In semi-intensive carp culture, increasing the availability of natural food types in the culture systems plays a crucial role in enhancing fish production. As stated earlier, the commonest method used for increasing natural food supply is through the application of organic and/or inorganic fertilizers. No specialized live food production facilities are needed for the rearing of mrigal fry. However, research has revealed the importance of live food in rearing of advanced mrigal fry and fingerlings (Jana and Pal, 1987; Jana and Chakrabarti, 1990a, 1990b; Chakrabarti and Jana, 1998).

In India and Bangladesh, intensive mrigal, catla and rohu culture is rarely practiced and semi-intensive aquaculture is only a recent initiative, hence the demand for compounded complete feeds is relatively low. Most farmers use farm-made feeds, made from locally available ingredients such as rice bran and oilcakes. In the southern Indian state of Andhra Pradesh, where large-scale carp culture is practiced, feed forms an important input and is required in large quantities. To meet the demand, a large number of small-scale and a few large-scale feed manufacturers have appeared. However, at this stage pellets are not commonly used and their quality is poor. The proximate composition of factory-made feeds is reported to be 20-30 percent protein, 2-4 percent fat, 10-15 percent fibre, 30-40 percent carbohydrate, and 8-10 percent ash (Nandeesha, 1993). Often these feeds are claimed to have been enriched with lysine, methionine, vitamins and minerals. Some examples of formulated feeds used for Indian carps have been provided by New (1987) and these are presented in Table 9. 

A wide variety of feed ingredients are available in India, Bangladesh and other Asian countries where carp culture is practiced on a commercial scale. However, many ingredients are not used due to irregular supply and high cost. A list of feed ingredients of plant and animal origin that can be used in carp feeds, with their optimum inclusion levels are provided in Table 10. For various reasons these research findings are not often translated into practice but provide some idea regarding their nutritional value as ingredients for Indian major carp feeds.

Fishmeal is the generally preferred protein source but because of the high cost and erratic supply it is rarely used. Efforts have been made to partially substitute fishmeal either completely or partially with locally available feed ingredients of both plant and animal origin. In particular fishmeal replacement studies have focused on the use of oilseed meals and cakes, legumes, cereal byproducts and aquatic plants (Garg, Kalla and Bhatnagar, 2002).

There are no generalized feeding schedules for the use of supplementary feeds in Indian major carp culture. The most commonly used feeding practices are summarized in Table 12. The feeding rate for Indian major carp larvae is determined according to the increment in weight during the 15 day rearing period. The traditional supplementary feed (a mixture of dried and powdered oil cakes with rice bran at a 1:1 ratio) is provided daily at a rate of double the weight of fry at the time of stocking. From the 6th to the 10th day after stocking, the amount of feed is increased to three times of the weight of the fry at the time of stocking and between day 11 and 15 the rate is increased to four times of the original weight of the fry. As a standard practice, the larvae/early fry are fed twice a day (in the morning and in the afternoon when dissolved oxygen content in the water is high). However, recent polyculture studies with catla, rohu and mrigal have shown that feeding three times daily results in higher growth and better feed utilization in mrigal fingerlings (Biswas et al., 2006). Quantitative requirements of feed are important since underfeeding depresses growth while over-feeding results in wastage of food. Feed is generally applied at a rate of 5 percent of the initial biomass for the first month and at 3 percent and 1 percent in subsequent months, based on the biomass estimated at monthly intervals. However, experimental studies by Sen, Rao and Mohanty (1980) and Khan, Ahmed and Abidi (2004) reported maximum growth of mrigal fingerlings at a feeding rate of 6 percent BW/day, decreasing to 5 percent of BW/day.

Standard feeding schedule recommendations are available for carp polyculture involving either three species of Indian major carps (catla, rohu and mrigal) or six species of carps (three Indian major carps plus silver carp, grass carp and common carp). In the ‘six species polyculture system’, Indian major carps are stocked in equal proportions at about 40 percent of the total number. Under these conditions it is recommended that the fish are fed at two to 3 percent BW/day with a 1:1 rice bran: oil cake (uncooked) feed. However, standard practices have not been universally adopted due to the non-availability of fingerlings of all species and the poor market demand for exotic carps in some areas (Nandeesha, 1993).  Feeding is generally done by broadcasting once a day preferably in the morning.

Mixed feeding schedules, i.e. the use of different feeds at different feeding times, have been shown to have beneficial effects on fish growth and reducing feed costs. A significant cost savings have been achieved in pilot-scale trials by either feeding the fish for two days with a high protein feed and alternating this with one day of low protein feed; or alternating high and low feeding rates; or feeding the fish with intermittent fasting periods; or alternating feeds with protein of animal origin and plant origin (Mukhopadhyay and Chattopadhyay, 2002). However, there is little information on the use of mixed feeding schedules under farming practices.