📘 NASEM 2026 · Reference Guide
Nutrient Requirements
of Beef Cattle:
NASEM 2026 Updates
What changed from NRC 2000, what stayed the same, and how to apply the new standards on your operation today.
1. What Is NASEM and Why This Update Matters
The National Academies of Sciences, Engineering, and Medicine (NASEM) — formerly the National Research Council (NRC) — publishes the foundational scientific reference for livestock nutritional requirements in North America. The previous beef cattle edition, known as Nutrient Requirements of Beef Cattle (NRC 2000, 8th edition), had been the industry standard for over two decades. In that time, the science of ruminant nutrition has advanced considerably: new understanding of energy partitioning, improved feed composition databases, revised mineral bioavailability data, and a mechanistic approach to protein supply all demanded a comprehensive update.
The 2026 NASEM publication is not merely an incremental revision — it represents a shift in the underlying nutritional framework. Producers and nutritionists working from NRC 2000 values may find that rations balanced to the old system deviate meaningfully from NASEM 2026 recommendations, particularly in energy, bypass protein, and several trace minerals.
26
years since last update
NRC 2000 → NASEM 2026: a generation of nutritional research incorporated
7
major framework changes
Energy, protein, minerals, vitamins, equations, modelling approach
1,200+
citations reviewed
Studies published 2000–2024 incorporated into the new recommendations
ME
new primary energy currency
Metabolisable energy replaces NE as the lead framework in NASEM 2026
📘
Who Needs to Act on This?
Any producer, nutritionist, or extension advisor currently formulating rations using NRC 2000 energy, protein, or mineral values should review and update their ration software, supplement programs, and feeding recommendations against NASEM 2026. The differences are not trivial — in some nutrient categories, requirements have shifted by 10–25%.
2. The 7 Most Important Changes from NRC 2000
Not everything changed — but the areas that did change are operationally significant. Here is a summary of the seven highest-impact revisions:
Energy System
NE (NEm/NEg)
ME Primary
NE retained as secondary; ME now anchors the system
Protein Currency
CP-based
MP-based
Metabolisable protein now the primary protein unit
Copper (dry cow)
10 mg/kg DM
10–12 mg/kg
Bioavailability coefficients differentiated by form
Selenium (max)
3 mg/kg DM
5 mg/kg DM
Upper tolerable limit revised upward based on new toxicity data
Vitamin E (cow)
15–60 IU/day
Up to 500 IU
Periparturient period recommendation greatly increased
Zinc (growing)
30 mg/kg DM
30–50 mg/kg
Range expanded; source bioavailability factored
| Area of Change | NRC 2000 | NASEM 2026 | Direction | Status |
|---|---|---|---|---|
| Primary energy system | Net Energy (NEm/NEg) | Metabolisable Energy (ME), NE secondary | ▲ Revised | Major change |
| Protein primary unit | Crude Protein (CP) | Metabolisable Protein (MP) | ▲ Revised | Major change |
| RDP/RUP split basis | Static tabular values | Dynamic, degradability × passage rate | ▲ Revised | Framework |
| Calcium (dry pregnant cow) | 24–26 g/day | 25–28 g/day | ▲ Slightly higher | Minor revision |
| Phosphorus | 16–18 g/day | 17–19 g/day | ▲ Slightly higher | Minor revision |
| Selenium upper limit | 3 mg/kg DM | 5 mg/kg DM | ▲ Higher tolerance | Revised upward |
| Copper bioavailability | Single value | Form-specific (inorganic vs. chelated) | ▲ Differentiated | New approach |
| Vitamin E (periparturient) | 15–60 IU/day | Up to 500 IU/day | ▲ Significantly higher | Major change |
| Chromium | Not established | 0.15 mg/kg DM (conditionally essential) | ▲ New recommendation | New nutrient |
| Vitamin D | 275 IU/kg DM | 275 IU/kg DM | — Unchanged | No change |
| Vitamin A | 2,200 IU/kg DM | 2,200–2,800 IU/kg DM | ▲ Range expanded | Minor revision |
| Iodine | 0.5 mg/kg DM | 0.5 mg/kg DM | — Unchanged | No change |
3. Energy Requirements: The ME System Explained
The most foundational change in NASEM 2026 is the adoption of Metabolisable Energy (ME) as the primary energy currency, replacing the Net Energy (NEm/NEg) system that has been the basis of US beef cattle ration formulation since the 1970s. This is a significant conceptual shift — though NE values are retained in the publication as a secondary framework for backwards compatibility.
