No abstract

This report shows that pig manure can be used for algal production in small farms. Huge pig sludge amounts produced using actual methods in large-scale pig breeding farms is a major issue due to the lack of disposal options and potential water pollution. This issue may be solved by using pig sludge for algal biofuel production. Therefore, we studied an economical method of algae production on pig sludge that can be operated on animal farms in Hungary with modest levels of investment. We analyzed four algae species, Chlorella vulgaris, Scenedesmus quadricauda, Scenedesmus dimorphus, and Arthrospira platensis, in the laboratory and C. vulgaris in outdoor conditions. The following parameters were studied: pot size, illumination, temperature, filtered versus unfiltered pig manure, water depth, aeration, CO 2 enrichment, inoculums solution, fertilization level, and length of rotation period. Produced alga biomass was measured every 4 days, and the protein-and lipid content was analyzed using the method of Bradford (1976) and Erickson (1993). Our results show first that the unfiltered pig manure is not suitable for algae production due to illumination shortage. By contrast, using filtered pig manure, we found that C. vulgaris yield in 70-l indoor pots was 64% higher than in smaller pots. In a larger outdoor system, the annual dry yield of C. vulgaris reached 141-259 t/ha during 12-day-long rotation periods. Here, we demonstrate that only filtered liquid pig manure can be recommended for algae production. C. vulgaris is the most suitable alga species for use in large-scale experiments on pig sludge. Based on our outdoor experiments, the adaptation of a 12-to 14day rotation period could be considered the most reasonable. An algae farm can therefore be operated with relative modest amount of capital, can hence address the issue of sludge management, and provide a substrate for energy production.

The nutrient composition of yellow mealworm (YM) Tenebrio molitor varies based on the stages of the life cycle, the rearing conditions, and the feeding substrate. This study monitored the growth of yellow mealworm larvae at 8, 10, and 12 weeks of age, separating samples into large-sized and small-sized insects. During the experiment, we measured the nutrient composition: dry matter (DM), crude protein (CP), crude fat (CF), crude fibre, chitin, crude ash, and nitrogen free extract (NFE) of YM at different age groups and sizes. We measured the nutrient composition of the pre-moult, moult, cuticle, and pupae as well. The results show that there is no significant difference between the compositions of the different age groups, but larger-sized individuals had a higher DM and crude fibre and lower chitin and NFE than the smaller sizes. The pre-moult and moult stages showed no significant difference in nutrient composition. Although the cuticle had a high DM (97.5%), that did not cause any significant difference between the DM of the moult and pre-moult, because it is only a negligible part of the total wet weight. With the increased DM, the crude protein content and the chitin content, fibre, ash content, and NFE increased, while the fat content decreased. The DM, CF, and chitin contents of pupae are significantly lower than those of the pre-moult and moult stages. Our results show that it is the size and not the age that has a positive effect on the nutrient composition of YM.

Hungary is one of the largest common carp-production countries in Europe and now, there is a large number of local breeds and strains in the country. For proper maintenance of the animal genetic resources, information on their genetic diversity and structure is essential. At present, few data are available on the genetic purity and variability of the Hungarian common carp. In this study, we genetically analyzed 13 strains in Hungary and, in addition, the Amur wild carp, using 12 microsatellite markers. A total of 117 unique alleles were detected in 630 individuals. Low levels of genetic differentiation (Fst and Cavalli–Sforza and Edwards distance) were estimated among strains. The AMOVA showed the low but significant level of genetic differentiation among strains (3.79%). Bayesian clustering analysis using STRUCTURE classified the strains into 14 different clusters. The assignment test showed that 93.64% of the individuals could be assigned correctly into their original strain. Overall, our findings can be contributed to complementing scientific knowledge for conservation and management of threatened strains of common carp.

The harvesting of plant biomass is usually implemented as an effective tool for plant management and removing the nutrients absorbed in plant tissues. Here, the influence of harvesting different biomasses (50%, 33%, 25%, and 0% (no harvest)) of watercress (Nasturtium officinale) was investigated in integrated recirculating aquaponic systems (IRASs) for rearing common carp (Cyprinus carpio). Twelve independent IRASs were designed (4 × 3); each system consisted of a fish rearing tank, a waste collection tank, and a hydroponic bed. Water quality parameters and the growth of both fish and plants were measured in all the systems, and then the nutrient removal capacities of the hydroponic beds were calculated. The results revealed that increasing the biweekly harvested biomass of the plants decreased the growth of the watercress, while it did not affect the growth of the common carp. Increasing the harvested biomass of the plants also decreased the nitrate nitrogen and orthophosphate removal efficiencies of the aquaponic systems, while it did not affect the ammonia and nitrite nitrogen removal efficiencies. Therefore, a biweekly harvesting of less than 25% of the biomass of the growing watercress is recommended for efficient nutrient removal and the sustainable growth of both watercress and the common carp in aquaponic systems.