A. Dees

Effects of rearing density on rainbow trout welfare, determined by plasmatic and tissue parameters

Abstract The work aimed to determine the welfare status of rainbow trout (50±15 g), intensively reared to commercial size in two concrete raceways (V1, V2) at different stocking densities, to reach final load of 40 kg/m3 and 20 kg/m3, respectively. Throughout the out-phase, plasma parameters and hepatic glycogen content were determined every three months and compared with those of rainbow trout of the same age and mean weight, reared extensively (VE). At the end of the trial significant differences of the monitored parameters were found between rainbow trout reared in raceways (V1, V2) and those held in the reservoir (VE). Plasma triglycerids, total cholesterol and alkaline phosphatase in fish reared intensively were significantly different from fish reared in extensive conditions. The highest levels of these parameters in V1 and V2 could be justified mostly by the administration of balanced feeding and consequent modifications of energetic metabolism and in small part to the high density of the intensive rearing conditions. Transaminases (AST, ALT) increased in V1 and V2 only at the first sampling. Afterwards, the activity of these two enzymes returned to the normal range at the subsequent assays, suggesting a capacity of the rainbow trout to adapt to the severe conditions of confinement, typical of out-basins. No significant differences among groups were observed for total protein, glucose, CK and LDH. A similar situation was also shown for liver glycogen content.

Largemouth bass (Micropterus salmoides Lacépède): reproduction management and larval rearing in Italy

Riassunto Persico trota (Micropterus salmoides, Lacépède): gestione della riproduzione e allevamento larvale in Italia. Il black bass sta assumendo un’importanza crescente nel nostro Paese sia per la pesca sportiva che per l’alimentazione. Nel biennio 2001-‘02 prove sulla possibilità di riprodurre e allevare gli stadi giovanili di black bass in Italia sono state intraprese a partire da uno stock selezionato di pesci di taglia adeguata. In aprile, alla deposizione delle uova fecondate dai maschi in stagni precedentemente fertilizzati, ha fatto seguito la cattura delle larve e la fase di allevamento in ambiente controllato. La quantità e la tipologia di alimento naturale ed artificiale nei primi mesi di vita e il ricorso a frequenti calibrature sono alla base del successo di questa tecnica che, nell’arco di circa 70 giorni, ha consentito di ottenere giovanili del peso di 1 g. La successiva fase di allevamento ha avuto luogo in stagno dove, a fine ottobre, si è riscontrata una pezzatura media di 5 g ed una sopravvivenza superiore al 50%.

Natural and synthetic pigments used in the pink-red coloration of salmon flesh: methodology of quali-quantitative assessments and sampling results

Abstract In Europe Atlantic salmon leads the first position in the farmed species contest with more than 763,000t (FES, 2007). In the year 2006, Norway produced alone beyond 603,000t followed by the United Kingdom with 128,000t. In these last years, the demand of organic salmon is gradually increased both in domestic and foreign markets. In these fish the pink-red coloration of flesh is obtained by supplementing the feed with shrimp waste meal. In Italy, Coop Italia since three years has started the commercialization in the context of “prodotti a marchio” of Atlantic salmon farmed following prescriptions reported in terms of specification that prohibits the use of synthetic and GM pigments in the feeds. In collaboration with this supermarket company, the Faculty of Veterinary Medicine of Camerino University carried out the quali-quantitative assessments on the presence of molecules and relative isomers that distinguish the natural carotenoid pigment from the synthetic one. Skinned portion of fillet (10g) were collected from dorsal muscle (retro-cranial, central and caudal region), mixed and homogenized and repeatedly extracted with acetone until they were colourless. The pooled extract were filtered and an aliquot (10ml) was centrifugated (2200xg, 5min). The astaxanthin content in the supernatant was determined by HPLC using a Varian ProStar instrument equipped with UV/vis detector using an external astaxanthin standard at detection wavelength 470nm. Analysis was performed on a Varian Kromasil 100 C 18 250x0.3 mm according to Bjerkeng et al. (1997). Identification and determination of stereoisomers were carried out by means of a Sumichiral a-phenylglicine 250x4.6mm column following Abu-Lafi and Turujman method (1999). The analysis performed on all the organic fish have demonstrated the exclusive content of natural pigment. In this group (b.w.=3.9-4.4kg), C-Card for salmonids ranged between 26±1 in 2004 and 21.5±1.3 in 2005 and 21.5±2.1 in 2006. Astaxanthin and isomers decreased from 5.6±0.3mg/kg in 2004 to 2.9±1.1mg/kg in 2006. The low-cost non organic salmon group (b.w.=4.5-4.6kg) resulted pigmented only with synthetic carotenoids and C-card for salmonids ranged between 27.3 in 2004 and 23.7 in 2005 whereas in 2006 it was observed equal to 27. Also in this batch, astaxanthin and isomers decreased passing from 6.5mg/kg in 2004 to 4.9mg/kg in 2006.

