India has the largest livestock population in the world and is expected to grow at a rate of 0.55 percent in the coming years. Although, India is one of the leading producers of animal products (milk, meat, and eggs), the productivity of animals is 20-60 percent lower in India as compared to the global average. Major constraints in livestock production in developing countries include scarcity, fluctuating quantity and quality and the year-round availability of green fodder. Often, the shortage of fodder is therefore compensated with commercial feed, resulting in increased costs in meat and milk production. The success of livestock production depends largely on increasing production without an escalation in feeding costs. Moreover, as commercial feed which is mixed with urea and other artificial milk boosters, has a negative effect on the quality of products and the health of the animals. In this context, the search for alternatives to traditional green fodder and commercial concentrates led to a wonderful plant Azolla and uses of Azolla as animal feed.
Azolla – A Multipurpose Plant
Azolla commonly called mosquito fern/duckweed fern/ fairy moss/water fern is a unique freshwater floating fern genus including seven species belonging to the family Salviniaceae. It is one of the fastest-growing plants due to its symbiotic relationship with a ‘blue-green alga’ called Anabaena azollae, which is responsible for the fixation of atmospheric nitrogen. In return, Azolla provides a favorable environment for the growth and development of the algae. This unique symbiotic association makes a unique plant with high protein content. Azolla is often referred to as a Super plant or Green gold mine or multipurpose plant due to its fast-growing habit, high nutritive value and multiples use. The most common uses of Azolla include biofertilizer especially in rice crops and livestock feed. There are reports of its use as human food also.
Nutrient Content of Azolla
The nutritive value of Azolla is well documented which shows that it is a good source of protein with almost all essential amino acids required for animal nutrition. It also provides minerals like calcium, magnesium, potassium, and vitamins like vitamins A and B12. It is reported that 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. Azolla is also rich in iron (1000–8600 ppm dry weight), copper (3–210 ppm dry weight) manganese (120–2700 ppm dry weight), vitamin A (300–600 ppm dry weight.), vitamin A (300–600 ppm dry weigh), chlorophyll and carotenes. It contains 4.8–6.7% dry weight crude fat. The carbohydrate and fat content of Azolla is very low.
Azolla production technology
Several organizations including NIANP, Bangalore and NARDEP, Kanyakumari, have developed economical and easy to use production methods for Azolla production in farmers’ homesteads. These methods mainly involve digging up of small pits of 2 x 2 x 0.2 m 2 x 2 x 0.2 m on the ground which are lined with polythene sheets and supported by bricks. 2 kg Cow-dung slurry supplemented with 30 g Super Phosphate in water is commonly used as a substrate for Azolla production in these ponds. 500 – 600 g of Azolla can be harvested daily from 15 days of initial inoculation of Azolla culture. 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 the rapid multiplication of the Azolla and to maintain the daily yield of 500 g. With this method, the cost of production of Azolla is less than Rs. 0.65 per kilogram.
Some workers suggested the use of alternative inputs like fresh biogas slurry, wastewater from bathroom and cattle shed or water left after washing clothes in areas where there is a problem of freshwater availability.
Azolla as Animal Feed
The nutrient composition of Azolla makes it a highly economical, efficient and effective feed substitute and a sustainable source of feed for livestock. Livestock easily digests it, owing to its high protein and low lignin content, and they quickly grow accustomed to it. Azolla can be used as an unconventional feed supplement for many species including ruminants, poultry, pigs and fish. Due to ease of Azolla cultivation, high rate of growth without inorganic nitrogen fertilization, an aquatic habitat that does not require displacement of existing crops or natural ecological systems, high productivity and good nutritive value strongly support its use as a beneficial fodder supplement.
When introducing Azolla as livestock feed, the fresh Azolla should be mixed with commercial feed in a 1:1 ratio to feed livestock. After a fortnight of feeding on Azolla mixed with concentrate, livestock may be fed with Azolla without added concentration.
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 in milk yield of about 15 percent when 1.5 – 2 kg of Azolla per day was combined with regular feed. Further, the increase in the quantity of the milk produced was higher than that 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 carotenoids, 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, the 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. Their feeding trials showed that 20–25% of commercial feed could be replaced by supplementing it with fresh Azolla, in poultry with the addition of Azolla feed also having a variety of benefits.
High nutritive value, rapid growth and low cost of production make Azolla a popular choice and an ideal feed for cattle, fish, pigs, and poultry. It can also be used as a bio-fertilizer for wetland paddy. It is cultivated widely in countries like China, Vietnam, and the Philippines, but has yet to be taken up in India, in a big way. Recently, dairy farmers in Kerala and Tamilnadu have started taking up low-cost Azolla production technology. The Azolla technology may be taken up more widely by dairy farmers, in particular, those who have too little land for fodder production in the coming years.
P. Kamalasanan Pillai, S. Premalatha, S. Rajamony. (2002). AZOLLA – A sustainable feed substitute for livestock. LEISA India, Volume 4 number 1, March 2002.
K. Giridhar, A. V. Elangovan, P. Khandekar, Sharangouda and K. T. Sampath (2012). Cultivation and use of Azolla as a nutritive feed supplement for the livestock. Indian Farming 62(2): 20-22, May 2012.