Dietary Protein Requirement During Juvenile Growth of Zebrafish (Danio rerio)

Abstract

A standard diet for zebrafish, based on their specific nutritional requirements, is of primary importance to improve experimental outcomes with this model organism and optimize its large-scale production. However, the main basic nutritional requirements of zebrafish are yet to be determined. This study aimed at contributing to fill this gap by evaluating the dietary protein requirement of zebrafish juvenile. Ten isoenergetic fishmeal-based diets with increasing protein levels (15%-60%) were formulated, and each diet was assigned to duplicated groups of zebrafish (53.6 mg/17.8 mm initial mean body weight/fork length), fed to apparent satiation during 8 weeks. Weight gain, protein retention, and feed efficiency significantly increased in fish fed diets with increasing protein levels up to 35%-40% and then stabilized. Based on dose-response models, the dietary protein requirement of zebrafish juvenile was estimated at 37.6% and 44.8% for maximum weight gain and maximum protein retention, respectively (with a crude protein-to-energy ratio of about 22.5 g/MJ), corresponding to a protein intake of 14 mg/g average body weight/day. Feed intake increased linearly when fish were fed diets with decreasing protein levels below the estimated requirement, suggesting that zebrafish would regulate feed intake primarily to meet protein needs. On the other hand, the efficiency of protein utilization and retention linearly decreased when fish were fed diets with increasing protein levels above the estimated requirement, indicating that the excess of dietary protein would be deaminated, contributing to increased ammonia excretion. The whole-body composition of fish was affected by the dietary protein level, with fish fed diets with higher protein levels having higher water and protein contents and lower energy content. Considering that zebrafish juveniles are often reared with diets containing excessive amounts of protein, we suggest that the estimated protein requirement should be taken into account to formulate a more suitable, cost-effective, and less pollutant diet for this species.

Zebra Balığının (Dania rerio) Diyetsel Protein Gereksinimi

“…However, since the right side of the curve did not display a clear descending trend, a great caution should be exercised before a definite conclusion is reached in terms of inhibition level of dietary protein. The descending trend at the right side of SGRs curve is inconsistent with previous observations in zebrafish (Fernandes et al 2016;O'Brine et al 2015), who found a plateau at high protein levels. We can conclude that our SGR data appears to be suitable for estimation of only minimum dietary protein using the TBPLM model level but not for the inhibition level.…”

“…This is consistent with the results reported by Akpιnar et al (2012) and Fernandes et al (2016), who observed an inverse relation between feed intake and dietary protein in juvenile shi drum (Umbrina cirrosa) and zebrafish. This phenomenon could be attributed to compensatory response to get more protein in fish fed lower dietary protein levels, as argued by several authors (Akpιnar et al 2012;El-Dakar et al 2011;Fernandes et al 2016;O'Brine et al 2015). Therefore, at restricted feeding regimes at the estimated requirement level in this study fish may not meet their daily protein requirements and significant attention should be paid to feeding levels in zebrafish laboratories.…”

“…Therefore, at restricted feeding regimes at the estimated requirement level in this study fish may not meet their daily protein requirements and significant attention should be paid to feeding levels in zebrafish laboratories. Our results related with FCR showed a quadratic decrease in response to the increase in dietary protein, being consistent to a certain degree with those of Fernandes et al (2016), who observed an improvement in feed efficiency up to 35% protein level, then a plateau.…”

“…This could be resulted from several factors including growth depensation in zebrafish, differences in strain and in number of sexes in experimental tanks and maturational stages as underlined previous authors (Biga and Goetz 2006;Eaton and Farley 1974). Since we did not define maturational situation and sexes of the individuals in the present study, we were unable to conclude their contributions to the differences in our results and those of O'Brine et al 2015and Fernandes et al (2016).…”

“…Dietary protein level in fish is considered as one of most important criterions since it is most the expensive nutrient and affects a number of functions from molecular level to growth related traits (Lawrence 2007;NRC 2011;Ulloa et al 2011;Ulloa et al 2014). Despite its fundamental importance in nutritional physiology, dietary protein requirement of juvenile zebrafish has been studied recently by Fernandes et al (2016), who estimated the minimum dietary requirements between 37.6 and 44.8% for maximum weight gain and protein retention using a four-parameter saturation kinetics model (SKM) and broken line model (BLM). O'Brine et al (2015) also studied protein and lipid requirements of older zebrafish (ca.…”