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Abstract A two-month trial was carried out in China to evaluate the possibility of recycling animal manure through pond tilapia production. And the effects of chicken manure, cattle manure and chicken-cattle mixture together on the water quality and tilapia production were investigated. The results showed that the yield of tilapia was 3.46, 3.89, 2.49 and 3.20 kg in the control, chicken M, cattle M, and chicken-cattle M, respectively, and the tilapia yields following the order of chicken M>control>chicken-cattle M>cattle M. The tilapia yield in chicken M group increased by 12.43% compared with the control. Chicken manure could increase the tilapia production, but cattle manure has no the effect. And the effect of animal manure on water quality showed that adding chicken manure into tilapia pond could make water quality decreased at the beginning 20 d, but could increase water quality after 20 d and stabilize the phytoplankton structure.
Key words Chicken manure; Cattle manure; Tilapia production; Water quality; Aquaculture
It is reported that more than 1 billion people in the world rely on fish as an important source of animal proteins (i.e., fish provides at least 30% of their animal protein intakes)［1］. Aquaculture is an important way to increase fish production, which was achieved through higher fish stocking density and the application of artificial feeding. Unfortunately, the cost of feed is enormous. Therefore, interest has been diverted to other sources of enrichment of the water, such as using of animal manure. Using animal manure to culture fish had been widely used in many countries in the world in order to increase plankton production, decrease feed coefficient and enhance fish production［2］. The manure is directly consumed by fish, and the released nutrients support the growth of mainly photosynthetic organisms［3-4］. Additionally, the manures were applied to produce some necessary plant nutrients which serve as a soil fertilizer by adding the organic matter［5］. Therefore, compared with the feeding, manuring has been considered as a cheaper way to increase fish production.
Tilapia, which originated in Africa and Middle East, has become one of the most produced and internationally traded food fish in the world［6-8］with China taking the lead producing. In some areas of China, especially in Guangdong Province located in southern China producing almost half of the countrys total tilapia production［9］, tilapia aquaculture has the trend of changing from intensive aquaculture systems to integrated aquaculture systems for the economic reason. For tilapia has excellent tolerance even in bad environmental water condition, integrated tilapia culture system with pig, duck and other animals is very common for grow-out tilapia production［10］. This kind of integrated tilapia culture system can decrease economy input, and what is more, tilapia manuring farming could be of interest in recycling animal manure in order to reduce the adverse environmental effect of intensive chicken, duck, pig and cattle farming. Different kinds of manure can be utilized. Cattle, poultry dung and semi-liquid pig manure are of the highest interest［11-12］. Among manures used, chicken is preferred because of its ready solubility and high level of phosphorus concentrations［13］. However, the use of manure, classified as hazardous organic matter originating from animal feces, poses a risk to the water environment［14］, and the information about the effect of manuring on water quality and fecal contamination is scarce. So the goal of this research was to assess the possibility of using chicken and cattle manures in tilapia farming system.
Materials and methods
Experimental design
The tests were carried out in round plastic tanks (with a diameter of 1.3 m and a height of 1 m, in which the actual water depth and actual water quantity were 0.77 m and 1 t, respectively) in the Experimental Station of Freshwater Fisheries Research Center of Chinese Academy of Fishery Sciences.
The tanks were supplied with dechlorinated tap water that had been aerated for 20 d before the experiment. In order to make the aquatic microorganism, especially phytoplankton and zooplankton, in the test tanks with more species, high diversity and similar to the natural pond water environment, the aquatic microorganisms in Taihu lake (which is the water resource for pond aquaculture in Taihu Lake Basin) were gained by phytoplankton net, and then were poured into every tank. Before the experiment, water pumpers (2 000 L/h, SOBO WPR 4000, China) were used to cascade all the tanks, and recirculate water between tanks sufficiently for 24 h to make the aquatic environment of every tank the same.
The test water was not changed during the experiment. If the test water was lower than the water level that we have set because of water evaporation and water sampling, new water would be poured into the tank; and a level-control hole was set in the tank at the water level we have set, so if the test water was higher than the level-control hole in the rainy season, the excessive water would flow out through the hole. That is to say, the volume of test water did not change during the experiment.
