257 Ruminal volatile fatty acid concentration and microbial populations as a proxy for of feed efficiency in beef steers
Bibliographic record
Abstract
Breeding and management of animals to achieve improved feed efficiency is a significant priority for the beef industry. Feed conversion ratio (FCR) and residual feed intake (RFI) have become popular measurements for feed efficiency, although both have limitations and practical challenges. The identification of additional, cost-effective indicators of feed efficiency is needed to improve breeding programs. We hypothesized that volatile fatty acids (VFAs), the end products of rumen microbial fermentation and the primary energy source for ruminants, could potentially dictate feed utilization for growth and production. In this study, we tested whether residual VFA (rVFAs) could serve as a predictor of feed efficiency. Rumen content was collected from a total of 204 beef (Angus, Charolais, and Kinsella composite) steers raised under a Growsafe® system, and VFA concentrations (mol/L) were analyzed by gas chromatography. Microbial populations were estimated using total copy numbers of 16S rRNA genes for bacteria and archaea using quantitative PCR (qPCR). Animal phenotypic measures including body weight (BW), dry matter intake (DMI), average daily gain (ADG), feeding frequency, RFI, and carcass performances were collected. The feed was collected at the time of rumen sample collection, and its nutrient content was analyzed. VFA concentrations and production rates were predicted using the Molly mathematical model for each animal based on observed BW, DMI, and ration composition. Residual VFA concentrations were calculated as observed minus predicted VFA concentration. The relationships among digestion parameters and rVFA were tested using stepwise, backward linear regression, which was also used to test rVFA as a predictor of feed efficiency. Residual acetate (ResAc), propionate (ResPro), and total VFA concentrations were significantly correlated with BW, DMI, and breed. Residual butyrate (ResBu) was correlated only with DMI. Total bacterial copy number was negatively correlated with eating frequency (P < 0.05) and ResAc (P < 0.01) and positively associated with ResPro (P < 0.01) concentrations. Total archeal copy number was inversely related to ResPro. RFI was significantly affected by DMI (P < 0.01) and ResAc and showed a significant negative relationship with ResPr and ResBu (P < 0.05). Similarly, FCR was significantly affected by DMI, ADG, and breed. Both ResPr and ResBu had non-significant (P < 0.1), inverse relationships with FCR. Although the work needs to be independently evaluated, our preliminary results identified the potential of using rVFA concentrations to predict feed efficiency traits in beef steers.
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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) | 0.000 | 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 | 0.000 |
| 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 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".