Gregarines are a group of parasitic protozoa widely spread, with a prevalence of 10 to 90% in marine shrimp. Two main genera are distinguished, Nematopsis and Cephalolobus, with a third genus that has only been described in post-larvae of Litopenaeus Vannamei under culture conditions, the genus Paraophioidine.

The gregarines have an indirect biological cycle, where polychaete worms and bivalve mollusks act as intermediate hosts. Inside these invertebrates, the parasite develops up to the phase of gymnoespora, the infecting phase for shrimp. The gymnaspores germinate in the shrimp, resulting in the sporozoites that invade the intestinal epithelium. Direct transmission of the parasite through contaminated faecal material has also been reported.

The symptomatology associated with gregarine infestation is due to intestinal damage caused by sporozoites, which results in decreased absorption of nutrients and therefore less growth. In massive infestations, a yellowish coloration of the intestine is observed.

Intestinal optimizer pronutrients stimulate immunity in shrimp, increasing the ability of the intestinal epithelium to break down the cycle of gregarines, avoiding their multiplication.

1. Objective

Evaluate the effect of intestinal optimizer pronutrients on the prevention of parasitation by gregarines in shrimp (Litopenaeus vannamei).

2. Material and methods

A total of 12 shrimp culture tanks were used divided into two experimental groups:

• Control group: standard diet
• Pronutrient group: standard diet + intestinal optimizer pronutrients at a dose of 1.5 kg/t.

The weight of a significant number of animals was assessed on a weekly basis, as well as feed consumption. The trial lasted 21 weeks.

3. Results

The results obtained in relation to live weight throughout the trial are shown below.

The group with intestinal optimizer pronutrients obtained a final average weight of 20.4 g, 8% (1.5 gr) higher than the weight obtained in the control group, whose final weight was 18.9 gr.

At the same time the feed conversion rate was evaluated in both experimental groups, obtaining a value of 1.6 in the group with intestinal optimizer pronutrients and 1.72 in the control group.

Mortality in both groups was 10% at the end of the trial.

4. Conclusion

Intestinal optimizer pronutrients are active molecules of botanical origin, which allow to enhance immunity in shrimp, promoting the control of infestations by gregarines.

By reducing the multiplication of the gregarines, the intestinal damage caused by these parasites is avoided, which favors the absorption of nutrient and, thus, improves the growth and conversion rate of shrimp. In addition, intestinal optimizer pronutrients can be used throughout the production cycle, as they are of natural origin and do not leave residues in shrimp.

Intestinal optimizer pronutrients are marketed under the name Alquernat Zycox from Biovet S.A.