Fertilizing method
There were 4 treatments in the test, including control group (no use of manure), chicken manure treatment group (adding 0.5 g/L of the manure every time, chicken M), cattle manure treatment group (adding 0.5 g/L of the manure every time, cattle M), chicken and cattle manure treatment group that with equal amount of chicken and cattle manure (adding 0.25 g/L of the chicken manure and cattle manure both every time, chicken-cattle M). Every treatment had three replicates. Chicken manure and cattle manure were all fermented manures, obtained from Jiangsu Shuyang Blue Sky Organic Fertilizer Factory. Manures were added into tank one time every 10 d during the first 20 d, and then one time every 20 d after 20 d according to the water transparency and for the convenience of the analysis. Culture and sampling methods
The test lasted for 2 months from June 14 to August 13. The stocking density was 50 individual/tank, and the initial weight and length of tilapia were (2.49±0.58) g and (3.85±0.34) cm (n=30), respectively.
The total daily feed input was 5% of the tilapia biomass, with a commercial fish feed (Ningbo Tech-bank Co., Ltd, China), and the feed were divided into 3 equal amounts and fed fish 3 times every day, that is 9:00, 12:30 and 16:00, respectively. And the total daily feed input was adjusted every week with estimated weight gains by the way of weighing 5 tilapia catch from the control group randomly. And the feed was soon and completely consumed by the tilapia every time after feeding.
Sampling of the water was done at 0, 20, 40 and 60 d after starting the experiment at 10 am of the sampling day. The sampling depth was 0.5 m under the surface.
Parameters and measurements
Temperature (T), pH value (pH), transparency (SD), dissolved oxygen (DO), total phosphorus (TP), orthophosphate (PO3-4-P), total nitrogen (TN), nitrate nitrogen (NO-3-N), nitrite nitrogen (NO-2-N), total ammonium nitrogen (TAN), permanganate index (CODMn), chlorophyll a (Chl. a) and total organic carbon (TOC) of test water were monitored one time every 20 d. T, pH, SD, DO, TN, NO-2-N, NO-3-N, TAN, TP, PO3-4-P, CODMn and Chl. a of test water were analyzed according to methods for the examination of water and wastewater published by the State Environmental Protection Administration of China (2002)［15］. TOC of test water was analyzed using TOC analyzer (HACH IL500, America).
TP, TN and TOC of feed, manure and tilapia were measured. TP and TN of feed were analyzed according to Method for the Determination of Crude Protein in Feedstuffs GB/T 6432-94 (China) and Method for the Determination of Phosphorus in Feedstuffs Photometric Method GB/T 6437-2002 (China), respectively. TP and TN of feed were all analyzed according to the standard of Organic Fertilizer NY 525-2002 (China). TP and TN of tilapia were analyzed according to National Food Safety Standard Determination of Protein in Foods GB 5009.5-2010 (China) and Determination of Phosphorus in Foods GB/T 5009.87-2003 (China), respectively. TOC of feed, manure and tilapia were all analyzed using TOC analyzer (HACH IL500, America).
Tilapia were counted and weighed at the end of the test.
Water quality assessment methods
Parameters will be compared to Water Quality Standard for Fishery GB 11607-89 (China). And the comprehensive Trophic Level Index (TLI(∑)) which uses TN, TP, Chl. a, SD and CODMn as assessment factors together was used to assess the water quality according to Meng et al.［16］. Statistical analysis
Statistical analyses were performed using SPSS 15.0. Significant differences were analyzed with one-way analysis of variance (ANOVA). Tukeys multiple comparison was used for statistical comparison with P<0.05 being considered significant.
Results and Analysis
Input of C, N and P
The total amount of manure added to every treatment tank is showed in table 1. The total amounts of feed put into every test and control groups were all 2.61 kg. The C, N and P concentrations in manure, feed and tilapia are showed in Table 2. The total amounts of C, N and P put into the aquaculture water during the aquaculture process are showed in Table 3.
Weight and yield of tilapia
Survivals were all 100% in the test groups. Final mean weight and yield of tilapia are shown in Fig. 1. From the Fig. 1, it can be seen that the final mean weight of tilapia was 69.20, 77.86, 49.83 and 63.94 g in the control, chicken M, cattle M and chicken-cattle M, respectively; and the yield of tilapia was 3.46, 3.89, 2.49 and 3.2 kg in the control, chicken M, cattle M and chicken-cattle M, respectively. The tilapia yield in the chicken M group increased by 12.43% compared with the control. The final mean weight of tilapia in the chicken M group was higher than that in the control, and significantly (P<0.05) higher than that in the cattle M and chicken-cattle M groups. However, the final mean weight of tilapia in cattle M was significantly (P<0.05) lower than that in the control.
