Ecological Archives E089-087-A2

Martyn G. Murray and David R. Baird. 2008. Resource-ratio theory applied to large herbivores. Ecology 89:1445–1456.

Appendix B. Variables and units used in the model of body size competition.


Variable Units Definition

V kg.ha-1 Vegetation standing biomass
CWS kg.ha-1 Cell wall standing biomass
CCS kg.ha-1 Cell contents standing biomass
W kg Body size
GC g DM Gut Capacity - dry matter food contents in the gut
RT h Mean whole gut retention time / passage time of food
RTadj   Effect of food quality on RT
FILLd g DM.d-1 Gut capacity constraint on daily food intake
Rmax g.min-1 Maximum instantaneous cropping rate
b g.m-2 Vegetation biomass at which intake is half maximum
tmax min Maximum daily feeding time (=13 h = 780 min)
CROPd g DM.d-1 Feeding rate constraint on daily food intake
Cd g DM.d-1 Daily food intake
CCi g DM.d-1 Daily CC intake
CWi g DM.d-1 Daily CW intake
pCCi   Proportion of CC ingested (0 <= p <= 1)
pCCs   Proportion of CC in the sward (0 <= p <= 0.45)
NDF g.kg-1 Proportion of CW in the standing biomass
DOM g.kg-1 Observed in vivo digestibility of organic matter
INDF g.kg-1 Indigestible fraction
PED g.kg-1 Potential extent of digestion
PDCWd g DM.d-1 Potentially digestible cell wall intake
k2 h-1 Rate of digestion of CW
CCa g DM.d-1 Assimilated (digested) CC
CWa g DM.d-1 Assimilated (digested) CW
eCC MJ.g-1 Energy content of CC = 0.041
eCW MJ.g-1 Energy content of CW­ = 0.0185
ECC MJ.d-1 Energy intake from CC
ECW MJ.d-1 Energy intake from CW
GEd MJ.d-1 Gross energy content of digested food
FEd MJ.d-1 Energy content of faeces
UEd MJ.d-1 Energy content of urine
PEd MJ.d-1 Energy content of methane
MEd MJ.d-1 Energy intake available to metabolism
r MJ.kg-1 Work of rumination per kg ingested fibre
Er MJ.d-1 Total work of rumination
Eh MJ.d-1 Heat production due to fermentation and digestion
HEd MJ.d-1 Heat increment
Ebasal MJ.d-1 Basal energetic requirements of a fasting, inactive animal
NEd MJ.d-1 Net energy available for maintenance and growth
Eact MJ.d-1 Activity allowance
Emaint MJ.d-1 Maintenance requirement
Gd Emaint Profit, or energy available for growth, as multiples of maintenance


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