Growth performance of European whitefish [Coregonus lavaretus (L.)] under a constant light and temperature regime

Growth, feed intake and maturation were monitored in a fast‐growing benthivore morph of European whitefish [Coregonus lavaretus (L.)] held under constant light (LD 24:0) and temperature conditions (10°C) for 415 days. Their growth was best described by polynomial regression model and no indication of seasonal patterns (e.g. winter depression) in growth rates was found. There was no significant difference in food conversion ratio (FCR) between periods during the experiment and the FCR was favourable (0.84). Furthermore, there were no differences in growth between males and females. None of the fish became sexually mature by the time the experiment was terminated, although they had reached a mean size of about 444 g. The European whitefish seems to be a promising aquaculture species as the growth rate was relatively high with a remarkable homogenous growth performance between individual fish within each experimental unit, a relatively favourable FCR, a low degree of agonistic behaviour and negligible growth depression due to internal biological rhythms or gonad maturation. These results were obtained at relatively low temperatures that should be beneficial for sustainable cost‐effective farming conditions in cold climate condition in northern Scandinavia.     

Food safety on the slaughterline: inspection of pig heads

This paper summarises information on the current inspection procedures for pig heads on the slaughterline and their impact on food safety, and considers the implications for food safety of certain lesions. It is argued that although a modified slaughter and inspection technique would decrease the contamination of the carcase with pathogenic microorganisms, leaving lesions in the head undiscovered would be of little or no importance either for human health or for the overall supervision of animal health.     

Observations on Uterine Prolapse in Beef Cattle

Serum samples were obtained from 26 beef cows with uterine prolapse and from 15 with minor dystocia (controls). The serum of animals with uterine prolapse had significantly lower calcium concentration (mean ± S.D. = 8,22 ± 0,69 mg/dL, P≤0,01), higher phosphorus concentration (mean ± S.D. = 4,78 ± 1,75 mg/dL, P≤0,05) and lower calcium to phosphorus ratios (mean ± S.D. = 1,99 ± 0,88, P≤0,01) than for the control animals (means ± S.D. = 8,91 ± 0,75 mg/dL, 3,54 ± 1,41 mg/dL and 2,99 ± 1,41 respectively). Mild hypocalcemia (6,9 mg/dL-7,9 mg/dL) was present in 11 (42,3%) of the cows with prolapse as compared to only one (6,7%) of the controls. Hypophosphatemia was present in 11 (42,3%) of the animals with prolapse and in ten (66,7%) of the controls.

Eighteen (69,2%) of the animals with prolapse were alert and ambulatory when treated and 15 (57,7%) were known to have required help to deliver the calf. Of the cattle group with uterine prolapse, 14 (53,8%) were two years old, six (23,1%) were three years old, and six (23,1%) were four years of age or older.

It was concluded that mild hypocalcemia and some degree of dystocia were associated with the uterine prolapses. The phosphorus results were equivocal but the high incidence of hypophosphatemia may reflect a phosphorus deficient diet.

     

The absorption of lactic acid is more synchronized with the absorption of glucose than with the absorption of short-chain fatty acids — A study with sows fed diets varying in dietary fibre

Sows were fed one of three diets varying in level and type of dietary fibre (DF). A low DF diet (LF; 17% DF) based on wheat and barley and two generic high DF diets (HF1, high in soluble DF and HF2, high in insoluble DF;  41% DF) where the cereals were substituted with co-products (sugar beet pulp, potato pulp, pectin residue, pea hull, brewer's spent grain and seed residue (ray grass)) from the vegetable food and agro industries. Six sows were fitted with a catheter in the portal vein and the mesenteric artery and a flow probe around the portal vein. The sows were fed 2 kg/d of the three experimental diets in a repeated 3 × 3 crossover design. Blood samples were collected the last day in each period at − 120, − 60, 0, 15, 30, 45, 60, 90, 120 and then at 60-min intervals up to 600 min after feeding. Although lactic acid (LA) is formed by microbial fermentation, the absorption profile of LA was more comparable with the absorption profile of glucose than with that of other SCFA.     

