Nowadays, greta emphasis is being laid on the evolvement of high-yielding, nutritive and short-duration varieties of fodder crops, since the possibilities of increasing the area under cultivated fodder crops beyond 4.4% are very bleak. With the availability of high-fodder-yielding varieties of season-bound and perennial fodder crops, there is a glut of fodder during the peak-periods of growth and scarcity during other periods. The best way to regulate the supply of palatable and nutritive fodder during the lean periods of October and November and May to July is to conserve the surplus fodder in the form of hay and silage.

A similar situation is also experienced in the case of grassland species which essentially comprise the monsoon grasses. These grasses give abundant fodder during the monsoon, but in the post-monsoon period and summer the forage production is almost negligible owing to their dormancy with the advent of winter and acute moisture stress. Thus it is essential that surplus fodder should be conserved during the period of excess growth, in the form of hay, silage, etc. The need for the conservation of fodder is all the more warranted in the drought-prone areas where crop failures are frequent.

Silage-making. nbsp Silage is the product obtained by packing fresh fodder in a suitable container, and allowing it to ferment under anaerobic conditions ,  without undergoing   much loss of   nutrients. Fermantation under anaerobic conditions preserves the nutritive value and enhances the keeping quality of the fodder. The process of conserving green fodder in this way is termed as ensiling.

QUALITIES OF GOOD SILAGE.   The quality of a  very good silage is determined by the colour and odour of the conserved material. A good silage should  be greenish or yellowish brown, with pleasant odour, and possess a high acid content. On the  other hand, if the silage has content of butyric acid, is yellow and emits offensive odour or has become dark brown and gives out tobacco-like odour owing to heating, it is poor silage, though it may be palatable to the livestock, but decidedly its feeding value is very low. Shephered et al. (1948) have classified the silage into the following categories :

1. Very good silage. Silage having acidic taste and odour, being free from butyric acid, moulds, sliminess, showing a pH range of 3.4-4.2, and with ammoniacal nitrogen less than 10% of the total nitrogen.
2. Good silage. Silage possessing acidic taste and odour, traces of butyric acid, pH 4.2-4.5 and ammoniacal nitrogen 10-15% of the total nitrogen.
3. Fair silage. Ensiled material with some butyric acid, a slight proteolyses, some moulds, pH 4.8 and above and ammoniacal nitrogen 20% of the total nitrogen.

CROPS SUITABLE FOR SILAGE MAKING.   Generally, the fodder crops rich in soluble carbohydrates and low to medium in protein content are ideally suitable for silage-making. A high content of soluble carbohydrates provides an excellent growth medium for the anaerobic bacteria to form abundant acids which increase the keeping quality of the silage. Thus maize, jowar, bajra, guinea grass, para grass and Napier grass are highly suitable for making good-quality silage. On the other hand, leguminous fodders, which normally have high moisture and high crude protein and low soluble carbohydrates at the comparable growth stage, are not considered fit for silage making. Some of the problems encountered in the case of these crops owing to high moisture and high protein are :

(a) A high moisture level in the fodder causes a tremendous loss og digestible nutrients in the form of an effluent and, to some extent, by a high rate of fermentation.

(b) A high protein content induces a buffering action owing to which there is a gradual decline in the pH value, resulting in an unstable product.

Types of silos.   The term silage and the conservation of fresh foder into such a form has come from the Western countries, where owing to prolonged spells of snowfall and severe winters practically nothing is available for feeding to the licvestock during such exigencies. Thus silage making is adopted out of necessity there. Different kinds of structures, varying in design and cost, are used for silage making and storage. The size and the shape of the structure depends upon the livestock strength, soil and financial inputs available with the livestock owner. Some of the important types are briefly described below :

TOWER SILOS.   Tower silos or upright silos are among the permanent types and are relatively costly. They are constructed above the ground level in the form of cylindrical towers. The diameter, and height above the ground level vary according to the needs. The loss of dry matter in such silos is 5 to 10 per cent only.

PIT OR TRENCH SILOS.   Pit silos are less costly than the tower silos and are widely adopted for silage making. They may be pucca or katcha, depending upon the climatic conditions. Pits of desired size are dug in well-drained soils. In the case of katcha silos, the floor should preferably be bric lined, so as to avoid contact between the chaffed material and the excessive soil moisture and easy percolation of excessive moisture from the ensiled product. In the case of such silos, when opened for feeding, a definite top layer of the silage (5-7 cm or more) is uniformly removed and fed daily to prevent spoilage.