Main physicochemical parameters of test water
Physical and chemical conditions of test water are shown in Fig. 2- Fig. 6. pH in the control, chicken M, cattle M and chicken-cattle M groups ranged from 6.56 to 8.27, 6.61 to 8.28, 6.93 to 8.27 and 7.04 to 8.27, respectively. pH in all the groups conformed to Water Quality Standard for Fishery GB 11607-89 (China), however, pH had a decrease trend in all groups. DO in the control, chicken M, cattle M and chicken-cattle M groups ranged from 3.13 to 6.77 mg/L, 2.09 to 6.77 mg/L, 0.40 to 6.77 mg/L and 0.20 to 6.77 mg/L, respectively. DO in the control group conformed to Water Quality Standard for Fishery GB 11607-89 (China) and was higher than that in the manure treatment groups; and DO in the chicken M, cattle M and chicken-cattle M groups at 40 d didnt conform to Water Quality Standard for Fishery GB 11607-89 (China). SD in the control, chicken M, cattle M and chicken-cattle M groups ranged from 7 to 62 cm, 9 to 62 cm, 8 to 62 cm and 6 to 62 cm, respectively. SD in manure treatment groups was higher than that in the control. And SD in all groups decreased with the test time delaying. Agricultural Biotechnology2019
TAN in the control, chicken M, cattle M and chicken-cattle M groups ranged from 0.33 to 9.13 mg/L, 0.33 to 2.63 mg/L, 0.33 to 6.40 mg/L and 0.33 to 5.97 mg/L, respectively. TAN in the control was higher than that in the chicken M, cattle M and chicken-cattle M groups, following the order of control>cattle M>chicken-cattle M>chicken M. NO-2-N in the control, chicken M, cattle M and chicken-cattle M groups ranged from 0.010 to 6.109 mg/L, 0.010 to 3.570 mg/L, 0.010 to 2.426 mg/L and 0.010 to 2.081 mg/L, respectively. NO-2-N in the control was higher than that in the chicken M, cattle M and chicken-cattle M groups, following the order of control>chicken M>cattle M>chicken-cattle M. NO-3-N in the control, chicken M, cattle M and chicken-cattle M groups ranged from 1.548 to 12.133 mg/L, 1.548 to 7.343 mg/L, 1.548 to 1.835 mg/L and 1.548 to 1.835 mg/L, respectively. NO-3-N in the control was higher than that in the chicken M, cattle M and chicken-cattle M groups, but no regularity could be found between different manure treatment groups. TN in the control, chicken M, cattle M, chicken-cattle M groups ranged from 2.08 to 28.48 mg/L, 2.08 to 21.33 mg/L, 2.08 to 13.98 mg/L and 2.08 to 12.68 mg/L, respectively. TN in the control was higher than that in the chicken M, cattle M and chicken-cattle M groups, following the order of control>chicken M>cattle M>chicken-cattle M. NO-2-N, NO-3-N and TN in all groups increased with the test time delaying; and TAN in all groups increased with the test time delaying during the first 40 d, but decreased at 60 d.
PO3-4-P in the control, chicken M, cattle M and chicken-cattle M groups ranged from 0.017 to 0.730 mg/L, 0.017 to 2.970 mg/L, 0.017 to 12.270 mg/L and 0.017 to 3.640 mg/L, respectively. TP in the control, chicken M, cattle M and chicken-cattle M groups ranged from 2.075 to 11.007 mg/L, 2.075 to 11.786 mg/L, 2.075 to 12.770 mg/L and 2.075 to 11.794 mg/L, respectively. PO3-4-P and TP in the control were all lower than that in the chicken M, cattle M and chicken-cattle M groups, following the order of cattle M>chicken-cattle M>chicken M>control. PO3-4-P and TP in all groups increased with the test time delaying.
