Histological methods in the assessment of different feed effects on liver and intestine of fish

Abstract

This manuscript describes the importance of using histological methods to assess the effects of feed on the liver and intestine of fish. Due to the constantly increasing world production of fish and other aquatic organisms, it is necessary to replace fishmeal and fish oil in diets with less expensive raw materials of plant origin. Due to the increased fiber content, increased presence of carbohydrates, antinutritional factors, and inappropriate content of amino acids and new compounds can have negative effects on the digestive system of fish and therefore on fitness, health and production characteristics of cultivated fish. The liver and intestines are the most important organs for the digestion and absorption of nutrients from feed. Therefore, monitoring histological structure of fish liver and intestine is the method of choice in assessing the effects of nutrient mixtures that use raw materials of plant origin. For both of these vital organs the normal histological structure and the most important results obtained by research are discussed. This paper presents a critical review of the histological methods used in research on feed effects. Results related to the negative effects of raw soy-based feed on the occurrence of enteritis in carnivorous fish species are discussed. The results point out that use of modern approach in fish pathology such as improved histochemical, stereological, scoring, and other analytical methods could be a beneficial approach in an accurate assessment of new feed effects on fish.

U radu je prikazan značaj upotrebe histoloških metoda u proceni efekata hrane na jetru i crevo riba. Usled konstantno rastuće svetske proizvodnje riba i drugih vodenih organizama pokazalo se neophodnim da se riblje brašno i riblje ulje u hranljivim smešama sve više zamenjuju manje skupim sirovinama biljnog porekla. Zbog povećanog sadržaja vlakana, povećanog prisustva ugljenih hidrata i antinutricionih faktora, te neodgovarajućeg sadržaja amino kiselina u ovim sirovinama delovanje novih smeša može negativno da utiče na digestivni sistem riba a time i na kondiciju, zdravstveno stanje i proizvodne karakteristike gajenih riba. Budući da su jetra i creva najvažniji organi u procesu varenja i apsorpcije hranljivih materija iz hrane, praćenje histološke građe jetre i creva riba je metoda izbora pri proceni efekata hranljivih smeša u kojima se koriste sirovine biljnog porekla. Za oba pomenuta vitalna organa je prikazana normalna histološka građa i najvažniji rezultati dobijeni u istraživanjima autora i iz literaturnih izvora. U radu je dat kritički osvrt na histološke metode koje se koriste u ovoj vrsti istraživanja i na najvažnije dobijene rezultate. Posebna pažnja je posvećena negativnom delovanju sirovina na bazi soje koje uzrokuju pojavu enteritisa kod karnivornih vrsta riba. Ukazuje se i na mogućnosti unapređenja metodologije procene efekata hrane korišćenjem savremenih pristupa u patohistološkim istraživanjima kao što su unapređene histohemijske, stereološke i druge metode.