Browsing by Person "Focken, Ulfert"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Publication
    Development of supplemental diets for carp in Vietnamese upland ponds based on locally available resources
    (2010) Nguyen Ngoc, Tuan; Focken, Ulfert
    Cyprinids play very important role in aquaculture, especially in Asia and Pacific regions. Vietnam is not an exception. Although aquaculture in Vietnam increased dramatically recently, its high value products such as catfish, tiger prawn seem to be unaffordable for the people in rural areas, especially for the mountainous ethnic minority in the North who are more independent to herbivorous and omnivorous fish such as grass carp, Indians carp, and common carp. Yen Chau is a district of Cyprinids play very important role in aquaculture, especially in Asia and Pacific regions. Vietnam is not an exception. Although aquaculture in Vietnam increased dramatically recently, its high value products such as catfish, tiger prawn seem to be unaffordable for the people in rural areas, especially for the Son La province, located in mountainous region in North-Western Vietnam. In this district, Black Thai ethnic minority accounts for approximately 54% population. Besides producing huge amount of grain and tuber crop such as maize and cassava for selling, aquaculture in a small poly-culture pond system is also a very typical activity which supplies an important nutritional source for human consumption and income generation as well. However, even though most of farmers in Yen Chau own at least one pond each, the demand on the local market cannot be covered (Steinbronn, 2009). Recently, unknown diseases causing high mortalities could be the reason of the decrease of grass carp production. To avoid risk from losing grass carp, farmers are tending to change the composition of the fish species stocked in favour of e.g. common carp and mud carp without having an appropriate feed base for these species. So far, no high quality feed was applied into the pond system. Therefore, the study entitled ?Development of supplemental diets for carp in Vietnamese upland ponds based on locally available resources? was conducted to not only contribute to an improvement of income and food security in the region but also meet the appeal of improvement of scientific knowledge on cyprinids which is inadequate with their great contribution. In the study, most of the possible feed ingredients were collected and analyzed for nutritive and non-nutritive values. Based on the results of the analysis a number of diets were formulated for 30% of CP and 10% of CL then tested by common carp. In total, four experiments were designed. The first was conducted in laboratory in which common carp were fed by local pelleted feed with 25, 50, and 75% protein derived from local ingredients. Results of this trial were confirmed by the trial 2 which was implemented under pond condition at Hanoi University of Agriculture. Trial 3 was conducted to compare different protein (full fat soybean meal and soybean cake) and carbohydrate sources (maize and cassava powder). Furthermore, sweet potato leaves were preliminarily investigated in fish feed inclusion. The last trial, trial 4, was carried out to evaluate the use of earthworm for common carp. Trial 1, 3 and 4 were designed for a recirculation system in which five common carp were stocked in each aquarium of 40 l with 3 replicates. Water flow through the aquaria was maintained at 6-7 litters per minute. Water temperature, DO and pH were kept at 25-27°C, above 4 mg/l and around 7.0-8.0, respectively. The photoperiod was set up at 12 hrs light:12 hrs dark. Fish were fed daily five times metabolic body mass requirement for eight weeks. The trial 2 consisted of four feeding groups (3 test diets and 1 control), each having three replicates. In each net, 45 common carp were stocked, Fish were fed three times per day (8h, 12h, and 16h) at a feeding rate of 5 times of maintenance requirement manually. Feed amount was adjusted every ten days after taking the weight of fish. The total trial lasted for 2 months. Analytical results show that all of local materials have good nutritive values, similar or better that those in other regions. Besides, fish meal and many other ingredients can be used as source of protein such as full fat soybean meal, soybean cake, meat meal, as well as earthworm powder. This earthworms Perionyx excavatus show a suitable quality for fish feed, high protein (71% of DM) and amino acids in comparison with many conventional protein sources, including fish meal. Replacement of 70% of protein (~ 20% of DM) by earthworms can significantly improve growth of fish. However, it is still unclear in full replacement fish meal by this material. Using maize and cassava in Yen Chau is also feasible because these materials not only are cheap but also are the most available. Among all plant materials, full fat soybean seems to be the best ingredient with high protein and lipid content. In contrast, fish seem to be deficient of nutrient by feeding sweet potato leaf inclusion diets. In conclusion, except for sweet potato, all of local ingredients can be used for fish feed formulation. The local feeds were well digested, utilized by omnivorous common carp. Despite local feed ingredients did not give the best growth of fish, they gave the best results in term of economic return. Local ingredient feed gave the lowest cost of feed as well as the lowest cost of fresh fish produced. The field trial fish performance seems to be better than in the laboratory due to receiving certain amount of natural food. Thus, fish utilize feed more efficiently resulted in reduction of feed conversion ratio as well as cost of feed per unit of fish produced. Transfer knowledge about low-cost feed to the local farmer together with basal techniques of producing, storing, and effective using fish feed is an important issue which could help farmers to improve production of fish in the region as well as contribute to poverty alleviation in the rural areas in Vietnam.
