Feed characterization using CHO and protein fractions in feeds, DMI prediction, rumen models, growth requirement, aminoacid, MP system, and computer models
60 refs
Net energy systems
Feed characterization:
CHO and protein
Metabolizable protein and ruminaly degraded protein
1200 (beef) refs
1900 (dairy) refs
The next question
is how did we get to the current requirements?The NRC provides recommendations most often
used as a basis for ration formulation systems.Having been involved with 6 NRC committees
over the past 20 years, it is my observation that these committees do an
excellent job of summarizing the accumulated data and making recommendations,
based on published data.The weight
of the evidence indicates we have a lot of accumulated knowledge of cattle
nutrient requirements.The 1963 Beef
NRC had 60 references; the 1996 beef NRC had about 1200 references and the
2001 Dairy NRC had about 1900 references. The 1966 Dairy NRC had a short
paragraph about crude protein requirements and 10 references; the 2001 Dairy
NRC had 42 pages and 770 references on protein requirements.
I’ll do a quick
review of the major improvements that I have seen and used in the field that
improved accuracy of predicting requirements.1) The introduction of the NE system in 1970 and 1971 improved the
accuracy in predicting energy requirements for maintenance, growth, and
lactation and the useful energy in feeds to meet those requirements.2) In the 80’s, improved methods to
describe feed carbohydrate and protein fractions were developed. 3) In 1989
and 1996 the metabolizable protein system was introduced to improve the
accuracy in meeting ruminal N requirements and undegraded diet protein to
supplement microbial protein.4)Accumulated knowledge led to considerable
refinement in requirements in 1996 and 2001 NRC: a) Description of feeds by
carbohydrate and protein fractions, (b) Equations to predict feed energy
values from feed analysis, (c) improved accuracy in predicting DMI, (D) rumen
models that predict ruminal N, microbial protein production and escape of
undegraded feed protein and amino acids, (D) systems to accurately predict
growth requirements for cattle with different mature sizes, (e) amino acid
requirements for growth and milk, and (f) computer models to integrate and
apply the accumulated knowledge.