INTRODUCTION

Among the Neotropical fish species, the lambari, Astyanax altiparanae, has been highlighted as one of the most relevant species for the Latin American aquaculture (^{Campelo et al., 2018}) as its production has served not only for human consumption but also for the live bait market. The omnivorous feeding habit of A. altiparanae also favors its captive breeding. Furthermore, the A. altiparanae has several advantages (e.g., rapid growth, short life cycle, ease of captive production associated with its small size) that contribute to this species potential as an experimental organism model (^{Pontes et al., 2019}), which means that studies conducted with A. altiparanae can support the production of other fish species of commercial interest, especially those of omnivorous eating habits.

Aquaculture is still dependent on ingredients from industrial fisheries such as fishmeal and fish oil (^{Tacon and Metian, 2008}) as these ingredients are relevant sources of energy (^{Bell et al., 2003}) and rich fatty acids such arachidonic (ARA; 20: 4n6), eicosapentaenoic (EPA; 20: 5n6) and docosapentaenoic (DHA; 22: 6n3) (^{Ng and Wang, 2011}). However, in recent years, there has been a decline in industrial fishery resources, causing fluctuations in these products’ supplies and prices, which has raised discussions about potential alternative sources to replace fish oils (^{Bell et al., 2002}; ^{Turchini et al., 2010}; ^{Tacon and Metian, 2015}). Among the ingredients that may replace fish oil as lipid source, the vegetable oils has presented considerable potential. However, the vegetable oils are usually poor in fatty acids such as ARA, EPA and DHA (^{Paulino et al., 2018}).

Some tropical fish species are capable of synthesizing ARA, EPA and DHA from fatty acid precursors as the linolenic (18: 3n3) and linoleic (18: 2n6) acids (^{Tocher, 2015}) that must be presented in their diets. However, enzymes that act on the bioconversion of fatty acids have higher affinity for n3 series fatty acids (^{Henderson and Tocher, 1987}), which may lead to higher EPA formation compared to ARA formation (^{Bell and Koppe, 2010}), reinforcing the idea that the diets has to present adequate dietary ratios of precursor for n3 and n6 fatty acids.

The fishes’ fatty acid profiles are directly related to the profile of their consumed diets (^{Tocher, 2010}). Alteration in dietary fatty acid profiles may influence fish lipid metabolism, which can lead to changes in growth, carcass fatty acid profile and centesimal composition (^{Bell et al., 2002}; ^{Castro et al., 2016}). Thus, this study was conducted aiming to evaluate the growth performance and whole body composition of A. altiparanae fed on diets containing different sources of saturated and unsaturated fatty acids.

MATERIAL AND METHODS

This study was conducted at the Fish Bioclimatology and Nutrition Laboratory of the Fish Farming Sector at the Universidade Federal de Viçosa (UFV), Minas Gerais, Brazil (20°45′S, 42°52′W) and was approved by ^{CEUAP (2017)}, protocol 017/2017.

A completely randomized experimental design with five treatments and six replications was used. The treatments consisted of five isoproteic (300.46g crude protein kg^-1 diet) and isoenergetic (4353.4kcal crude energy kg^-1 diet) diets that contained different lipid sources. Were used the following treatments: T1) linseed, chia and sunflower oils; T2) linseed and corn oils; T3) linseed, chia, corn and sunflower oils; T4) sunflower, corn and fish oils; T5) linseed, chia, sunflower, corn oils and bovine fat. The percentage composition, chemistry and fatty acid profile of the diets are shown in Table 1 and Table 2.

In order to avoid potential interference of the fatty acid macro-ingredients profiles, the soybean and wheat bran, the fish- and cornmeals were degreased before experimental diets were prepared. To this, three liters of chloroform was added for each kilo of ingredient. After mixing the mixture (3 min), it was vacuum filtered through a Büchner funnel (with filter paper) connected to a Kitasato flask. This process was repeated three times for each ingredient and the solid material was dried at room temperature. After degreasing, the macro-ingredients were milled in hammer mills (with 0.5 mm diameter sieve) and were manually mixed with the micro-ingredients and the different oil source proportions. The diets were pelletized in a meat grinder (FILIZOLA, P-22, São Paulo, SP, Brazil), dried in a forced ventilation oven (Marconi Equipamentos para Laboratórios, MA 035, Piracicaba, SP, Brasil) at 50ºC, ground in a manual mill (BOTIMETAL , Bilac, SP, Brazil) and sifted to obtain 0.8 mm pellets.

The analyzes for chemical composition and fatty acid profiles of the diets were conducted, respectively, at the Food Analysis Laboratory of the Department of Animal Science (at UFV) and at the Natural Resources Laboratory of the Institute of Ecology and Environmental Science at Republic University, Montevideo, Uruguay.

Three hundred A. altiparane specimens (average weight of 4.0 + 0.5g) were distributed in 30 aquariums (80L) containing 50L of dechlorinated water, at a density of 10 fishes per aquarium. The aquariums were maintained in a 2.5L min^-1 flow recirculation system, and were equipped with mechanical and biological filters, constant aeration and thermostatically controlled heating. The experimental units were covered with white nylon mesh (2mm) to prevent fish escaping. The laboratory was maintained at a 12h photoperiod by using fluorescent lamps (60 watts) controlled by analog timer. The water temperature (28 ± 0.5°C) was daily measured, before each feeding, by means of a common alcohol thermometer (0 to 100ºC). The pH (7.0 + 0.2) and total ammonia (0.22 + 0.20ppm) parameters were weekly measured by using colorimetric kits, and dissolved oxygen (6.5 + 0.5mg L^-1) measurement was achieved by an ProPlus Multiparameter Equipament (YSI incorporated, Yellow Springs, OH, USA).

