Casein infusion rate influences feed intake differently depending on metabolizable protein balance in dairy cows: A multilevel meta-analysis
Bibliographic record
Abstract
The effects of casein infusion have been investigated extensively in ruminant species. Its effect on responses in dry matter intake (DMI) has been reviewed and indicated no significant effect. The literature reviewed in the current meta-analysis is more extensive and limited to dairy cows fed ad libitum. A total of 51 studies were included in the meta-analysis and data were fitted to a multilevel model adjusting for the correlated nature of some studies. The effect size was the mean difference calculated by subtracting the means for the control from the casein-infused group. Overall, casein infusion [average of 333 g of dry matter (DM)/d; range: 91 to 1,092 g of DM/d] tended to increase responses in DMI by 0.18 kg/d (n=48 studies; 3 outliers). However, an interaction was observed between the casein infusion rate (IR) and the initial metabolizable protein (MP) balance [i.e., supply minus requirements (NRC, 2001)]. When control cows were in negative MP balance (n=27 studies), responses in DMI averaged 0.28 kg/d at mean MP balance (-264 g/d) and casein IR (336 g/d), and a 100g/d increment in the casein IR from its mean increased further responses by 0.14 kg/d (MP balance being constant), compared with cows not infused with casein. In contrast, when control cows were in positive MP balance (n=22 studies; 2 outliers), responses in DMI averaged -0.20 kg/d at mean casein IR (339 g/d), and a 100g/d increment in the casein IR from its mean further decreased responses by 0.33 kg/d, compared with cows not infused with casein. Responses in milk true protein yield at mean casein IR were greater (109 vs. 65 g/d) for cows in negative vs. positive MP balance, respectively, and the influence of the casein IR on responses was significant only for cows in negative MP balance. A 100g/d increment in the casein IR from its mean increased further responses in milk true protein yield by 25 g/d, compared with cows not infused with casein. Responses in blood urea concentration increased in casein studies (+0.59 mM) and the influence of the casein IR was greatest for cows in positive MP balance (0.26 vs. 0.11 mM per 100g/d increment). Responses in DMI were also correlated negatively with responses in blood urea concentration only for cows in positive MP balance. Together, these results suggest an association between satiety and deamination and oxidation of AA supplied in excess of requirements for cows in positive MP balance. Therefore, casein stimulated appetite in cows fed MP-deficient diets possibly via the supply of orexigenic AA or through a pull effect in response to an increased metabolic demand. Conversely, casein induced satiety in cows fed diets supplying MP in excess of requirements. Not precluding other factors involved in satiety (e.g., insulin, gut peptides), casein could have increased the supply of AA (e.g., Ser, Thr, Tyr), which might depress appetite at the brain level or increase the deamination and the oxidation of AA in oversupply in agreement with the hepatic oxidation theory.
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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 | 0.014 | 0.021 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.010 | 0.043 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 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".