Urea treatment of rice straw: A modelling approach of its degradation kinetics in the rumen

Abstract

This study aimed to compare between rice straw and urea-treated rice straw with regard to their chemical composition and degradation kinetics in the rumen by employing a modelling approach. Data were collected from various journal articles that comprised of chemical composition (crude protein [CP], neutral detergent fiber [NDF], acid detergent fiber [ADF] and lignin) and degradation kinetic parameters of organic matter (soluble fraction, degradable, undegradable, degradation rate and lag time). Comparison was performed by using a statistical mixed model methodology in which treatments (control vs urea-treated rice traw) were considered as fixed effects whereas different studies were considered as random effects. These data were then used as parameters to build a dynamic model of rice straw degradation in the rumen. Results showed that urea treatment increased CP (P<0.001) while decreased NDF (P<0.01) contents of rice straw. The ADF and lignin contents were similar between the control and urea-treated rice straw. Proportion of degradable fraction and degradation rate of rice straw were enhanced due to urea treatment (P<0.001). However, the treatment did not influence soluble fraction and lag time of the material. Microbial biomass and total volatile fatty acid production in the rumen changed dynamically over time and the values were higher for the urea-treated rice straw.