This piece, authored by Dr Brett Glencross, was first published in International Aquafeed Magazine, July 2023
In the last issue of International Aquafeed I wrote about the journey that we have made in science over the past twenty plus years in terms of improving the outcomes for aquaculture through the three pillars of nutritional research: management / ingredients / requirements. This last of those pillars; requirements, forms the basis by which we design the specifications for feeds and thereby allows us to optimise the nutrients we supply, and directly impact growth and feed use efficiency of the animals we feed. However, one of the things we noted in reviewing the science on this, was that most of the big gains in things like feed efficiency have already been made, at least certainly so for the main aquaculture species. Increasingly we can see that the science around defining requirements is becoming increasingly precise, to the point where we are now seeing the development of a precision nutrition approach to feed design.
So, what does “precision nutrition” entail? In the early days of aquaculture nutrition, feeds were typically designed based on species alone. We had salmon feeds, shrimp feeds, and so on. Now, we typically see up to ten different feed specifications applied to salmon from first feeding through to harvest. In that regard what we tend to see among those ten different feed specifications is changes in protein and energy balance, with further tailoring things like EPA and DHA, and specific essential amino acids, and various other micronutrients. We also see a similar trend in shrimp feeds, though perhaps not as many feeds and certainly the changes in protein and energy balance are not as dramatic. There is a good reason for this, as it reflects the changes in demands for key nutrients and energy as the animal grows. And it has been derived from a growing understanding of the precise requirements of animals at different stages of production that has led to this precision approach.
Another aspect to that precision nutrition story has been to move away from crude feed specifications towards diets being designed based on digestible, or in some cases, net nutrient, and energy supply. This advance has considerably opened the capacity of feed formulators to use a wider range of ingredients and ensure consistency of animal performance. After all it’s the digestible nutrients that an animal uses, not the crude nutrients. So, it makes logical sense to approach formulating that way, but this has taken a step-change in our understanding of both nutrient utilisation and ingredient management to be able to make that advance. A recent development of our understanding of the net energy concept in aquaculture has led to the realisation of the actual energy available from different nutrients (protein, fat, starch) within various ingredients and how that is not consistent across many species. Some species like tilapia seem to use starch well, whereas others not-so-much.
So, now in the 21st century, we see that through a precision nutrition approach we are formulating different feeds for different species and different life stages. We can also do this based on variable nutrient supply from various ingredients, and through a better understanding how some species can use starch, while others less so, be more precise in ensuring that both the nutrients and energy being supplied, are done so in an effective way. And just when you might have thought we almost had it all covered, we are now finding that further dimensions exist in terms of both the health-status and the environment in which the animals are being raised. We are now also seeing feeds for immune-enhancement, recirculating aquaculture systems (RAS) and high-water temperatures, among other things. But I guess this is the nature of a precision approach, it all just continues to get a little more precise?