Diel interactions between sprat and mackerel in a marine lough and their effects upon acoustic measurements of fish abundance

We have investigated how diel changes in fish behaviour may affect acoustic estimates of fish abundance in a marine system. Studies in Lough Hyne (Ireland), a marine lake with only a narrow and shallow connection to the sea, showed the presence of large numbers of sprat (Sprattus sprattus), mackerel (Scomber scombrus), and zooplankton. Fish species were identified from regular rod and line fishing. Zooplankton were identified from net hauls. Acoustic measures of zooplankton were low with little diel variation. The sprat formed dense schools during the day and dispersed into the water column at night. The acoustic estimate of sprat abundance at night, obtained by means of a standard hydroacoustic technique and protocol, was more than double the estimated biomass during the day. We have considered whether the lower fish estimate during daytime resulted from acoustic shadowing due to aggregation of the fish into dense schools. However, no decrease in echo energy was evident from the top to the bottom of the schools, and there was no reduction in the seabed echo beneath the schools. Acoustic shadowing was therefore not responsible for the diel differences in the estimates of abundance. Instead, we suggest that the target strength of individual sprat diminished during the day as a result of attacks from predatory mackerel. We observed echoes from gas released by the sprat as they gathered into dense plumes close to the seabed. Compression of the gas remaining within the swim bladder as the fish were moving deeper would also reduce swim bladder volume. Finally, negative buoyancy due to reduced swim bladder volume may in addition have forced the fish to change tilt angle to compensate for sinking. All these effects will reduce the target strengths of individual fish and lead to underestimation of fish abundance based on daytime surveys.     

A simplified method to estimate Diphyllobothrium spp. infection in salmonids

Some fish parasites constitute severe management problems as they may cause mortality of their fish host or are important zoonoses of humans. Parasite assessments are therefore critical to keep track of infections. If conventional sampling techniques can be simplified, parasite assessments might be easier to obtain, less time‐consuming and more extensive. In this study, we compare the assessed number of Diphyllobothrium spp. cysts (CYST) with the counted number of Diphyllobothrium spp. plerocercoid larvae recovered using a conventional digestive technique (LARV). The aim was to determine the potential of using CYST as a simplified methodology for assessing Diphyllobothrium spp. infection in salmonids. In total, 365 brown trout and 424 Arctic charr were sampled from nine lakes in subarctic Norway. Strong correlation, significant linear relationship and large amount of explained variation were found between log₁₀CYST and log₁₀LARV in both fish species. The method had a slight, but not significant tendency to work better in charr compared to trout. In addition, absolute difference between CYST and LARV increased at parasite intensities >100 indicating that the method has reduced functionality when estimating parasite intensity in heavily infected salmonid populations. However, overall, using this simplified and less time‐consuming methodology, a good indication of Diphyllobothrium spp. intensity, abundance and prevalence was obtained. We suggest that this method provides a sound proxy of the Diphyllobothrium spp. burden and have the potential to be used in parasite assessment during fish monitoring and fisheries management surveys, particularly if the time and resources for detailed parasite studies are not available.     

Estimation of weight loss in stored potatoes by determination of their ash content

Zusammenfassung Gewichtsverluste w?hrend der Kartoffellagerung wurden gew?hnlich berechnet, indem gewogene Muster in Netzen ans Lager gelegt und bei der Auslagerung wieder gewogen wurden. Diese Methode ist beschwerlich und gleichzeitig auch Fehlern verschiedenen Ursprungs unterworfen. Eine andere Methode, die diese Nachteile nicht aufweist, wird vorgeschlagen. Diese beruht auf der Bestimmung eines unver?nderlichen Bestandteiles vor und nach der Lagerung einerseits und der Ermittlung des Verh?ltnisses dieses Bestandteils zum Frischgewicht an diesen Daten andererseits. Es wird darauf hingewiesen, dass Bestimmungen des Aschegehaltes oder von darin enthaltenen specifischen Komponenten, zum Beispiel Kalium oder Phosphor, dieser Anforderung entsprechen würden. Eine zufriedenstellende Anwendung dieser Methode setzt voraus, dass der Aschegehalt in den gelagerten Kartoffeln ziemlich konstant ist, und es wird notwendig sein festzustellen, wie gross ein Muster sein muss, um eine repr?sentative Angabe zu gew?hrleisten. Ferner ist grosse Genauigkeit bei der Analyse erforderlich. Eine Abweichung von zum Beispiel 0,9 auf 1,0 im Prozentgehalt an Asche ergibt eine Differenz von 10% im Gewicht der 1 kg Asche enthaltenden Kartoffeln, was mehr ist als der Gewichtsverlust w?hrend der Lagerung oftmals betr?gt. Eine ziemlich gute übereinstimmung zwischen den wirklichen und den mittels Ascheanalysen vor und nach der Lagerung errechneten Gewichtsverlusten, ist in unsern Ergebnissen erzielt worden, indem Muster von 1,5 kg verwendet wurden (Tabelle). Genügende Genauigkeit dürfte bei Verwendung von Mustern von 3–5 kg zu erreichen sein. Es ist notwendig, den Luftstrom und die Temperatur im Muffelofen zu kontrollieren. Besondere Aufmerksamkeit muss der Tatsache gewidmet werden, dass die Temperatur im Ofen von Ort zu Ort differieren kann. Sofern ein Flammenphotometer verfügbar ist, wird vorgeschlagen, die Berechnungen auf der Basis von Kalium auzustellen, das leicht mit einer Genauigkeit von 1% bestimmt werden kann.

