Probiotics help fish grow up faster and healthier

This research could help increase the success of raising rare ornamental fish to adulthood. It also has implications for aquaculture, since accelerating the development of fish larvae--the toughest time for survival--could mean a more efficient and safe system for bringing fish to the dinner table.

Tiny zebrafish are often used in genetic research because scientists can easily track changes in their development and the fish grow quickly. They also share many of the same genes as humans and can be used for studying cellular and physiological processes and their impact on human disease.

"This is really exciting," said Jacques Ravel, a leading genomic scientist studying the role of the human microbiome in health and disease at the University of Maryland School of Medicine Institute for Genome Sciences. "Knowing you can colonize the gut of a zebrafish with a probiotic strain and improve its development becomes an interesting model for us to study the beneficial effect of probiotics in children and adults." He and his colleagues are currently looking into the effect of Lactobacillus rhamnosus probiotics on the gut development of premature infants.

In the zebrafish experiment, researchers added Lactobacillus rhamnosus, a probiotic strain sometimes used in yogurt, to the zebrafish water. The fish drank the probiotic through their gills, and it landed in their gastrointestinal tract, preventing bad bacteria from taking over and promoting growth, including advancing the development of bone, vertebrae, and gonads.

"If you have increased growth and survival from each batch of hundreds of thousands of eggs, that is a huge benefit," said study co-author Dr. Allen Place of the Institute of Marine and Environmental Technology.

Probiotics helped the zebrafish get through the touch-and-go time when their gastrointestinal tract is maturing. They are still living off yolk with which they are born, and it is during this weaning period when most mortality occurs. Adding probiotics to the water increases the survival rate of zebra fish larvae from 70% to 90%.

"We did not anticipate the enhancement in maturation," said Place. "When you look at various molecular markers of stress, the overall stress in the fish that were treated with the probiotic were lower--which may be the reason for the development."