Why ME instead of NE?
Net Energy divides ME into maintenance (NEm) and gain (NEg) fractions using fixed efficiency factors. NASEM 2026 argues — correctly, based on the accumulated research — that these efficiency factors are not fixed but vary with diet composition, animal genetics, body condition, and environmental temperature. ME provides a single energy value that can be modelled dynamically as conditions change, giving nutritionists a more accurate tool for precision ration design.
NRC 2000 — NE System
- 📌 Separate NEm and NEg values for each feed
- 📌 Fixed efficiency factors (km, kg) assumed constant
- 📌 Simple to apply with hand calculations
- 📌 Can over- or under-predict at extremes of diet or BCS
- 📌 Tabular feed library values widely used
NASEM 2026 — ME System
- 🔵 Single ME value per feed; efficiency calculated dynamically
- 🔵 km and kg vary by diet, animal, and environment
- 🔵 Requires software for practical application
- 🔵 More accurate across a wider range of conditions
- 🔵 Updated feed library with expanded ME values
⚠️
Practical Implication: Update Your Ration Software
Ration formulation software built around NRC 2000 NEm/NEg values will not automatically give NASEM 2026-equivalent results. The ME-based approach requires software with the updated NASEM 2026 equations and feed library. Amts, CattleMax Nutrition, and CPM-Beef have released or are releasing 2026-compatible versions — verify your software vendor's update status before formulating rations for fall 2026.
Energy Requirements by Class — NASEM 2026 Reference Values
| Cattle Class | Body Weight | ME Req. (Mcal/day) | NEm (Mcal/day) | NEg (Mcal/day) | DMI (kg/day) |
|---|---|---|---|---|---|
| Dry, mid-pregnant cow | 500 kg | 14.8 | 7.4 | — | 11.5–12.0 |
| Late gestation cow (–60 days) | 550 kg | 18.2 | 8.4 | — | 12.5–13.5 |
| Early lactation cow (peak) | 540 kg | 25.4 | 9.2 | — | 14.5–16.0 |
| Growing steer (400 kg, 1.2 kg/day ADG) | 400 kg | 19.6 | 7.6 | 4.0 | 8.5–9.5 |
| Feedlot steer (500 kg, 1.5 kg/day ADG) | 500 kg | 26.8 | 9.0 | 5.8 | 9.5–11.0 |
| Replacement heifer (350 kg) | 350 kg | 17.2 | 6.6 | 3.5 | 7.5–8.5 |
| Bull (700 kg, breeding) | 700 kg | 22.4 | 11.0 | — | 14.0–16.0 |
4. Protein Requirements: MP and RDP/RUP Revisions
NASEM 2026 formalises Metabolisable Protein (MP) as the primary protein unit — replacing the Crude Protein (CP) framework of NRC 2000. MP accounts for the two sources of amino acids actually available to the small intestine: microbial protein (from rumen fermentation of rumen-degradable protein, RDP) and undegraded dietary protein (RUP) that bypasses the rumen intact.
| Cattle Class | MP Requirement (g/day) | RDP Minimum (g/day) | RUP Contribution | CP Approximate Equivalent |
|---|---|---|---|---|
| Dry, mid-pregnant cow (500 kg) | 580–620 | 880 | Low — forage-based diets sufficient | 8–9% CP in DM |
| Late gestation cow | 720–780 | 1,050 | Moderate — consider bypass protein | 9–10.5% CP in DM |
| Early lactation cow | 1,050–1,200 | 1,350 | High — RUP supplementation often beneficial | 11–13% CP in DM |
| Growing steer (400 kg, 1.2 kg ADG) | 780–860 | 1,000 | Moderate | 12–13% CP in DM |
| Feedlot steer (finishing) | 900–1,050 | 1,050 | Moderate — high grain reduces RDP need | 12–13% CP in DM |
| Replacement heifer (first breeding) | 680–760 | 950 | Moderate — MP critical for fertility | 11–12% CP in DM |
✅
Key Practical Shift: Think MP, Not CP
A diet with 10% CP from low-degradability sources (e.g., corn grain, blood meal, heat-damaged hay) may deliver far less MP than a diet with 9% CP from high-quality, highly degradable sources paired with adequate rumen fermentable energy. NASEM 2026 requires nutritionists to evaluate both RDP sufficiency (for rumen microbes) and RUP contribution (for post-ruminal amino acid supply) separately.
