Three, multiparous Holstein crossbred dairy cows with initial body weight of 385±19 kg were
randomly allocated to 3 treatments of rice straw (T1 = untreated rice straw; T2 = 5.5% ureatreated
rice straw(5 g urea in 100ml water to 100 g air-dry (91% DM) straw); T3=2.2% urea+
2.2% calcium hydroxide treated rice straw (2.0 g urea and 2.0 g Ca(OH)2 in 100 ml to 100 g airdry
(91% DM) straw) according to a 3×3 Latin square design. Each period lasted for 21 days in
which feed, feces and rumen fluid were collected during the last 7 days for chemical analyses.
The findings revealed significant improvements in dry matter intake and digestibility by using
5.5% urea-treated rice strawand 2.2% urea+2.2% calcium hydroxide treated rice straw. Ruminal
pH and NH3-N were found higher (Pb0.05) as compared with urea-treated rice straw fed
group, while blood urea nitrogen and milk urea nitrogen were in normal ranges. Volatile fatty
acid concentrations especially those of acetic acid were decreased (Pb0.05) and those of
propionic acid were increased (Pb0.05), thus acetic acid:propionic acid was subsequently
lowered (Pb0.05) in cows fed with 5.5% urea-treated rice straw and 2.2% urea+2.2% calcium
hydroxide treated rice straw, respectively. Moreover, ruminal viable and cellulolytic bacterial
counts were enhanced by urea and calcium hydroxide treatments. Milk protein and fat
concentrations were additionally increased by respective treatments while 3.5% fat-corrected
milk was highest; ranking from 2.2% urea+2.2% calcium hydroxide treated rice straw, 5.5%
urea-treated rice strawand urea-treated rice strawfed groups. Based on this study, implications
could be made that using 2.2% urea+2.2% calcium hydroxide treated rice straw for straw
treatment could be an alternative treatment to 5.5% urea treatment with regards to its
effectiveness and treatment cost for lactating dairy cows.