The fish were manually fed for nine weeks, three times a day (8:00 am, 12:00 am and 5:00 pm) until apparent satiety. At the end of the experiment, the fish were euthanized using a clove, Syzygium aromaticum, essential oil overdose (400mg L^-1) and weighed on an analytical balance (MB45 Toledo ® 0.01g, São Bernardo do Campo, SP, Brazil) with 0.01g accuracy to evaluate the following zootechnical variables: Weight Gain = Final Weight - Initial Weight, Specific Growth Rate = ((ln final weight - ln initial weight) X 100)/time (in days), Carcass Yield = ((final weight - offal weight) / final) X 100, Hepatosomatic Index = (liver weight / final weight) x 100, Viscerosomatic Index = (viscera weight / final weight) x 100, Visceral fat index = (visceral fat weight / final weight) x 100.

For the whole body composition, a fish pool from each treatment was dried in a forced ventilation oven at 60°C for 24h. The samples were processed in a ball mill (Botimetal, Bilac, SP, Brazil Brazil). By following methodologies previously described elsewhere (^{Dettmann et al., 2012}), we determined the crude protein, crude energy, ether extract, dry matter and ash contents.

The obtained data were submitted to the Lilliefors test to verify the normality of the errors and the Bartlett test to verify the homogeneity of the variances. All the results were subjected to an unidirectional analysis of variance (ANOVA) with significance of 5% (P < 0.05), and when needed, the mean comparison test (Tukey test, P < 0.05) was applied. All statistical analyzes were conducted by using the estatistical software R (version 3.3).

RESULTS AND DISCUSSION

In this study, no differences (P> 0.05) were observed in the weight gain, specific growth rate, carcass yield and hepatosomatic, viscerosomatic and visceral fat indices in fish fed diets containing different lipid sources (Table 3). These results show that A. altiparanae can efficiently use lipid sources of plant and animal origin for both energy and fatty acid supplies.

Since lipids are the main source of digestible energy for fishes (^{Lim et al., 2011}), the sources used in the present investigation probably supplied the A. altiparanae fatty acid requirements. The complete replacement of fish oil by the mixture containing soybean and linseed oils also did not affect the performance of these fishes in previous investigation (^{Pontes et al., 2019}). These findings are similar to these ones described for other fish species such as surubim (Pseudoplatystoma coruscans) (^{Martino et al., 2002}), panga (Pangasius hypophthalmus) (^{Asdari et al., 2011}), murray cod (Macullochella peelii peelii) (^{Turchini et al., 2011}) and Nile tilapia (Oreochromis niloticus) (^{Ng et al., 2013}), where diets containing vegetable lipid sources did not negatively affect the fish growth.

Such lack of differences in the A. altiparanae performance fed in our experimental diets may also be associated with the omnivorous eating habits of these animals. Astyanax altiparanae, like most of other especies belonging to the Genus, is an omnivorous species that can feed on algae, insects (eggs, larvae and adults) as well as fruits and seeds (^{Vazzoler and Menezes, 1992}; ^{Vaz et al., 2000}). Therefore, these fihses are well knowing for having high feeding flexibility (^{Abilhoa, 2007}). It is also possible that tested fishes have adapted to the different sources of lipids used, which resulted in the absence of growth losses.

Another possible explanation for our findings would be the fatty acid ratios of the n6 and n3 series of tested diets, which although composed of different lipid sources were efficient in providing the requirements for essential fatty acids for A. altiparanae. For investigations unsing other omnivorous eating habit fishes, diets containing different n6/n3 ratios were not capable of interfering in the fish production performance (^{Paulino et al., 2018}). Similar results were also observed for carnivorous species such as murray cod Maccullochella peelii peelii (^{Senadheera et al., 2010}) and rainbow trout, Oncorhynchus mykiss (^{Thanuthong et al., 2011}) when these fishes fed on diets containing different n6/n3 fatty acid ratios obtained from mixtures of vegetable oils. As demonstrated for these omnivorous/carnivorous previous fish species, our results for fish whole body compositions were unaffected by the tested diets (Table 4). However, for the same species in this study, the total replacement of fish oil with vegetable oil mixtures altered the carcass lipid content (^{Pontes et al., 2019}). In addition, fish fed the diet containing only linseed oil had the lowest fat deposition in the carcass (^{Pontes et al., 2019}).

The use of alternative sources to fish meal and oils without harming the animals has become a fundamental tool for the aquaculture growth, especially regarding the sustainability of production. Such aspects becomes even more relevant given the sharp decline in fishery resources, which has caused fluctuations in the supply and price of both fish meal and oils (^{Bell et al., 2002}; ^{Turchini et al., 2010}; ^{Tacon and Metian, 2015}).

CONCLUSIONS

A. altiparanae can efficiently use both lipid sources of vegetable origin (alone or mixed with animal-originated oils) without exibiting any growth disadvantages.