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under alkaline or acidic conditions. Among the chemicals used, alkali agents are
extensively explored and practically accepted under farm conditions. During straw
treatment, basic chemicals, such as sodium hydroxide, urea, or ammonia are
absorbed into the cell wall and react with the lingo-cellulosic contents of the straw
to break the ester bonds between lignin and hemicellulose and cellulose. The alkali
absorbed into the straw directly causes the structural fibers to swell making it free
for microbial fermentation (Chenost and Kayouli 1997; Lam et al. 2001).
7.3.2.1 Sodium Hydroxide (NaOH) Treatment
The use of NaOH in the treatment of cereal straw has been done since the 1940s
(Mcanally 1942). The straw is treated using 1.5% NAOH w/w for 24 h in a container. The treated straw is rinsed with cold water and subjected to in vitro digestibility. Results showed that the NAOH treated straw is more digestible than the pure
straw by as much as 28%. The Beckman method, which is similar to the procedures
of Mcanally (1942) for the NAOH treatment of straw, has been recommended by
FAO (2012). The Beckman method also uses 1.5% NAOH but the treatment period
is within 18–20 h before rinsing with tap water. The NAOH acts on the straw by
reducing proteolysis and increasing delignification by unlocking the linkage
between the lignin and cellulosic contents of the straw to give more time for microbial enzymatic action to take place. Treatment of rice straw and other crop residues
using NAOH has been reviewed by Jackson (1977), Berger et al. (1994), Arieli
(1997), and Wang et al. (2004). These authors concluded that chemical reactions of
NAOH on the cell wall contents of rice straw is advantageous for the breakdown of
the esterified bonds between the phenols group and the cellulosic components of
straw thus favoring the enzymatic hydrolysis.
Feeding NAOH-treated straw in cattle showed better performance than ammonia
treatment of straw. Similar improvement in animal performance was also reported
by Chaudhry and Miller (1996) and Vadiveloo (2000) when NAOH-treated rice
straw was fed to cattle compared to untreated straw. This was due to the improvement in palatability and intake of the animals and increase in digestibility of treated
straw. The adoption of NaOH treatment of rice straw, however; is not widely practiced by farmers. This is because NAOH costs more than urea treatment and it is not
always available. In addition, NaOH, when used at higher concentrations, poses
health problems for animals if the amount exceeds 10 g of the daily sodium requirement of mature animals. It can also cause pollution problems due to sodium accumulation in the environment (Sundstol and Coxworth 1984).
7.3.2.2 Ammonia (NH 3 ) Treatment of Rice Straw
Treating rice straw using anhydrous and aqueous ammonia, urea, and other
ammonia- releasing substances have been investigated and have been proven to
enhance the degradability of the straw (Abou-EL-Enin et al. 1999; Selim et al. 2004;
7 Rice Straw-Based Fodder for Ruminants
under alkaline or acidic conditions. Among the chemicals used, alkali agents are
extensively explored and practically accepted under farm conditions. During straw
treatment, basic chemicals, such as sodium hydroxide, urea, or ammonia are
absorbed into the cell wall and react with the lingo-cellulosic contents of the straw
to break the ester bonds between lignin and hemicellulose and cellulose. The alkali
absorbed into the straw directly causes the structural fibers to swell making it free
for microbial fermentation (Chenost and Kayouli 1997; Lam et al. 2001).
7.3.2.1 Sodium Hydroxide (NaOH) Treatment
The use of NaOH in the treatment of cereal straw has been done since the 1940s
(Mcanally 1942). The straw is treated using 1.5% NAOH w/w for 24 h in a container. The treated straw is rinsed with cold water and subjected to in vitro digestibility. Results showed that the NAOH treated straw is more digestible than the pure
straw by as much as 28%. The Beckman method, which is similar to the procedures
of Mcanally (1942) for the NAOH treatment of straw, has been recommended by
FAO (2012). The Beckman method also uses 1.5% NAOH but the treatment period
is within 18–20 h before rinsing with tap water. The NAOH acts on the straw by
reducing proteolysis and increasing delignification by unlocking the linkage
between the lignin and cellulosic contents of the straw to give more time for microbial enzymatic action to take place. Treatment of rice straw and other crop residues
using NAOH has been reviewed by Jackson (1977), Berger et al. (1994), Arieli
(1997), and Wang et al. (2004). These authors concluded that chemical reactions of
NAOH on the cell wall contents of rice straw is advantageous for the breakdown of
the esterified bonds between the phenols group and the cellulosic components of
straw thus favoring the enzymatic hydrolysis.
Feeding NAOH-treated straw in cattle showed better performance than ammonia
treatment of straw. Similar improvement in animal performance was also reported
by Chaudhry and Miller (1996) and Vadiveloo (2000) when NAOH-treated rice
straw was fed to cattle compared to untreated straw. This was due to the improvement in palatability and intake of the animals and increase in digestibility of treated
straw. The adoption of NaOH treatment of rice straw, however; is not widely practiced by farmers. This is because NAOH costs more than urea treatment and it is not
always available. In addition, NaOH, when used at higher concentrations, poses
health problems for animals if the amount exceeds 10 g of the daily sodium requirement of mature animals. It can also cause pollution problems due to sodium accumulation in the environment (Sundstol and Coxworth 1984).
7.3.2.2 Ammonia (NH 3 ) Treatment of Rice Straw
Treating rice straw using anhydrous and aqueous ammonia, urea, and other
ammonia- releasing substances have been investigated and have been proven to
enhance the degradability of the straw (Abou-EL-Enin et al. 1999; Selim et al. 2004;
7 Rice Straw-Based Fodder for Ruminants