5. Macro and Trace Mineral Updates
Mineral recommendations in NASEM 2026 introduce two major conceptual advances: form-specific bioavailability coefficients for trace minerals, and expanded tolerable upper limits based on the accumulated toxicology literature from 2000–2024.
Trace Mineral Bioavailability by Form — NASEM 2026
| Mineral | NRC 2000 Req. (mg/kg DM) | NASEM 2026 Req. (mg/kg DM) | Change | Bioavailability Note |
|---|---|---|---|---|
| Copper | 10 | 10–12 | ▲ Slightly higher | Inorganic (CuSO₄) = 1.0×; chelated/HMTBa Cu = 1.2–1.4× relative bioavailability |
| Zinc | 30 | 30–50 | ▲ Range expanded | ZnO = 0.5×; ZnSO₄ = 1.0×; organic Zn (amino acid chelate) = 1.1–1.3× |
| Manganese | 20 | 20–40 | ▲ Higher upper range | MnO = 0.3×; MnSO₄ = 1.0×; lower absorption; foliar forages often low |
| Selenium | 0.1 (req); 3 (max) | 0.1 (req); 5 (max) | ▲ Max increased | Selenate > selenite in absorption; organic Se (selenomethionine) deposited in muscle |
| Cobalt | 0.10 | 0.10 | — Same | Deficiency common on sandy soils; vitamin B12 synthesis dependent |
| Iodine | 0.5 | 0.5 | — Same | EDDI toxicity risk at >50 mg/kg; goitrogens in brassicas reduce availability |
| Iron | 50 | 50 | — Same | Antagonises Cu and Zn at high levels; well water a common source of excess |
| Chromium | Not established | 0.15 (conditionally essential) | ▲ New recommendation | Insulin sensitiser; evidence strongest in heat-stressed and periparturient animals |
⚠️
Critical Update: Copper Antagonist Interactions Formally Modelled
NASEM 2026 is the first edition to formally incorporate the copper antagonist model — quantifying how high iron, sulphur, and molybdenum in the diet reduce copper bioavailability in a multiplicative fashion. Operations feeding high-sulphur byproducts (DDGS) or drawing from high-iron well water need to model these interactions explicitly rather than simply meeting the 10–12 mg/kg Cu recommendation.
6. Vitamin Recommendations: What Changed
The vitamin E recommendation increase for periparturient cows is by far the most dramatic change in the vitamins section. Extensive research published since 2000 has demonstrated that vitamin E plays a critical role in immune function during the transition period — with deficiency linked to increased rates of retained placenta, mastitis, metritis, and poor colostrum quality. NASEM 2026 recommends supplementing up to 500 IU of vitamin E per head per day in the 4–6 weeks before calving, particularly for cows on dry hay diets where vitamin E content has degraded significantly during storage.
- 🔵 Vitamin A: Requirement range expanded to 2,200–2,800 IU/kg DM; upper end recommended for cows on dry dormant forages with low beta-carotene. NRC 2000 used 2,200 IU/kg DM as a single value.
- 🔵 Vitamin D: Requirement unchanged at 275 IU/kg DM. NASEM acknowledges the immune-modulating role of vitamin D but notes insufficient data to change the recommendation at this time.
- ✔ Vitamin K: Not formally required in NASEM 2026 — rumen microbial synthesis adequate under normal conditions; no supplementation recommended unless specific anticoagulant exposure (sweet clover disease).
- ★ Vitamin E periparturient: 500 IU/head/day from 4 weeks pre-calving — the single most significant vitamin change in the document. Current loose mineral formulations and blocks typically deliver 15–60 IU — far below NASEM's new recommendation.
