Nutritional composition of beef: a comparison of commercial North American grass- and grain-finishing systems
Bibliographic record
Abstract
Beef's fatty acid and mineral profile is influenced by finishing diets, yet the nutritional variability within both grass- and grain-fed beef samples from commercial operations remains underexplored. Understanding potential differences is important for producers and consumers. This study profiled grass- and grain-fed beef from commercial North American producers and retailers, and evaluated relationships among grazing practices, forage quality, soil characteristics, and beef fatty acid and mineral composition. Beef samples (grass-fed, n = 253; grain-fed, n = 84), along with forage and soil samples where possible, were collected from 108 commercial producers and retailers. Fatty acids were analyzed using gas chromatography-flame ionization detection (GC-FID), and minerals were quantified using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Statistical models evaluated differences and correlations between and within finishing practices using Welch's t-test and Pearson's correlation analysis. Grass-fed beef had a lower omega-6:3 ratio (2.14 vs. 8.28, P < 0.001) and higher concentrations of the fatty acids alpha-linolenic acid (ALA; 0.99 vs. 0.27%), eicosapentaenoic acid (EPA; 0.28 vs. 0.07%), docosapentaenoic acid (DPA; 0.41 vs. 0.17%), conjugated linoleic acid (CLA; 0.49 vs. 0.31%), and the minerals calcium (9.26 vs. 3.08 mg/100 g), copper (0.253 vs. 0.129 mg/100 g), iron (2.29 vs. 1.92 mg/100 g), and selenium (0.012 vs. 0.002 mg/100 g) compared with grain-fed beef (all P < 0.05). However, considerable nutritional variation exists, particularly within grass-finished beef, with omega-6:3 ratios ranging from 0.62 to 11.45. Animals finished on biodiverse pastures exhibited fatty acid profiles characterized by higher omega-3 to total polyunsaturated FA content, resulting in a higher omega balance (r = 0.30, P = 0.02). However, some grass-fed samples, particularly several retail-purchased samples, displayed fatty acid compositions with relatively low omega-3 content, resulting in an omega balance similar to grain-fed beef. These findings highlight the need for clearer guidance on "grass-fed" management definitions and more transparent labeling that reflects measurable nutritional attributes, such as omega-3 content, omega-6:3 ratio, and/or omega balance.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".