Carbonate and Fatty Acids as Precursors of Amino Acids in Casein

Black, Arthur L.; Kleiber, Max; Smith, Arthjjr H.

doi:10.1016/s0021-9258(18)55685-4

Cited by 49 publications

(2 citation statements)

References 10 publications

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“…However, it was not until the work of the "Davis Tracer Team" that the absolute essentiality of the same AA was confirmed for dairy cows. In one such experiment, 14 C-labeled carbonate and the 3 major VFA were injected into the blood of lactating cows and the labeling pattern determined in milk AA (Black et al, 1952). The presumption was that only NEAA would contain 14 C. The 7 NEAA analyzed were heavily labeled, whereas the 7 EAA analyzed (Thr and Trp were not determined) were labeled to only a fraction of that observed in the NEAA.…”

Section: Early Recognition Of Importance Of Aamentioning

confidence: 99%

A 100-Year Review: Protein and amino acid nutrition in dairy cows

Schwab¹,

Broderick²

2017

Journal of Dairy Science

205

129

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Considerable progress has been made in understanding the protein and amino acid (AA) nutrition of dairy cows. The chemistry of feed crude protein (CP) appears to be well understood, as is the mechanism of ruminal protein degradation by rumen bacteria and protozoa. It has been shown that ammonia released from AA degradation in the rumen is used for bacterial protein formation and that urea can be a useful N supplement when lower protein diets are fed. It is now well documented that adequate rumen ammonia levels must be maintained for maximal synthesis of microbial protein and that a deficiency of rumen-degradable protein can decrease microbial protein synthesis, fiber digestibility, and feed intake. Rumen-synthesized microbial protein accounts for most of the CP flowing to the small intestine and is considered a high-quality protein for dairy cows because of apparent high digestibility and good AA composition. Much attention has been given to evaluating different methods to quantify ruminal protein degradation and escape and for measuring ruminal outflows of microbial protein and rumen-undegraded feed protein. The methods and accompanying results are used to determine the nutritional value of protein supplements and to develop nutritional models and evaluate their predictive ability. Lysine, methionine, and histidine have been identified most often as the most-limiting amino acids, with rumen-protected forms of lysine and methionine available for ration supplementation. Guidelines for protein feeding have evolved from simple feeding standards for dietary CP to more complex nutrition models that are designed to predict supplies and requirements for rumen ammonia and peptides and intestinally absorbable AA. The industry awaits more robust and mechanistic models for predicting supplies and requirements of rumen-available N and absorbed AA. Such models will be useful in allowing for feeding lower protein diets and increased efficiency of microbial protein synthesis.

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Section: Early Recognition Of Importance Of Aamentioning

confidence: 99%

A 100-Year Review: Protein and amino acid nutrition in dairy cows

Schwab¹,

Broderick²

2017

Journal of Dairy Science

205

129

View full text Add to dashboard Cite

show abstract

“…Carbon-14-labeled casein was used to study the alteration of a protein in the rumen system. The casein had been isolated from a milk sample collected 3 hours following intravenous injection of butyrate 2-carbon-14 into a dairy cow (5). The distribution of the isotope in the casein had been determined by separation of the amino acids, after hydrolysis, on an ion exchange column (4).…”

Section: Methodsmentioning

confidence: 99%