RESUMO
Tenebrio molitor (TM) is considered as one of the most promising protein sources for replacing fish meal in aquafeeds, among other things because it is rich in protein, a good source of micronutrients and has a low carbon footprint and land use. However, the main drawback of TM is its fatty acid profile, in particular its low content of n-3 PUFA. This study evaluates the effects of partially replacing plant or marine-derived with full-fat TM meal at two different levels on growth performance and lipid profiles of Senegalese sole (Solea senegalensis). For this purpose, a control diet (CTRL) and four experimental isoproteic (53%) and isolipidic (16%) diets were formulated containing 5 and 10% TM meal replacing mostly fish meal (FM5 and FM10), or 10 and 15% TM meal replacing mostly plant meal (PP10 and PP15). Fish (215 g) were fed at 1% of their body weight for 98 days. The final body weight of fish fed the experimental diets containing TM meal was not different from that of fish fed the CTRL diet (289 g). However, the inclusion of TM meal resulted in a gradual improvement in growth rate and feed efficiency in both cases (replacement of fish or plant meals), and significant differences in specific growth rate (SGR) were observed between fish fed the CTRL diet (SGR = 0.30% day-1) and those fed diets with the highest TM meal content (PP15; SGR = 0.35% day-1). The experimental groups did not show any differences in the protein content of the muscle (19.6% w/w). However, significant differences were observed in the total lipid content of the muscle, with the FM10, PP10, and PP15 groups having the lowest muscle lipid contents (2.2% ww). These fish also showed the lowest neutral lipid content in muscle (6.6% dw), but no differences were observed in the total phospholipid content (2.6% dw). Regarding the fatty acid profile, fish fed FM10, PP10 and PP15 had lower levels of linoleic acid (18:2n-6) and higher levels of oleic acid (18:1n-9) in liver and muscle compared to fish fed CTRL. However, no differences were found between fish fed CTRL and TM-based diets for docosahexaenoic acid (22:6n-3) and total n-3 PUFA in liver and muscle. In conclusion, our study demonstrated that full-fat TM inclusion up to 15% in S. senegalensis diets had no negative effects or even some positive effects on fish survival, growth performance, nutrient utilization and flesh quality.
RESUMO
Resumen El pejelagarto es una especie importante para la acuicultura en el sureste de México. Se han realizado varios estudios sobre nutrición y fisiología digestiva; sin embargo, el uso de microcápsulas para la alimentación de larvas que permitan mejorar el crecimiento y la supervivencia no ha sido realizado. En este sentido, se evaluaron cuatro alimentos microencapsulados en el crecimiento y supervivencia de larvas de pejelagarto (Atractosteus tropicus). Los tratamientos consistieron en cuatro dietas experimentales y un control: 1) Microcápsula con base en harina de pescado (DP), 2) Microcápsula con base en una combinación de harina de cerdo y pollo (Re), 3) Microcápsula con base en Nannochloropsis gaditana (Ng), 4) Microcápsula con base en un preparado enzimático, pancreatina (PE) el tratamiento control 5) Nauplios de Artemia (Na). Los resultados de las dietas indican que las larvas alimentadas con Nauplios (Na) tuvieron el mayor crecimiento y supervivencia (3.93 cm, 0.19 g y 82 % respectivamente). Mientras que en el caso de las larvas alimentadas con las dietas microencapsuladas, los mejores valores de supervivencia se observaron con las dietas Nannochloropsis gaditana (Ng) y preparado enzimático (PE) (20.0 y 19.2 % respectivamente). Nuestros resultados demuestran que el uso de microencapsulados para la alimentación de larvas de A. tropicus es factible, aunque se requieren más investigaciones para optimizar su diseño y elaboración para mejorar el crecimiento y supervivencia de los organismos.
Abstract Tropical gar is an important species for aquaculture purposes in Southeast Mexico. Several studies regarding nutrition and digestive physiology have been done; however, the use of microcapsules for larvae feeding to improve growth and survival has not been conducted. In this sense, four microencapsulated diets were evaluated with respect to the growth and survival of tropical gar Atractosteus tropicus larvae. The treatments consisted of four experimental diets and one control diet 1) fish meal, 2) a combination of pork and poultry meals, 3) Nannochloropsis gaditana meal, 4) enzyme preparation and the control treatment 5) Artemia nauplii. The evaluation indicated that the larvae fed the Artemia nauplii obtained the greatest growth and survival (3.93 cm, 0.19 g y 82 % respectively), which justifies a correct culture system operation. While larvae fed microencapsulated diets best values in survival were observed with diets Nannochloropsis gaditana and enzyme preparation (20.0 and 19.2 %). Our results showed that microencapsulated could be used to feed A. tropicus in feasibly form. However, more information concerning to optimize the design and manufacturing are required to improve the growth and survival of organisms. Rev. Biol. Trop. 66(3): 1298-1313. Epub 2018 September 01.
