A research team from China and the United States recently found that using a less expensive feed with a specific carbon/nitrogen ratio may improve performance in a shrimp biofloc system.
In their study, researchers conducted a two-factor experiment to evaluate the effects of two commercial shrimp feeds and four different C/N ratios on biofloc development, water quality, growth performance, feed utilization and input cost in an outdoor tank system stocked with Litopenaeus vannamei juveniles under high-density and zero-exchange conditions. The two feeds used were a less expensive feed formulated for semi-intensive production systems and a more expensive one designed for hyper-intensive systems.
“Organic carbon (molasses) was added daily to provide calculated carbon to nitrogen (C/N) ratios of 12:1, 15:1, and 18:1 based on the carbon-nitrogen content of the feed and the carbon content of the molasses throughout the experiment. No molasses was added in the control group which had a C/N ratio of 9:1.”
Results found that feed and C/N ratio had effects on the performance of biofloc-based, zero-exchange shrimp culture systems, and that the best water quality and performance of Litopenaeus vannamei were achieved with the C/N ratio of 12:1 for both feeds.
Initiating the culture with biofloc-rich water and then adding a small amount of organic carbon regularly could effectively sustain the continued development of mixotrophic bioflocs in zero-exchange high-density shrimp culture systems.
In addition, the study found that economic benefits were improved using the less expensive feed of SI-35 under the tested conditions, and input costs could be decreased using a C/N ratio of 12:1, due mainly to reduced molasses and NaHCO3 usage.
This article includes excerpts from the study abstract, published in the Journal of Aquaculture