  • Thumbnail Image
    Publication
    Nutrient flow in improved upland aquaculture systems in Yen Chau, province Son La (Vietnam)
    (2014) Pucher, Johannes Gregor; Focken, Ulfert
    In South-East Asia, pond aquaculture plays an important role in the integrated agriculture aquaculture systems of small-scale farmers and contributes to their food security and income. In mountainous regions, aquaculture differs from aquaculture that is practiced in the lowland due to differences in climate and availability of feeds, fertilizers and water. In Northern Vietnam, the traditional aquaculture is a polyculture of 5-7 fish species. The macro-herbivorous grass carp (Ctenopharyngodon idella) is stocked as the main species. Common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), mrigal (Cirrhinus mrigala), mud carp (Cirrhinus molitorella) and Nile Tilapia (Oreochromis niloticus) are stocked as secondary species and are often insufficiently nourished by farm by-products. Manure is used by farmers as fertilizer for natural food resources. Ponds are managed as a constant water flow-through system. The inflowing water introduces soil particles eroded from the sloping fields of intensively cultured maize and cassava into the ponds, and cause high turbidity that limits both the primary and secondary production. The fish production of this system is low at about 1.5 ± 0.3 t ha-1 a-1 and is mainly limited by the poor quality of pond inputs, low availability of natural food resources, low oxygen production in the ponds and the occurrence of a species-specific disease that causes high mortality in grass carp. To improve the local fish production of small-scale farmers, changes in the traditional pond management were designed and tested in farmers’ ponds in the uplands of Northern Vietnam. These changes included the reduction of water flow through the ponds to reduce the introduction of eroded particles and reduce the turbidity. Chemical fertilizers were added to increase the productivity of natural food resources and encourage higher primary production. The disease-prone grass carp was replaced as the main species by common carp that command a similarly high price on the local markets. To feed the omnivorous common carp, supplemental pellet feeds based mainly on locally available resources were applied to the ponds. In a pond trial, the traditional and modified pond managements were compared for water quality parameters, availability of natural food resources, fish yields, nutrient utilisation efficiencies and monetary net benefit. In a 15N tracer experiment, the nitrogen dynamics in the natural food web in local ponds were compared under the two types of pond management. Acceptability of the modifications by local farmers was evaluated. In a net cage trial, the suitability of earthworm meal as a replacement for fishmeal in supplemental pellet feeds for common carp was tested. In another net cage trial, the effect of pesticide contaminated grass feeds on the feed intake and health condition of grass carp were tested. When compared with traditional pond management, the modified pond management was found to result in reduced water turbidity, deeper phototrophic zones, higher availability of natural food resources, higher primary production and higher fish yield. In addition, the small plankton benefited from the changes and allowed significantly higher growth rates of filter feeding fish. Common carp and grass carp had higher yields due to the changes. Under both types of pond management, nitrogen compounds were assimilated rapidly into the natural food web and there were high rates of sedimentation and re-mobilization of settled nitrogen from the pond bottom. Generally, the modifications to pond management were associated with increased nutrient utilisation efficiencies and resulted in higher net benefits and more stable pond culture conditions. It was shown that plant material from pesticide-treated fields should only be used cautiously as feeds for grass carp because pesticide residues reduce feed intake and adversely affect fish health. Low cost modifications were well accepted by the farmers. Application of supplemental feeds and chemical fertilisers, which required a continual monetary investment, were less well received. The better-educated farmers are more likely to further invest in aquaculture and might act as local adopters. To reduce the costs of feeds for common carp, earthworm has been shown to be suitable as a replacement for fishmeal in feeds. Vermiculture might therefore be a suitable additional farming activity in combination with the implementation of pond management modifications. Formation of fish farmer cooperatives might further increase the acceptability of innovations. The improvements to pond aquaculture that have been developed here may have a beneficial impact on fish production, food security and income of small-scale farmers in the uplands in South-East Asia if the information is suitably transferred through education programmes that train farmers in technologies that have been specially adapted to conditions in the uplands.
