Sustainable Overwintering Systems for Beef Cows on the Canadian Prairies: Challenges and Solutions
Bibliographic record
Abstract
The goal of this thesis was to provide an in-depth description of winter bale grazing (BG) for beef cows, including the impacts on animal, soil and forage productivity and the potential environmental costs and benefits. A winter trial with 60 pregnant beef cows was conducted over two, 21-day periods (P1 and P2) with the following treatments: drylot (DL), BG, and BG with supplementation (dried distillers grains with solubles; BGDG) at a rate of 8.3 kg cow-1 every three days. All treatments received low-quality (11% CP) forage ad libitum. Dry matter (DM) intake in P1 for the DL and BG systems was 13.4 and 12.2 kg cow-1 d-1 while average daily gain was 0.45 and -0.28 kg cow-1 d-1, respectively. Enteric methane emissions (L d-1 and % GEI) were greatest from the BG system in P1. Forage DM yield decreased by 68% following application of manure from the BGDG treatment compared to a control field and was attributed to smothering by waste feed. Concentrations of residual soil extractable nitrogen (N) and phosphorus (P) were 15 and 2.5 times greater, respectively, at the centre of bale placement areas compared to a control. Detailed grid soil sampling revealed that 40 area-weighted mean extractable N and P samples, collected in a 4:1 ratio from waste feed affected and unaffected areas of the field, were required to determine field mean nutrient status without compromising precision. A system-scale nutrient budget model was used to determine efficiency of N and P inputs in BGDG and DL systems. Surpluses were 448 and 225 kg N ha-1 and 52 and 26 kg P ha-1, and efficiency was 0.4 and -0.3% N and 8.7 and 12.1 % P for the BGDG and DL systems, respectively. This research provides scientific information regarding, DM intake, enteric methane and N and P surpluses from extensively overwintered beef cows. These studies suggest that in some production systems bale grazing may have increased enteric methane emissions and decreased nutrient utilization efficiency compared to DL systems. These results must be considered along with economic costs and benefits to more fully assess the sustainability of overwintering systems.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.004 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".