Improving Nutritional Qualities Of Straw With Urea

Straws are the main source of roughage for feeding ruminants in the tropics but do not supply sufficient nutrients even for maintenance of the animals. Efforts have been made in different parts of the world to improve the nutritional quality of straws, using various treatments. Among these, substantial research has been conducted on the urea treatment of straws, writes T Walli, Chief Technical Advisor at the National Dairy Research Institute, India.
calendar icon 5 July 2011
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While the developed countries used direct ammoniation process for treating straws, urea treatment was suggested as its cheaper version for the tropical countries. Studies were carried out on optimising conditions e.g. the urea level, moisture content, duration of the treatment, shape of the stack and the type of cover/covering material.

The treatment increased crude protein (CP) and energy content of straw resulting in increased straw intake, growth rate and the milk yield of the animals. It appeared to be a cost-effective technology and the farmers were satisfied with the results as long as the nutritionists and the extension specialists were involved with the on-farm trials.

However when the farmers were left on their own, they stopped treating their straw. Only some farmers with larger herds and a lack of green fodder continued with this technology. The major constraints to use of the technology were the cumbersome and labour-demanding aspects of treatment, marginal returns, requirements of large quantities of clean water and covering material, and spoilage of straw if not properly covered. If the spraying of the urea solution could be mechanised, the adoption of this technology would increase.


To improve the nutritive value of fibrous crop residues, urea treatment of straw was developed as an alternative to caustic/corrosive sodium hydroxide treatment, for use mostly in tropical countries.

A large number of on-station and on-farm trials conducted in several countries under different conditions have shown that feeding urea-treated straw vis-a-vis untreated straw increases feed intake by 10 to 15 percent, growth rate of calves by 100 to 150 g/day and milk yield by 0.5 to 1.5 litres/day.

Urea-treated straw is more palatable and digestible. The dry matter (DM) digestibility increases by approximately 10 per cent, the total digestible nutrient (TDN) value increases by 10 to 15 per cent and the CP content increases almost three times. The feedback received from the farmers involved in on-farm trials has been largely positive. In spite of the technology appearing to be quite sound, it was almost entirely rejected by livestock farmers in the tropical region, barring some exceptional situations (Walli et al., 1988; Schiere and Nell, 1993).

Experiences of Applying Technology/ Practice In the Field

During the mid-seventies when it became clear that sodium hydroxide, a strong alkali, is capable of breaking the ligno-hemicellulosic bonds in straw and making it more digestible, scientists started looking for less corrosive alternatives to sodium hydroxide.

During the eighties, some developed countries used ammoniation for upgrading straw. However a cheaper version of ammoniation i.e. urea treatment was suggested for the developing countries of the tropical region because urea was easily available, given to farmers at cheaper/subsidised rates and is readily hydrolysed to ammonia under the warmer tropical climate (Saadullah, Haque and Dolberg, 1981).

A number of national and international research projects on urea treatment of straw were undertaken in Asian countries, e.g. Bangladesh (DANIDA/IDRC/ ODA/ADAB/USAID), Malaysia (ABAB), Philippines (ADAB), Sri Lanka (ADAB/The Netherlands), Thailand (ADAB/IFS), Indonesia (ADAB) and India (Indo- Dutch) to optimise treatment conditions under their respective situations.

The research activities were mainly directed towards optimisation of urea and moisture levels and the duration of the treatment. The other aspects investigated were the method of spraying urea solution and the manner the stack has to be shaped and covered and with what kind of materials. On the basis of these studies, a broad consensus on using four per cent urea and keeping the moisture level at 40 per cent was developed. The duration varied from two to three weeks, depending upon the ambient temperature of the place, the duration being higher for the colder places (Walli et al., 1988).

Several institutions including National Dairy Research Institute (NDRI), Karnal, Southern Regional Station of NDRI, Bangalore, Bharatiya Agro Industries Foundation (BAIF), Pune and Pantnagar University of Agriculture and Technology, Uttrakhand were involved in the Indo-Dutch project in India.

The author was a part of the team working on this project at NDRI, Karnal. After conducting research on optimisation of the conditions for the treatment, we moved into the rural areas of Karnal for conducting on-farm trials.

