Rumen degradability of urea treatment rice straw in ruminants

Abstract

Rice straw, both its leaves and stems, could be an important product of the harvest of rice to be used in animal nutrition because of its high availability. Increasing regulations and restrictions on the practice of burn rice straw have stimulated the exploration of other purposes for such straw, including animal feeding. The in-situ method has been widely used in the evaluation of the ruminal degradability rate of several animal feeds. The objective of this study was to evaluate the effect of urea addition on the dry matter (DM) degradability of rice straw. Six levels of urea addition were tested: 0, 5, 10, 20, 30 and 40 g kg DM-1. The rice straw was chopped to 2.0 cm long pieces or grinded to 2.0 mm particles and incubated in presence of urea for 10 days at a moisture content of 66% at a temperature of 40 °C to simulate optimum environmental conditions. Eight fistulated Holstein Friesian cows were used to study the Dry Matter Digestibility at 48 and 96 hours, and were separated into two groups: one fed with a High Ruminal Activity (AAR) diet based on 5 kg of lucerne (Medicago sativa L) hay, ad libitum forage mixture (made of Pennisetum clandestinum Hochst. ex Chiov, Lolium perenne L and Dactilys glomerata L) and 1.8 kg of concentrate, per day. While the other group received a Low Ruminal Activity (BAR) diet composed only of the ad libitum forage mix and the concentrate. Degradability data was analyzed using a Stepwise Multiple Regression. The results show that degradability of DM increases with higher levels of urea addition, the same as with the AAR diet and with higher ruminal incubation time. Different particle sizes didn’t show any difference. The conclusion is that this straw could be an important fiber source for ruminants if treated with urea, especially in the tropical region.