Delay of Initial Feeding of Zebrafish Larvae Until 8 Days Postfertilization Has No Impact on Survival or Growth...

The use of early-stage zebrafish for biomedical research spans early organogenesis to free-swimming larva. A key benefit of this model organism is that repeated assessments spanning several days can be performed of individual larvae within a single experiment, often in conjunction with administered drugs. However, the initiation of feeding, typically at 5 days postfertilization (dpf), can make serial assessments challenging. Therefore, delayed feeding would increase the utility of the model. To ask whether feeding could be delayed without adversely affecting larval growth and development up to 39 dpf, we systematically raised zebrafish and introduced feeding at 5 dpf or delayed initial feeding up to 9 dpf. We assessed survival into the juvenile stage (39 dpf) and anterior-posterior length at this age as proxies for growth and development. Delaying feeding initiation up to 8 dpf did not decrease baseline survival of greater than 90%; survival decreased to 66% only when delayed to 9 dpf. Larval length was no different under any of these conditions. Our findings define 9 dpf as the critical age before which larval zebrafish must be fed when raising to 39 dpf. The option to delay feeding to 8 dpf will broaden experimental applications for the zebrafish larval model.