Abstract
A series of trials has been carried out to determine the level of voluntary intake and digestibility of clipped orchardgrass and alfalfa fed at several growth stages to wethers. The rectilinearity of the relationship between digestible crude protein intake (Y_<DCPI> : g/kg^<0.75>) and crude protein intake (X_<CPI> : g/kg^<0.75>) : Y_<DCPI>=a + b X_<CPI> and the curvilinearity of the relationshipe between crude protein digestibility (Y_<CPD> : %) and crude protein intake (X_<CPI> : g/kg^<0.75>) : Y_<CPD>=b + a/X_<CPI> seem to be the result of certain interrelationships among the potential crude protein digestibility (=b) and excretion of delayed residues flow through gastrointestinal tract (=a). The regression equations are shown below : orchardgrass : YD_<CPI>=-1.2 + 0.82 X_<CPI,> (r=0.99, p < 0.01, n=102) Y_<CPD>=78 - 87/X_<CPI>, (r=-0.94, p <0.01) alfalfa : Y_<DCPI>=-1.8 + 0.88 X_<CPI> (r=0.99, p < 0.01, n=55) Y_<CPD>=88 - 167/X_<CPI>, (r=-0.78, p <0.01) The fill of undigested crude protein (UCPF : g/kg^<0.75>) would equal the crude protein excretion added to (a). The rate of passage (Kp) can be represented by Kp=crude protein excretion/UCPF The rate of digestion (Kd) can be represented by Kd=(crude protein intake - UCPF × Kp)/UCPF Metabolic fecal crude protein excretion (MFCPE : g/kg^<0.75>) can be represented by MFCPE=a + (true digestibility - potential digestibility) × crude protein intake Estimated average values of total amount of crude protein present in the gut (fill), Kp, Kd and true digestibility (TD) are shown below : orchardgrass : fill=7.8 g/kg^<0.75>, Kp=0.69, Kd=1.40, TD=92% alfalfa : fill=10.8 g/kg^<0.75>, Kp=0.69, Kd=2.45, TD=96%