  • Thumbnail Image
    Publication
    Saponin fractions from fenugreek (Trigonella foenum-graecum L.)as dietary supplements for Nile tilapia (Oreochromis niloticus L.)and common carp (Cyprinus carpio L.)
    (2012) Stadtlander, Timo; Focken, Ulfert
    The future role and importance of aquaculture for the world food supply is more and more recognized by the public. High quality feed for semi-intensive and intensive aquaculture operations are necessary to guarantee a future continuous growth of fish production. Nutrient utilization efficiency has in the past been augmented by addition of feed additives, mainly anti-biotics and hormones. That practice is prohibited in the European Union since 1st of January 2006 and the consumer acceptance of products produced in that way is low. Around a decade ago saponins, secondary plant metabolites, have been found to be potential alternatives for aquafeeds. Saponinmixtures derived from the South American soap bark tree Quillaja saponaria, have been found to have beneficial effects on growth, feed and nutrient utilization and on metabolism of common carp Cyprinus carpio and Nile tilapia Oreochromis niloticus. Furthermore, in one of the early experiments a sex ratio in favor of males was observed in saponin fed tilapia compared to control fish not supplemented with saponins. An influence on sex ratio of Nile tilapia would be highly desirable since industrially Nile tilapia production is only financially viable if all male populations are produced since mixed sex tilapia populations tend to reproduce uncontrollable. The production of all male tilapia populations is mainly conducted by feeding the potentially environmentally hazardous and carcinogenic synthetic hormone 17--methyltestosterone to sexually undeveloped tilapia fry. The above mentioned problems led to a joint research project with partners in Israel and Palestine in which this dissertation has been conducted. The aim of the project was the fractionation of crude saponin extract derived from fenugreek Trigonella foenum-graecum and its testing in vitro and in vivo. It was assumed that a higher biological activity could be achieved if saponin fractions instead of crude mixtures would be applied. After in vitro testing, different saponin fractions or eluates, have been tested on their effects on growth, feed and nutrient utilization, metabolism, proximate composition, gene expression of GH and IGF-1, sex ratio, reproduction and gonad histology. Most of the feeding experiments were conducted with Nile tilapia but one experiment was also conducted with carp. Three of the feeding experiments have been conducted in a system capable of measuring continuous respiration of the fish. Another experiment has been conducted at a field station at Jericho, Palestine. The experiments conducted to evaluate the influence of saponin fractions on sex ratio of undifferentiated tilapia fry have been conducted primarily in a flow-through system. The tested saponin fractions and a tested sapogenin are not suitable to produce male monosex tilapia populations. The sex ratios after supplementation of diets of mixed sexed tilapia fry did only in one case show a significantly higher proportion of males than the control. In a larger scale repetition of that experiment the previous observations could statistically not be proofed. It must be assumed to be random effects or be the result of initially biased sex ratios after stocking undifferentiated tilapia fry. An experiment in which genetically female tilapias were fed with two fenugreek saponin fractions and positive and negative controls supported that finding. A long term feeding experiment conducted at Jericho revealed no influence of the long and short term supplemented Q. saponaria saponin mixtures on sex ratio and reproduction of genetically female tilapia. A similar laboratory experiment with fenugreek saponin fractions could not be evaluated in that regard. The experiments evaluating the effects of the saponin fractions on growth, feed and nutrient utilization, gene expression of GH and IGF-1 and proximate composition revealed no significant differences. But in all experiments one fraction eluated with 60%/40% (v/v) methanol/water showed numerically improved values compared to control and other fractions. Furthermore one fraction eluated with 40%/60%/ (v/v) methanol/water gave constantly numerically inferior results of tested parameters compared to control. That supports the conclusion that the 40% methanol fraction contains saponins generally referred to as anti-nutrients. In only one experiment, conducted at Jericho, significantly higher growth was observed after long term supplementation with a Q. saponaria saponin mixture containing elevated sapogenin content. The presented data in this thesis is not supporting an application of the tested saponin fractions as environmentally friendly alternative to methyltestosterone to produce all male populations of tilapia or to inhibit uncontrollable reproduction. Additional experiments are needed to evaluate different modes of application like immersion treatments or injections since during the experimental work of this thesis all tested saponins were added to the feed. An application of the tested fenugreek saponin fractions as growth promoters yields a higher potential although the experimental results are based upon low sample sizes due to capacity restrictions of the respirometric system. Therefore a repetition under near commercial or commercial conditions must be considered.