Index
- Evolution of fish consumption in the last decades
- Implementation of aquaculture
- Diets for fish farms
- Ingredients of vegetal origin: limitations in carnivorous species
- How to improve diet utilization when using alternative protein sources
- Conclusions
1. Evolution of fish consumption in the last decades
Prior to understanding the use of alternative protein sources in aqua feeds, we need to talk about the exponential growth of human population since the mid-20th century, which led to greater food demand. This adds up to the increasing percentage of middle-class population in China and other South Asian countries that demand for high-quality protein sources [1].
These factors caused a great increase in fish demand and, consequently, aquaculture gained importance as a fish source for human consumption [2]. Another reason why aquaculture is gaining weight as a fish source is that fisheries are not sustainable in the long term (see chart 1).
2. Implementation of aquaculture
Nowadays, aquaculture accounts for almost 50% of the marine food and it is forecasted that, in 2030, fish from aqua farms will exceed fish from fisheries.
Aquaculture is the sector in food production that experienced the greatest growth in the last three decades, as it is a cheaper, simpler, and more sustainable way to obtain high-quality protein.
Fish is a valuable source of nutrients and micronutrients and has an important role in human nutrition and in the food chain globally.
3. Diets for fish farms
Traditionally, fish meal was the base of aqua feeds, but the increasing demand and the exploitation of seas and rivers has put in risk the availability of this protein source. Because of it, there is a trend to decrease the use of fish meal and fish oil for aquaculture diets.
Some plant-based ingredients are used to replace this protein source. Usually, these ingredients are easy to obtain and their cost per unit is low, compared to that of fish meal. However, even though using vegetal protein sources reduces feed costs, it is sometimes difficult to reach good performance results.
This is particularly relevant in aqua farms of carnivorous species, such as salmonids, whose protein requirements are high and above 50% in fingerlings. For this reason, vegetal sources are usually combined with animal sources, such as feather meal, MBM, among others) [3].
4. Ingredients of vegetal origin: limitations in carnivorous species
There is a great variety of protein sources from a vegetal origin available for aqua feeds, such as soybean meal, corn gluten meal or rapeseed meal. These ingredients, particularly soybeans and other leguminous, have important limitations that mainly affect the carnivorous fish species, who require protein of an excellent quality at high concentrations.
- Soybean (and other leguminous) contain antinutritional factors (ANFs) that negatively affect feed digestibility and gut health. Among these factors, there are the antitrypsin, which inhibits the proteases in charge of protein digestion, and lectins, which cause inflammation of the gut epithelia.
These ANFs have a greater impact on health and performancein carnivorous species because their organism is specialized in digesting high-quality protein and they are not used to plant-based ingredients, making their flora and intestinal cells more susceptible to antinutritional factors, including fiber and carbohydrates.
- Another drawback of leguminous such as peas, beans, soybean, or canola is that, despite having a more consistent composition than fish meal, they can decrease feed palatability.
- Besides, their protein content is lower than that of other ingredients such as fish or meat meals (see table 1).
5. How to improve diet utilization when using alternative protein sources
Inclusion of functional additives in aqua diets is an effective mechanism to counteract limitations related to plant-based protein sources. These additives have two main areas of action: enhancement of digestive system’s functions and ANFs minimization or inactivation.
The former is based on active plant-based active molecules called intestinal conditioner pronutrients capable of activating enterocyte functions and, this way, they optimize feed digestion and nutrient absorption to enhance the bioavailability of protein and other nutrients.
The latter refers to enzymes that inactivate ANFs and help to digest proteins and carbohydrates. The inclusion of efficient enzymes that are particularly designed according to the diet composition favor fish growth and welfare. These additives are of great importance in carnivorous fish farming, as the endogenous production of these enzymes is inexistent or limited in these species.
However, there are other mechanisms designed to reduce ANFs impact in aqua feeds, some of them are still under development and are poorly accepted by the consumers, such as the production of genetically modified soy whose genes related to ANFs production are silenced; and others that are currently being used such as amino acid, vitamin and mineral supplementation to meet the species requirements [4].
6. Conclusions
Plant-based ingredients in aqua feeds are gaining importance as they are cheaper and more sustainable than fish protein sources.
These ingredients can cover an important part of protein requirements, but their success, particularly in carnivorous fish farming, depends on the inclusion of functional additives that enhance protein digestibility and minimize the effects of ANFs. Intestinal conditioner pronutrients and multienzyme products with proteases and carbohydrases stand out among these additives.
In Delta Labs, we offer the feed formulation and analysis service to optimize feed composition and recommend the best functional additives. To use this service, please contact us through our webpage www.globalvetslab.com or send email to info@globalvetslab.com.
References
- [1] K. Hua et al., “The Future of Aquatic Protein: Implications for Protein Sources in Aquaculture Diets,” One Earth, vol. 1, no. 3, pp. 316–329, 2019.
- [2] J. Bostock et al., “Aquaculture: global status and trends,” Philos. Trans. R. Soc. B, vol. 365, pp. 2897–2912, 2010.
- [3] F. Y. Ayadi, K. A. Rosentrate, and K. Muthukumar, “Alternative Protein Sources for Aquaculture Feeds,” J. Aquac. Feed Sci. Nutr., vol. 4, no. 1, pp. 1–26, 2012.
- [4] K. S. Medale Fracoise, “Protein sources in feed for farmed fish,” Cah. Agric., vol. 18, no. 2, pp. 103–111, 2009.