A 100-Year Review: Protein and amino acid nutrition in dairy cows.
Level 5 - mechanism / opinion, no new human data
Level 5 by design analogy (narrative historical review of animal nutrition literature)
PubMed 29153157 · doi:10.3168/jds.2017-13320
What was done
This historical review summarizes a century of developments in dairy cow protein and amino acid nutrition, covering crude protein chemistry, ruminal microbial protein synthesis, measurement methodologies for protein degradation and flow, and the evolution of predictive nutritional models.
What was found
The abstract reports no numerical findings or effect sizes. It qualitatively summarizes that ammonia derived from ruminal amino acid degradation is critical for bacterial protein formation; urea serves as a viable nitrogen supplement in lower-protein rations; microbial protein represents the majority of high-quality protein flowing to the small intestine; lysine, methionine, and histidine are most frequently identified as limiting amino acids; and protein feeding frameworks have shifted from crude protein standards to complex models predicting rumen-available nitrogen and absorbable amino acids.
Why it matters
It outlines how dairy nutrition science has progressed from crude dietary nitrogen estimates to targeted amino acid balancing, supporting strategies to lower total dietary protein while sustaining milk production.
Limits
The abstract contains no quantitative data, statistical metrics, or search methodology. As a narrative historical review focused on bovine physiology, it synthesizes general historical milestones rather than systematically assessing study quality or effect sizes.
Cited by
- supports Cattle and other ruminants obtain their protein by fermenting fiber into microbes, which serve as the actual protein source for the animal.