actating Friesian cows with body weights, ranging from of 480 to 600 kg

::‘my distributed into four similar groups (three for each group). The

rations were formulated as foiows ration I (R: 50 % concentrate

(CFM) + 50 % clover hay CH, ration 2 (R2): 50 % CFM +10% CH+40 %

rice straw (ARS), ration 3 (R3): 50 % CFM + 20 % CH + 30 % ARS. and

4): 50 % CFM +50 % ARS . These proportions were chosen to achieve

rations containing about 12-15% CP necessary for optimal and

of roughages ¡n the rumen. The target cf 12-15% CP in each

diets was achieved ¡n all diets since the ingredients were analysed

iulating the experimental diets. The apparent digestibility of CF, NDF, ADF,

ADL and unavailable NDF (UNDF) were significantly (p < 0.05) higher with

ammoniated rice straw as the only roughage or when combined with clover

feeding on clover hay alone, the DCP% was significantly (p < 0.O5) higher

D— was used or supplemented with ARS than feeding on ARS alone. The

.e reed value (RFV) was significantly (p < 0.05) higher when feeding on 50% CH

:s CH + 30% ARS than feeding on 50% ARS or 10% CH + 40% ARS, while the

feed quality (RFQ) and quality index (QI) values were higher (pcO.05) when

z ; on 50% CH than the other ones. The TDN/CP ratios were significantly

: 5) higher when feeding on ARS with or without CH.

The effective NDF (eNDF) values ranged from 42.44 to 49.67 with different

:rs.. The highest value (pcO.O5) was recorded when feeding on 10%CH + 40%

general, the data indicated that the substitution of clover hay by ammoniated

-c straw at a level of at least 10% (DM basis) would provide adequate fermentable

‘ as well as fermentable fiber, and above this level of clover hay may not be

-ecessary. The increase in DM intake when feeding on CH alone might have affected

::er digestion because of an increase in the rate of passage of digesta.