elaboration d’aliments extrudes ecologiques et performants pour l’elevage de la truite arc-en-ciel (oncorhynchus mykiss. walbaum, 1792) au niveau de la station piscicole ain aghbal (azrou, maroc)

Abstract

There have been an exponential growths of aquaculture during the last two decades. This has led to the development of new practices and new ways in order to assure that the exploitation of the sector is sustainable. One of the first challenges facing aquaculture development is to succeed in substituting the fish meal as the main component of feed with a vegetable ingredient. Regarding this challenge, the main goal ofthis study was to test the feedsusually used in the rearing of rainbow trout and then choose the high-performance feed from a zootechnical and environmental point of view and later on come up with an adequate feed made up with national ingredients. This feed must meet the biological requirements of rainbow trout and obey to liquid discharge standards. The first part of this work was devoted to the assessment of the effect of three categories of feed (A, B and C) whose differences are based on biochemical compositions; zootechnical performances and on the quality of finished product (fatty acids and salmonisation) as well as the effect of the effluents discharges on the environment. The experimental test, which was carried out during 222 days, in the concrete tanks of Ain Aghbal fish farm located near OumEr-Rbia springs situated about 70 km from the city of Azrou (Morocco). The water quality of Oum Er-Rbia riveroffers trout a suitable and friendly environment for optimal growth. The growth and zootechnical performance of rainbow trout fed on all three feeds (A, B and C) showed that feeding trout with feed B resulted in very high growth with a feed conversion rate (B = 1043g / ICb = 0.90) compared to that found using feed A and C. In terms of fish wastes, the effluent from the rearing tanks for trout fed with B feed yielded very low levels of phosphorus, nitrogen and suspended solids. So, did B feed yield the best performances in terms of biochemical quality of the flesh (Omega 3 and Omega 6). Therefore, feed B was found to be the best feed and it would chosen to develop an efficient and ecological formulation adapted to the rainbow trout rearing in Morocco. The two formulas proposed F1 (60% animal protein and 40% vegetable protein) and F2 (40% animal product and 60% vegetable product) allowed a better zootechnical performance of the rainbow trout with a final weight of 1080g during a short rearing period of 43 days (11, 76 g / day). The low feed conversion ratios obtained were 0.82 for F1 and 0.73 for F2 compared to those of food B (reference feed) (0.90). In addition, these two formulations helped coming up with a friendly environmentally feed since the levels of phosphorus, nitrogen and suspended solids released into the water of OumErRbia river wereextremely low.