Ground Rice Straw Research Articles

N-butylamine and acid-steam explosion pretreatments of rice straw and hardwood: Effects on substrate structure and enzymatic hydrolysis

Without pretreatment, ground rice straw and hardwood substrates are poorly hydrolysed by cellulase (<10%), even though untreated rice straw has a large pore volume accessible to cellulase (0.5–0.9 ml g −1), while hardwood has a much lower value (0.05 ml g −1). Hence the pore volume accessible to cellulase may be necessary but is not sufficient. Partial acid hydrolysis with explosive decompression (PAHE) removes the hemicellulose and modifies, but does not remove the lignin. PAHE increases the pore volume accessible to cellulase of the hardwood from <0.05 to 0.5–0.6 ml g −1. PAHE at 200 or 220°C removes more than 90% of hemicellulose in both substrates. Pretreatment with n-butylamine (nBA) partially removes the lignin but not the hemicellulose. The latter pretreatment was more effective on rice straw (70% hydrolysis by cellulase in 48 h) than on hardwood (about 40% in 48 h). Both pretreatments greatly increase the initial rate of cellulase hydrolysis of rice straw.

Passage and rumination of inert particles varying in size and specific gravity as determined from analysis of faecal appearance using multicompartment models

Plastic particles of defined length (2, 5 mm) and specific gravity (sp.gr. 1.10, 1.34, 1.77) were administered just before feeding into the reticulo-rumen of four cattle and four swamp buffaloes given a diet predominantly of rice straw ad lib. Simultaneously, doses of ground rice straw marked with Cr and Yb were likewise given. Plastic particles were recovered from faeces for 12 d after dosing, and divided into non-ruminated (NR) and ruminated (R) particles. Excretion data of plastic particles were interpreted using a four-pool model incorporating passage of NR (kp) and R from the reticulo-rumen, post-ruminal passage, rate of chewing (kr) and two lag times. An inverse relationship was found between kr and sp.gr. The kr was higher for 5 mm than that for 2 mm particles. In contrast, kp was greatest for particles of sp.gr. 1.34, with higher kp for 2 mm than for 5 mm particles. Rates of passage and rumination (kp, kr) were higher for buffaloes than for cattle. Rumination time was related to kr, most highly (r2 0.96) with kr of 2 mm, 1.10 sp.gr. particles. Fragmentation of 5 mm particles by rumination tended to increase the rate of passage from the rumen. Ruminal passage rates of Yb and Cr markers were poorly correlated with each other and with kp of any of the plastic markers. Reanalysis of published data from plastic particle studies supported the relationships between sp.gr., size, kp and kr.(ABSTRACT TRUNCATED AT 250 WORDS)

The response of rice seedlings to O2 released from CaO2 in flooded soils

The efficacy of CaO2 as an oxygen-supplying seed coating on the emergence of rice seedlings from flooded soils was studied. Seedling response became increasingly dependent on coating rates of 0–40% (by weight of seed loading with 60% CaO2 material) as the depth of planting increased from 0–2.5 cm. No emergence occurred from 5 cm. The emergence response to 40% CaO2 at 1.5 cm depth of planting was inhibited by the presence of 0.25% finely ground rice straw but was stimulated by increasing pH levels. The organic substrate likely increased microbial competition for available O2 while increasing pH levels improved the rate of CaO2 dissolution during the day 2–8 period of germination. Soil type effects on seedling response were speculated to be due to differences in O2 consumption rates between soils. The addition of CaO to the CaO2 coating improved the emergence response on an unlimed acid soil.

Moisture Absorption, Mold Growth, and Decomposition of Rice Straw at Different Relative Humidities1

AbstractMoisture and humidity relationships of rice straw are important in relation to the extent of decomposition that may occur during the winter season. Ground rice straw was exposed to constant relative humidities to measure moisture absorption, decomposition, and mold growth. Moisture absorption by rice straw was very rapid during the first few hours and approached equilibrium within 1 to 4 days depending upon the relative humidity. Moisture content at equilibrium at a given relative humidity was always greater at 8 than at 25 C. The relation between moisture absorption and relative humidity above 70% followed a parabolic function of the form M = a + bR + cR2 where M = % moisture, R = relative humidity, and a, b and c are constants. The rate and extent of straw decomposition were found to increase and the lag period of decrease with increasing relative humidity and temperature. The transition between slow and active decomposition of rice straw was at about 90% relative humidity. The threshold moisture content of rice straw for mold growth, defined as the highest moisture content at which it takes infinite time for the initiation of fungal growth, was found to be 7.5%.

Level and Form of Rice Straw in Steer Rations

Two feedlot trials were conducted to study the performance of steers fed rations containing different levels, forms and grinding screen size of rice straw. Steers receiving 20% ground rice straw consumed more concentrate and gained faster resulting in heavier carcasses than steers fed 20% pelleted or long rice straw or 5% ground, pelleted or long rice straw (P<.05). There was no significant differences in the concentrate intake, gains or carcass weight of steers fed 5% rice straw in any form or long or pelleted rice straw fed at the 20% level. The performance of steers fed 5% rice straw and all-concentrate rations was similar. The size of the grinding screen had no significant influence on performance of steers fed 5 or 20% rice straw rations. Molasses levels of 10 or 25% did not appear to influence gain or carcass weight but feed efficiency was slightly decreased when 25% molasses was included in the 20% rice straw ration. Ruminal fluid from steers fed 20% ground rice straw was higher in acetate and lower in propionate for steers fed 5% rice straw or all-concentrate rations. There was very little difference in ruminal fluid due to the grinding screen size or molasses level.