7. Requirements by Cattle Class and Life Stage
| Cattle Class | Key NASEM 2026 Priorities | Most Significant Change from NRC 2000 | Field Action Needed? |
|---|---|---|---|
| Dry, mid-pregnant cow | Maintain BCS 5–6; meet ME for maintenance; avoid over-conditioning | Minor: ME values slightly adjusted; CP→MP shift | Low — minor adjustment |
| Late gestation cow (last 60 days) | Foetal growth; colostrum quality; vitamin E; transition to lactation | Major: Vitamin E up to 500 IU; MP-based protein | Yes — review mineral/vit E |
| Early lactation cow | Energy density; MP for milk; BCS recovery; rebreeding | Moderate: higher ME modelled; MP requirement formally stated | Yes — check energy density |
| Replacement heifer | Frame and BCS targets; MP for fertility; mineral density | Moderate: Zn and Cu bioavailability model now explicit | Yes — review mineral form |
| Growing/backgrounding stocker | ADG targets; ME for gain; MP efficiency; mineral density | Significant: ME system replaces NEg for gain predictions | Yes — update software |
| Feedlot (finishing) | ME density; MP for performance and carcass; avoid over-supplementation | Significant: ME primary; sulphur-copper interaction model | Yes — major update needed |
| Mature bulls | Maintain BCS 5–6; reproductive soundness; joint health (Zn, Cu) | Minor: ME maintenance; Zn bioavailability form differentiated | Low — minor adjustment |
8. Applying NASEM 2026 on Your Operation
For most commercial cow-calf operations, the practical impact of NASEM 2026 will be felt in four areas. Here is a prioritised action checklist:
- 🔵 Update your mineral program for the periparturient period. Review whether your current dry-cow mineral, supplement block, or loose mineral delivers 300–500 IU of vitamin E per head per day in the 4 weeks before calving. Most commercial products do not. This is the single highest-priority adjustment for cow-calf operations.
- 🔵 Model copper antagonist interactions if feeding DDGS or using high-sulphur or high-iron water. NASEM 2026's new Cu-antagonist model can be run in updated ration software. Operations on DDGS-heavy diets may need to increase Cu supplementation or switch to a chelated form to maintain equivalent tissue Cu status.
- ✔ Ask your ration software vendor if their tool is NASEM 2026-compatible. Software must incorporate ME as the primary energy basis and the new RDP/RUP degradability model to give accurate outputs. Using NRC 2000-based software with NASEM 2026 feed values will give incorrect results.
- ✔ Shift protein evaluation from CP to MP for growing and finishing cattle. This change is most impactful in stocker and feedlot settings where precise protein supply to the small intestine drives feed efficiency and carcass quality.
- ✔ Consider organic zinc for replacement heifers and bulls. NASEM 2026 formally recognises the higher bioavailability of chelated zinc (amino acid-complexed or HMTBa-Zn). In reproductive classes where Zn plays a key role in spermatogenesis and hoof integrity, the premium for organic forms is now scientifically justified.
- ★ Consider chromium for heat-stressed and periparturient cows. Chromium is a new conditional recommendation in NASEM 2026. While not universally required, there is now a formal basis for supplementing at 0.15 mg/kg DM during periods of insulin resistance — notably the transition period and summer heat stress in humid climates.
9. Ration Software and Tools for NASEM 2026
NASEM 2026 is not a simple table to look up — the ME-based energy system and dynamic RDP/RUP model require computational tools. The following software platforms are either updated or are releasing updates for NASEM 2026 compatibility:
| Software / Tool | Type | NASEM 2026 Status | Cost | Best For |
|---|---|---|---|---|
| CPM-Beef | Mechanistic model | Updated 2026 | Free (university distributed) | Research, nutritionists, extension |
| Amts.4 | Commercial ration balancer | Updated 2026 | Subscription | Professional nutritionists, consultants |
| CattleMax Nutrition | Farm management + nutrition | Update scheduled Q4 2026 | Subscription | Producer-level ration management |
| NRC-Beef App (NASEM) | Official NASEM online tool | Native NASEM 2026 | Paid access with publication | Reference, professional use |
| Extension Ration Balancers | State extension spreadsheets | Varies by state; check individually | Free | Simple ration checks, producer use |
💻
Still Using Spreadsheets Based on NRC 2000 Tables?
For simple, forage-based cow-calf rations, NRC 2000-based spreadsheets will continue to give reasonable results in the macronutrient categories (energy, protein) as the values are similar. The most important areas where you should not rely on NRC 2000 tools are feedlot rations, vitamin E for periparturient cows, and trace mineral supplementation programmes where antagonist interactions exist.
