Stabilising water quality with pelleted feeds

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In Andhra Pradesh, progress has been made with the partial replacement of DORB with pelleted feeds to produce large 4-5kg rohu

 

The rohu Labeo rohita, an Indian major carp (IMC) is often farmed together with another IMC, the phytoplankton feeder fish, catla Labeo catla in polyculture systems, mainly to maximise the use of the pond stratum. Traditionally farming in large ponds, 50-80 acres (20-32ha) is common; the rohu is fed de-oiled rice bran (DORB) and 5% groundnut cake, placed in perforated bags at strategic locations in the pond. The small number of catla in the ponds, usually 5% of biomass depend on the phytoplankton in the ponds for growth.

Kenneth Chin (right) with Yeo Keng Joon, Director, Bharat luxindo holding a 5kg fish from a 28-acre(11ha) pound in Bondada Lanka, Andhra Pradesh. The Harvest was more than 100 tonnes

Market demand is mainly for  rohu fish weighing 1kg.  Farmers stock 150-200g juveniles and it takes 8 -12 months to reach this market size. There is  also a niche market in Kolkata, West Bengal and in neighbouring Bangladesh for 4-5kg rohu which will require another 6-8 months of grow-out. This is an attractive market as larger fish fetch higher prices on per kg basis; prices for 4-5 kg fish can reach INR155/kg (USD2.21/kg) in comparison to only INR100/kg (USD1.42/kg) for the smaller 1kg fish.

“However, not all farmers can grow rohu to this large size. Keeping the fish longer in the pond is risky especially as grow-out will extend into the hot summer months. The chances of mass mortality from low dissolved oxygen is highest if ponds are not well managed. The usual practice is to continue stocking ponds and perhaps clean and dry out after 5 crop cycles or more. They need to do so before the monsoon rains. Imagine the layers of anoxic uneaten feed and fish waste on the pond bottom. With the huge stocks in large ponds, losses usually reach several crores (one crore =INR10,000,000 or USD140,100),” said Kenneth Chin, Bharat Luxindo Agrifeeds Pvt Ltd, Palakol Mandal, West Godavari, Andhra Pradesh.

Partial replacement of DORB

DORB has been the traditional feed for IMC for the past 40 years or more. Farmers believe DORB stimulates the growth of plankton in the ponds while the catla helps to control pond phytoplankton and pond water quality. Pelleted feeds for the rohu have been in the market for several years but changing farmers mind-set is not easy particularly when pelleted feeds cost from INR26-33/kg (USD0.36-0.46/kg) as compared to DORB at INR15.4/kg (USD0.21/kg, CLFMA, November 2019).

An Indian study in 1990 gave a 30% crude protein (CP) requirement for the rohu. Since farmers could not accept the high cost of a 30% CP feed, Chin developed two  feeds with different ranges: a lower 18-20% CP feed and another with a higher range CP of 28-29%. The protein source is 100% plant meal. “We then recommended the 18-20% CP feeds to farmers stocking at less than 2,000 fish/acre and the higher range for ponds with >2,000 fish/acre.

Adoption by enterprising farmer

For the last 10 years, adoption was slow despite various strategies by the sales teams. Chin said, “The next step was to encourage farmers to use pelleted feeds for at least 30% of their total feed requirements and wait for consistent results. Success came in 2019. We were lucky as we were working together with an enterprising farmer in Bondada Lanka who was very innovative in feed and farm management. He started by using 30% of pelleted feeds for his ponds in a previous cycle. When he saw a more stable water quality in his pond, in the last quarter of grow-out, he increased to 50% of pelleted feeds. In the next cycle, he used 60:40 (pelleted feed: DORB). Pelleted feeds are placed into perforated feed bags with DORB.

“In terms of feed conversion ratio (FCR), results with the last crop are not available yet but we can estimate that using 60% pelleted feed of 18% CP, it can be 2 to 2.5. With the higher CP feeds, FCR can be less than 2.”

However, it also helped that the farmer used juveniles produced at the Bharat Luxindo’s hatchery using broodstock which have been selected for growth.  Two-inch (5cm) juveniles were sold to the farmer who cultured the fish in his nursery for 8 months prior to stocking into the grow-out ponds. “We decided to support farmers with quality juveniles as we realised that grow-out results may be significantly influenced by juvenile quality,” said Chin.

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