Abstract
Efficient ruminant productivity is only possible if a
steady supply of quality forage in sufficient amounts is
made available to them. In Pakistan, there are two
important fodder scarcity periods, one is during winter
months (November to January) and other is during
summer months (May to July) and in rest of the year
fodder availability is fairly regular and abundant. This
abundant fodder if not properly managed is the
wastage of fodder resource. This situation calls for the
exploration of different means to improve quality and
quantity of roughages without sacrificing the area under
cash crops. Manipulating this surplus fodder can bridge
the gap between supply and demand. Silage making is
one of the important techniques in this regard (Tauqir
et aI., 2007).
The main goal of silage making is to preserve as much
of the nutritional value of the original crop as possible.
Preservation is achieved by acidity and by maintaining
an oxygen-free (anaerobic) environment. Acids are
produced by bacteria that convert fermentable
carbohydrates into organic acids, predominantly lactic
and acetic acids. As fermentation progresses, more
acids are produced, pH drops, and eventually the
acidity level is adequate to inhibit or kill most bacteria
and other microorganisms. At this pH if protected from
exposure to air and water seepage, silage can be
preserved for a long period. Concentrations of
fermentable carbohydrates in the forage, its buffering
capacity, dry matter (OM) content and the number and
type of bacteria present on the forage are the main
factors that could affect the rate of pH decline and final
pH of the silage (Boisen et al., 1996; Higginbotham, et
al., 1998). Grasses have relatively low buffering
capacity and low concentrations of fermentable
carbohydrates, therefore, pH decline is not rapid and
final pH is usually high. Leguminous fodders on the
other hand, have a high buffering capacity (due to high
protein and mineral content), and relatively high
concentrations of fermentable carbohydrates,
therefore, pH drop in leguminous crop silages was also
slow and loss of nutrients could be high (Boisen et al.,
1996).
Leguminous crops that are extensively wilted prior to
ensiling to lower the moisture content undergo very
limited fermentation and final pH values are usually
between 4.5 and 5, which are higher than that of nonleguminous silages. Therefore, for a rapid and
extensive fermentation to occur, the forage must have
high concentration of fermentable carbohydrates, low
buffering capacity, relatively low dry matter content (20-
40%), and adequate lactic acid bacteria present prior to
ensiling. Any fodder, which has sufficient amount of
fermentable carbohydrates, can be ensiled, but the
most popular fodder is maize (Woolford, 1984).
However, jambo and mott grasses, lucerne and
berseem (legumes fodders) can be used for silage
making provided that a source of fermentable
carbohydrates is added before ensilation (Tauqir N. A.
2007). The choice of crops for ensilage depends
primarily on the local environment. Generally high
yielding multicut fodders can be a good choice for
silage making.
Various silage additives like molasses, starch, nitrogen
(N), bacterial inoculants and different types of
absorbents are available and are used for different
reasons. Additives are used to improve nutrient
composition of silage to reduce storage losses by
promoting rapid fermentation, to reduce fermentation
losses by limiting the extent of fermentation and to
improve bunk life of the silage (increase aerobic
stability). Various additives like molasses (Boisen, et
al., 1996) and crushed grains (De Visser, et aI., 1998)
are added in non-leguminous fodders as a source of
soluble carbohydrates before ensilation to increase the
lag phase in silage. While, leguminous fodders are
already high in crude protein (CP) and moisture
content. So, before ensiling the leguminous fodders,
the moisture content is reduced either by field wilting or
by the addition of some absorbent (Fransen and Strubi,
1998). Dry roughages high in OM and low in N like
wheat straw can be used to improve the OM of
berseem and lucerne before ensilation (Tauqir N. A.
2007). However, the scientific evidence regarding the
nutritive value of silages of grasses and legumes as
affected by the use of various additives, fermentation
periods and moisture absorbents is limited and
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Tauqir, Nisa, Sarwar and Bhatti
inconsistent. .Therefore, the objective of this review is
to examine the effect of additives, fermentation periods
and moisture levels on nutritive value of various silages
in growing and lactating animals.
