Cataract preventative role of mammalian blood meal, histidine, iron and zinc in diets for Atlantic salmon (Salmo salarL.) of different strains

Abstract

In the period from winter 1996 to autumn 1999, three feeding trials were conducted to study the possible role of mammalian blood meal in preventing lens opacities in Atlantic salmon. In addition to blood meal supplemented feed, experimental diets were formulated, aiming to mimic the total concentrations of selected elements present in blood meal (BM) enriched diets; the amino acid histidine (His) and the mineral iron (Fe). In addition, these diets were supplemented with Zn. The trials included different rearing conditions, sizes and strains of Atlantic salmon; one small scale feeding experiment with presmolt of Strain A in fresh water (Trial 1) and two semi large trials with sub-yearling (S0s) and yearling (S1s) smolts of Strains A and B in seawater (Trials 2 and 3). The trials included duplicate or triplicate feeding groups and lasted 6-12 months. Standard commercial diets not supplemented with BM were used as controls. High prevalence of cataract developed over time in all three studies, with end point ranges as follows; Trial 1: 40-52 %; Trial 2: 51-83 %; Trial 3: 63-100%. The cataracts normally first appeared in the anterior and/or posterior cortical region and later affected the perinuclear region. In all the experiments, there was a significant cataract preventative effect of both the BM supplemented and experimental diets compared to the respective control diets. To some extent, cataract incidence was reduced, but primarily cataractogenesis was less severe in these groups. A concurrent positive effect on growth of both added BM and experimental diets was observed in the two seawater trials, probably related to maintaining vision and feed uptake ability. In one of the trials, there were significant differences in cataract susceptibility between the two strains, measured both as frequency and severity of cataractous changes. Our data suggest that elevated concentrations of dietary His and/or Fe mitigate cataract formation. KEY WORDS

Clustering of ingredients with amino acid composition similar to the nutritional requirement of Nile tilapia

“…Dietary deficiency of His cause poor growth, low feed efficiency, cataract, increased mortality and incidence of lordosis (Breck et al, 2003); on the other hand, excess in dietary His decrease the growth rate and feed efficiency (Ravi and Devaraj, 1991;Murthy and Varghese, 1995;Ahmed and Khan, 2005).…”

Criteria for Safe Use of Plant Ingredients in Diets for Aquacultured Fish

“…Blood meal is a rich source of the amino acid histidine. Leaving out blood meal as feed ingredient seems to uncover critical roles of histidine in the Atlantic salmon, especially in lens cell volume regulation (Breck et al 2003;Bjerkås et al 2006). The histidine level required to prevent cataracts in Atlantic salmon smolt was found to be in excess of the established minimum requirement for growth (NRC 1993).…”

N-acetylhistidine, a novel osmolyte in the lens of Atlantic salmon (Salmo salar L.)

“…Feeding trials have shown that supplementing the diet of Atlantic salmon with histidine significantly reduced the incidence of cataract (4,6,7). Interestingly, it has been shown that N-acetylhistidine (NAH), a histidine metabolite found in the lenses of poikilothermic vertebrates (2), increased more than 10-fold in the lenses of salmon fed a histidine-supplemented diet (HD) following transfer from fresh to seawater (7).…”

“…Several recent studies have investigated the possible causes of cataract in farmed salmon (6,9,30), although the mechanisms involved remain to be elucidated.…”