Effects of feeding frequency on growth, feed utilization, digestive enzyme activity and body composition of Litopenaeus vannamei in biofloc-based zero-exchange intensive systems

An eight-week feeding experiment was conducted to investigate the effects of daily feeding frequency on the growth, feed utilization, digestive enzyme activity and body composition of Litopenaeus vannamei juvenile reared in biofloc-based zero-exchange intensive culture systems. The experiment was carried out in twelve tanks with 800 L of biofloc-rich water. Juvenile shrimp (1.52 +/- 0.37 g) were stocked into tanks at 240 shrimp tank(-1 )(300 ind m(-3)). Three feeding frequencies of three, six, twelve times were evenly set in the 24 h of a day for experimental groups of F3, F6, F12 respectively. Each group had four randomly assigned tanks, and the shrimp were cultured for eight weeks with the same daily ration based on the monitoring of feeding trays in F3 group. During the experiment, all the monitored water quality parameters were maintained within acceptable ranges for shrimp culture. M the end of the experiment, the shrimp survival rate was higher than 89.03% in all the three groups. Notably, with the increase of daily feeding frequency from three times to six and further to twelve, significant differences were found as follows: (1) the final weight, growth rate and yield of the shrimp increased; (2) the feed conversion rate decreased while the protein efficiency ratio and protein productive value increased; (3) the specific activities of protease and amylase in the stomach of the shrimp and the specific activity of lipase in the digestive gland increased; (4) the crude protein content of the whole body of the shrimp increased while the moisture content decreased. Taken together, these results demonstrate that daily feeding frequency can affect the growth, feed utilization, digestive enzyme activity and body composition of L. vannamei juvenile reared in biofloc-based zero-exchange intensive systems. Distributing a controlled ration of daily feed at frequent times during 24 h of a day is beneficial for the growth, feed utilization, nutrient digestion, and protein deposition of L. vannamei in biofloc-based systems under controlled conditions.