Azolla: a sustainable feed for livestock
by P. Kamalasanana Pillai, S. Premalatha and S. Rajamony
The demand for milk and meat in India is creating new potential in the profitability of animal husbandry as an occupation. Yet, at the same time, there is a substantial decline in fodder availability. The area under forest and grasslands is decreasing as is the amount of various crop residues available for feed, largely due to the introduction of high yielding dwarf varieties. The shortage of fodder is therefore compensated with commercial feed, resulting in increased costs in meat and milk production. Moreover, as commercial feed is mixed with urea and other artificial milk boosters, it has a negative effect on the quality of milk and the health of the livestock.
The search for alternatives to concentrates led us to a wonderful plant azolla, which holds the promise of providing a sustainable feed for livestock. Azolla is a floating fern and belongs to the family of Azollaceae. Azolla hosts a symbiotic blue green algae, Anabaena azollae, which is responsible for the fixation and assimilation of atmospheric nitrogen. Azolla, in turn, provides the carbon source and favourable environment for the growth and development of the algae. It is this unique symbiotic relationship that makes azolla, a wonderful plant with high protein content.
Nutrient content and its impact on growth
Azolla is very rich in proteins, essential amino acids, vitamins (vitamin A, vitamin B12 and Beta- Carotene), growth promoter intermediaries and minerals like calcium, phosphorous, potassium, ferrous, copper, magnesium etc. On a dry weight basis, it contains 25 - 35 percent protein, 10 - 15 percent minerals and 7 - 10 percent of amino acids, bio-active substances and bio-polymers. The carbohydrate and fat content of azolla is very low. Its nutrient composition makes it a highly efficient and effective feed for livestock (see Table 1). Livestock easily digest it, owing to its high protein and low lignin content, and they quickly grow accustomed to it. Moreover it is easy and economic to grow.
The Natural Resources Development Project (NARDEP), Vivekananda Kendra, carried out trials in Tamil Nadu and Kerala using azolla as a feed substitute. The trials on dairy animals showed an overall increase of milk yield of about 15 percent when 1.5 - 2 kg of azolla per day was combined with regular feed. The increase in the quantity of the milk produced was higher than could be expected based on the nutrient content of azolla alone. Hence, it is assumed that it is not only the nutrients, but also other components, like carotinoids, bio-polymers, probiotics etc., that contribute to the overall increase in the production of milk. Feeding azolla to poultry improves the weight of broiler chickens and increases the egg production of layers. Azolla can also be fed to sheep, goats, pigs and rabbits. In China, cultivation of azolla along with paddy and fish is said to have increased the rice production by 20 percent and fish production by 30 percent.
Close-up view of an azolla plant. The size of the plants are 1 - 3 cm.
NARDEP has been working on azolla for the last three to four years, studying its potential as a feed and exploring cost effective methods for the mass multiplication of azolla in farmers’ homesteads.
.In our method, a water body is made, preferably under the shade of a tree, with the help of a silpauline sheet. Silpauline is a polythene tarpaulin which is resistant to the ultra violet radiation in sunlight. A pit of 2 x 2 x 0.2 m is dug as a first step. All corners of the pit should be at the same level so that a uniform water level can be maintained.
The pit is covered with plastic gunnies to prevent the roots of the nearby trees piercing the silpauline sheet, which is spread over the plastic gunnies. About 10 - 15 kg of sieved fertile soil is uniformly spread over the silpauline sheet. Slurry made of 2 kg cow dung and 30 g of Super Phosphate mixed in 10 litres of water, is poured onto the sheet. More water is poured on to raise the water level to about 10 cm. About 0.5 - 1 kg of fresh and pure culture of azolla is placed in the water.
This will grow rapidly and fill the pit within 10 - 15 days. From then on, 500 - 600 g of azolla can be harvested daily. A mixture of 20 g of Super Phosphate and about 1 kg of cow dung should be added once every 5 days in order to maintain rapid multiplication of the azolla and to maintain the daily yield of 500 g. A micronutrient mix containing magnesium, iron, copper, sulphur etc., can also be added at weekly intervals to enhance the mineral content of azolla.
NARDEP method of azolla production
1. It is important to keep azolla at the rapid multiplication growth phase with the minimum doubling time. Therefore biomass (around 200 g per square meter) should be removed every day or on alternate days to avoid overcrowding
3. The temperature should be kept below 25 °C. If the temperature goes up the light intensity should be reduced by providing shade. If possible, it is best to place the production unit where it is shady.
5. About 5 kg of bed soil should be replaced with fresh soil, once in 30 days, to avoid nitrogen build up and prevent micro-nutrient deficiency.
7. The bed should be cleaned, the water and soil replaced and new azolla inoculated once every six months.
9. The azolla should be washed in fresh water before use to remove the smell of cow dung.
Azolla should be harvested with a plastic tray having holes of 1 cm2 mesh size to drain the water. Azolla should be washed to get rid of the cow dung smell. Washing also helps in separating the small plantlets which drain out of the tray. The plantlets along with water in the bucket can be poured back into the original bed. When introducing azolla as feed, the fresh azolla should be mixed with commercial feed in 1:1 ratio to feed livestock. After a fortnight of feeding on azolla mixed with concentrate, livestock may be fed with azolla without added concentrate. For poultry, azolla can be fed to layers as well as broilers.
P. Kamalasanana Pillai, S. Premalatha and S. Rajamony. Natural Resources Development Project, Vivekananda Kendra, Kanyakumari 629 702, India. Email: firstname.lastname@example.org
This article is a summary of the article “AZOLLA – A sustainable feed substitute for livestock” by P. Kamalasanana Pillai, S. Premalatha, S. Rajamony. The full article was published in LEISA India, Volume 4 number 1, March 2002. It is available on the website www.leisa.info.
Trying it out
After reading the article on azolla in the March 2002 issue of the LEISA India, the LEISA India columnist and organic farmer Mr. Narayan Reddy decided to test the production of azolla on his farm. As his grandchildren were visiting, they were set to dig the first bed of 2 x 3 x 0.15-0.2 m. To simplify the construction, Mr. Reddy made some adaptations:
He lined the bed with a simple plastic sheet, fixed the sheet with the dug out soil together with some concrete along the edges, taking care that the plastic above the water was well covered – as otherwise the sun will rapidly deteriorate the plastic. After fixing the plastic, about 2 - 3 cm of stone free soil was carefully put back in the bottom of the bed which was filled with water. The water depth is important;
too little water will allow the azolla roots to grow into the mud, making it difficult to harvest. Too much water will reduce the production as the roots do not reach close enough to the nutrients at the bottom. After filling the bed, Mr. Reddy went off to the closest university to ask for some azolla plants and put them in the water. He added 0.5 - 1 kg of neem cake to prevent possible pest problems and every three weeks he adds slurry of cow dung and water (10 kg fresh cow dung).
He empties and cleans the bed once every half year and starts it up again with some plants, neem cake and cow dung. When the temperatures soar in the summer, the bed is covered with a roof of loose palm leaves to give some shade and reduce light and temperature. However, the use of a simple plastic sheet for lining makes the bed very vulnerable – it can easily be damaged during harvesting or cleaning and Mr. Reddy therefore makes sure that he carries out these tasks himself.
With this simple system, the only costs are for the plastic sheet and for 2 kg of neem cake per year – plus his own labour.
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