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NRC Nutrient Requirements of Beef Cattle
8th Revised Edition · 2016
Energy (NEM/NEG), crude protein, RDP/RUP, minerals, vitamins, and DMI prediction for growing, finishing, cow-calf, and bull classes. Environmental adjustments for cold, heat, and mud stress per NRC Table 9-3.
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NASEM Nutrient Requirements of Dairy Cattle
8th Revised Edition · 2021
NEL, MP, factorial Ca/P, DCAD, trace minerals, and vitamins for lactating, dry, and close-up cows. DMI from NASEM Eq. 5-1 with parity and DIM. Fiber minimums from NASEM Ch. 7.
How the 100-Point Score Works
Every nutrient is individually scored against its NRC/NASEM requirement, then averaged across all nutrients and scaled to 100.
Full credit. A buffer above 100% reflects real-world feed variability.
Curved penalty steepest near requirement — the optimizer always has a gradient to push toward.
Gradual credit loss discourages wild over-supply of one nutrient.
Entire ration scores 0. Correcting toxicity always takes priority.
Fiber minimums (NDF, ADF) use a floor model: at or above the minimum earns full credit; below the floor is penalised proportionally. Ca:P ratio and DCAD are shown as advisory values and do not alter the score.
Antagonist & Toxic Indicators
Five minerals are monitored for interactions that can impair absorption or harm animal health, regardless of whether the individual nutrient shows as deficient. Thresholds are drawn from NRC Beef 2016 and NASEM Dairy 2021 maximum tolerable levels.
Antagonist — depresses absorption of a secondary mineral; score not zeroed but a warning badge appears Toxic — exceeds maximum tolerable level; entire ration score drops to 0 Sulfur (S)NRC 2016 / NASEM 2021
⚠ Antag. ≥ 0.25–0.30% DM*⚠ Toxic ≥ 0.30–0.40% DM*
Reduces Cu & Se absorption; causes polioencephalomalacia at high levels
Iron (Fe)NRC 2016 Table 9-4
⚠ Antag. ≥ 250 ppm⚠ Toxic ≥ 500 ppm
Cu antagonist — impairs hepatic Cu storage
Zinc (Zn)NRC 2016 Table 9-4
⚠ Antag. ≥ 300 ppm⚠ Toxic ≥ 500 ppm
Cu antagonist — competes for intestinal absorption
Potassium (K)NRC 2016 Ch. 9
⚠ Antag. ≥ 2.0% DM⚠ Toxic ≥ 3.0% DM
Mg antagonist — primary driver of grass tetany
Calcium (Ca)NASEM 2021 Ch. 8
⚠ Antag. ≥ 1.5–2.0% DM†⚠ Toxic ≥ 2.0–3.0% DM†
Depresses absorption of Zn, Mn, Fe, and Cu at excess
* Sulfur thresholds are interpolated by forage % of ration DM: lower thresholds apply to concentrate-heavy diets (<15% forage), higher thresholds to forage-based diets (≥40% forage).
† Calcium thresholds differ by species: dairy thresholds are lower (NASEM 2021 MTL = 1.5% DM for lactating cows).