Investigating the effects of replacing fish meal and fish oil with plant sources in feeding rainbow trout

Dissertation

To receive a master's degree

Natural resources engineering - reproduction and breeding of aquatic animals

Abstract:

The purpose of the present study is to investigate the possibility and effects of replacing plant sources in the diet of colored trout It is a bow. For this purpose, a combination of vegetable protein sources with the main source of wheat gluten along with corn gluten and soybean meal at 2 levels of 50 and 100% and vegetable oil sources of a combination of rapeseed (40%), linseed (30%) and safflower (30%) oils at 100% level were substituted for fish oil. Sources of protein and dietary oil of the control group were fish meal and Kilka fish oil. In order to investigate the effects of replacing 100% of dietary fish oil with the combination of vegetable oils, defatted fish powder (defatted by hexane and ethanol solvents) was used as a dietary protein source. This study was in the form of 8 experimental treatments. Protein and fat sources in experimental groups in treatment 1 (fish powder + fish oil), treatment 2 (vegetable protein + combination of vegetable oils), treatment 3 (vegetable protein + combination of vegetable oils + fish oil), treatment 4 (vegetable protein + fish oil), treatment 5 (fish powder + vegetable protein + combination of vegetable oils), treatment 6 (fish powder + vegetable protein + fish oil), treatment 7 (defatted fish powder + fish oil) fish) and treatment 8 (defatted fish powder + combination of vegetable oils). A number of 1200 fish were selected and after the adaptation period, they were transferred to 300 liter tanks with a density of 50 fish in each tank with an average initial weight of 15±2 grams and were fed with experimental diets for 60 days. The experimental diets were at the same level in terms of protein (47±0.2), fat (20±0.15) and energy (5±0.1 Kcal/g). In this study, indicators of growth and nutritional efficiency, chemical composition and fatty acid composition of muscle tissue, activity of digestive enzymes, blood factors, immune response and resistance to oxygen deficiency stress are investigated. According to the results, the final weight index by replacing 44% of the diet fish meal (50% of the total protein of the diet) with plant sources in treatment 5 (69.00±1.5) and treatment 6 (72.45±3) did not have a significant difference with the control group (71.08±1.8). Also, no significant negative effect was observed in other growth indicators, nutritional efficiency, apparent digestibility of fat and protein, chemical composition of muscle tissue, activity of digestive enzymes, humoral immune system activity, blood biochemical factors and resistance to oxygen stress compared to the control group. However, by replacing 100% of ration fish meal with vegetable protein sources, it had a negative and significant effect on growth indicators, nutritional efficiency, apparent digestibility of fat and protein, and the activity of digestive enzymes of fish, but did not cause a significant difference in the composition of fatty acids of fish muscle tissue. Replacing dietary fish oil with the combination of vegetable oils decreases the percentage of fatty acids C16:0, C22:0, C16:1n7, C18:1n9, C20:2n6, C20:4n6, C20:3n3, C20:5n3 and C22:6n3 and increases the percentage of fatty acids C18:0, C20:0, C18:1n7, C18:2n6 and C18:3n3 relative to total fatty acids compared to diets containing fish oil. The composition of fatty acids in fish muscle tissue was directly related to the composition of fatty acids in the diet of fish. Substitution of fish oil with vegetable sources in different protein sources did not affect the growth indices of fish. But it decreased the percentage of fatty acids C14:0, C16:0, C16:1n7, C20:3n3 and C20:5n3 and increased the percentage of fatty acids C18:2n6 and C18:3n3 compared to the total fatty acids compared to diets containing fish oil.

Key words: plant sources, growth, digestive enzymes, immune response, carcass composition, acids Fatty, oxygen stress

-1-Introduction:

Aquaculture is very important in order to meet the nutritional needs of humans and to use protein materials of animal origin that have good quality. According to the estimate of the World Food Organization, the amount of fish demand for human consumption is about 110 million tons in 2010 and the share of aquaculture in the total world production is 38%. Due to the high production rate in some species and the ease of production of aquatic products compared to other protein products and their high nutritional value, today aquaculture is considered as one of the fastest growing activities effective in increasing food production (Hasan., 2002)..

The unique characteristics of rainbow trout (Oncorhynchus mykiss), including the high adaptability of this fish to the climatic conditions of Iran, have made this fish become one of the most important farmed species in the country and take a high share of production. The production and supply of food for the growing population of the earth is one of the most important problems of human societies and it is expected to become one of the basic problems of mankind in the not too distant future. The increasing use of natural resources and the reduction of these resources and, on the other hand, numerous problems in artificial aquaculture are among the current limitations of aquaculture producers (Satari, 1380).

The global increase in aquaculture production and the simultaneous decrease in fish stocks used for the production of fish meal and fish oil have made the replacement of fish meal and fish oil in fish diets a necessity for the sustainable development of the aquaculture industry (Bell et al. al., 2002; Mourente et al., 2005; Miller et al., 2007). Because the global production of oils obtained from vegetable seeds has increased steadily in recent years, so that their prices are relatively stable and their availability is more (Table 1-1) (Mourente et al., 2005; Mourente and Bell, 2006; Huang et al., 2007). Vegetable oils that are rich in 18-carbon short-chain unsaturated fatty acids (C18 PUFA) and mostly free of n-3 group unsaturated fatty acids (n-3HUFA), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), can be good representatives to replace fish oil in fish diets (Mourente et al., 2005; Mourente and Bell, 2006; Huang et al., 2007). Some fish, such as rainbow trout and common carp, are able to lengthen the carbon chain and unsaturate 18-carbon fatty acids, especially linolenic acid, to 20- and 22-carbon HUFA fatty acids of the n-3 series, especially eicosapentaenoic acid and docosahexaenoic acid (Webster and Lim, 2002). The ability to synthesize EPA and DHA from linolenic acid allows nutritionists to formulate diets containing cheaper vegetable oils containing linolenic acid (such as flaxseed oil, canola, etc.) instead of using more expensive marine fish oils that are rich in EPA and DHA (Lovell, 1988; Websterand Lim, 2002). It is an aquatic feed that is also used in many poultry and livestock breeding centers. Raw materials of plant origin are cheaper than raw materials of animal origin. Therefore, the producers of aquatic feed tend to replace materials of plant origin instead of materials of animal origin (fish powder). Oilseed meal is produced by extracting oil from oilseeds, which have less protein than animal powders (30 to 50% protein). Their amount of mineral salts is low, but they have a significant amount of cell wall compounds, while they also contain more anti-nutritional substances. Soybean meal is widely used in the feeding of most farmed fish due to its high availability, stability, reasonable price and especially favorable nutritional value. The value and importance of oilseeds in terms of providing the energy needed by humans, livestock, poultry and aquatic animals has a special place among crops. The global production of oils obtained from vegetable seeds has increased steadily in recent years, so that their prices have been relatively stable and their accessibility has increased. Meals, which are products of oilseeds, are used as a suitable protein source in feeding aquatic animals. As mentioned, proteins are the most expensive part of the diet of aquatic animals, so in order to reduce the cost of diets, vegetable protein sources are used instead of fish protein sources.

Given that the aquaculture industry is going through a completely upward trend and the demand for fish meal and fish oil is increasing day by day. Finally, for the sustainability of this process, a solution must be thought of so that the growth and development of this industry does not face stagnation and marine resources are not endangered and preserved for future generations.