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L-carnitine beneficial to rotifer under ammonia stress in culture medium

Inclusion of L-carnitine (LC) in culture medium may significantly improve the growth performance of rotifer (Brachionus rotundiformis) under ammonia stress. The study in China cited that the volume at one −100 mg L−1 may achieve this result. 

“Overall, our results indicate that the rotifer growth can be inhibited by ammonia (AC), and under AC stress, LC can also improve the population growth, anti-stress ability of rotifer, and the bacterial numbers in the medium. The amelioration of rotifer-growth may be linked to the anti-stress ability and the bacterial numbers,” Yong-sheng Gao et al. said in their study, “L-carnitine can improve the population growth and anti-stress ability of rotifer (Brachionus rotundiformis) under ammonia stress”. The team is from the Jilin University and the Fishery Technical Extension Station of the Province of Jilin. The study was published in Aquaculture Reports.

Rotifer, a first live food for larval fish, has a fast reproductive cycle that allows mass production. Intensive culture systems, however, result in an increase in ammonia levels that are enough to cause mortality. AC build-up is caused by rotifer carcasses, feed residues and rotifer excretions.

Microscopic in size, rotifer is a slow swimmer and has the ability to be enriched with adequate nutritional supplements

The study investigated the effects of LC on growth performance, antioxidant enzymatic activity, bacterial numbers, and eradication of AC toxicity in rotifer. Experiments used LC concentrations of zero to 1,000 mg L−1 and AC concentrations of zero to 20 mg L−1. A batch culture experiment treated with LC and AC was performed.

During the seven-day experiment, the population density of rotifer exposed to LC significantly increased relative to the control group, and the specific growth rate and the population density reached the maximum on day four and day six, respectively.

The importance of controlling the concentration of AC in rotifer culture was stressed since irotifer have low AC tolerance and cannot tolerate high AC concentration for a long time. AC median lethal concentration (LC50) was identified at -24 h and was 12.24 mg L−1 . This was based on data on survival of rotifer exposure to AC levels pf 0 -20 mg L−1, observed from zero to 72 hours.

Exogenous LC could mitigate the adverse effect of AC on rotifer growth, the authors explained, by increasing the antioxidant enzyme activity. 

“LC can also promote the bacterial growth in cultured medium. And there was a significant correlation between bacterial numbers and the rotifer population density,” they said.