A STEADY supply of fodder is essential for the productivity and economic returns from the dairy farming. The bulk of the feed is contributed in rural areas by crop residues and green fodder. About 70 per cent cattle and buffalo population is present in Punjab where no pasture is available to graze.

In some arid zones, the dairy animals are allowed to graze the post-harvest residues in irrigated tracts and natural grasses after the rainy season. In remaining part of the country, the situation is almost the same.

In peri-urban areas, the dairy animals receive some quantity of concentrates, but the fodders and crop residues still are crucial.

The irrigated regions of Punjab and Sindh are the foremost source of green fodder supply which is transported every day in bulk to meet the demands. The major Rabi fodders are berseem, Lucerne, and oat, whereas, for Kharif are maize, sorghum, millet, cowpeas, and guar.

The total Rabi and Kharif fodder area is 1.18 million and 1.34 million hectares, respectively. However, per acre yield of traditional fodders is low because of a number of reasons, including the poor seed quality and inappropriate agronomic techniques.

The area under fodder cultivation is decreasing because of the ever-increasing demand of cereal grains for humans and usually small land holders prefer to grow cash crops instead of the fodders. Some multi-cut hybrid grasses like sada-bahar, mott grass and jambo grass have recently been introduced to improve the fodder situation. However, fluctuations in availability affect the performance and productivity of dairy cattle.

There are periods of abundant fodder growth from February to April and July to September. However, under adverse climatic conditions, there is hardly any growth of quality fodder. There are two periods of scarcity, one in winter from December to January and in summer from May to July. The situation calls for exploration of means to regularize the fodder availability without sacrificing the area under cash crops. Preservation of green fodder as silage is imperative to deal the issue.

Silage is a high moisture fermented green fodder preserved under anaerobic fermentation with minimal nutrients loss. The aim is to preserve nutritive value of fodder that is achieved by maintaining an oxygen-free (anaerobic) environment. Under anaerobic conditions bacteria convert fermentable carbohydrates (sugars) into organic acids, predominantly lactic and acetic acids (vinegar).

These inhibit or kill the bacteria and thus preserve fodder in its original value for a long period. Factors affecting the rate of pH decline (acid production) and quality are fodder specie, plant age/maturity, dry matter, fermentable sugars and protein concentrations of the original forage and the type and amount of bacteria present.

The choice of crop for ensiling depends primarily on specie of fodder and its availability. Non-leguminous fodders like maize, sorghum, sada-bahar, jambo and millet are preferred crops for ensiling because of their moisture fermentable sugar and protein contents. However, berseem, lucerne, shaftal and cowpeas that are leguminous fodders could be ensiled after wilting and addition of additives.

A key point for best quality silage is to make a good balance between the carbohydrate and protein contents in fodder crop. This balance can be achieved by ensiling cereal and legumes together. Fermentable carbohydrates for lactic acid bacteria are provided by non-leguminous fodders and simultaneously the protein content of silage is increased because of leguminous fodders.

Grass and legume, if grown in combination for ensiling, result in higher biomass yield, protein contents, and also enhances soil fertility. The time of fodder harvest influences the silage quality.

Well-preserved silage of high nutritional value is achieved by harvesting the crop at proper stage of maturity+ADs- minimizing the activities of plant enzymes and undesirable, epiphytic micro organisms (i.e., those naturally present)+ADs- and encouraging the dominance of lactic acid bacteria.

Available energy, digestible protein and daily intake of silage are decreased with advancing fodder maturity. Recent national and international research reports have recommended harvesting of maize, sorghum and millet at milk growth stage for better dry matter, crude protein and total digestible nutrient yields and for ensiling.

However, jambo, oat and mott fodders should be harvested at 50 days of maturity for ensiling. It is recommended that berseem, shaftal and lucerne fodders should be harvested at 1/10th bloom stage.

