Alligator weed : A potential indigenous fodder resource of Manipur
- A case study -

R Joseph Koireng / N Rakesh Singh / Ch Kennedy Singh *

Shrinkage of cultivable land due to urbanization and shortage of water limit the possibility ofproducing more feed and fodder to livestock from land. Water channels, ponds, wasteland remains untapped and the Alligator weed resources have got immense potential to fill the gap in Manipur. Alligator weed locally known as Kabo Napi has been used as a source of food, feed, fodder since time immemorial.

In Manipur Alligator weed (Altemanthera philoxeroides) is considered as one of the best options for dairy feed. Semi dried Alligator weed is found more beneficial than fresh and dried feed. Milk production has been found to increase by using Alligator weed as part of the diet. This may be Its to the presence of a high percentage of protein.

ENVIRONMENTAL REQUIREMENTS

A. philox.oides is a perennial herb which grows as an emerged, aquatic plant, rooted in the soil or in the substrate below shallow water. It also grows in terrestrial habitats. Roots are short and filamentous in water, rising mainly from the nodes. This plant has an amazing ability to grow vigorously in terrestrial situations forming a massive underg.round rhizomatous root system.

Under these conditions, alligator weed can survive without any water for several months (Gun.sekera and Adair, 2000). Low temperatures stop the plant establishing and prevent it from reaching high levels. Growth rate increases exponentially with ambient temperatures in the range 14- 29oC, growth ceasing below 13oC. Frost is a major cause of leaf mortality in these regions. The growth of Alligator weed is affected by low air humidity, ranging from 15-40 percent relative humidity.

CHARACTERISTICS

Alligator weed is a perennial, stoloniferous plant. Its morphology varies depending on whether it is growing on the edge of a water body (with its long stems floating out over the water surface) or growing in a low-lying, poorly drained site away from the water's edge. Hence, the literature often refers to two so-called 'forms' an aquatic form and a terrestrial form.

'While not true genetic forms, such morphological plasticity enables the species to survive and dominate across a range of aquatic and semi-aquatic habitats. When growing away from open water, the plant produces deep taproots and a total roots mass up to seven times heavier than plants growing over open water. The loaves of terrestrial plants are smaller and have fewer flowers.

When floating over water the plant grows more vigorously and has taller, thicker stems with large internal air spaces and larger, darker leaves. The aquatic form is still rooted in soil near the water's edge or in under-water substrate. Severe frosts kill stems, but regrowth occurs quickly from stems or underground rhizomes buried in soil when favourable conditions return.

Optimum growth occurs in fresh water with a high nutrient level, which results in higher fodder yield. It can tolerate brackish water and, once established on land, will survive extreme by periods. Considering its vigorous growth and ability to re-establish from stem fragments, alligator weed has the potential to establish in all areas and inland agricultural and urban areas (where water is not a limiting factor). Alligator weed can feed 7.5 cows/ha for about 300 days in the year (Alford, 1952).

CHEMICAL COMPOSITION

Like most other aquatic plants, alligator weed has very high moisture content, the dry matter generally varies between 5-9 percent. The crude protein content of the whole plant is about 16-20 per cent, although a level as its as 12 per cent was reported in studies. Sushil Kumar and Kamlesh Vishwalcarma (2005) reported that the crude protein of the fresh green part of Alligator weed from India was 14.58 percent DM.

The crude protein content of the leaf appears to be higher than the whole plant and varies between 21-22 percent. Like most other aquatic plants, the crude lipid content of Alligator weed is usually its and varies between 2-4 percent on a dry matter basis regardless of whole plant or leaves (Sushil Kumar and Kamlesh Vishwakarma 2005).

The ash content of whole plants varies between 12-16 percent (Davis, 1970). Crude fibre content is usually high in Alligator weed and ranges between 16-17 percent, irrespective of whole plant or leaves.

Davis, (1970) and Sushil Kumar and Kamlesh Vishwakarma (2005), in a review also reported levels of some other components: celluloses 21.3 per cent; tannin 1.2 percent; caloric 3.46 k cal/g; pectin 1-2 percent; Ca 2-3 percent: Mg 2-3 percent; phosphorus 0.18 percent; total phenolics 4.1 (mg 100 g-1); total carbohydrates 15.4 (mg g-1) and total free amino acid 1.92 (mg g-1).

PALATABILITY

The palatability of alligator weed, in addition to their high moisture content, restricts the ability of the animals to obtain adequate nourishment The palatability of the feed process from alligator weed is comparable with that of conventional feed. Alford, (1952) also reported that cattle sometimes almost swimming, into the fields to graze alligator weed.

They readily eat the dead part on top, then pull the green stems from below the surface. Dairy cattle voluntarily consumed Alligator weed, but animal performance was best when the amount of Alligator weed was less than 50./0 of the complete diet, but beyond this amount the animal suffers from mineral imbalance, which leads to reducing the body weight.

This might be due to the high level of mineral or toxic substances present in the fodder crops. Semi dry feeding of Alligator weed was found more palatable and beneficial as compared with fresh feeding. Further research is required for improvement of this nutritious fodder crop.

HARVESTING AND CONSERVATION

A.philox.oides can be fed as pasture, green chop, silage, or hay. Pasture is harvested by the animal, and if it is not managed correctly, harvest losses can be severe. Harvest losses of pasture are greatly reduced when intensively managed grazing is practiced If animals are allowed to graze a large land area at one time, much of the forage will be trampled, contaminated with manure, or otherwise wasted.

Alligator weed are commonly harvested, and used for stall fodder purposes. The productivity varies widely and is dependent on the cutting management practices. Delay in cutting results in poor regeneration, 20 days interval cutting results in higher fodder yield, compared with delayed cutting.

Storage losses are very high due to high moisture cont.; however, with a proper post harvest management technique these losses can be minimized. Sun drying for about 3 his before storing reduced storage loss.

FEEDING TECHNIQUE

Fresh A.philoxeroides are rich in moisture and mineral nutrient, fresh feeding results in high risk of diarrhoea and mineral imbalance. Sun drying about 3 his or shade drying for 48 his help in reducing from such risk. Feeding of Alligator weed was found more beneficial, when feed with less than 50% of the complete diet, or in the ratio of 50:50 with rice straw. Use of a chaff cutter increased palatability.

TOXICITY

Normally the alligator weed is free from high poisonous effects. But higher quantity and continuous feeding of fresh alligator weed result in high risk of diarrhoea in dairy cattle. The risk of diarrhoea is highest at the early stage, decreasing progressively as the plant matures. In Australia some cases of photosensitization are reported in daily cattle due to the intake of alligator weed (Bourke and Rayward. 2003).

PRODUCTION

Alligator weed grows in all types of freshwater, lentic and lotic. They are productive plants since they are warm water species with deep taproots and a total root mass up to seven times heavier than plants growing over open water. The productivity varies widely and is dependent on the management, environmental factors, number of cuts and depth of water under which it grows.

Delay in cutting results in poor regeneration, 20 days interval cutting results in higher fodder yield. Stagnant water gave higher yield than running water. Yields of A.philox.oides may increase up to 835 tonnes/ha/year. Alford, (1952) reported that Alligator weed can feed 7.5 cows/ha for about 300 days in the year.

However, further expansion in area and improving in management practice of this fodder crop may not be possible, these plants are considered as noxious weeds.


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