Reproduction and larval rearing of chub (Leuciscus cephalus L.): comparison between different broodstocks origin

Abstract During 2006, trials about induced reproduction and larval rearing of chub were carried out with the aim to compare results obtained from broodstocks stocked in captivity with those of specimens caught in a river and immediately stripped. In Autumn 2005, a total of 35 chubs, were collected by electrofishing in an Apennine river and stocked in a 10m3 outdoor basin supplied with well water. The fish were fed with natural and balanced feeds. During the month of May 2006, other 8 fluent and mature broodstocks (5 males and 3 females) were fished by hook in the same area of origin of the other chubs (water temperature = 19°C), and immediately stripped. After fertilization, the eggs were disagglutinated and transported to the hatchery. Incubation took place in Zugg bottles at the temperature of 20±1°C (C1). At the same time, broodstocks from the outdoor basin were transferred inside the hatchery subdividing them in 2-1.5m3 tanks (C2, C3) connected with a closed circuit system. Water temperature was 17±1°C. All the males (12) were treated with carp pituitary (3mg/kg b.w.) (Lukovicz and Proske, 1971; Linhart et al., 1995) in coincidence of the second injection of females. The females of the two sub-groups (C2, C3) were treated with two different dosages of carp pituitary (5 and 10 mg/kg b.w.) divided in two fractions (1/10 and 9/10), injected at 24 h interval. After stripping and fertilization, the same method of eggs incubation used for the wild chubs was applied. On day 4, hatching took place and ranged between 85% (C3) and 90% (C1). The larvae of the different groups were reared in 3-500l tanks connected to a closed circuit and fed with Artemia salina nauplii (420±20µm) until day 11 when a cold extruded micronized feed for marine larvae was also supplied. The total substitution took place on day 20. The number of larvae obtained per kg b.w./batch was between 15,817 (C2) and 18,441 (C3). On day 30, larvae had reached a mean length of 16mm in the three groups without significant differences and body weight ranged from 20.7mg (C2) to 21.5mg (C3) as found by Harzewili et al. (2003). The survival rate resulted 70% (C1), 69% (C2) and 71% (C3).

Comparison of zootechnical performances, welfare condition and quality traits of hybrid striped bass (Morone chrysops x Morone saxatilis) reared in different Italian farms

Abstract Growth performances of sunshine bass (initial m.b.w.=200±50 g) were examined in 3 different rearing conditions: concrete square basins (HSB-1); raceways (HSB-2); natural ponds (HSB-3). Fish received the same extruded feed (prot. 48.8%; lip. 17.8%). The trial lasted 16 months in HSB-1 and HSB-2 and only 12 months in HSB-3 due to unfavourable welfare status and low growth performances. At harvest (after 16 months), sunshine bass reached a satisfactory mean weight without significant differences between groups. HSB-2 fish were longer with a smaller circumference, probably due to different hydrodynamics of the raceway. Glucose, cholesterol, triglycerides, protein, lactic dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatine kinase (CK), glycogen of plasma or tissue were not affected by rearing conditions as well as the proximate composition and the fatty acid profile of the fillet.