CODMn in the control, chicken M, cattle M and chicken-cattle M groups ranged from 3.80 to 77.93 mg/L, 3.80 to 55.61 mg/L, 3.80 to 57.05 mg/L and 3.80 to 61.37 mg/L, respectively. TOC in the control, chicken M, cattle M and chicken-cattle M groups ranged from 2.6 to 86.3 mg/L, 2.6 to 64.5 mg/L, 2.6 to 59.6 mg/L and 2.6 to 57.6 mg/L, respectively. CODMn and TOC in the control were all higher than that in the chicken M, cattle M, chicken-cattle M groups at 40 and 60 d, but no regularity could be found between different manure treatment groups. CODMn and TOC in all groups increased with the test time delaying. Chl. a in the control, chicken M, cattle M and chicken-cattle M groups ranged from 1.21 to 26.95 μg/L, 1.21 to 10.89 μg/L, 1.21 to 45.66 μg/L and 1.21 to 39.31 μg/L, respectively. And no regularity could be found between different treatment groups. However, Chl. a in chicken M was more stable than that in other groups.
TLI(∑) in the control, chicken M, cattle M and chicken-cattle M groups ranged from 59.4 to 104.4, 59.4 to 99.4, 59.4 to 101.9 and 59.4 to 103.0, respectively. TLI(∑) in the chicken M, cattle M and chicken-cattle M groups were higher than that in the control at 20 d, but lower than that in the control at 40 and 60 d. However, no regularity could be found between different manure treatment groups. Chl. a and TLI(∑) in all groups increased with the test time delaying.
Discussion
In this study, the final mean weight of tilapia in the groups followed the order of chicken M>control>chicken-cattle M>cattle M. So it could be concluded that chicken manure was better than cattle manure, and could be used in tilapia farming. Lu et al.［17］found a similar phenomenon when they used chicken manure as fertilizer in tilapia pond, and concluded that chicken manure not only increases plankton production in water, but also could be eaten directly by tilapia. However, Zoccarato et al.［2］found an inversing phenomenon that the fish productions followed the order of feed only group>manure and feed group>manure only group, when they used pig manure as fertilizer in carp culture pond in Northern Italy. Maybe different fish species have different environment adaptation, and tilapia is more eutrophication resistant compared with carp, so they resulted in different results. Therefore, it is important to choose a suitable fish species when using animal manure to culture fish.
DO stands for O2 dissolved in water. DO is necessary to aquatic organisms. If there is no oxygen in water, all the aquatic organisms except anaerobic microorganisms will die. DO can oxidize the organic materials in water and ample DO is necessary to maintain good water quality. In our test, DO in the control group was higher than that in the manure treatment groups, Zoccarato et al.［2］and Chen et al.［18］also found the similar result when they used pig manure as fertilizer in carp culture pond in Northern Italy and used chicken manure as fertilizer in aquaculture pond, respectively. Simultaneously, we found that DO had a decrease trend in all the manure treatment groups, Dai et al.［19］also found the similar result when they used duck manure as fertilizer in aquaculture pond. For there are a lot of organic materials in animal manure, and oxidization process will consume DO, the DO decreased in manure treatment group. The phenomenon suggested that aeration is needed in aquaculture pond used manure as fertilizer, especially in high temperature season, for the temperature would influence the saturated concentration of DO in water, the higher of the temperature the lower of the saturated DO in water［20］. SD means the clarification of water. The more of suspended solid is in water, the lower of transparency. Our results showed that SD in all manure treatment groups decreased with the test time delaying, which revealed the suspended solid increased with the test time delaying. Chen et al.［19］also found the similar result when they used chicken manure as fertilizer in aquaculture pond, and what is more, they found SD in manure treatment groups was lower than that in the control. However, different from Chen et al.［19］, we found SD in manure treatment groups was higher than that in the control, revealing manure could decrease suspended solid in tilapia pond.