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Résumé On évalue habituellement les pertes de poids pendant le stockage des pommes de terre en enfermant des échantillons pesés dans des filets dans le magasin et en les repesant à l'enlévement. Cette méthode est à la fois incommode et passible d'erreurs pour de multiples causes. Une autre méthode est proposée qui est basée sur la détermination d'un constituant invariable des tubercules avant et après le stockage et sur la relation de celui-ci au poids frais à ces moments. Il est suggéré que les déterminations de la teneur en cendre ou de constituants spécifiques de celleci, par exemple le potassium ou le phosphore, pourraient rencontrer cette exigence. Une application satisfaisante de la méthode présuppose que la teneur en cendre des pommes de terre stockées est raisonnablement constante et qu'il y aura lieu de déterminer l'importance nécessaire de l'échantillon pour obtenir une représentation valable. En outre, une grande précision de l'analyse est essentielle. Ainsi une variation de 0,9 à 1,0 dans le pourcentage de cendre se traduit par une différence de 10% dans le poids d'une quantité de tubercules contenant 1 kg de cendre, soit une différence plus grande que la perte habituelle de poids pendant la conservation. Nos résultats, basés sur des échantillons de 1,5 kg (tableau) donnent une bonne concordance entre les pertes réelles de poids et celles calculées des analyses de cendre avant et après la conservation; il se peut qu'une précision suffisante puisse être obtenue en utilisant des échantillons de l'ordre de 3 à 5 kg. Il est nécessaire de régler le courant d'air et la température dans le four à moufle. et il y a lieu d'accorder une attention spéciale au fait que la température peut varier d'un endroit à l'autre dans le four. Si on utilise le photomètre à flamme, l'auteur propose de baser les calculs sur le potassium, qui peut être déterminé avec une précision de 1%.

     

Moderately virulent African swine fever virus infection: blood cell changes and infective virus distribution among blood components

Blood samples of pigs infected with a moderately virulent African swine fever virus (ASFV) isolate, obtained from the Dominican Republic (DR-II), were monitored temporally for viremia, infective ASFV association with major blood components, differential changes in blood cell composition, and plasma antibodies to ASFV. After intranasal/oral virus inoculation, pigs underwent acute infection and illness that resolved. Acute illness began on postinoculation day (PID) 4 and continued to PID 11, and pigs were febrile, with maximal infective ASFV titers detected in blood. By PID 11, initial antibody titers to ASFV antigens were detected in plasma. The WBC numbers were maintained near preinoculation counts; however, lymphocyte counts decreased slightly with a compensatory increment in neutrophil and monocyte numbers. From PID 11 to PID 25, rectal temperatures gradually returned to preinoculation values, titers of viremia began to decrease, plasma antibody to ASFV antigens increased to peak titers, and WBC numbers increased slightly. Percentages of lymphocytes returned to preinoculation values, neutrophil percentages decreased to slightly below preinoculation values, monocyte percentages were mildly increased, and eosinophil percentages were unaffected. From PID 25 to PID 46, titers of viremia further decreased, and plasma titers of antibodies to ASFV antigens remained high. In pigs with DR-II viremia (PID 4 to PID 46), most viral infectivity (greater than 95%) was RBC associated. Plasma contained less than 1% infectivity, and less than 0.1% of virus was in the WBC fraction (monocytes, lymphocytes, and granulocytes). After PID 46, viremia was no longer detectable.     