Proper moisture contents have more influence on good quality silage. Moisture content must be below 70 per cent for better fermentation. To avoid excessive seepage from silo (storage structure), moisture should be between 65 to 68 per cent.

Seepage during ensiling carries with it many water-soluble plant nutrients such as sugar, simple proteins and organic acids. Loss of these results in 5-7 per cent loss in dry weight of the forage, but can be as high as 10-15 per cent. However, the impact of seepage on silage quality goes beyond just dry matter loss.

Forages ensiled high in moisture also have a dilution effect on the fermentation acids produced which can result in either not enough concentrated acids for preserving or extending the fermentation process which results in increased loss of nutrients towards fermentation rather than for animal requirement.

The loss of nutrients for extended fermentation will most noticeably be the soluble carbohydrates such as sugars and starches. These carbohydrates are digestible by silage and rumen bacteria and when they are lost, the remaining carbohydrate will mostly be fibre which has a lower digestibility than sugar and starch.

Thus it is important to harvest the fodder crop at proper stage to ensile with the recommended moisture level. Leguminous crops need extensive wilting prior to ensiling to lower their moisture contents. An alternative approach to reduce the moisture contents of fodder is to ensile fodder with crop residues (wheat straw, rice straw or corncobs). This approach not only reduces the moisture contents of ensiling material but also increases the nutritive value of crop residues. It is recommended that wheat straw can be used up to 20 per cent of legume fodder dry matter before ensiling.

After harvesting, next important step is to ensile. Silos should be filled rapidly. In Pakistan where erect steel silos are not available silage can be made in trench silos (pit) that could be covered with plastic sheets and plastered with mud and wheat straw to provide anaerobic conditions.

The fodder should be chopped and trench silos may be filled with this chopped fodder and must be pressed properly to remove air to have good an-aerobiasis. Packing of fodder is imperative to help exclude air from the silo because fodder tissue respiration results in the loss of nutrients which would otherwise be available for the anaerobic bacteria to use for lactic acid production. The temperature of fodder will increase when oxygen is present that can damage the silage. Further presence of oxygen encourages growth of fungi which causes greater instability and susceptibility to aerobic deterioration.

The silo can become anaerobic within five hours if the silage is well packed and sealed immediately after filling, whereas it can take up to 90 hours to become anaerobic if sealing is delayed. With berseem it has been shown that a delay of as little as 12 hours in sealing the silo causes a butyric acid type of fermentation to occur instead of the more desirable lactic acid type of fermentation.

Various silage additives like molasses, starch, urea, bacterial inoculants and absorbents are available and can be considered when required. Duration of ensiling is also important factor for silage quality. It is recommended that fodder should be ensiled for at least 30 days for better fermentation and preservation.

When the silos are opened, oxygen usually has unrestricted access to the silage at the face of opening. The silage should be removed immediately and the pit or silo should be covered again to minimize the exposure of air. Further, it is essential that silage should be harvested from silo only in a quantity that is needed for one time feeding. The more exposure to air at this stage can lead to nutrient loss and production of toxic compounds in the silage.

Recent national research on silage indicates that it could replace the conventional fodder without any ill-effect on intake, digestibility, milk yield and its composition in dairy animals. The following recommendations were made for ensiling and its feeding to dairy cattle.

The berseem and lucerne fodder ensiled at 30 per cent DM level with two per cent molasses have similar nutrient intake, digestibility and could safely replace the conventional leguminous fodder in the diets of lactating buffaloes. The jambo grass and mott grass ensiled with two per cent molasses for 30 days could safely replace the conventional grass fodder (75 per cent DM) in the diets of lactating buffaloes.

Maize, sorghum and millet fodders harvested at milk growth stage ensiled for 30 days can replace conventional fodders up to 75 per cent DM in the diets of lactating buffaloes and dairy cattle.

Ensiling of fodder is imperative to regularize green fodder availability around the year in Pakistan for dairy farming and to save labour cost. It can go a long way in vacating the land for cultivation of cash crops.