Nitrogen and phosphorus are essential for all living things, however, excessive nitrogen and phosphorus, especially higher TAN and NO-2-N, is hazardous to aquatic organism directly or indirectly. The nitrogen and phosphorus in pond water mainly come from feed residual, fish feces, fertilizer; and for nitrogen, the microorganisms are also an important source, such as blue algae, could fix nitrogen from the air. In this study, TAN, NO-2-N, NO-3-N, TN in the control were higher than that in the manure treatment groups, revealing manure could decrease nitrogen concentration in aquaculture water to some extent. However, Lu et al.［17］found an inversing phenomenon in TN when they used chicken manure as fertilizer in tilapia pond. As to PO3-4-P and TP, in this study, PO3-4-P and TP in the control were lower than that in the manure treatment groups. Lu et al.［17］also found the similar result in TP when they used chicken manure as fertilizer in tilapia pond. Furthermore, our results showed TAN, NO-2-N, NO-3-N, TN, PO3-4-P and TP in all test groups increased with the test time delaying, Dai et al.［19］also found the similar result in TP when they used duck manure as fertilizer in aquaculture pond. For the water in all the test groups were not changed during the experiment, so this phenomenon is normal, which revealed the accumulation of TAN, NO-2-N, NO-3-N, TN, PO3-4-P and TP in aquaculture water.
CODMn and TOC are always used as the index standing for organic pollution, and CODMn is also used as the index standing for reductive inorganic pollution, such as nitrite and sulfide. In this study, CODMn and TOC had the similar change trend, and CODMn and TOC in all test groups increased with the test time delaying, Dai et al.［19］also found the similar result in CODMn when they used duck manure as fertilizer in aquaculture pond. As to the concentrations of CODMn and TOC, our result showed that CODMn and TOC in the control were all lower than that in the manure treatment groups for the first 20 d, Lu et al.［17］found a similar phenomenon in CODMn when they used chicken manure as fertilizer in tilapia pond. However, after 20 d, the CODMn and TOC in the control were significant higher than that in the manure treatment groups. It is known that CODMn is the index standing for organic pollution and reductive inorganic pollution. Because a lot of organic manure was put into manure treatment groups, the CODMn in the control was lower than that in the manure treatment groups for the first 20 d, and the result of our experiment that TOC in the control was lower than that in the manure treatment groups demonstrates our conclusion. For TOC was lower and NO-2-N was higher in the control than that in the manure treatment groups for the first 20 d, it might be concluded that the organic material was the main source of CODMn for the first 20 d. And the reason of the phenomenon that CODMn in control was higher than that in the manure treatment groups after 20 d might be that the reductive inorganic materials and organic materials in the control was higher than that in the manure treatment groups, and the results of our experiment that NO-2-N and TOC in control were all significant higher than that in the manure treatment groups demonstrates our conclusion. Chl. a can represent the quantity of phytoplankton to some extent, and the higher Chl. a means the higher quantity of phytoplankton. In this study, Chl. a in chicken M was more stable than that in other groups and there was a violent increase in Chl. a in the control, cattle M and chicken-cattle M groups at the end of the test. The phenomenon showed that phytoplankton structure in chicken M was more stable than that in other groups and there was a violent increase in phytoplankton in the control, cattle M and chicken-cattle M groups at the end of the test.
TLI(∑) is usually used as an index reflecting the trophic level of water body. And the TLI(∑) is calculated according to five parameters, that is total nitrogen (TN), total phosphorus(TP), transparency (SD), chlorophyll a (Chl. a) and permanganate index (CODMn). The higher of TN, TP, SD, Chl. a and CODMn, the larger of TLI(∑), revealing the severer of the trophic level; and the reverse is the same. And according to the value of TLI(∑), the trophic level of water quality can be classified as oligotrophic level (TLI(∑) value is between 0 and 30, mesotrophic level (TLI(∑) value is between 30 and 50 and eutrophic level (TLI(∑) value is higher than 50［16］. In this study, TLI(∑) in the control was lower, for the first 20 d, and was higher, after 20 d, than that in the manure treatment groups, revealing the water quality in the control was better, for the first 20 d, and was worse, after 20 d, than that in the manure treatment groups.
Conclusions
Chicken manure could increase the tilapia production, rather than cattle manure. And the tilapia yields followed the order of Chicken M>control>Chicken-Cattle M>Cattle M, and the tilapia yield in the Chicken M group increased by 12.43% compared with the control.
Adding chicken manure into tilapia pond could make water quality decreased at the beginning 20 d, but could increase water quality after 20 d and stabilize the phytoplankton structure.
References
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［3］MOAV R, WOHLFARTH G, SHROEDER GL, et al. Intensive polyculture of fish in freshwater ponds. 1. Substitution of expensive feeds by liquid cow manure［J］. Aquaculture, 1977(10): 25-43. ［4］LITTLE DC, EDWARDS P. Alternative strategies for livestock-fish integration with emphasis on Asia［J］. AMBIO A J. Hum. Environ, 1999, 28(2): 118–124.
