Comparative effects of zilpaterol hydrochloride and ractopamine hydrochloride on growth performance, carcass characteristics, and longissimus tenderness of feedlot steers fed barley-based diets
Bibliographic record
Abstract
A randomized complete block design experiment was conducted with 4,114 beef steers in a commercial feedlot in western Canada that were fed barley-based diets to evaluate the effects of ractopamine hydrochloride (Optaflexx) and zilpaterol hydrochloride (Zilmax) on health, performance, carcass traits, and LM tenderness. Treatments consisted of feeding ractopamine hydrochloride at 30 mg/kg (100% DM basis) for 32 d at the end of the feeding period or zilpaterol hydrochloride at 8.3 mg/kg (100% DM basis) for 20 d at the end of the feeding period, followed by the required minimum 4-d meat withdrawal period before slaughter (range 6 to 10 d). No differences (P > 0.05) were detected in mortality, number of railers (animals shipped to slaughter before the rest of their pen), ADG, G:F, or DMI between steers fed zilpaterol hydrochloride or ractopamine hydrochloride. Steers fed zilpaterol hydrochloride had heavier HCW (8.4 kg, P < 0.0001), greater percentage of overweight carcasses (2.1 percentage units, P=0.006), greater DP (1.0 percentage unit, P=0.0001), greater percentage of YG 1 carcasses (7.0 percentage units, P=0.01), lower percentage of YG 3 carcasses (4.8 percentage units, P=0.02), lower percentage of prime carcasses (0.32 percentage units, P=0.05), and a lower percentage of Canadian AAA carcasses (5.6 percentage units, P=0.04) compared with steers fed ractopamine hydrochloride. No differences in LM tenderness (P > 0.05) were detected between steers fed zilpaterol hydrochloride or ractopamine hydrochloride. Based on the marketing grid on which these feedlot steers were sold, the additional economic value of zilpaterol hydrochloride at 8.3 mg/kg to ractopamine hydrochloride at 30 mg/kg was $30.36 (Canadian) per steer. Feeding zilpaterol hydrochloride for 20 d to finishing steers resulted in leaner carcasses and greater carcass weight without compromising tenderness compared with feeding ractopamine hydrochloride at 30 mg/kg.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".