APPLICATION OF ENZYMES FOR IMPROVING FEED DIGESTIBILITY AND PERFORMANCE IN CARP CULTURE
Supplementation of enzymes to improve the digestibility is a well-established practice in production animals but not been exploited in aquatic animals to its full potential. Indian major carps (IMC) are freshwater fishes mainly reared in India; the species include rohu (Labeo rohita), catla (Catla catla) and mrigal (Cirrhinus mrigala). Around 65% of IMC cultured in India are fed exclusively with mash feed, and 35% are fed with mix of mash and pellet feed. The mash feed prepared by farmers majorly consists of de-oiled rice bran (DORB) - 80%, groundnut cake - 10%, cotton seed cake/ sunflower cake - 10%. IMC also feed on zooplankton, phytoplankton and higher plants. The native enzymes in IMC include trypsin, lipase, amylase, glucosidase, maltase, sucrase, lactase, melibiase, and cellobiase. We hypothesized that supplementation of additional enzymes would improve the digestion of feed and phytoplankton.
Considering the type of feeding materials being used and amount of endogenous enzymes present in IMC, an enzyme formulation was developed specifically for carp culture. The formulation was further fine-tuned after taking into account the feeding pattern of carps, which includes phytoplankton, waterweeds, insects, mollusks etc. The formulation was tested for in vitro feed digestibility using DORB as a substrate, individually and in combination with IMC gut enzyme preparation. Crude enzyme extract from fish intestine was prepared by grinding the whole intestine of rohu ((Labeo rohita) fingerling in chilled phosphate buffer saline, the protein content of the extract was determined in the supernatant of crude extract which was used as enzyme mix for the studies. An improvement in digestibility was measured based on in vitro sugar release.
The combination of enzymes in the formulation was observed to give improved sugar release as compared to the individual enzymes when used alone. A significant increase in sugar release was observed when the formulation was supplemented with or without the gut enzyme extract from fish. We also noted a synergistic effect for the formulation when used in combination with the gut enzyme extract from fish.
In carp culture farms in India, the feed is supplemented in submerged feed bags which posed a concern on the leaching of enzymes and possible requirement of higher dosages. A study was conducted with enzyme supplemented feed bags submerged in water for 3 h, and the leaching was measured based on release of cellulase in to water. It was observed that only less than 1 % of the total enzymes are leached in to water during this time period.
The formulation, Kemzyme® Aqua was tested at commercial carp culture systems. It was observed that supplementation of Kemzyme® Aqua in feed improves the body weight and enhances pigmentation in IMC. This would enable the farmers to reduce the culture period and fetch a better price for the produce as the pigmentation improves market price for IMC.