Ruminant Nitrogen Usage (1985) / Chapter Skim
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3 Comparison of New Protein Systems for Ruminants
3 Comparison of New Protein Systems for Ruminants
Pages 7-22
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From page 7... ...
As higher milk production requires more total protein and available DIP exceeds that converted to BCP, more undegradable protein 7 sources increase the efficiency of N use. A similar situation prevails in the rapidly growing animal.
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From page 8... ...
in the newer systems is still variable and directly related to milk production as in the NRC system based on total protein or crude protein (CP) (Table 1~.
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- ~ - ~ o c-' ~ - ;> cc ~ in So .= ~ ~ ~ ~ O tiC CD D 1)
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From page 11... ...
Digestible Nucleic Acid Nitrogen per Unit of Crude Nucleic Add Nitrogen Only three systems specify any rate for NCP. The Danfaer model assumes a proportional 0.85 for digestible nucleic acid N as protein equivalent (DNP)
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From page 12... ...
The total protein requirement includes that for fecal metabolic protein, maintenance, and production. The maintenance requirement may include fecal ~netabolic protein, urinary endogenous protein, and surface protein.
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From page 13... ...
for by their consideration of fecal metabolic protein as a separate component of total requirement. No equivalent factors can account for the lowest requirement in the ARC system; however, the failure to include a fecal metabolic protein factor probably contributes to its smallness.
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From page 14... ...
; bound protein; nonstructural carbohydrate, potentially digestible organic matter; rates of digestion for each protein, nonstructural carbohydrate and potentially digestible organic matter subfractions; and rates of passage for liquids and solids.
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From page 15... ...
Six variables with a high sensitivity, i.e., a change in protein flow greater than 40 percent from the possible range in input variable, were: potential degradability of protein, fractional outflow rate of water, fractional outflow rate of microbes, energy required for microbial maintenance, salivary flow, and proportion of rumen ammonia available for microbial growth. Faichney et al.
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From page 16... ...
The Burroughs, ARC, and Satter systems require a much lower IP percentage than other systems at higher milk production. The probable causes of their low requirements are the highest efficiency for converting AP to milk assumed in the Burroughs system; the second lowest AP requirement for lactation plus a low AP requirement for maintenance with no separate fecal metabolic protein requirement in the ARC system; and no fecal metabolic protein requirement as a function of DM intake either alone or as a component of maintenance in the Satter system.
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From page 17... ...
. ~DM, dry matter; TDN, total digestible nutrients; ME, metabolizable energy; FE, Scandinavian feed energy unit; OM, organic matter; DE, digestible energy; DOM, apparently digested organic matter; UFL, French net energy unit; NEL, Swiss net energy unit; SE, starch equivalent; IOM, indigestible organic matter.
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From page 18... ...
This difference probably resulted from the high undegradability and the low microbial protein production per unit of DOM. Fecal Crude Protein Equivalent Excretion Relative to Crude Protein Percentage Fecal crude protein (F P)
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From page 19... ...
The Satter system and the ARC system, to a lesser degree, predict low outputs that are nearly constant because they assume zero fecal metabolic protein per unit of feed DM. The Chalupa, Danfaer, and Burroughs systems predict low outputs that decrease gradually with increasing milk production because they assume a minimal fecal metabolic protein.
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From page 20... ...
Urinary Crude Protein Equivalent Excretion Relative to Milk Production Urinary crude protein (UP) equivalent was calculated as the algebraic sum of rumen efflux of crude protein (REP)
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From page 21... ...
First, a fecal metabolic protein fraction is needed for FP excretion to correspond to in vivo data. Second, this fecal metabolic protein fraction should be considered either a separate component of total requirement or a feed reduction component and not be included in mainte 60 50t 40 ' L K ~_ 10 _ O O JO 1 1 1 20 30 40 M l ~ K (kg/day)
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From page 22... ...
Operationally, this is much simpler than either having the fecal metabolic protein for a part of dietary DM included in maintenance and the remainder accounted for in the production requirement as in the NRC (1978) system or having one-third of the total fecal metabolic protein requirement per unit of DM in maintenance (Chalupa, 1980a)
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