PRELIMINARY STUDIES ON THE EFFECTS OF FRESH AND FERMENTED PIG MANURE ON FISH PRODUCTION

Yang Yejin, Zhu Yun, Hua Dan and Wan Junhua

Asian Pacific Regional Research and Training Centre
for Integrated Fish Farming
Wuxi, China

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PRELIMINARY STUDIES ON THE EFFECTS OF FRESH AND FERMENTED PIG MANURE ON FISH PRODUCTION

Yang Yejin, Zhu Yun, Hua Dan and Wan Junhua

ABSTRACT

The growth of several cultivated fishes of Cyprinidae was studied using cognate fresh and fermented pig manure and the equivalent fertilizers N and P as sole inputs to different experimental groups of fish ponds.

Experiment I was conducted from June to October 1986, experiment II from March to October 1987. The proportions of fish production from chemical-fertilized ponds (C), fermented pig manured ponds (F1), and fresh pig manured ponds (F2) were 100:156:226 and 100:294:382 respectively. The ratio of fish production of F1 ponds to F2 ponds was 100 to 145 in experiment I and 100 to 130 in experiment II, respectively.

The chlorophyl content, zooplankton biomass, bacterial activity and BOD were lower in the C ponds than in the F1 and F2 ponds, while the DO concentration was higher. There was little difference in the concentration of NH4-N and PO4-P among the experimental ponds. The physico-chemical parameters in the F1 and F2 ponds were not always in conformity with the fish production. Some parameters were contradictory in these two experiments. In the experiment I, the content of NH4-N in the F1 ponds was lower than that in the F2 ponds, and the content of chlorophyl and the biomass of zooplankton in the F1 ponds were greater than those in the F2 ponds. In contrast, in experiment II all these three parameters were reversed in the F1 and F2 ponds.

These results indicate that part of the fish production in the C ponds came from the natural planktonic food chain, while in the F1 and F2 ponds, much of the production was derived from the manure detritus as well as from the planktonic food chain. The nutrient value of fermented pig manure is probably less than that of fresh manure because of bacterial decomposition during fermentation. There is a complicated relationship among various physico-chemical factors after manure application in the F1 and F2 ponds.

During the experiments, it was found that the application of fresh pig manure would not cause any fish diseases; it is not necessary therefore to ferment pig manure before application.

INTRODUCTION

Animal manures are used in fish farming in China. This is one of the main constituents of the traditional integrated fish farming in China. Long-term practice has proved that this is a good method of eliminating contaminants and increasing fish production. In recent years, the research work in other countries (Barash H. et al., 1984; Buck D.H. et al., 1976; Lee C.S. et al., 1986) also had proved this point. They not only cultured freshwater fishes but also marine shrimps with animal manures (Lee C.S. et al., 1986; Moriarty D.J.W., 1984).

It is on account of fermentation, which can kill the eggs of parasites in manure, avoid consuming a large amount of oxygen in pond water and accelerate the recycling of the materials involved (Lei Huiseng et al., 1981) that most of the authors, home and abroad, in their experiments used fermented manure and only a few used fresh manure or fermented manure (Buck D.H. et al., 1976). But whatever type is used, fresh manure or fermented manure, none of the authors realized that the function of manure in fish ponds is to nurture and multiply various trophic levels of natural foods, and that manures are used indirectly to supply food for fish. In China, some experienced aquaculturists thought that the cultivated freshwater fish species could directly feed on fresh manure. In view of some problems in integrated fish farming, which cannot be well explained on the integration of theory and practice, this needs further verification. Part of these problems were listed on the research projects of our centre in collaboration with IDRC and NAC. This paper describes the preliminary research results of a subproject.

MATERIALS AND METHODS

Ponds: 6 ponds were used on the Dawan Aquafarm of the Centre, each with an area of 300 m² and with an average water depth of 1.2 m average. The ponds were newly built at the end of 1985 and in 1986.

Grouping: These ponds were divided into 3 groups, namely, fresh pig manured F2 group, fermented pig manured F1 group with an input equivalent to the fresh manure and chemical-fertilized C group with urea and superphosphate equivalent to the N and P content of the fresh manure.

Fish species: Plankton-feeders silver carp, Hypophythalmichthys molitrix and bighead carp, Aristichthys nobilis were the main species, and benthos-feeder common carp, Cyprinus carpio was the secondary. In experiment I, Japanese Koi Carrasius carassius cuvieri, which is similar to silver carp in feeding, was also stocked. The stocking densities are shown in Table 1.

Table 1. Stocking and harvesting in test ponds.

* Sc Silver carp; Bc Bighead carp; Cc Common carp; Jk Japanese koi

Manuring: In the vicinity of the experimental ponds, there was a pigsty. Buried on the pond dyke were 2 pottery vats, which could contain 1000 kg of fresh manure each. Pig manure was transported from the pigsty to the vats for storage for a week or two and then, was used as fermented manure. Fresh manure was obtained directly from the pigsty to the ponds. In the experiment I, fresh manure was fermented for 2 weeks and in the experiment II, just for 1 week. The cognate and equivalent features of pig manures were emphasized in each experiment. Chemical fertilizers equivalent to the N and P contents of the fresh manure were dissolved in a keg before application. From mid August, chicken manure was used instead, because of lack of pig manure. The types and quantities of manure are shown in Table 2.

