Conventional sources of feeds are not enough to mitigate the shortage of feeds and fodder and to make animal production viable and profitable in tropical countries. India had 70 million hectares under grassland in the year 1947 has reduced to 38 million hectares today. As a result, the net deficit of green fodder is around 60 percent, apart from the feed deficit of around 64 percent. In order to bridge this gap and to ensure optimum production of livestock throughout the year, we have to make greater use of non-conventional feed resources as supplement or replacement of conventional feed, but without compromising the quality of nutrient supply. The supplementary resources in India also include aquatic macrophytes which have rich nutrients and mineral profile.
Throughout the world, and particularly in Asia, farmers have harvested naturally produced aquatic plants for a number of purposes including animal feed, green manure and for their family feed resources. The best known among these include the free floating plants; water lettuce (Pistia), water hyacinth (Eichhcornia), duckweed (Lemna) and Azolla and some bottom growing plants. In recent years, Azolla has attracted the attention of scientists as a feed resource for livestock and even called it as Green gold mine or super plant due to its high nutritive value and faster growth.
THE FERN- AZOLLA
Azolla (mosquito fern, duckweed fern, fairy moss, and water fern) is a small free floating aquatic fern native to Asia, Africa, and America. Azolla is a genus of six species of aquatic ferns, the only genus in the family Azollaceae. It grows naturally in stagnant water in drains, canals, ponds, rivers and water bodies including marshy lands. Out of the six species, Azolla pinnata and Azolla micrphylla are common in Indian subcontinent. Azolla microphylla is reported to be most suitable for livestock feeding.
Azolla leaf consists of two lobes, an aerial dorsal lobe, which is chlorophyllous, and a partially submerged ventral lobe. Each dorsal lobe contains a leaf cavity, which houses the symbiotic Anabaena azollae. The fern Azolla has a symbiotic blue green algae Anabaena azollae, which is responsible for the fixation and assimilation of atmospheric nitrogen. This fact makes the Azolla tend to contain relatively high levels of nitrogen and be an attractive protein source for animal feed, not only the livestock and poultry but also in aquaculture species. Azolla, in turn, provides the carbon source and favorable environment for the growth and development of the BGA symbiont.
METHODS OF AZOLLA PRODUCTION
Several methods of Azolla production had been explored like in cement tubs, permanent concrete tanks, natural water bodies, brick-lined or semi grounded brick-lined pits etc. However, for better productivity and less weed infestation, the grounded pits and brick-lined raised pits are advisable for the farmers. Semi grounded and semi grounded brick-lined pits are even better.
NUTRITIONAL ASSESSMENT OF AZOLLA
The variations in the nutrient composition of Azolla is due to differences in the response of Azolla strains to environmental conditions which consequently affect their growth, morphology and chemical composition. The macronutrient composition of Azolla microphylla based on last five years study at NDRI, Kalyani is listed in Table 2.
Among different Azolla strains, Azolla microphylla has been found to be the best source of amino acids so best used as animal feed. Lysine, arginine, isoleucine, leucine, phenylalanine, glycine and valine have been reported to be predominant amino acids in Azolla.
In general Azolla was reported to be rich in mineral profile, the fern was found to be a rich source of calcium, phosphorous, potassium, manganese, copper, magnesium and zinc. It has been found a very good source of essential fatty acids like Lenolenic Acid and several antioxidants. On fresh material, the carotene content ranged from 206 to 619 mg/kg on dry matter (DM) basis. Some anti nutritional factors like nitrate and polyphenol have also been found, but are within acceptable range.
FEEDING OF AZOLLA TO DIFFERENT LIVESTOCK SPECIES
White Leghorn females fed commercial poultry feed supplemented with fresh Azolla at levels of 5 % grew faster than the control group. Fresh Azolla can partially replace whole soya beans up to a level of about 20% of the total crude protein in diets of fattening ducks without any adverse effects on growth rate or health. The birds that received normal feed with 5% extra supplementation of Azolla showed 10–12% increase in the total body weight. Dietary inclusion of sun dried Azolla up to 5% levels had no adverse effect on production performance of broiler chicken. The feed cost per kg gain is reduced and net profit per bird being higher.
Azolla is an appropriate supplemental feed for herbivorous fish such as tilapia (O. niloticus). Some trials have shown that tilapia can consume azolla @50 – 80% of their weight per day. Azolla meal protein can replace up to 100% of the soybean meal protein in diet of black tiger shrimp without any adverse effect. Low cost feed has been formulated using Azolla as a protein supplement in extensive system of fish rearing. Azolla based diets have given quite encouraging results when fed to juvenile tilapia (Oreochromis nilotica).
Cattle & Buffalo
Feeding of Azolla after replacing 50% of groundnut cake nitrogen, improved growth performance of buffalo calves. Feed conversion efficiency and economics of feeding was significantly improved. Dried Azolla meal has been reported to replace about 25 per cent of the total protein in the concentrate mixture without any adverse effect. In a field trial an overall increase of milk yield of about 15 percent has been observed when 1.5 – 2 kg of fresh Azolla per day was combined with regular feed.
At NDRI , Kalyani series of feeding trials show
Supplementation of fresh Azolla @ 2kg /day/animal caused an increase in milk yield by 11.2% and FCM yield by 12.5% in Jersey cross bred cows without any adverse effect on milk composition
Supplementation of dried Azolla microphylla meal to male jersey cross bred calves @ 60 g / animal (equivalent to 1 kg fresh azolla) replacing 10 % of concentrate mixture caused an increase in growth rate by around 9 %. The feed conversion efficiency and Feed conversion ratio have also improved significantly
Supplementing fresh Azolla microphylla to cross bred heifers @ 1.5 kg /animal replacing equivalent weight of concentrate mixture on DM basis significantly improved the average growth rate and feed conversion efficiency by around 15%
In the Eastern part of India fodder cultivation is an uncommon practice due to lack of land and fragmentation of land holding. The state like West Bengal is not having a single large farmer in terms of land holding. Farmers usually utilize their cropping land for food crop cultivation. As a result in many cases the animals are not offered any cultivated green roughages in their ration. With growing human population and decreasing size of arable land, the fodder shortage is going to be very alarming in coming years. Under such circumstance Azolla can serve well as it can be grown by minimum input of labour or land throughout the year and can supply at least some green feed to the animals.
Azolla can serve as a potential alternative nutrient supplement for the Livestock for the improvement of productivity in terms of growth, milk, meat etc with high economic efficiency.
by Anupam Chatterjee, A. Goswami & A. Mohammad
National Dairy Research Institute, Eastern Regional Station, Kalyani