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Removal of deposited eggs could be a useful control strategy for the damaging fish ectoparasite Argulus foliaceus, but focused control requires knowledge of egg-laying patterns. Here, we investigated diel changes in the egg-laying behaviour of a natural population of A. foliaceus. Data were collected from 17-28 May 2004. Days were divided into 3 time periods: 06:00-14:00, 14:00-22:00 and 22:00-06:00 h. Significantly more egg clutches were laid from 06:00-14:00 h than during the other 2 time periods, which were not significantly different from each other. Significantly more egg clutches per hour were laid during hours of daylight as compared to hours of darkness. Significantly more egg clutches were laid in the top 1 m of the water column than at the bottom, and this was consistent throughout all 3 time periods. It is suggested that the increase in egg-laying activity during daylight hours may be due to a higher motivation to search for hosts during the night and an increased ability to locate silhouetted egg-laying sites during the day. These data can provide information useful for egg removal and control strategies.

Argulus foliaceus is a damaging fish ectoparasite for which new control measures are being developed based on egg-removal. In an attempt to develop further understanding of seasonal and vertical egg-laying patterns in this parasite, egg-laying activity was monitored over the period 14 April to 17 November 2003 in 2 rainbow trout Oncorhynchus mykiss fisheries in Northern Ireland, UK. At Site 1, egg-laying was continuous from 21 April to 17 November, when water temperature was above 8 to 10 degrees C. At Site 2, egg-laying was continuous from 4 June to 29 October. In the early months of the season, egg-laying was recorded mainly within the top 1 m of the water column; however, a significant shift to deep water egg-laying was recorded between 7 July and 17 November at Site 1 and between 20 August and 29 October at Site 2. Egg clutches were preferentially laid at depths of up to 8.5 m during this time (Site 2), a feature of egg-laying hitherto unappreciated. Temperature and dissolved oxygen did not differ significantly among depths, but there was an increase in water clarity over time. However, the precise environmental triggers for deep water egg-laying are still unclear. These new insights into the reproductive behaviour of this species will be useful in developing control methods based on egg-removal.

1. The influence of different rates of wing flapping on the rate of post-mortem glycolysis in the Pectoralis major (PMI) muscles of commercially-processed broilers was investigated. This was achieved by applying 300 pulses of low voltage electrical stimulation (ES) shortly after slaughter at various frequencies and pulse widths. The rate of post-mortem glycolysis was assessed by measuring muscle pH values at 20 min post mortem (pH(20 min)). 2. ES gave a mean pH(20 min) value of 6.01, significantly lower than that of the control carcases which had a mean value of 6.45. Within ES treatments, variation in pulse frequency between 1/s and 10/s and in pulse width from 5 to 20 ms had no influence on pH(20 min) values as measured by direct probe. However, differences between mean pH(20 min) values attributable to pulse frequency were detected when measured by the iodoacetate method. 3. A further experiment was carried out to determine how different rates of wing flapping would affect the eating quality of PM muscles from commercially-processed broilers stored at chill temperatures for 24 h post mortem. This was achieved by using pulse frequencies of 1/s, 5/s and 10/s, all other ES variables being standardised. Pulse frequency had no effect on ultimate pH, sarcomere length, cooking loss or tenderness of PM muscle compared to controls. 4. We concluded that the rate of wing flapping post-slaughter has no effect, per se, on the extent of post-mortem glycolysis in broiler PM muscle or on its subsequent meat quality assessed after holding the carcases under chill storage conditions for 24 h.

1. An experiment was conducted to investigate the development of shortening-induced toughness in the Pectoralis major (PM) muscles of commercially processed broilers, air-chilled at 0 degrees C and -12 degrees C, as a function of muscle pH early post-mortem. Electrical stimulation was used immediately after stunning and neck cutting to provide carcases with pH values 15 min post-mortem (pH15 min) ranging between 6.79 and 5.85. 2. The deep PM muscle temperatures of carcases chilled at -12 degrees C were lower (cooler) after primary chilling and at 215 min post-mortem than those chilled at 0 degrees C, although chilling regimen had no major effect on pH values over the 24 h post-mortem period. However, carcases chilled at -12 degrees C had longer sarcomeres, lower cooking losses and lower shear force values than those chilled at 0 degrees C. 3. Correlation analysis of the results for both chilling regimens clearly demonstrated that over the pH15min range 6.79 to 5.85, carcases with the lowest pH15min values had the shortest sarcomeres, the highest cooking losses and the toughest meat. In addition, there was no evidence to support the occurrence of cold shortening within this population. This suggests that an early onset of rigor at higher temperatures in broiler carcases, as well as inducing rigor shortening and toughness, might also induce greater protein denaturation and subsequent loss of water holding capacity as manifested in increased cooking losses. 4. Quadratic regression curves showed that over the pH15min range 6.80 to 6.30, only the fast chilling regimen at -12 degrees C could inhibit rigor shortening and minimise changes in cooking loss and shear force values. However, neither chilling regimen was effective in preventing severe rigor shortening, increased cooking losses and adverse toughness in carcases with pH15min values below 6.30. 5. The benefits of fast chilling carcases with pH15min values above 6.3 can also be quantified in terms of carcases exceeding a 4.00 kg/cm2 toughness threshold. Only 1.9% of these carcases chilled at -12 degrees C exceeded this limit (maximum shear force value of 4.72 kg/cm2) compared to 34.9% of the carcases chilled at 0 degrees C (maximum shear force value of 8.46 kg/cm2), further emphasising the considerable reduction in textural variability and improvement in tenderness gained by fast air-chilling at -12 degrees C.

