International Journal of Aquaculture, 2016, Vol.6, No.12, 1
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Lipid content of Coppens
®
was higher compared to those observed in Multifeed
®
(Figure 2), however, vitalfeed
had the least lipid content both in open and airtight conditions of storage. Ayuba and Iorkohol, (2013) also
reported differences in lipid content of Coppens
®
, Dizengoff, Durante and Adolf calyx fish feeds. Types and kind
of feed ingredient used in the feed formulation, as well as feed nutritional specification as determined by the
manufacturer, may have led to this variation. The lipid content of Coppens
®
and vitalfeed reduced as the storage
time increased for open storage condition (Figure 2), however, Multifeed
®
slightly varied but was not much
pronounced as the other feeds. These trends could be attributed to lipid oxidation at various degrees based on the
susceptibility of the lipid in the feed ingredient to deterioration. According to NRC, (1981), feed stored longer
than 90 days (three months) at ambient temperature is subjected to the breakdown of oil, and vitamin along with
peroxidation of lipid component. Rancidity resulting from lipid oxidation is the most outstanding deteriorative
changes in feed during storage. Feed ingredients containing lipids which are highly poly-unsaturated such as fish
meals are susceptible to oxidations (Pezzuto and Park, 2002; Sidhuraju and Backer, 2003). Chan, (1987) reported
that poly-unsaturated fats can quickly autoxidize at ambient or sub-ambient temperatures. AIN, (1980) however
reported that diets containing fish oil are more susceptible to autoxidation than diets containing other
polyunsaturated fats. It is an established fact that different variables are involved in oil shelf-life; processing,
storage conditions, light exposure, type of packing material, availability of oxygen and addition of antioxidants do
affect the quality and characteristics of fats and lipids containing products (Lawson, 1995; Polvilloet al., 2004)
this study as justified the fact that storage affects lipid content of feeds.
Figure 2 Monthly percentage lipid changes of Coppens
®
, Multifeed
®
and Vitalfeed under airtight and open conditions stored for the
period of six months
The magnitude of oxidative changes was monitored by the periodical measurement of peroxide value (POV), and
free fatty acid. The peroxide value levels increased in all diet groups over the storage period and was higher in
Multifeed
®
while least value was observed in coppen for both storage conditions (Figure 3; Figure 4; Figure 5).
This could be attributed to storage time and long exposure to air. Esterbauer et al., (1986; 1991), reported that
POV of fish oil diets constantly increased with time exposure to air and under normal feeding conditions.
Peroxide formation is likely to occur as susceptible poly-unsaturated fatty acids are available in the oil. Increases
in POV are catalyzed by free radicals attacks at sites. This might explain the observed higher rate of dietary
peroxide formation attained towards the end of the storage. Fritche and Johnson, (1988), reported an extremely
rapid autoxidation of diets with added fish oil as measured by peroxide value rapid oxidation (POV). Rasheed et
al., (1963), reported a high oxidation in diets containing fish oil. However, the value of free fatty acid (FFA)
increased slowly among the feed under airtight and open conditions throughout the storage period (Figure 6;
Figure 7; Figure 8).