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［15］State Environmental Protection Agency of China. Standard method for the examination of water and wastewater［M］. Beijing: China Environmental Science Press, 2002.
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Key words Chicken manure; Cattle manure; Tilapia production; Water quality; Aquaculture
It is reported that more than 1 billion people in the world rely on fish as an important source of animal proteins (i.e., fish provides at least 30% of their animal protein intakes)［1］. Aquaculture is an important way to increase fish production, which was achieved through higher fish stocking density and the application of artificial feeding. Unfortunately, the cost of feed is enormous. Therefore, interest has been diverted to other sources of enrichment of the water, such as using of animal manure. Using animal manure to culture fish had been widely used in many countries in the world in order to increase plankton production, decrease feed coefficient and enhance fish production［2］. The manure is directly consumed by fish, and the released nutrients support the growth of mainly photosynthetic organisms［3-4］. Additionally, the manures were applied to produce some necessary plant nutrients which serve as a soil fertilizer by adding the organic matter［5］. Therefore, compared with the feeding, manuring has been considered as a cheaper way to increase fish production.
Tilapia, which originated in Africa and Middle East, has become one of the most produced and internationally traded food fish in the world［6-8］with China taking the lead producing. In some areas of China, especially in Guangdong Province located in southern China producing almost half of the countrys total tilapia production［9］, tilapia aquaculture has the trend of changing from intensive aquaculture systems to integrated aquaculture systems for the economic reason. For tilapia has excellent tolerance even in bad environmental water condition, integrated tilapia culture system with pig, duck and other animals is very common for grow-out tilapia production［10］. This kind of integrated tilapia culture system can decrease economy input, and what is more, tilapia manuring farming could be of interest in recycling animal manure in order to reduce the adverse environmental effect of intensive chicken, duck, pig and cattle farming. Different kinds of manure can be utilized. Cattle, poultry dung and semi-liquid pig manure are of the highest interest［11-12］. Among manures used, chicken is preferred because of its ready solubility and high level of phosphorus concentrations［13］. However, the use of manure, classified as hazardous organic matter originating from animal feces, poses a risk to the water environment［14］, and the information about the effect of manuring on water quality and fecal contamination is scarce. So the goal of this research was to assess the possibility of using chicken and cattle manures in tilapia farming system.
Materials and methods
Experimental design
The tests were carried out in round plastic tanks (with a diameter of 1.3 m and a height of 1 m, in which the actual water depth and actual water quantity were 0.77 m and 1 t, respectively) in the Experimental Station of Freshwater Fisheries Research Center of Chinese Academy of Fishery Sciences.
The tanks were supplied with dechlorinated tap water that had been aerated for 20 d before the experiment. In order to make the aquatic microorganism, especially phytoplankton and zooplankton, in the test tanks with more species, high diversity and similar to the natural pond water environment, the aquatic microorganisms in Taihu lake (which is the water resource for pond aquaculture in Taihu Lake Basin) were gained by phytoplankton net, and then were poured into every tank. Before the experiment, water pumpers (2 000 L/h, SOBO WPR 4000, China) were used to cascade all the tanks, and recirculate water between tanks sufficiently for 24 h to make the aquatic environment of every tank the same.
The test water was not changed during the experiment. If the test water was lower than the water level that we have set because of water evaporation and water sampling, new water would be poured into the tank; and a level-control hole was set in the tank at the water level we have set, so if the test water was higher than the level-control hole in the rainy season, the excessive water would flow out through the hole. That is to say, the volume of test water did not change during the experiment.
Fertilizing method
There were 4 treatments in the test, including control group (no use of manure), chicken manure treatment group (adding 0.5 g/L of the manure every time, chicken M), cattle manure treatment group (adding 0.5 g/L of the manure every time, cattle M), chicken and cattle manure treatment group that with equal amount of chicken and cattle manure (adding 0.25 g/L of the chicken manure and cattle manure both every time, chicken-cattle M). Every treatment had three replicates. Chicken manure and cattle manure were all fermented manures, obtained from Jiangsu Shuyang Blue Sky Organic Fertilizer Factory. Manures were added into tank one time every 10 d during the first 20 d, and then one time every 20 d after 20 d according to the water transparency and for the convenience of the analysis. Culture and sampling methods
The test lasted for 2 months from June 14 to August 13. The stocking density was 50 individual/tank, and the initial weight and length of tilapia were (2.49±0.58) g and (3.85±0.34) cm (n=30), respectively.