The effect of dietary carbohydrates and Trichuris suis infection on pig large intestine tissue structure, epithelial cell proliferation and mucin characteristics

Two experiments (Exps. 1 and 2) were performed to study the influence of Trichuris suis infection and type of dietary carbohydrates on large intestine morphology, epithelial cell proliferation and mucin characteristics. Two experimental diets based on barley flour were used; Diet 1 was supplemented with resistant carbohydrates from oat hull meal, while Diet 2 was supplemented with fermentable carbohydrates from sugar beet fibre and inulin. In Experiment 1, 32 pigs were allocated randomly into four groups. Two groups were fed Diet 1 and two groups Diet 2. Pigs from one of each diet group were inoculated with a single dose of 2000 infective T. suis eggs and the other two groups remained uninfected controls. In Experiment 2, 12 pigs were allocated randomly into two groups and fed Diet 1 or Diet 2, respectively, and inoculated with a single dose of 2000 infective T. suis eggs. All the pigs were slaughtered 8 weeks post inoculation (p.i.). The worm counts were lower in pigs fed Diet 2 in both experiments, but not significantly so. Both diet and infection status significantly influenced the tissue weight of the large intestine. In both experiments, pigs fed Diet 2 had heavier large intestines than pigs fed Diet 1 and in Experiment1 the infected pigs of both diets had heavier large intestines than their respective control groups. Diet and infection also significantly affected the morphological architecture and mucin production in both experiments. Pigs fed Diet 1 had larger crypts both in terms of area and height than pigs fed Diet 2 and T. suis infected pigs on both diets in Experiment 1 had larger crypts than their respective control groups. The area of the mucin granules in the crypts constituted 22-53% of the total crypt area and was greatest in the T. suis infected pigs fed Diet 1. Epithelial cell proliferation was affected neither by diet nor infection in any of the experiments. The study showed that both T. suis infection and dietary carbohydrates significantly influence the morphological architecture and the production and composition of mucins in the large intestine of pigs and suggests that both factors are important in large intestine function and that carbohydrates may play a role in the susceptibility to intestinal helminth infections.     

Intestinal morphology and enzymatic activity in newly weaned pigs fed contrasting fiber concentrations and fiber properties

The main objective of this study was to determine the effect of fiber source and concentration on morphological characteristics, mucin staining pattern, and mucosal enzyme activities in the gastrointestinal tract of pigs. The experiment included 50 pigs from 10 litters weaned at 4 wk of age (BW 8.6 +/- 1.4 kg) and divided into 5 treatment groups. Diets containing fiber of various physico-chemical properties and concentrations were formulated to contain 73, 104, or 145 g of dietary fiber/kg of DM. The diets were based on raw wheat and barley flours. Pectin and barley hulls, representing soluble and insoluble fiber sources, respectively, were used to increase the fiber concentration. The pigs were fed the experimental diets for 9 d, and then the pigs were euthanized and the entire gastrointestinal tract was removed. Tissue samples were taken from the mid and distal small intestine and from the mid colon. Inclusion of pectin in the diets significantly decreased (P < 0.001) ADFI and ADG compared with pigs fed no pectin. The villi and the crypts were shorter in pigs fed pectin-containing diets, but the villous height/crypt depth ratio was unaltered. Pectin significantly decreased the area of mucins in the crypts of the small intestine, indicating that the pigs fed the pectin-containing diet would probably be more susceptible to pathogenic bacteria, although this cannot be separated from the impact on ADFI. The lectin-binding pattern of the intestinal mucosa was unaffected by diet. The activity of lactase and maltase was increased in pigs fed diets with high fiber content, whereas sucrase activity was increased in pigs fed the pectin-containing diets. The activity of the peptidases, aminopeptidase N and dipeptidylpeptidase IV, was increased when feeding high fiber diets, whereas the activity of gamma-glutamyl transpeptidase remained unaffected by the experimental diets. In conclusion, the reduced feed intake observed with the pectin-containing diets could explain the lower villous height and crypt depth observed in this study. However, direct effects of pectin also are possible, and thus further study is warranted. Feeding pigs high insoluble fiber diets improved gut morphology by increasing villi length and increased mucosal enzyme activity when compared with pigs fed pectin-containing diets. The mucin content as determined by staining characteristics suggests that pigs fed high insoluble fiber diets might be better protected against pathogenic bacteria than pigs fed diets high in soluble fiber.