DM *  0.007 lb P/1 lb SBM DM = 0.02 lb P
• 0.55 lb limestone * 0.0002 lb P/1 lb limestone = 0.00 lb P
• Total P = 0.31 lb P

P requirement is met.  Is Ca:P ratio correct?

Potassium

• 10 lb hay DM * 0.01 lb K/1 lb hay DM = 0.1 lb K
• 86.32 lb corn DM (corn contains almost no K) = 0 lb K
• 3.13 lb SBM DM * 0.0221 lb K/1 lb SBM DM = 0.07 lb K
• 0.55 lb limestone (limestone contains no K) = 0 lb K
• Total K = 0.17 lb K

K shortage = 0.6 -.17 = 0.43 lb K

Substitute KCl for corn:

• KCl contains 50% K so 0.43 lb K * 1 lb KCl/.5 lb K = 0.86 lb KCl

Salt

Substitute 0.3 lb salt for corn

Final diet                 

XI. Mixing diets.
A. Mix smallest amount of ingredients as a premix.
B. Add premix to carrier (ground corn) for supplements.
C. Mix supplement into main ingredients.

• Vertical or horizontal mixer.
• Pitchfork for method of top dressing for small feedlots.

XII. Bunk management for full-feeding.

A. Self-feeding.
B. Bunk feeding.

XIII. Implants.

A. Growth promotants

• Synovex-C (estradiol benzoate, progesterone)
• Synovex-S, Steer-oid (estradiol benzoate, progesterone)
• Synovex-H, Heifer-oid (estradiol benzoate, testosterone)
• Ralgro (resorcyclic acid = zeranol)
• Compudose (estradiol-17 beta)
• Finaplex (trenbolone acetate) 

XIV. Heat suppressant and growth promotant: MGA (melengesterol acetate).

XV. Feed efficiency improvers.

A. Rumensin (monensin sodium).
B. Bovatec (lasalocid sodium).

XVI. Ractopamine hydrochloride

Beta-agonist that increases muscle deposition and decreases fat deposition during the last 28 to 42 days of feeding when the animal would be gaining mostly fat.