Optimalisering van de groei bij de karper (Cyprinus carpio L.) : een op de visteelt gericht onderzoek

In course of time carp culture - in Europe already practiced since the Middle Ages - has been subjected to different patterns of intensification e.g. fertilization of ponds and supplementary feeding. Mechanisation in pond farm management has also proved to be important.The aim of these measures has always been to increase the ratio of fish production to financial and/or labour investment.The experiments reported in this thesis also aimed to investigate the possibilities of intensification of carp culture using running water systems. Attention has been paid to the different stages of carp culture, e.g. reproduction, fry-raising and the rearing of larger carp.In chapter I different patterns of intensification in present day pond farm management has been briefly described.In chapter II the experimental unit, the pelleted food, the methods and calculations, employed in this research have been described.Experiments concerning induced reproduction using carp pituitaries have been dealt with in chapter III. The technique of hypophysation has proved to be a very reliable addition to normal procedures for reproduction of carp in ponds (fig. III). Furthermore it is possible to induce reproduction of carp independent of the season with very good results. For this purpose carp have been kept in warm water (23° C) before hypophysation: this treatment subjects the fish to a certain amount of heat (in ° days). The characteristic of high temperature treament which is essential for successful induction of spawning is the actual water temperature.During this time no influence of light has been observed (table V).The relationship between temperature and amount of heat followed the same pattern as the temperature dependancy of metabolic rate as described by Ege and Krogh (1914) and by Winberg (1956).In chapter IV a method has been reported for raising carp fry under artificial conditions in a hatchery. Carp fry kept in aquaria with running water of 23° C have been fed larvae of Artemia salina until they attained a weight of 70 mg. Fry over this weight accepted commercial pelleted food. Fingerlings cultured in this way have proved to be good stocking material for ponds and for other production units.Experiments in raising larger carp have been reported in chapter V. This stage is of great economic importance in carp culture because it takes a long time and needs large amounts of food. Therefore some essential characteristics of growing carp have been studied more thoroughly.The first section of this chapter deals with growth rate of carp. At 23° C experiments have been carried out in order to determine the relationship between food ration, specific growth rate and food conversion using carp of different weights (1.5-10, 30-90 and 100-1,000 gram). At 17° C the same relationship have been determined using carp of 30 gram (fig. V and VI).In the graph relating the feeding level and the specific growth rate (fig. VI) the "geometrical optimal feeding level" ("G.O.-level") has been determined by constructing the tangent to the curve from the origin. From the point of view of fish production other criteria relating final cost price are important; a high, but not maximal growth rate with a worse but still acceptable food conversion, might be preferred. These high feeding levels must be harmless to the fish. Therefore a "productive optimal feeding level" ("P.O.-level") has been approximated for carp of several sizes.As a result of the analyses of body constituents and calorific content of carp kept at different feeding levels (table XIV and XVI) it has been proved that when feeding a "G.O.-level" the specific growth rate based on fresh weight was as high as based on dry weight and on calorific value (fig. VIII). The optimum between gross conversion efficiency (K 1 ) and feeding levels has been found at the "G.O.-level". This optimum was the same for K 1 expressed in fresh weight, dry weight or calorific value (fig. IV and XI).As a consequence of this the work of Paloheimo and Dickie (1966b) has been criticized. linear relationship between log K 1 and the feeding level is given by these authors. It has been shown here that this relationship is only valid to the range of feeding levels above the "G.O.-level". Furthermore it has been shown that K 1 was negatively influenced by increasing weight (fig. X). An influence of temperature on K 1 could also be established (fig. XI).In the second section of this chapter the oxygen consumption of fasting and growing carp of different weights has been investigated. For fasting carp the relationship between oxygen consumption (T, in ml/h) and fish weight (W. in grams) could be described by the equation: T = 0.372 W 0.816(fig. XIII).Measurements at 17° C showed that the influence of temperature on oxygen consumption was similar to that found by Ege and Krogh (1914).For growing carp the relationship between oxygen consumption (ml/kg0.8/h) and feeding level (% of body weight per day) has been established. With increasing feeding levels oxygen consumption increased. However, no further increase of oxygen consumption could be demonstrated at levels above the "P.O.-level" (fig. XIV). For "P.O.- level" the relationship between oxygen consumption (T, in ml/h) and fish weight (W, in grams) could be described by the equation: T = 0.861 W 0.776(fig. XVI).At "P.O.-levels" the amount of oxygen consumed for each kg of food was 147 l, independent of fish weight and water temperature (table XXIV). Based on these data a simple equation could be derived relating in a running water system the oxygen content of the inflowing water (O i , in ml/l), the oxygen content of the water at discharge (O u , in ml/l), and the flow rate (D, in l/sec) to the amount of food per day in kg:(O i - O u ). 86.4/147 . D = kg of food per day.The value for O u in the equation could be fixed at 2.1 ml/l as has been shown by the relationship between food conversion and oxygen content of the water (fig. XV).Based on the results obtained in the first and second section, in the third section of this chapter both gross and net efficiencies for maintenance and production have been calculated. Carp requires 171.6 kcal gross energy/kg 0.8/week for maintenance. The utilization of the gross energy for maintenance was found to be 45.2% efficient. The percentage of metabolizable energy (% ME) of the rations fed and eaten has been determined by measuring the energy content of the food, of the depositions during growth and of the heat production, the latter being calculated from the oxygen consumption. Both % ME and gross production efficiency decreased with increasing feeding levels, the respective values varying between 23.8-56.8% and 15.3-44.1% (fig. XVIII). The amount of ME required for maintenance amounted to 110.4 kcal/kg 0.8/week. The efficiency of the utilization of the ME above maintenance proved to be almost the same for alle, feeding levels used and varied between 85.6-89.4% (fig. XIX).The content of ME of the food dry matter originated from these experiments were much lower than those reported in the literature for fish fed natural food. However, most of those data in the literature have been calculated by measuring the calorific value of the food ration and of the feacal material. The analysis of the detailed study of Kelso (1972) suggested that a large error is introduced by this method for calculating the ME content for the consumed food (table XXVII and XXVIII).In chapter VI methods have been described by which the results obtained by this study can be put into practice in carp culture. Integration of the above mentioned nursery procedures in hatcheries with cage culture of carp in warm water discharges and with conventional pond farming appears to be an excellent way to improve the efficiency and intensification of carp culture.</p

