Urea in feeds for sea water farmed Atlantic salmon: effect on growth, carcass quality and outbreaks of winter ulcer

Abstract

The main objective of the present study was to evaluate whether dietary supplementation of urea might reduce the incidence of winter ulcer in sea water-farmed Atlantic salmon. Salmon destined to be S0 smolt were fed with a urea-supplemented diet (0 or 20 g kg )1 urea) over an 8-week period prior to sea water transfer and were then fed supplemented diet (0, 5, 10 or 20 g kg )1 urea) during the ®rst and second winters in the sea. During the ®rst winter positive relationships between dietary urea and plasma urea and between plasma urea and plasma osmolality were observed. Further, plasma osmolality displayed a negative relationship to mortality. Of the salmon that died during the ®rst winter in the sea 90% had one or more skin ulcers. Both during the ®rst and second winter there were fewer salmon with ulcer among ®sh fed with the diets supplemented with urea. Salmon fed with 20 g kg )1 urea tended to have higher percentage water in the muscle. Mortality and incidence of salmon with ulcer seemed to relate to plasma osmolality amongst ®sh fed on diets that diered in levels of urea supplementation, suggesting that an osmotic imbalance may contribute to the development of winter ulcer in farmed salmon. Salmon fed with 20 g kg )1 urea showed signi®cantly greater body weight during the second winter in sea. Fish killed without prior starvation had signi®cantly higher level of muscle urea in the 20 g kg )1 urea group compared with ®sh fed with the unsupplemented diet. However, a 13-day starvation period reduced urea content in the muscle to the level of the control. No eects of dietary urea supplementation on the sensory quality of market size Atlantic salmon were observed. KEY WORDS

Body temperature and seawater adaptation in farmed Atlantic salmon and rainbow trout during prolonged chilling

“…The present blood plasma osmolality and muscle moisture content in the Atlantic salmon after 39 h of chilling, therefore, are consistent with results showing that salmon may survive at subzero temperatures. However, the relatively stable seawater adaptation throughout the present study, seems to contradict the dramatic changes reported by Lega et al (1992), who showed blood plasma osmolality >400 mosmol l 1 at 1 C in post-smolts averaging 121 g. Since substantially larger salmon were tested in the present study, the difference may be explained by fish size which is consistent with increased salinity tolerance with increasing fish size in many salmonid species (Parry, 1958;Houston, 1961;Conte & Wagner, 1965;Landless, 1976;Johnsen & Clarke, 1988;Rørvik et al, 2000bRørvik et al, , 2001. This may be partly due to growth regulating factors control by the maturation of the hypo-osmoregulatory system (Conte, 1969).…”

Qualidade da corvina (Micropogonias furnieri) eviscerada em diferentes períodos de estocagem a 0°C

“…Outras aplicações incluem sua utilização na determinação da estabilidade e na estimativa da vida útil de produtos, especialmente dos alimentos e bebidas (STONE & SIDEL, 1998). A ADQ foi empregada na avaliação de salmão do atlântico defumado, fermentado e curado (MORZEL et al, 1999), na avaliação do reflexo de uma dieta rica em uréia na qualidade da carne do salmão do Atlântico (RORVIK et al, 2001) e em truta do ártico -Salvelinus alpinus (GINÉS et al, 2004). O presente trabalho objetivou, a partir de métodos físico-químicos e sensoriais, avaliar o estado de conservação da corvina armazenada em diferentes períodos a 0°C.…”

Análise descritiva quantitativa (ADQ) e teste de aceitabilidade na avaliação do frescor da tainha (Mugil Liza, Valenciennes, 1836)

“…Este método já foi empregado na avaliação de salmão (MORZEL et al, 1999;RORVIK et al, 2001) e de corvina (BORGES et al, 2007;TEIXEIRA, 2005).…”