Several beef forequarter muscles were investigated for fibre-type composition, total pigments, total nitrogen, non-protein nitrogen, anserine, carnosine and inorganic phosphorus contents, ultimate pH (pH(u)) and acid buffering capacities. In general, the predominantly 'red' fibre-type muscles had significantly higher (P<0·05) pH(u) values and total pigment concentrations than the predominantly 'white' fibre-type muscles which had significantly higher (P< 0·05) total nitrogen, non-protein nitrogen and carnosine contents and also significantly higher (P< 0·05) acid buffering capacities. The relationships between the various biochemical parameters of all the muscles studied and their acid buffering capacities were investigated by correlation matrix. The higher buffering capacities of the 'white' fibre-type muscles over the pH range pH(u) to pH 5·0 were attributed to their higher contents of carnosine and inorganic phosphorus. However, over the pH ranges pH(u) to pH 4·5 down to pH(u) to pH 3·0, the higher buffering capacities of the 'white' fibre-type muscles were attributed primarily to their higher lactic acid concentrations, as indicated by their low pH(u) values, and also to their higher non-protein nitrogen contents., (Copyright © 1989. Published by Elsevier Ltd.)

Data concerning the efficiency of protein extraction from meat waste tissues are presented. The tissues investigated were the lungs, stomach and small and large intestines of the ox, sheep and pig. Practically all of the protein, with the exception of connective tissue proteins, was solubilised under optimum extraction conditions both with alkali and anionic detergent. The disadvantages of isoelectric precipitation of alkaline extracted proteins have been investigated in detail using polyacrylamide gel electrophoresis incorporating sodium dodecyl sulphate (SDS). The compositions of the protein isolates from the various tissues studied differed from those of the soluble extracts and supernatants or wheys. However, a component of MW 75,000 daltons was characteristic of the wheys from each tissue. The compositions of both isolates and wheys are discussed in the light of structural and cytoplasmic proteins present in smooth muscle tissues. The usefulness of anionic polysaccharides as a means of whey protein recovery is discussed, together with similar benefits achieved using SDS., (Copyright © 1980. Published by Elsevier Ltd.)

The water-holding capacities (WHC) of six different beef muscles were measured over the pH range 5·7 to 4·0. Corresponding changes in the morphology of muscle fibres and connective tissue were observed by light microscopy. WHC increased over the pH range 5·1 to 4·0 in all muscles, with the M. longissimus dorsi (LD) having significantly higher (p < 0·05) swelling ratios than the other muscles at pH 4·3 and pH 4·0. In all muscles, swelling increased across and along the muscle fibre axis between pH5·1 and pH4·4. However, towards pH4·0, increased muscle fibre swelling occurred in predominantly 'white' fibre-type muscles, in particular the LD, whereas muscle fibre shrinkage occurred in predominantly 'red' fibre-type muscles. Increased swelling of perimysial collagen and endomysial reticulin was observed in all muscles between pH4·5 and pH4·0, while the appearance of elastin was unaffected by pH. Consequently, interactions between muscle fibre swelling and connective tissue swelling determined the extent of total muscle swelling in different muscles between pH 4·5 and pH 4·0., (Copyright © 1989. Published by Elsevier Ltd.)

Previous studies have indicated the beneficial influence of higher than normal ultimate pH (pH(u)) on the tenderness of cooked meat. Such benefits have been indirectly linked to the influence of increased pH on the water-holding capacity (WHC) of meat above the iso-electric point (IEP) of the myofibrillar proteins. In the present study, relationships between WHC and the tenderness of some beef muscles were investigated under pH conditions within and below the IEP of the myofibrillar proteins, such that the maximum range of meat swelling was achieved. It was found that increased WHC, as measured by swelling ratio in both raw and cooked meat, markedly influenced cooked meat tenderness, irrespective of the connective tissue content of the muscles. The results fitted a series of exponential decay equations relating swelling ratio to cooked meat toughness. Additionally, strong linear decreases in toughness were apparent over the pH range 4·6 to 4·1 for the three muscle types studied., (Copyright © 1985. Published by Elsevier Ltd.)