Straw

Inadequate production of green fodder in the country compelled the farmers to utilize dry roughages as livestock feed particularly for the ruminants. In one estimate, it has been found that in the country, there are about 310 million tones of these dry roughages produced annually. Among these straw, bhusa, karbi and hay are noteworthy. In all developed countries, feeding of high quality hay is in practice. Due to unavailability of high quality dry roughages, straw, bhusa and karbi form  the major  bulk  of  livestock feed in India. Obviously, feeding of inferior  quality dry roughage is reflected in low productivity of animals.

Farmers utilize these poor quality dry roughages as energy feed, which unfortunately varies between 40-50% in digestible energy. Voluntary intake of animals is so low that it is barely sufficient to yield adequate energy to meet their maintenance needs. For some roughages, more energy are spent by the animal in chewing and digesting the roughages than what the animal derives from the dry roughages. 

The poor nutritive value of these roughages may be attributed to the following facts:

1.  The  digestibility of straw is limited  due  to the  formation of strong physical and/  or chemical bonds between  lignin and the structural  polysaccharides  (hemicellulose and  cellulose).  Although cellulose   by  itself  has  a  highly   ordered   crystalline structure,  it has very strong association with lignin with the result that even most the potent cellulosic enzymes can not have easy access to the cellulose unless the bondage between  lignin and cellulose is broken. The lignin thus acts as a barrier in the efficient utilization  of cellulosic  plant materials even as a source of energy. Whether,  the inhibitory  mechanism  involves  the presence  of  ligno-cellulosic or ligno-hemicellulosic  chemical  bonds  or  the  three  dimensional  macromolecular lignin  network  by  itself  acts as a protective  barrier in the efficient  utilization  of cellulose  as a source of energy is yet fully  understood  and established

2. Crystalline   structure   of   cellulose   is   also   responsible   for   low   digestibility   of cellulose

3.  Highly   deficient  in  other  nutrients  like  minerals,  vitamins,  fatty   acids  and   in proteins. The minimum  crude protein requirement for efficient lignocellulose breakdown  of roughages  fed as the sole diet is claimed to be from  3.8-5.0%

4. High  silica  content of straws known to  depress  organic matter digestibility

5. Due  to  dustiness of straw, the  total  intake  is markedly affected