|Bioconversion of Organic Residues for Rural Communities (UNU, 1979)|
|Indian experience with treated straw as feed|
A simple method of treating straw with alkali has recently been developed that can boost the rate of gain of growing animals and the output of adult stock substantially and cheaply. The digestibility of straw is low - only 40 - 50 per cent - and thus it does not give much energy to the animals that eat it. The alkali treatment of straw increases digestibility to 50 - 60 per cent. Animals also eat 10 - 20 per cent more of the treated straw. As a result they get much more energy (up to 50 per cent more) when straw is treated.
The method of treatment is simple and requires nothing more than a garden sprinkling can, a hay fork, a pair of rubber gloves, and a pair of goggles. The latter two are for safety, as caustic soda can burn the skin and eyes if it splashes. Care must, therefore, be taken in handling it. In case of accident, the affected area should be immediately washed with large amounts of clean water Once the alkali is sprinkled on the straw it is no longer harmful. The straw must be broken or chaffed in order to be treated uniformly and easily. The straw to be treated is piled onto a pucca floor. One man sprinkles the caustic soda solution over the straw and another man turns the pile simultaneously with the hay fork. It is important to achieve uniform wetting of the straw.
The caustic soda solution can be made from solid flakes or from a lye solution. The latter contains 50 - 60 per cent caustic soda and is less difficult to handle when making up the solution for treatment, but must be stored and transported in drums, which is not as convenient as handling caustic soda flakes in bags. Usually the cost of caustic soda (dry flakes equivalent) is less, often only half the cost, in the form of lye than in the form of flakes, and for this reason is preferred. If flakes must be used, it is advisable to make up a 50 per cent stock solution in a drum; this makes the daily preparation of the dilute solution used in treatment more convenient. For treating the straw, make up a 2 per cent (2 kg/100 I) solution of flakes, or a 4 per cent (4 kg/100 I) solution of lye. Two litres of solution are needed for each kilogramme of straw. The sprayed straw will be moist, dark yellow in colour, and have a slight smell of caustic soda. A fresh batch should be prepared every day, though it should not be fed until 24 hours after it is treated. This is because the caustic soda continues to react slowly with the straw for 24 hours. Other feeds should be mixed with the treated straw only at the time of feeding it.
In order to obtain the maximum benefit from treated straw, it should further be treated with urea. The urea should be made into a solution (1 kg/10 1) and sprinkled on the straw at the rate of 1 1/10 kg of straw just before feeding. A complete mineral mixture should also be added to the diet.
Experiments have shown that a combination of alkali and urea treatment of straw can boost the daily rate of gain in growing stock by at least 0.2 kg/day. This will be equivalent to doubling the rate of weight gain or more, which means a much earlier first calving for heifers and start of working life for bullocks.
These recommendations are for average animals. Those fed large amounts of concentrates and/or green forage may not respond to straw treatment unless the amount of alkali is increased. If straw constitutes only about half of the diet (on a dry-feed equivalent basis), it should be treated with a 4 per cent solution of caustic soda flakes or an 8 per cent solution of lye. All additional feeds should be mixed at the time of feeding. Urea treatment may be dispensed with. A mineral supplement will, however, still be desirable.
Animals given treated straw will need to drink more water than usual, and provision should be made for this.