Based on a review of various production principles of fish silage, this paper discusses the prospects of introduction of this method, as an alternative to fish meal, to utilize low value fish and waste products, particularly in developing countries. The paper covers the biochemistry, microbiology, and nutritional aspects of fish silage, as well as production technology and economy.

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A growing concern for the high consumption of antibiotics in aquaculture has initiated a search for alternative methods of disease control. Improved resistance against infectious diseases can be achieved by the use of probiotics. Probiotics are live microorganisms supplemented in food or feed which give beneficial effects on the intestinal microbial balance. In the present study a dry feed containing lactic acid bacteria (Camobacterium diver gens) isolated from Atlantic cod (Gadus morhua) intestines was given to cod fry. After three weeks of feeding the fry was exposed to a virulent strain of Vibrio anguillarum. The death rate was recorded during further three weeks of feeding with lactic acid bacteria supplemented feed. A certain improvement of disease resistance was obtained, and at the end of the experiment lactic acid bacteria dominated the intestinal flora in surviving fish given feed supplemented with lactic acid bacteria. No obvious growth inhibition of V. anguillarum was observed in an in vitro mixed culture of this bacterium and the C. divergens isolated from cod intestines.

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Two different peptones obtained by enzymatic hydrolysis of yellowfin tuna (Thunnus albacares) head waste have been shown to be effective in promoting the growth of lactic acid bacteria (Lactobacillus bulgaricus Persian Type Culture Collection (PTCC) 1332, Lactobacillus acidophilus PTCC 1643, Lactobacillus casei PTCC 1608, Lactobacillus delbrukii PTCC 1333, Lactobacillus plantarum PTCC 1058, Lactococcus lactis PTCC 1336, and Lactobacillus sakei PTCC 1712). Peptones obtained from the enzymatic hydrolysis with Alcalase or Protamex were used instead of the standard peptones used in commercial MRS media. Peptones produced by Alcalase and Protamex had a 34% and 19% degree of hydrolysis, respectively. The resultsshowed that the peptones from Alcalase and Protamex were better at promoting lactic acid bacteria (LAB) growth than the commercial MRS media (P<0.05). The choice of proteolytic enzyme used to produce the fish hydrolysate had a considerable impact on the performance of the resulting hydrolysate, both in terms of maximum growth rate and biomass production. Peptones produced using Alcalase, with a higher degree of hydrolysis, induced better growth and performed better overall as an LAB substrate than those using Protamex. Current study revealed that enzymatic-modified fish by-products can be used as low cast nitrogen source for bacterial growth.

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