The effect of slaughter method on the quality of rainbow trout (Salmo gairdneri) during storage on ice

Novel euthanasia technique for zebrafish using electric shock in standard group housing aquaria

Zebrafish are widely used in research, accounting for approximately 50% of all laboratory fish across Europe. Due to their rapid reproduction and aging, effective and practical euthanasia methods are necessary for managing large stocks. This study investigated whether adult zebrafish can be euthanised by delivering an electrical current directly via the water in their housing aquaria. For this, portable plate electrodes were developed for 3.5 and 8.0 L Tecniplast™ housing aquaria. Our results show that adult zebrafish can be euthanised in groups (5 fish per litre) with electrical fields and current densities of at least 6 or 7 VRMS cm-1, and 0.7 or 0.8 ARMS dm-2 in 3.5-8 L aquaria, respectively, when delivered for 30 s in water at 28 °C with a conductivity of 800 µS cm-1 at 50 Hz. If widely implemented, this technique could improve the welfare of the vast number of zebrafish used across the world.

Assessment of the textural variation of iced stored Anabas testudineus (Bloch, 1792) muscle tissue with emphasis on their collagen and myofibrillar protein content

Post-mortem biochemical and physiological changes of climbing perch (Anabas testudineus) muscle evaluated during iced storage of 18 days compared with muscle protein content. Changes in the protein fractions, rigor index, pH value, water holding capacity, expressible water content, cook loss, textural parameters, and histochemical properties of the post mortem fish muscle were studied. The whole fish were in full rigor condition till fifth day of storage. Initial muscle pH value of 6.97 was dropped to 6.90 when the fish reached in full rigor condition, this then increased to 7.10 on the final day of storage period. The myofibrillar protein decreased with an initial value of 29.76% and a final value of 13.49%. 40.27% decrease in total collagen content was observed during the storage period. The water holding capacity of fish muscle decreased when the fish muscle entered in post rigor stage while cook loss and expressible water content were significantly increased. The histochemical studies and textural profile analysis of fish muscle proved that the degradation of both collagen and myofibrillar protein induces the post-mortem tenderization and the resultant quality deterioration of iced stored Anabas testudineus fish.

Evaluation of different methods of stunning/killing sea bass (Dicentrarchus labrax) by tissue stress/quality indicators

The aim of the study was to evaluate the effect on the final product quality of certain innovative stunning/killing methods for sea bass as substitutes for the most common methods used by European farmers. The changes in tissue stress/quality parameters were monitored from the first hours after death and during the shelf life of the fish. Two trials were conducted in July and November on n. 231 sea bass stunned/killed by ice-water slurry, by single gas or mixture of gases in ice-water and by single- or two-stage electrical stunning/killing methods. Behavioural responses, stun/death time, rigor index, muscular and ocular pH, lactic acid, ATP and catabolites at death and within the 24 h after death were determined. In the November trial, the sensorial evaluation, rigor index, IMP, inosine, hypoxanthine, and K1 values were also evaluated during refrigerated storage until spoilage. The stunning/killing in ice-water appeared to induce low effects on the analysed parameters and preserve a good product quality as indicated by the highest pH and ATP values at death, the delayed full rigor onset and the 1 day longer shelf life (14 days) in comparison with the single- or two-stage electrical stunning/killing. The gas mixture addition provided a 40 % shortening of the time to obtain stunning/killing and 14 days of shelf life. The actual level of quality loss with the different killing conditions and the actual impact of a significant shortage of rigor mortis onset and pH drop on the possible pre-rigor filleting remain to be studied in depth.

Muscle temperature at the point of filleting—Subsequent effect on storage quality of prerigor filleted raw- and cold-smoked Atlantic salmon

The impact of increased muscle temperature at the point of filleting on fillet quality of raw- and cold-smoked Atlantic salmon was investigated. Commercially reared fish (5.65 kg, Kf: 1.23, pH: 7.29, muscle temperature: 6.68 ℃) were killed and immediately tempered in three different containers. Muscle temperatures after filleting (<3 h postmortem) of the three groups were 2.08 ℃ (hereafter named T-2); 9.07 ℃ (hereafter named T-9), and 14.09 ℃ (hereafter named T-14), respectively. The pH after filleting was significantly low for T-14 (6.93) followed by T-9 (7.06) and T-2 (7.22). Raised temperature at point of filleting was found to significantly alter development of rigor mortis, which subsequently affected muscle pH and the reflective properties of the fillet surface during 14 days' ice storage. Of cold-smoked fillets, however, a more distinct effect of raised temperature was observed on visual perception resulting in lighter and more yellowish cold-smoked fillets after 14 days' storage. In addition, raised temperature also affects the development of muscle pH in cold-smoked fillets during refrigerated storage. No effects of raised muscle temperature were found regarding drip loss, water-holding capacity, or fillet firmness either for raw- or cold-smoked fillets throughout the storage period.

Methods Used to Kill Fish: Field Observations and Literature Reviewed

This paper reviews the impact on fish welfare of a wide range of slaughter methods used commercially around the world. Because the end result of the slaughter is a food product, and because of the well-known relationship between an animal's welfare and subsequent meat quality, the effects of the slaughter methods on the quality of the flesh are also reviewed where possible. Fish slaughter methods are incredibly diverse, but fall into two broad categories: those that induce loss of sensibility slowly, and those that achieve this rapidly. This paper shows that, in general, the methods that induce loss of sensibility over a long period of time tend to impinge more on the welfare of the animal and are detrimental to the overall quality of the carcass. Methods that cause a rapid loss of sensibility result in the best welfare, providing that they are carried out correctly. They may also produce the highest quality product from the stock offish.

Adenosine Triphosphate and Derivatives as Freshness Indicators of Gilthead Sea Bream (Sparus aurata)

Intensive production of farmed gilthead sea bream ( Sparus aurata) and the different slaughtering methods and postmortem treatments are prompting a need for early indicators to determine fish quality during chilled storage. Adenosine-5 -triphosphate (ATP) and derivatives and their relationship as Kvalue were measured in chilled whole and gutted gilthead sea bream killed by immersion in ice water, asphyxia, anesthesia followed by a blow to the head, or a blow to the head. ATP derivatives taken independently were not found to be useful indicators for this species. The evolution of Kvalue was linear but attained lower final values than in other species. No significant differences were found in relation to the method of slaughter or postmortem treatment.