This was during the year 1987–88, when India was facing a drought situation and we thought that it was an ideal situation to propagate the technology among the farmers. Normally, the dairy farmers around Karnal grow sufficient green fodder and are not keen to use the urea-treated straw.

Demonstration of urea treatment was carried out in 25 villages around Karnal and the farmers were asked to feed the treated straw in place of untreated straw. Feedback on feed consumption and milk yield was collected through personal observations and by interviewing the farmers.

Positive feed back from farmers. Out of the 54 observations collected for feed consumption, 76 per cent farms reported an increase in straw consumption and reduction of feed wastage. Out of the 32 observations on milk yield, 28 percent farmers reported 0.5 litre, 25 per cent reported 0.5–1.0 litre and 25 per cent reported 1.0–1.5 litre increases in yield.

The farmers could not monitor growth rates, but from visual observations they reported better growth and health condition of animals. The treated paddy straw was easier to chaff than untreated straw. While the untreated straw had to be given along with greens, the treated straw could be given as a sole source of roughage.

Negative feedback by farmers. After harvesting the paddy crop, the farmer has to prepare the field for the wheat crop, and there is neither the space available for drying of straw and nor the time for treating the straw. During the period when paddy straw is available, berseem (Trifolium alexandrinum), a leguminous fodder is available in plenty, and thus the effect of feeding treated-straw along with berseem gets masked.

Most of the farmers could not afford to purchase polyethylene sheets for covering the stack. The lack of proper cover caused wetness in the stack during rains, leading to fungal growth and spoilage of the straw. This also led to leaching of nutrients. It requires huge quantities of clean and fresh water @ 50 litres/100 kg of straw, which could be a constraint at times.

If water from a pond is used, it could result in spoilage of straw due to fungal infestation. For prepara- tion of the urea solution, which involves dissolving 4 kg of urea in 50 litres of fresh water, a drum of 100-litre capacity is required, which may not be available with the poor farmer. Preparing a stack of 2 500 kg of straw, apart from requiring 100 kg of urea and 1 250 litres of water, also needs at least three men for at least three hours to complete the process. All this appears to be a cumbersome and time consuming exercise and a costly affair for the poor farmer.

Some farmers did complain about the sticky dung from animals fed treated straw, which made the cleaning of the floor more time consuming. The pungent smell of ammonia coming from the treated straw was not liked by some farmers. Because of the higher consumption of urea-treated straw, the resource-poor farmers complained of rapid exhaustion of straw stocks and the need to purchase extra straw.

Status of application of technology/practice by farmers

Although the technology of urea treatment of straw is beneficial to the farmers, especially in terms of improving the productive performance of the animals, it was only partially successful in China and Vietnam. In these countries, the technology has been applied on a larger scale, as community projects on a cooperative basis.

Despite the beneficial effects observed by farmers themselves during on-farm trials, the discontinued use of urea treatment after initial demonstration has been disappointing. Even the best efforts made by the researchers and extension specialists have not been able to motivate farmers to adopt this technology. Most of the farmers around Karnal keep their dairy animals traditionally, i.e. to meet their milk requirement for home consumption and only the surplus milk is sold in the market.

A landless farmer possessing a few animals is not interested in using the technology of urea treatment of straw, as he allows his animals to go out for grazing on fallow lands and roadside grasses and does not want to incur any extra expenditure on the urea treatment. A farmer cultivating cash crops prefers to use urea for fertilising cash crops, rather than to use it for treating the straw. Urea treatment of straws could be adopted if:

  • Grasses and other greens are not available;
  • Straw is cheap and easily available;
  • Concentrates are relatively expensive;
  • Water is readily available;
  • Labour is cheap;
  • Farmer has good dairy farming skills;
  • Market for milk is available; and
  • Farmer gets good support price for milk.

Lessons Learnt

The most important constraints in the adoption of the urea treatment technology are its cumbersome and labour intensive nature and economic non-viability for the marginal and landless farmers. The returns are also marginal. The technology may prove to be successful if it is operated on a collective basis as a community project, as is done in China and Vietnam. It may be difficult for an individual resource-poor farmer to adopt this technology. future of the teChnology

The technology needs to be refined further, technically and made simpler for the farmer. If a mechanical process is developed for spraying and mixing of the urea solution during the threshing operation itself, larger farmers may come forward and adopt this technology

July 2011
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