Table 2. Manure application*

* Pig manure content 0.23%; N content 0.41% in experiment I, 0.34% in experiment II. The N content 46% in urea; 14% in superphosphate.
** Fermented chicken manure.
*** Fresh chicken manure.

Basal manure was applied into each pond one week before the experiment I at a rate of 150 kg/pond. Because of the low chlorophyl content in the pond water, basal manure was applied into each pond at a higher rate of 250 kg/pond in the experiment II.

Water quality monitoring: The pond water was sampled 6 times in the first week every month during the experiment I, and once every two weeks during the experiment II. The sampling time was 0830 AM. The measurements of physico-chemical parameters in pond water are shown in Table 3.

Table 3. Biological and physico-chemical parameters of water.

Schecules : Experiment I was conducted from the 30th of June 1986 to the 22nd of October 1986 with a time span of 114 days, and experiment II from the 21st of March to the 19th of October 1979 for a span of 211 days. During the experiments, the water temperature was between 17°C and 33°C and there was a +-0.5°C difference between the test ponds occasionally, but no indication was displayed on statistics. None of the fish diseases different from those in the other 2 groups was found in the F2 ponds. No feeds were provided and no aerator was used. In July-August during the experiment II, there were three heavy rains, resulting in overflowing of the pond water.

RESULTS AND DISCUSSION

The fields from these two experiments are shown in Table 1 and Fig. 1 The proportional fish production from C, F1 and F2 ponds in the experiment I and II were 100:156:226 and 100:294:382 respectively. The proportional fish production from F1 ponds to that from F2 ponds was in the ratio of 100 to 145 and 100 to 130, respectively (Fig 1). The results of the 2 experiments were analysed by means of variance analysis. The statistics showed that the difference of fish production among different experimental ponds as well as the difference of the effectiveness of different manures (F>F0.005; F>F0.01) was apparent.

Figure 1. The proportion of fish production of the different ponds from two experiments

Nutrition of fish was indirectly supplied after the manure application through different trophic levels of food chain. The difference of fish production and natural food between organic-manured ponds and inorganic-fertilized ponds was in conformity with the above-mentioned point of view. The fact that the fish production, cellulose digestibility rate, chlorophyl and planktonic biomass in the F1 and F2 ponds were higher than those in C ponds (see Table 3) indicate that pig manure supplied more bacteria and plankton than chemical fertilizers. However, by comparison, it was hard to explain the contradiction between the fish production and natural food of the F1 and F2 ponds: The fish production of the F2 ponds was always higher than the F1 ponds in both experiments, but some values which indicated the quantity of natural food were not always higher in the F2 ponds: The cellulose digestibility rate of the F1 ponds was a little higher than the F2 ponds; the average BODs were equal; the chlorophyl and planktonic biomass of the second experiment were contrary to those of the first experiment (see Table 3). Panov (He Zihui, 1987) demonstrated that silver carp could assimilate Chlorella detritus. Furthermore, Opuszyuski (1981) even realized that the quality of detritus was the inhibiting factor to the stocking density of silver carp. In 1950s–1960s, one of the authors (Yang) witnessed the competing activities among the cultivated fish species as they fed on fresh manures and found the manure clots recognizable in gut contents of anterior intestines of silver carp, Ctenopharyngodon idellus and Oreochromis mossambicus. From the results of these two experiments, the authors consider that the cultivated fish not only utilize various trophic levels of a natural food chain but also directly feed on manure detritus. From the view point of the fish production of the F2 and F1 ponds in experiment I and II, the respective ratios, F2:F1 = 145:100; F2:F1 = 130:100 indicated that the fish production of F1 ponds was relatively higher and considering the fermentation period, 2 weeks for experiment I, 1 week for experiment II, we could assume that the nutrients in pig manure which were not absorbed by pig and consumed by bacteria in fermentation was in direct correlation with the time of fermentation.

CONCLUSION

When using the cognate and equivalent fresh and fermented pig manure in fish farming, in spite of variation of the trophic levels of a food chain, the fish production of the F2 ponds was apparently higher than that of the F1 ponds. Therefore, it is evident that the cultivated fish not only utilize all the trophic levels of a food chain in a manured pond but also feed on manure detritus. The nutritional value of manure detritus has a tendency to decrease as the fermentation time extend. Thus, with a view to increasing fish production, it is not necessary to ferment pig manure before application.

ACKNOWLEDGEMENTS

This research project was financially supported by the International Development and Research Centre (IDRC). The authors wish to express their gratitude to Dr. F. Brian Davy of the IDRC and Mr. Chen Foo Yan, NACA Coordinator for their concern in this project. Dr. Jack A. Mathias gave very useful advice on this project. Mr. Huang Nenggang of the computer department of the centre helped the authors for mathematical statistics. We wish to thank them all.

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