From UPSC perspective, the following things are important :
Prelims level : Not much
Mains level : Paddy straw as animal fodder
Punjab has now proposed to use the paddy crop residue as fodder for animals, especially cattle.
Why such a move?
- In Punjab, the total availability of paddy straw is about 20 million tones per annum.
- The total value of this straw is Rs 400 crore approx., calculated on an average rate of Rs 200/quintal. Almost all of it is burnt in fields.
- This accounts for economic loss apart from the loss of 77,000 tonnes of nitrogen and 5.6 million tonnes of Total Digestible Nutrients (TDN) which could be used for ruminant production.
- Also nearly 30.4 per cent of rice straw is used for animal feed in Southeast Asia, Mongolia and China.
Economics behind paddy straw
- High silica and lignin content reduces its digestive properties.
- Higher selenium content in paddy straw also limits its use as fodder in animals as compared to wheat straw.
- However, if given in moderate quantities (up to 5 kg per animal per day), selenium poses no health hazard to the animal.
- Paddy straw also contains oxalates (2-2.5%) which leads to calcium deficiency so mineral mixture should always be fed along with the straw.
Treatments for feeding paddy straw to animals
- Paddy Straw cannot be directly fed to animals. It has to undergo some treatments.
- Two of them are: Urea-only treatment and urea plus molasses treatment.
[A] Urea treatment of paddy straw
- 14 kg of urea is dissolved in 200 litres water and spray on chopped paddy straw.
- The fermented straws have soft texture with 6.0-8.0 per cent crude protein, 3.0-4.0 percent DCP and 55-60 per cent TDN.
- This involves a combination of physical, chemical and biological treatments.
- The paddy straw is chaffed and moistened (physical) with urea solution (chemical).
- The breakdown of urea release ammonia gas, a part of which is utilised by microbes (biological) for their proliferation (enriching the straw with microbial protein).
- This in turn results in breakage of lingo-cellulosic bonds making cellulose and hemi-cellulose assessable for utilization by microbes in the rumen.
- The digestibility of cellulose increases from 40-45% in untreated paddy straw to 70-75 per cent in fermented wheat straw.
[B] Urea plus molasses treatment
- Also called “Urea-Molasses impregnated straw”, this method involves treating paddy straw with urea and molasses.
- Urea 1 kg and molasses 3 kg was mixed thoroughly and mixed with water 10 kg. This is mixed with chaffed paddy straw and fed to animals on same day.
- The experts however clarify that for maintenance of body weight in animals, paddy straw alone is not sufficient.
- Minerals and green fodder supplementation is required.
How does the nutritional value of paddy straw increase after urea treatment?
- The TDN values in urea treated paddy straw increased manifold as compared to untreated straw.
- Crude protein (CP) increased from 4.5% to 8%, digestible crude protein (DCP) from 1.5% to 4% and total digestible nutrients (TDN) from 40% to 55%.
- The feeding of urea treated straw (6 kg/day) to lactating buffaloes giving about 10 kg milk/day can result in saving about 60 per cent of oilseed cake in the ration.
- Feeding of paddy straw should be mixed with berseem, cowpea or Lucerne as it forms a maintenance ration.
- The straw should be fed with concentrate mixture and additional DCP or limestone should be given to the animals to reduce the effect of oxalates.
- Oxalates also interfere in carbohydrate metabolism perhaps due to non-availability of calcium as cofactor.
What are the potentially harmful effects?
- The intake of siliceous forages has been associated with urinary siliceous calculi in drier regions where water may be limited.
- There have been no definitive studies in India, but urinary calculi are associated with rice straw consumption.
- It has high selenium (0.5 to 4.5 % ) content which can cause serious health problems in dairy animals.