Aquaculture is one of fastest growing food production sectors in the world, it promises to meet the dietary protein needs for a growing population, and the region has been taking a leading role in aquaculture production over the past three decades. However, despite remarkable production, rapid development attributed to support of advances in science and technology have been a relatively recent phenomenon and many aquaculture practices are still very much empirical or a kind of art to some extent, with which precision of science has yet to be established. Trial and error is still the prevailing way of thinking and an important approach for farmers to tap into the maxima of system carrying capacities and production margins that are demanded by either the need for food security or chasing of commercial profit.

Imperfect science in combination of greed for blindly maximising production or profit through increasing magnitudes of inputs have often pushed farming systems to such a limit that disease outbreaks and crop collapse have become common occurrences and farmers suffer great economic loss. Such has been the case in intensive shrimp culture.

Feeding is the primary activity and the most important human intervention in fish farming that dictates system intensity, economic viability, and environmental compatibility of a farming operation. However, decisions on feeding by a majority of farmers often diverge from scientifically reasonable optima, resulting in excessive nutrient inputs, low feeding efficiency, self-pollution, high production cost, negative environmental impacts and in extreme cases causing crop crush and collapse. This is basically because:

• Precision feeding based on proper assessment of the biomass of cultured organisms, environmental factors and feeding behaviour cannot be easily achieved by most farmers especially the majority of small-scale farmers.
• They tend to believe that the more they feed the fish, the better the production while system carrying capacity is overlooked.

Innovations in feed and feeding technologies and farming practices to improve feed utilisation efficiency therefore are crucially important for sustainability of aquaculture. In this presentation the author tries to:

• Present some innovative feeding manipulations at farm level.
• Examine some farming systems and practices that favour higher ecological efficiency.
• Share some thoughts on innovations at farm level.

Some innovations in feeding manipulation

Pulse feeding refers to feeding regimes involving alternation of normal feeding and a certain period of fasting or restricted feeding. Research and farming practices have shown that properly managed pulse feeding can effectively reduce feed cost and improve feeding efficiency without impairing fish growth of some important cultured fish species such as tilapia, pangasius catfish, milk fish, and Indian major carps. In some cases, nearly 50% or more feed can be saved especially in semi-intensive fertilization-based systems.

Feeding differently in grow-out is another method to reduce feed costs. This includes utilising product substitution in feeds through alternative sourcing of ingredients and changing levels of nutrient contents especially protein to increase the protein sparing effect. This has been proven effective to reduce feed costs and improve FCR.

The concept of compensatory growth may be used in nurseries. Fasting or restricted feeding to tilapia fry over one month old for certain periods of less than four weeks may not affect subsequent survival and growth of fish when they are fed normally. This allows farmers to prolong nursing duration to adapt to fluctuations in market demand without significantly increasing feed input.

In contrast, break feeding schedules are practiced by some farmers, in which a ration is split into two to three parts and applied at certain time intervals. This practice tries to realise a close-to-satiation feeding in respect of size variation of cultured fish, hence to optimise growth of the whole cultured stock.

Floating feed can easily drift away with waves induced by prevailing winds. Feed waste occurs when feed pellets drift to places that fish do not access. Feeding rings of various designs can effectively prevent this from occurring. Using fine-mesh netting material to enclose the feeding area is one good example. Sinking feeds tend to mix with pond mud and cannot be accessed by fish or shrimp. For ponds with muddy bottoms it is difficult to maintain a solid feeding ground. Lining the feeding area with a plastic sheet is a technical option to improve feeding efficiency.

Adoption of feeding innovations at farm level often requires careful consideration and farmer experience. In general, "feed light and feed right" is the rule to follow.

Farming systems and practices that favour higher ecological efficiency

A proper farming system choice depends on many factors such as productivity requirements, resource availability, farmed species and production scale. Feeding efficiency in terms of feed nutrient utilisation is nevertheless the primary indicator to consider. Some example systems and farming practices that favour high eco-efficiency, low feed costs and environmental compatibility are:

• Semi-intensive fertilisation based system with energy rich supplementary feeding.
• Substrate supported periphyton enhancement system.
• Polyculture.
• Integrated multi-trophic aquaculture.
• Integrated rice-fish culture.
• Cages/raceways in ponds.
• Biofloc systems.
• Biological enhancement of nutritional value of on-farm feeds etc.

Some considerations

• On-farm feed management practices are important and mechanisms need to be developed to promote and communicate these innovations to other farmers.
• Farmer innovations may look insignificant, yet minor changes may result in big differences.
• The human dimension matters in feeding management.
• System solutions are sensitive to resource settings and adaptive learning is needed.
• Proximity to precision feeding should be pursued under all circumstances.