Aqua nutrition company Alltech Coppens has launched a feed formulation service based on net energy – an approach designed to neutralize the natural variation in raw materials and take into account the differences in efficiency of the different macronutrients.
“Differences in digestibility and nutrient composition of raw materials can potentially affect the performance of fish between batches of feed. By implementing the net energy concept in our feed formulation we can take these differences in the quality of raw materials into account and therefore assure a constant feed quality and fish performance,” Ruben Groot, aquafeed nutritionist at Alltech Coppens, told this publication.
Net energy explained
All animal feeds contain a certain amount of energy, which is mainly derived from protein, fat and carbohydrates. When feed is eaten, some of this energy is not digested and therefore not available to the fish. Of the digestible energy, again, part is lost as a result of metabolism. The energy that is available in the end for maintenance and growth of the fish is called net energy.
The use of net energy is not a new concept in animal nutrition and has been standard industry practice in pig feed evaluation for decades.
However, according to Alltech Coppens, most aquafeed companies still formulate their feed based on fixed digestible energy levels. Whilst this allows flexibility in terms of what materials can be included, it can result in formulations made up of lower quality raw materials and a variation in nutritional composition.
“The limited availability and increasing prices of some ingredients, such as fishmeal, requires aquafeed producers to be flexible in the use of raw materials. However, the quality of different raw materials can vary a lot,” said Groot.
Not all digestible energy forms equal
Research from the Alltech Coppens Aqua Centre (ACAC) and associated universities has shown that not all forms of this digestible energy (from protein, fat and carbohydrates) are utilized with the same efficiency.
“Energy from fat, can, for example, be used more efficiently than energy from carbohydrates and can therefore lead to a difference in the net energy of the feed,” explained Groot.
When formulating a ration on net energy, Alltech Coppens says it takes into account these differences in the utilization of digestible energy in the formulation software.
“When replacing fishmeal with plant protein, for example, you can introduce more carbohydrates into the formulation. And because we know that the utilization of energy from these carbohydrates is less than from fat, we can correct for this in the energy content in the feed,” said Groot.
“We therefore not only take into account the differences in digestibility of raw materials but also the differences in the nutritional composition of raw materials, thus taking one step further in aquafeed evaluation.”
The hypothesis that net energy could give a better prediction of performance than digestible energy was tested in over 150 feed performance trials conducted at the ACAC.
“These trials confirmed our belief that net energy evaluation will increase the accuracy with which feed can be formulated in aquaculture and will boost consistent feed performance,” said Groot.
High energy trout feed
At present Alltech Coppens has only implemented the net energy approach in high energy trout feeds, where carbohydrates represent a minor proportion of the total energy in the feed.
“The reason for this is that in pigs the utilization efficiency of different carbohydrates seems to differ, with starch being more efficiently utilized than other non-starch polysaccharides. Also, in a carnivorous species like trout it appears that the utilization of carbohydrates is limited at higher intakes.”
Groot said that a PhD project in cooperation with Wageningen University is exploring net energy evaluation and this carbohydrate fraction in feed formulation for salmonoids in aquaculture.
“The findings of this project will allow us to further implement net energy in aquafeed and increase the strength of these models in feed formulation,” said Groot.