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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996
SBW is shrunk body weight;
N is number of animals; and
DOP is days on pasture.
SUPPLY OF NUTRIENTS
Amounts are computed from actual dry matter intake when available or from predicted intake equation. Risk of use increases when predicted intakes are used versus actual DMI.
Ration energy values are computed by summing the energy contribution of each feed to arrive at a total energy content of the ration, using tabular energy values. Tabular energy values used include % TDN, ME (Mcal/kg), NEma (Mcal/kg), and NEga (Mcal/kg).
Supply of metabolizable protein (MP) is the sum of digested ruminally undegraded feed protein and digested microbial protein. Feed composition parameters used include percentage CP, percentage UIP, and percentage DIP.
Undegraded available feed protein is assumed to be 80 percent digestible. Hence,
The contribution of microbial protein to the MP supply is estimated from the microbial crude protein yield.
MCP is microbial crude protein, g/d;
eNDFadj is 1.0 if the effective NDF (eNDF) of the ration is >20%;
eNDFadj is 1.0-((20-eNDF) * 0.025) when eNDF =20%;
TDN is total digestible nutrients, g/d;
MCP is assumed to be 80% true protein and 80% digestible, hence,
Level 2 computes amino acid requirements and predicts energy and protein supply from feed physical and chemical properties. All energy and protein requirements are the same as level 1.)
AMINO ACID REQUIREMENTS FOR MAINTENANCE
MPmaint is metabolizable protein required for maintenance, g/d;
MPAAi is metabolizable requirement for the ith absorbed amino acid, g/day;
AATISSi is amino acid composition of tissue, Table 10–5.
AMINO ACID REQUIREMENTS FOR GROWTH
PB is protein content of empty body gain, g/100g;
EBG is empty body gain, g/d;
RPN is net protein required for growth, g/d;
RPAAi=growth requirement for the ith absorbed amino acid, g/d.
AATISSi is amino acid composition of tissue (Table 10–5);
EAAGi is efficiency of use of the ith amino acid for growth (Table 10–6), g/g, and
AMINO ACID REQUIREMENTS FOR LACTATION
AALACTi is the ith amino acid content of milk true protein, g/100g (Table 10–6);
Table 10–5 Amino Acid Composition of Tissue and Milk Protein (g/100 g of protein)