Effects of evening feeding and extended photoperiod on growth, feed efficiency, live animal carcass traits and plasma prolactin of beef heifers housed outdoors during two Manitoba winters
Bibliographic record
Abstract
The effects of evening feeding and extended photoperiod on feedlot performance, live animal carcass traits and plasma prolactin were investigated in crossbred beef heifers in two consecutive Manitoba winters (1998–1999; exp. 1 and 1999–2000; exp. 2) using a 2 × 2 factorial design. Heifers were fed in the morning (1000 exp. 1 and 0900 exp. 2) or evening (2000) and exposed to natural winter photoperiod (NP) of <15 h or extended winter photoperiod (EP) of 16–19 h (65 lux exp. 1, 51 lux exp. 2) in outdoor partially covered pens. Heifers (n = 48; 276.9 ± 19.4 kg, mean ± SD) in exp. 1 were given a 60% forage: 40% concentrate backgrounding ration for 56 d followed by a 25% forage: 75% concentrate finishing ration for 70 d. In exp. 2, heifers (n = 48; 228.8 ± 18.8kg) were given the backgrounding ration for 170 d. Mean ambient temperature during the backgrounding and finishing periods in exp. 1 was -13.7 and 0.5°C, respectively. During the backgrounding period of exp. 1, evening feeding increased (P = 0.05) growth rate 10.1%, and tended (P = 0.08) to improve feed efficiency by 9.0%; EP tended (P = 0.08) to improve feed efficiency by 9.0%. During the finishing period there was a time of feeding × photoperiod interaction (P = 0.02) for feed efficiency with a tendency for most efficient gains in the morning-fed NP heifers. There were no main or interaction effects of time of feeding and photoperiod on ultrasonically measured subcutaneous fat depth or longissimus dorsi muscle area in exp. 1. Plasma prolactin was elevated by EP on day 42 (photoperiod × day; P < 0.01) of exp. 1. Mean ambient temperature during exp. 2 was -5.1°C, and there were no main or interaction effects of time of feeding or photoperiod on weight gain, dry matter intake or feed efficiency. However, subcutaneous fat depth was reduced by EP on day 156 (photoperiod × day; P < 0.01). Plasma prolactin did not change during the first 107 d of exp. 2, but subsequently rose in all but the morning-fed EP treatment group. The results indicate that both evening feeding and extended photoperiod can impact growth and feed efficiency of beef cattle during winter-feeding. Key words: Feedlot heifers, beef cattle, evening feeding, extended photoperiod, light, prolactin
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".