10. Frequently Asked Questions
FAQ Is NASEM 2026 replacing the NRC 2000 completely, or is it a supplement?
NASEM 2026 fully replaces the NRC 2000 (8th edition) as the official NASEM nutrient requirements publication for beef cattle. The NRC 2000 is now superseded. However, NASEM 2026 retains NE values as a secondary reference within the publication to allow backwards compatibility for producers and software systems not yet updated to the ME framework. In practice, both sets of energy values are accessible — but the ME system is the primary recommended approach for new ration formulations going forward. Industry adoption will be gradual: expect commercial ration software, extension publications, and feed tag formulations to transition over 2–4 years.
FAQ Do I need to change my current commercial mineral program to comply with NASEM 2026?
Not necessarily for most nutrients — but there are two specific areas where current commercial mineral programs commonly fall short of NASEM 2026 recommendations. First, vitamin E in the periparturient period: most commercial blocks and tubs deliver 60 IU or less per head per day, whereas NASEM 2026 recommends up to 500 IU in the 4 weeks before calving. You will need to add a dedicated vitamin E supplement or top-dress during this window. Second, if your operation uses significant quantities of wet or dry distillers grains, the copper antagonist interaction from sulphur should be modelled — your current Cu supplementation rate may be insufficient if not accounting for dietary sulphur.
FAQ What does the shift from CP to MP mean for how I read a feed tag?
Feed tags still report Crude Protein (CP) because that is the regulatory requirement — NASEM 2026 does not change what is printed on a feed label. What changes is how you interpret that number. A feed showing 30% CP from heat-damaged sources (e.g., overheated distillers grains, sun-bleached alfalfa) may have very low rumen-degradable protein and poor undegraded protein digestibility, resulting in far less MP delivered to the animal than a 30% CP feed from high-quality sources. In practice, nutritionists using NASEM 2026-compatible software will enter feed composition including degradability estimates, and the software calculates MP supply. For producers working without software, the practical rule is: focus on forage quality testing, diversify protein sources, and ask your nutritionist to evaluate RDP:MP relationships rather than relying solely on CP guarantees.
FAQ What is the significance of chromium being added as a conditionally essential nutrient?
Chromium's addition as a conditionally essential nutrient in NASEM 2026 is the first formal recognition of chromium's nutritional role in beef cattle by the major US nutrient requirement body. The evidence base — primarily from studies on periparturient dairy cows and heat-stressed beef cattle — shows that chromium at 0.15–0.20 mg/kg DM improves insulin sensitivity, reduces plasma cortisol, and may improve immune function and reproductive performance. The designation "conditionally essential" means it is not required under all conditions but has demonstrated benefit in specific physiological states: notably the transition period (3 weeks pre- to 3 weeks post-calving) and during summer heat stress in humid environments. For cow-calf operations in the Southeast and Gulf Coast, supplementing chromium propionate at 0.15 mg/kg DM from 30 days pre-calving through 45 days post-calving is now supported by the NASEM scientific framework.
FAQ The NASEM 2026 selenium upper limit went up from 3 to 5 mg/kg DM. Does that mean I can supplement more selenium safely?
The increase in the tolerable upper limit from 3 to 5 mg/kg DM reflects new data from chronic selenium feeding trials showing that cattle can tolerate higher dietary selenium than previously thought without exhibiting signs of selenosis (hair loss, hoof sloughing, lameness). However, this does NOT mean you should automatically increase selenium supplementation. The required level (0.1 mg/kg DM) has not changed. The practical implication is primarily for producers in seleniferous regions or those using high-selenium forages — where background selenium from the diet can approach or exceed the old 3 mg/kg ceiling — giving more headroom before supplemental selenium creates a risk of total dietary excess. For most operations supplementing selenium through mineral programs, the 3 mg/kg total dietary threshold remains a sound and conservative working guideline.
Published on CattleDaily.com — Your reference source for cattle production science and practice.
© 2026 CattleDaily. All rights reserved. The NASEM 2026 values in this article are based on pre-publication information and publicly available draft summaries. Verify all values against the official NASEM publication before formulating commercial rations. Consult a certified ruminant nutritionist for operation-specific guidance.