Characteristics of Gelatin Extracted from the Swim Bladder of Yellowfin Tuna (Thunnus albacores) as Affected by Alkaline Pretreatments

ABSTRACT

Gelatins extracted from the swim bladder of yellowfin tuna (Thunnus albacores) using various alkaline pretreatments were characterized. Alkaline mixtures (Na₂CO₃:NaOH) at different ratios (9:1, 8:2, 7:3, and 6:4) with a concentration of 4% (w/v) were used. The corresponding gelatins termed “G1,” “G2,” “G3,” and “G4” had yields of 9.78, 14.91, 35.96, and 13.60% (dry weight basis), respectively. All gelatins had α-chains as the major components. Fourier transform infrared spectra of obtained gelatins revealed the significant loss of molecular order of the triple-helix. G3 having the highest imino acid content and exhibited the highest gel strength (p < 0.05), compared with others. The microstructure of G3 gel was finer with smaller voids, compared with others. With increasing proportion of NaOH, the L*-value of gelatin gel increased with coincidental decrease in ΔE*-value. Gelling and melting temperatures of swim bladder gelatin were 12.3–15.1 and 21.3–22.3°C, respectively.     

An outbreak of toe ulcers,sole ulcers and white line disease in a group of dairy heifers immediately after calving

Abstract

CASE HISTORY: An outbreak of severe lameness was reported on a 780-cow spring-calving dairy herd in the Manawatu region within 1–3 weeks of calving, which affected over 90% of a group of 150 dairy heifers. Approximately 3 weeks before the planned start of calving heifers had been fed maize and grass silage on a concrete feed pad for 3–4 h per day, and mixed with a group of adult cows.

CLINICAL FINDINGS: During treatment for lameness, the feet of 28 lame heifers were closely examined. Seventy lesions were recorded in the claws of these heifers. The predominant lesion was severe solar and white line haemorrhage, with much of the haemorrhage focussed at the site at which sole ulcers are normally seen. White line disease was seen in nine claws and sole ulcers in four. Additionally, a lesion which is not commonly recorded in New Zealand, a toe abscess arising from separation of the white line from the sole in the abaxial region of tip of the toe was recorded in 11 claws. The clinical impression was that the soles of the affected heifers were very thin. This was supported by examination of the feet of eight heifers using ultrasonography that indicated heifers with hoof horn haemorrhages had very thin soles (estimated mean 4.1 mm) and that these soles were thinner than those in non-lame heifers without haemorrhages.

DIAGNOSIS: The pattern of disease seen in these heifers closely matched that seen in an outbreak of lameness in heifers in Florida, which was linked to thin soles resulting from excess hoof horn wear. The clinical signs and findings of the examination using ultrasonography strongly implicated thin soles as the underlying cause of lameness on this farm. An on-farm investigation revealed a combination of heifer behaviour and prolonged exposure to wet concrete on the feed pad were the primary causes of excess wear that resulted in thin soles.

CLINICAL RELEVANCE: This was an unusual outbreak of lameness in a group of newly calved heifers. The problem highlights the value of good management during the transition of heifers at pasture to the lactating herd standing on concrete for long periods, in the control of lameness.     

Isolation of lymphocystis disease virus from sole, Solea senegalensis Kaup, and blackspot sea bream, Pagellus bogaraveo (Brunnich)

Two viruses were isolated from cultured sole, Solea senegalensis, and wild blackspot sea bream, Pagellus bogaraveo, and preliminarily characterized as lymphocystis disease viruses (LCDVs). Viral isolates were characterized by morphological, biochemical and biophysical properties. In addition, the susceptibility of four fish cell lines was also tested. LCDV isolates developed cytopathic effects on the SAF-1 cell line at 5 and 6 days post-infection and reached titres of 10(6) TCID50 mL(-1). The antigenic and structural protein analysis of the two new LCDV isolates showed identical profiles to that obtained for LCDV strain Leetown NFH (ATCC VR-342), used as a reference viral strain, and for an LCDV isolate collected from gilt-head sea bream, Sparus aurata, cultured in southern Spain. Molecular confirmation was performed by polymerase chain reaction. Specific primers for LCDV produced a 270-bp DNA fragment, the expected size for LCDV.     

Changes in the content of total lipid,lipid classes and their fatty acids of developing eggs and unfed larvae of the Senegal sole,Solea senegalensis Kaup

Total lipids, lipid classes and their associated fatty acids were quantified in developing eggs, yolk-sac larvae and starving larvae (from day 1 to day 5 after hatching) of the Senegal sole,Solea senegalensis Kaup. Larvae during early development and starvation consumed about 0.6% of its dry weight per day, mainly due to lipid catabolism. There was a net consumption of approximately 1.7% total lipid per day, and a net energy utilization of 1.3 kcal g^–1 dry weight biomass day^–1, mostly derived from lipid depletion. The overall decrease of total neutral lipids (mainly triacylglycerols and sterol esters) was 3.4 faster than that of total polar lipids (primarily phosphatidylcholine), with rates of 29.2 and 8.7 g mg^–1 dry weight biomass day^–1, respectively. There was a concomitant increase in PE, PS and phosphatidic acid during the period under study. Total saturated and total monounsaturated fatty acids were catabolized (primarily 160 and 161 (n-7)) as energy substrates at rates of 7.4 and 10.9 g mg^–1 total lipid day^–1, whereas total PUFAs were conserved. DHA was specifically retained in PE, whereas EPA and DHA were catabolized in PC and triacylglycerol. Total DMA and AA contents in total lipid increased during early development and starvation. The data denote a pattern of lipid metabolism during early development of Senegal sole similar to that of other marine larval fish, with eggs containing high amounts of total lipids (presence of oil globule/s), from temperate waters and with short developmental periods; the pattern contrasts with fish larvae from eggs of cold water fish species that contain low levels of total lipids (lack of oil globule/s) and have long developmental periods.Abbreviations AA all-cis-5,8,11,14-eicosatetraenoic acid (arachidonic acid, 204(n-6)) - C free cholesterol - DHA all-cis-4,7,10,13,16,19-docosahexaenoic acid (226(n-3)) - DMA dimethyl acetal - EPA all-cis-5,8,11,14,17-eicosapentaenoic acid (205(n-3)) - HUFA highly unsaturated fatty acids (C₂₀ with 3 double bonds) - PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PS phosphatidylserine - PUFA polyunsaturated fatty acid(s) - SE sterol ester - TAG triacylglycerol