Konrad Dabrowski

School of Environment and Natural Resources, Ohio State University, Columbus OH 43210,

Visiting headquarters of BARD and aquaculture program at the US-Israel Binational Agricultural Research and Development Fund in Rehovot, Israel

BARD is a competitive funding program that since 1979 until present, has supported1300 projects at a total value of $310 million. BARD funds research projects, fellowships, workshops and strategic grants based on agricultural, academic, and economical merits. Research areas include productions of plants and animals, prevention of biotic and abiotic stresses of plants and animals, water quality and quantity, food quality, safety and security, sensors and robotics technologies, agriculture economy and bio-energy systems, among others. Funded projects have addressed all phases of strategic and applied research and development in areas of mutual interest to both countries.

            Dabrowski, in collaboration with Rafael Jimenez-Flores (Department of Food Sciences at OSU) and two scientists, Drs. Sheenan Harpaz and Avner Cnaani from Agricultural Research Organization, the Secretary of Ministry of Agriculture of Israel, in Rehovot, proposed to utilize a new technology of production of the most expensive single cost in production of fish, replacement of fish meal and fish oils. Specifically, we are developing solutions for fish meal replacement with co-fermentation product of fish waste and acid whey in diets for zebrafish as a model species and rainbow trout and Nile tilapia as fish important for the industry in the U.S. and Israel.

I had the opportunity to meet Director of BARD program, Professor Yoram Kapulnik. BARD has recognized the importance of Aquaculture as its own discipline and as a result, the field will be considered separately from other fields of animal sciences in the next foundation cycle it. Aquaculture Department located in Rehovot has been historically best known for research on reproduction, genetics and nutrition of tilapia, common carp and four species of Asian carps used in the pond polyculture. Studies led by Dr. Harpaz addressed intensive culture of Nile tilapia in multifactorial design considering water temperature, oxygen concentration, fish density, light cycle as well as nutritional aspects (dietary protein level). A highly automatized system constructed for this purpose allowed investigators to separate the impact of these factors.  Current staff (A. Cnaani) works on molecular aspects of genetics and gene expression regulation at the intestinal brush border amino acid transporters in common carp and tilapia, analyzing basic mechanism of nutrient utilization. This research will contribute to improvements in diet formulation and selection of genetic lines of fish with enhanced capacity of food utilization, the most significant single cost in intensive aquaculture.

Our joint project with Israeli collaborators addresses the most significant dilemma in the present aquaculture industry and delivers more seafood for human consumption than commercial wild stock fishing output. A traditional protein source in fish diets for aquaculture has been fish meal, which is limited and needs to be replaced with alternative protein sources such as animal-by-products and plant and algae proteins. What has been given much less attention are fish by-products. To produce 1,000 kg of fish fillet, approximately 2,700 kg of fish is required, therefore the remaining 1,700 kg is fish waste. There is realization that fish processing waste is a valuable fish diet ingredient, but technologies explored thus far are in its infancy and demand eco-friendly, high quality alternative product. We propose that this fish waste can be enriched by fermentation using dairy industry by-product as inoculum, and at the same time stabilizing waste fish hydrolysate against the growth of mold and other pathogens. This technology will generate a new, enriched ingredient for aquafeeds and lower the cost of fish diets, contribute to the sustainable use of wild fish as a source of fish meal, and resolve a dilemma faced by the dairy industry looking for possible utilization of by-products from cheese and yogurt production.  The sustainability of aquafeeds in the aquaculture industry using fish meal and fish oil as their major feed ingredients is questionable. We focused our search on a potential low-cost feed ingredient as an alternative to fishmeal.

Specifically, we examined fish waste following processing by co-fermentation with dairy by-product and this could potentially eliminate cost of storage (freezing). We examined if the process in which nutritional value of fermentation product can be preserved and enriched simultaneously during storage. Fish waste used in the formulation of experimental diets was prepared by processing silver carp (Hypophthalmichthys molitrix) carcasses obtained from wild stocks (Illinois River). The fish waste product was co-fermented with acid whey for 14 days. The fermentation experiments were carried out with fish and dairy waste with added Lactobacillus rhamnosus, or both, a single species of Lactobacillus sp. or consortium of Lactobacillus, Pediococcus and Enterococcus strains. Resulting fermentation products and non-fermented fish waste were used to replace 50-75% of fish meal protein in control diets. The pH of acid whey itself was 4.9. While the fish waste pH was 6.3 it decreased to 4.4 within 2 days of fermentation. Rainbow trout alevins after yolk sac absorption were offered experimental feeds and studies continued until all treatment groups achieved a juvenile size of 10g. Growth was highest in fish fed a commercial control diet which achieved our target mean weight by 92 days, followed by fishmeal control at 104 days, with the non-fermented fish waste and 50% incorporation of co-fermentation product both at 111 days. We considered these as very promising results.

The most memorable time of my visit in Israel was a meeting and conversation with Dr. Samuel Rothbard, Holocaust survivor, investigator who contributed over many decades to accelerated progress of aquaculture in Israel. He was born in 1933 in Krakow (Poland) and soon after the beginning of the II World War was moved with his family to the ghetto. With the help of his mother who bribed guards, he was able to escape in the last day before ghetto was liquidated. He then spent the entire remainder of the war with a Polish friend of the family. In 1947 he emigrated to Israel and after training in Japan, established Fish Breeding Station in Gan Shmuel.

            Dr. Rothbard contributed to many areas of nutrition, reproduction and genetics of carp, Asian carps, and Nile tilapia. He described and utilized in practice, production technology that results in obtaining “fatherless” progeny. This technology allows in one generation production of “clones” of the mother and genetic selection can be accomplished ten times faster than with conventional selective breeding. Indeed, we follow Dr. Rothbard's methods when working on distant hybridization of cyprinids, koi carp, goldfish and Asian carps, bighead and silver carps. This might allow us to use this technology in conservation of biological diversity of fishes.

BARD Project No. US-5165-19, Utilization of fish processing waste enriched by fermentation in aquafeeds for fish of importance to Israel and USA    

Mayta-Apaza, A. C., I. Garcia-Cano, K. Dabrowski and R. Jimenez-Flores 2021. Bacterial diversity analysis and evaluation of proteins hydrolysis during the acid whey and fish waste fermentation. Microorganisms 9(1).

Rothbard, S.2013. The Green Horsemen. Available on Amazon

Acknowledgements: This research was in part funded by Binational (BARD) (No. US-5165-19), by The Parker Endowment for Dairy Foods of The Ohio State University, Ohio Agriculture Research and Development Center, and Postdoctoral Fellowships from Government of Egypt.