Автор - | 04.03.2019

The development of the fishing industry requires the introduction of new, better and more efficient feed. Since fishmeal is no longer able to fully satisfy all needs. Professor CHARLES S. NGUGI from Kenya, working on a fish farm, is actively using amaranth leaf, as an alternative to the usual fish meal.

What caused such a choice
Amaranth leaves are characterized by high nutritional properties. In addition, it should be noted the rapid growth, not Charles Nguit, the requirements for care, resistance to high air temperature and long dry periods.

If we talk about the nutrient content, Professor NGUGI notes that the dry matter obtained from amaranth leaves contains from 17.5 to 30.3% of protein, 5% of which is lysine, an important amino acid. Also there are vitamins A and C.

Among other important elements present in the leaves of amaranth, it is necessary to highlight such substances as:

  • sodium is necessary to maintain the balance of extracellular fluid;
  • potassium is necessary for the functioning of hemoglobin and maintaining the electrolyte balance and normal cellular function;
  • magnesium – required for enzyme exposure, muscle contraction, transmission of nerve impulses and bone health;
  • phosphorus – regulates acid-base balance and takes part in the formation of bones and cells.

Research amaranth leaves
Not so long ago, amaranth leaves were actively studied by an international research team of scientists from the United States and Kenya. The team, headed by Professor NGUGI, included Dr. Elija OYO from the Karatina University (Kenya), Professor YULIY MANYALA from the University of Eldoret (Kenya) and Professor KEVIN FITCSIMMONS from the University of Arizona (USA).

During the research, growth, nutrient formation, composition and digestibility of all nutrients by tilapia (Oreochromis niloticus) were analyzed – it was this fish that participated in the study as an experimental specimen, it was given protein concentrates from amaranth leaves.

According to Professor NGUGI, Kenya’s fisheries are currently small farms, and fish production is not very intensive.

“Today, Kenyan farmers have to rely on expensive, imported fish feed, so we thought it would be advisable to find alternative, cheaper sources of protein. We began our research with the Aytea shrimp (Caridina nilotica), but due to the limited amount of such a product, we paid attention to other options. Amaranth leaf, hydrolysates from leaves and concentrates showed a good protein content, and this became the basis of our research, ”says NGUI.

Features of the research
During the study, tilapia was fed 4 times a day for 160 days. Test diets were prepared in which 100 percent, 75 percent, 50 percent, 40 percent, 20 percent, and 0 percent of fish meal protein, respectively, were replaced with protein concentrates with the same percentage of amaranth leaves.

Diets have also been prepared using local feed ingredients such as wheat bran, perch, cassava fish-flour and mineral, vitamin premixes.

The results were evaluated for efficacy, nutrient utilization, body weight, nutrient survival and digestibility, and the feed conversion rate (FCR) and specific growth rate (SGR) were calculated.

“We assumed that alternative amaranth types of feed, which give similar growth rates, as when consuming fish meal, would be suitable for fish farms, because they are cheaper than fish meal,” said Professor NGUI.

Although fishmeal diets had a higher profile of various essential amino acids, phenylalanine and tryptophan rates were lower compared to amaranth leaves.

Growth efficacy was generally not dependent on replacing amaranth leaves without significant differences in terms of SGR, average weight gain and weight gain between diets of 100 percent fish meal and those containing 75 percent, 50 percent, 40 percent fish meal. respectively.

However, a diet containing 100% amaranth leaf concentrates gave a lower final weight, weight gain and FCR, and the maximum survival was observed in fry that received 100% fish meal.

Daily feed intake increased with an increase in the replacement of fish meal, and there were also significant differences in nutrient utilization parameters.

What conclusions have scientists come to?
The study showed that up to 80% of fishmeal can be replaced with amaranth leaves concentrates without affecting the growth and use of nutrients, but there are still differences.

For example, the essential amino acid composition of both was similar, with the exception of the levels of histidine, leucine, lysine and methionine, which were lower in amaranth leaves. This is expected to limit fish growth, especially low levels of lysine.

The presence of so-called anti-nutritional factors was also observed in amaranth leaves – these are phytates and oxalates, some of which remained associated with certain proteins in diets, making them inaccessible for digestive enzymes and, thus, reduced protein digestibility.

What can lead to a deterioration in the absorption of some essential amino acids in diets of amaranth leaves, which leads to a decrease in fish growth.

“The amaranth leaf still faces many problems,” explained Professor NGUGI. “The plant does have potential, for example, amaranth can help increase the concentration of essential amino acids. But there are other problems – for example, it is necessary to solve such a problem as effective processing and processing. Many farmers are unaware of the processing technologies required for feed production. ”

Professor of PNTU and his colleagues believe that their research will be important for fisheries. “More than 50% of Professor Charles Ngugiexperimental costs of farms go to purchase feed,” he says. – “The cost of feed is about 70% of the cost of protein ingredients. That is why fish meal and other protein ingredients of animal or vegetable origin are expensive. Finding cheaper alternatives will help generate more affordable feeds. In addition, farmers can study and implement the required technologies for the production of such feed and work at a lower cost. ”

Professor NGUHI and his team positively evaluate a greater number of different components in amaranth leaves, its protein concentrates and hydrolysates. They hope that in the future a wider choice of ingredients and components will allow farmers to develop their own food, the cost of which will be much lower than that of the current fish meal.

“We are currently working with researchers from the University of Arizona and the University of Eldoret on the technical aspects of amaranth leaf research,” said the professor. “We received funding from the Aquafish Innovation Lab project (a USAID-funded Aquafish Collaborative Research Support Program) to promote cheaper and more affordable alternative ingredients for protein feed for fish farms, and research projects are available for our graduate students. We are also open to other project proposals from researchers, covering the same topic as us. ”Fish

Although research on amaranth leaves as an alternative to fish meal, feed for fish grown in Kenya’s fisheries did not produce the expected results, but they are still extremely important data. And once again confirm the value of amaranth – it is increasingly being considered for use in various fields of human activity.

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