Effects of exercise on l-carnitine and lipid metabolism in African catfish (Clarias gariepinus) fed different dietary l-carnitine and lipid levels

African catfish (Clarias gariepinus) were fed four isonitrogenous diets (34 % crude protein), each containing one of two lipid (100 or 180 g/kg) and two l-carnitine (15 or 1000 mg/kg) levels. After 81 d of feeding, thirty-two fish (body weight 32 g) from each dietary group were randomly selected, sixteen fish were induced to a 3-h swim (speed of 1.5 body length (BL)/s), while the other sixteen fish were kept under resting condition. Fish fed 1000 mg l-carnitine accumulated 3.5 and 5 times more l-carnitine in plasma and muscle, respectively, than fish fed the 15 mg l-carnitine. Muscle l-carnitine content was significantly lower in exercised fish than in rested fish. High dietary lipid level (fish oil) led to an increase in muscle n-3 PUFA content and a decrease in SFA and MUFA content. In liver, the increase in dietary lipid level resulted in an increased levels of both n-6 and n-3 PUFA. l-carnitine supplementation significantly decreased n-3 PUFA content. Exercise decreased n-3 PUFA in both muscle and liver. Plasma lactate and lactate dehydrogenase, normally associated with increased glycolytic processes, were positively correlated with exercise and inversely correlated with dietary l-carnitine level. l-carnitine supplementation reduced significantly the RQ from 0.72 to 0.63, and an interaction between dietary l-carnitine and lipid was observed (P <0.03). Our results indicate that an increase in fatty acids (FA) intake may promote FA oxidation, and both carnitine and exercise might influence the regulation of FA oxidation selectivity

Viral, bacterial and fungal diseases of Siluroidae, cultured for human consumption.

