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irradiation. These processes promote physical changes in rice straw, such as reducing particle size, which lessens rumination time for the animal; enriching softness
of the straw’s fibrous components to make it more palatable to the animal; and
hastening nutrient digestion.
Soaking is a common and economical process of treating rice straw. This is being
done by soaking straw overnight in water which brings softness between the of
lignin and cellulose component of rice straw. Soaking of straw promotes higher
intake of the animal as well as nutrients digestibility. Soaking along with steaming
technique have direct effect on the cell walls delignification of rice straw, (Walker
1984). The effect of steam or exposure of the lignocellulosic contents of rice straw
under high pressure provides a good environment for the microbial enzymes for
faster fermentation of nutrients, thus increasing the rice straw digestibility (Walker
1984). Milstein et al. (1987) suggested that heat treatment leads to an increase in
cellulose digestibility from 20% to 40%.
Grinding, chopping or pelleting had beneficial effects in breaking down the cell
wall contents of rice straw. These physical processes reduced the particle size of the
straw thus, providing easy entries or access of the rumen microorganisms for degradation. The use of these techniques should properly consider the balance between
the particle size and the retention time or passage rate of the ingested treated straw.
The reduction in particles due to grinding or chopping of rice straw promotes animal intake and increase passage rate of the feed, however, this brings negative effect
in terms of decreasing the nutrients digestibility of straw. This is because of the less
time exposure of the feed materials for rumination and for microbial fermentation
in the rumen.
Pressure steaming rice straw is another process to consider. However, the process
may add cost for farmers due to the energy required during process. Rangnekar
et al. (1982) and Liu et al. (1999) have tried steam treatment under high pressure of
15 bar for 5 min at a moisture level varying between 30% and 70% (w/w) using different roughages and rice straw. They observed that the different fractions of rice
straw, such as hemicellulose, cellulose, lignin, and sugars were separated by steam
pressure. Similar observations were also reported by Ooshima et al. (1984) when
irradiated rice straw was subjected to 84% water content in microwaves (2450 MHz)
using sealed glass vessels with accessible partitions into cellulosic materials and
with increase digestible nutrients of the straw.
7.3.2 Chemical Treatment
The chemical method to improve the nutritive value of rice straw has been done for
more than 100 years (Kamstra et al. 1958) with the aim to increase animals’ intake
and feed digestibility. The chemicals, which are commonly studied and used in
treating rice straw to improve its palatability, intake, and digestibility, are sodium
hydroxide, ammonia, and urea. The mode of action of these chemicals is to break
the links between the lignin-cellulose structures of the straw, which are sensitive
D. Aquino et al.
irradiation. These processes promote physical changes in rice straw, such as reducing particle size, which lessens rumination time for the animal; enriching softness
of the straw’s fibrous components to make it more palatable to the animal; and
hastening nutrient digestion.
Soaking is a common and economical process of treating rice straw. This is being
done by soaking straw overnight in water which brings softness between the of
lignin and cellulose component of rice straw. Soaking of straw promotes higher
intake of the animal as well as nutrients digestibility. Soaking along with steaming
technique have direct effect on the cell walls delignification of rice straw, (Walker
1984). The effect of steam or exposure of the lignocellulosic contents of rice straw
under high pressure provides a good environment for the microbial enzymes for
faster fermentation of nutrients, thus increasing the rice straw digestibility (Walker
1984). Milstein et al. (1987) suggested that heat treatment leads to an increase in
cellulose digestibility from 20% to 40%.
Grinding, chopping or pelleting had beneficial effects in breaking down the cell
wall contents of rice straw. These physical processes reduced the particle size of the
straw thus, providing easy entries or access of the rumen microorganisms for degradation. The use of these techniques should properly consider the balance between
the particle size and the retention time or passage rate of the ingested treated straw.
The reduction in particles due to grinding or chopping of rice straw promotes animal intake and increase passage rate of the feed, however, this brings negative effect
in terms of decreasing the nutrients digestibility of straw. This is because of the less
time exposure of the feed materials for rumination and for microbial fermentation
in the rumen.
Pressure steaming rice straw is another process to consider. However, the process
may add cost for farmers due to the energy required during process. Rangnekar
et al. (1982) and Liu et al. (1999) have tried steam treatment under high pressure of
15 bar for 5 min at a moisture level varying between 30% and 70% (w/w) using different roughages and rice straw. They observed that the different fractions of rice
straw, such as hemicellulose, cellulose, lignin, and sugars were separated by steam
pressure. Similar observations were also reported by Ooshima et al. (1984) when
irradiated rice straw was subjected to 84% water content in microwaves (2450 MHz)
using sealed glass vessels with accessible partitions into cellulosic materials and
with increase digestible nutrients of the straw.
7.3.2 Chemical Treatment
The chemical method to improve the nutritive value of rice straw has been done for
more than 100 years (Kamstra et al. 1958) with the aim to increase animals’ intake
and feed digestibility. The chemicals, which are commonly studied and used in
treating rice straw to improve its palatability, intake, and digestibility, are sodium
hydroxide, ammonia, and urea. The mode of action of these chemicals is to break
the links between the lignin-cellulose structures of the straw, which are sensitive
D. Aquino et al.