Available information on the effect of ruminal pH on degradation of crude protein of various feeds is scarce. It has been reported that in a high concentrate diets, protein degradation is usually reduced (Molero et al., 2004). This reduction has been attributed to lower ruminal pH, which causes the changes in protein solubility (Loerch et al., 1983) and reduces fibrolytic activity of rumen microflora. There is also limited information concerning the requirements for rumen degradable N (RDN) when high-grain diets are given to steers, and most of that information has been obtained using urea as the source of RDN. The aim of the present experiment was to evaluate the effect of different concentrate to lucerne hay ratios (60:40, 70:30, 80:20 or 90:10) on ruminal crude protein degradation kinetic of lucerne hay, barley grain, soybean meal and fish meal

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