BUNKER SILOS.   These silos are constructed on the surface of the ground and mainly consist of two retaining walls, 2-2.5 m high, and with a slope of 2-3 cm so as to make the silage settle tightly against them. They should always be built on firm soils having good surface and sub-surface drainage.

STEPS FOR MAKING SILAGE.   For preparing a goo-quality silage, the following procedure should be followed :
(1) The fodder crops should be harvested and chaffed at the proper stage of growth so that the moisture, protein and carbohydrates contents are optimum for anaerobic fermentation. The carbohydrates are converted into lactic, acetic, and propionic acids and to some extent they serve the same purpose as vinegar does in the case of pickles by checking the growth of bacteria, moulds, etc., producing fouls smells. The early harvesting of crops affects the production of different acids, thereby reducing the storage period and affecting the quality of the silage. Thus the green fodder should have about 30-35 per cent dry matter. This is achieved by wilting the crops for certain periods before filling the silo pits, if they have excess moisture, or by sprinkling a small quantity of water on each layer of the chaffed material, if it has less moisture.
(2) In the case of katcha silo pits, their bottom and sides should be carpeted with dry grass of kadbi or the long straw of grasses, cereal crops, etc. so as to make a 5-6-cm-thick carpet all around. This carpeting helps to prevent the direct contact between the freshly chaffed material and the soil. The direct contact between the chaffed material and the soil decreases or increases the moisture content in the ensiled material, depending upon the soil type and the water-table.
(3) The fodder to be ensiled should be chaffed into small pieces, preferably of the size of 1-2 cm, either with the help of a manually operated chaff-cutter or with a power-driven chaff-cutter.
(4) The silo pits must be filled very quickly (say within 3-4 days) and the material must be compacted in such a way as to remove as much air as possible through constant pressing either by manual labour, or with bullocks or tractor or with combination of all three. The exclusion of air causes fermentation under anaerobic conditions. Fermentation under aerobic conditions causes excessive respiration, over-heating of the ensiled material and the loss of carbohydrates through the production of carbon dioxide.
(5) The level of the chaffed material should be about 1-2 metres above the ground level. During the course of fermentation, the material will gradually settle down.
(6) Urea at the rate of 3-4 kg per tonne of the chaffed material is mixed with, or sprinkled thinly and evenly on different layers, if the chaffed material happens to be very low in protein content, especially in the case of cereal fodders.
(7) The silo pits, after filling and compacting the material carefully, should preferably be given a dome-like shape. Such shape facilitates the drainage of rain-water, which otherwise would enter the ensiled material, and deteriorate the quality.
(8) The ensiled material is then covered with a polythene sheet or a tarpaulin from all sides so as to protect it from the direct rays of the sun and from rains.
(9) After a week, the polythene sheet is removed and the material is compacted again so as to consolidate the chaffed material and remove the air to the greatest possible extent. The polythene sheet is then placed back. However, if the polythene sheet is not available, a thick layer of straw is put on the chaffed material from all sides, and over the straw, a thick layer of moist soil (10-12 cm) is spread. The surface is covered in a mud plaster prepared by adding dung and water, to the earth, in suitable quantities. This avoids the contact of atmospheric nitrogen with the ensiled material, since the atmospheric nitrogen will prevent fermentation under anaerobic condition.
(10) The chaffed material ensiled by the above procedure is ready for feeding to the livestock after 2-3 months. A silo pit is opened and the material is removed daily for feeding by exposing as little as surface of the ensiled material as possible. This is done mainly to prevent the direct contact of the feeding material with sunlight and to prevent air-drying.
(11) The feeding of the silage should be regulated in such a way that the silage is used within a reasonable period. In other words, the silo pits are normally opened during a fodder scarcity. Long exposures to atmospheric action cause drying and deterioration in the keeping quality of the silage.
(12) Silage may be fed in small quantities (4-5 kg per cow) to start with, and later the quantity may be increased to 15-20 kg so that the animal is able to adjust itself to the new feed. During an acute fodder scarcity when nothing is available for feeding, it has been reported that silage is able to meet the full requirements of the animal in respect of dry matter and essential nutrients.

Hay-making.   Hay can be defined as the conversion of green forage into dry form without affecting the quality of the original material. It can be safely stored for long periods. The quality of hay largely depends on the species, the stage of harvesting and freedom from moulds and bacteria. A good-quality hay must retain a larger proportion of leaves which become brittle on drying and fall off quickly. In addition, the cured hay should have a natural green colour, pleasant aroma, optimum moisture content, freedom from moulds, etc. During hay-making, particularly in the hot summer, excessive and direct exposure to sunlight should be avoided, since it causes bleaching.