Four, lactating dairy crossbreds (50%50% Holstein FriesianNative Zebu cattle) were randomly assigned according to
a 22 factorial arrangement (two protein levels and two levels of mangosteen peel pellets (Mago-pel)) in a 44 Latin square design to
receive four dietary treatments. All cows received concentrate at a proportion of 1 kg concentrate per 2 kg of milk yield, and urea-treated
5% rice straw (UTRS) was given ad libitum. It was found that total dry matter intakes, nutrient digestibility, ruminal pH and NH3
-N
concentrations were not affected (p>0.05) by treatments. Concentrations of ruminal pH and NH3
-N were not affected by dietary
treatments although the concentration of BUN varied significantly (p0.05); however, copy numbers of Ruminococcus flavefaciens was increased when protein level increased (p