Based on an extensive literature search, the present overview discusses the economic relevant diseases of Siluroidei, cultured for human consumption. One herpes virus and two irido viruses play a significant role for channel catfish (Ictalurus punctatus), sheatfish (Silurus glanis ) and yellow bullhead (1. melas )culture, respectively. There is only one fish species-specific bacterial disease which has an economic impact in the catfish industry: Edwardsiella ictaluri. Secondary infections with opportunistic bacteria and fungi are of interest in all catfish species cultured both under intensive and extensive circumstances. Etiology, pathology, prevention and treatment are shortly discussed for all diseases. Also some diseases of unknown etiology, which occur in African (Clarias gariepinus ) and Asian (C. batrachus ) catfish, are described

Psychological factors associated with changes in physical activity in Dutch people with type 2 diabetes under societal lockdown: a cross-sectional study

Aims To investigate changes in physical activity (PA) and psychological factors during societal lockdown in people with type 2 diabetes.Methods A cross-sectional study among Dutch adults with type 2 diabetes. Data were collected using online questionnaires. A multivariate multinomial logistic regression was performed with change in PA during societal lockdown as outcome and perceived change in stress, anxiety, perceived risk for COVID-19 infection, emotional well-being and former PA status as determinants.Results Five hundred and sixty seven respondents filled out the questionnaire, 536 were included in the final analysis: mean age of 65.9 +/- 7.9 years; mean diabetes duration 13.3 +/- 8 years; 54% men; 47% reported no change in PA, 27% became less active and 26% became more active during societal lockdown. Participants who were more likely to become less active were participants who experienced more stress (OR: 2.27; 95% CI 1.25-4.13) or less stress (OR: 2.20; 95% CI 1.03-4.71). Participants who were more likely to become more active were participants who experienced more stress (OR: 2.31; 95% CI 1.25, 4.26). Participants with higher emotional well-being (OR: 0.98; 95% CI 0.97, 0.99) were less likely to become less active than to report no change in PA.Conclusions Changes in PA in people with type 2 diabetes during societal lockdown are associated with changes in psychological factors such as perceived stress and emotional well-being. People with diabetes and their caregivers should be aware of these possible changes.Public Health and primary carePrevention, Population and Disease management (PrePoD

Short-term prognosis of breakthrough venous thromboembolism in anticoagulated patients

Background: Evidence for guideline recommendations for the treatment of venous thromboembolism (VTE) during anticoagulant therapy is scarce. We aimed to observe and to describe the management of VTE occurring during anticoagulant therapy. Methods: This prospective multi-center, observational study included patients with objectively confirmed VTE during anticoagulant therapy (breakthrough event), with a follow-up of 3 months, after the breakthrough event. Results: We registered 121 patients with a breakthrough event, with a mean age of 56 years (range, 19 to 90); 61 were male (50%). Fifty-eight patients (48%) had an active malignancy. At the time of the breakthrough event, 57 patients (47%) were treated with a vitamin K antagonist (VKA), 53 patients (44%) with low-molecular-weight heparin (LMWH) and 11 patients (9%) with direct oral anticoagulants, unfractionated heparin, or VKA plu

Magnetic Resonance Direct Thrombus Imaging (MRDTI) Can Distinguish Between Old and New Thrombosis in the Abdominal Aorta: a Case Report

A 43-year-old man complaining of abdominal angina for several months showed a large suprarenal aneurysm of the abdominal aorta with extensive circumferential wall thrombosis, complete occlusion of the right renal artery and a critically stenosed left renal artery on CT angiography. He suffered from severe hypertension and renal failure. A percutaneous transluminal angioplasty (PTA) was planned. After the PTA procedure, which was complicated by the development of left renal artery occlusion, successful rescue revascularization surgery was performed. Since we were hesitant to start anticoagulant treatment because of a high bleeding risk, magnetic resonance direct thrombus imaging was performed to assess the age of the extensive arterial thrombosis. The aortic thrombus showed a low signal intensity, which is indicative of chronic rather than acute thrombosis. Therefore, oral anticoagulant treatment was not started. The patient recovered without major complications

Obituary J. W. ten Cate

Thrombosis and Hemostasi