The total daily feed input was 5% of the tilapia biomass, with a commercial fish feed (Ningbo Tech-bank Co., Ltd, China), and the feed were divided into 3 equal amounts and fed fish 3 times every day, that is 9:00, 12:30 and 16:00, respectively. And the total daily feed input was adjusted every week with estimated weight gains by the way of weighing 5 tilapia catch from the control group randomly. And the feed was soon and completely consumed by the tilapia every time after feeding.
Sampling of the water was done at 0, 20, 40 and 60 d after starting the experiment at 10 am of the sampling day. The sampling depth was 0.5 m under the surface.
Parameters and measurements
Temperature (T), pH value (pH), transparency (SD), dissolved oxygen (DO), total phosphorus (TP), orthophosphate (PO3-4-P), total nitrogen (TN), nitrate nitrogen (NO-3-N), nitrite nitrogen (NO-2-N), total ammonium nitrogen (TAN), permanganate index (CODMn), chlorophyll a (Chl. a) and total organic carbon (TOC) of test water were monitored one time every 20 d. T, pH, SD, DO, TN, NO-2-N, NO-3-N, TAN, TP, PO3-4-P, CODMn and Chl. a of test water were analyzed according to methods for the examination of water and wastewater published by the State Environmental Protection Administration of China (2002)［15］. TOC of test water was analyzed using TOC analyzer (HACH IL500, America).
TP, TN and TOC of feed, manure and tilapia were measured. TP and TN of feed were analyzed according to Method for the Determination of Crude Protein in Feedstuffs GB/T 6432-94 (China) and Method for the Determination of Phosphorus in Feedstuffs Photometric Method GB/T 6437-2002 (China), respectively. TP and TN of feed were all analyzed according to the standard of Organic Fertilizer NY 525-2002 (China). TP and TN of tilapia were analyzed according to National Food Safety Standard Determination of Protein in Foods GB 5009.5-2010 (China) and Determination of Phosphorus in Foods GB/T 5009.87-2003 (China), respectively. TOC of feed, manure and tilapia were all analyzed using TOC analyzer (HACH IL500, America).
Tilapia were counted and weighed at the end of the test.
Water quality assessment methods
Parameters will be compared to Water Quality Standard for Fishery GB 11607-89 (China). And the comprehensive Trophic Level Index (TLI(∑)) which uses TN, TP, Chl. a, SD and CODMn as assessment factors together was used to assess the water quality according to Meng et al.［16］. Statistical analysis
Statistical analyses were performed using SPSS 15.0. Significant differences were analyzed with one-way analysis of variance (ANOVA). Tukeys multiple comparison was used for statistical comparison with P<0.05 being considered significant.
Results and Analysis
Input of C, N and P
The total amount of manure added to every treatment tank is showed in table 1. The total amounts of feed put into every test and control groups were all 2.61 kg. The C, N and P concentrations in manure, feed and tilapia are showed in Table 2. The total amounts of C, N and P put into the aquaculture water during the aquaculture process are showed in Table 3.
Weight and yield of tilapia
Survivals were all 100% in the test groups. Final mean weight and yield of tilapia are shown in Fig. 1. From the Fig. 1, it can be seen that the final mean weight of tilapia was 69.20, 77.86, 49.83 and 63.94 g in the control, chicken M, cattle M and chicken-cattle M, respectively; and the yield of tilapia was 3.46, 3.89, 2.49 and 3.2 kg in the control, chicken M, cattle M and chicken-cattle M, respectively. The tilapia yield in the chicken M group increased by 12.43% compared with the control. The final mean weight of tilapia in the chicken M group was higher than that in the control, and significantly (P<0.05) higher than that in the cattle M and chicken-cattle M groups. However, the final mean weight of tilapia in cattle M was significantly (P<0.05) lower than that in the control.
Main physicochemical parameters of test water
Physical and chemical conditions of test water are shown in Fig. 2- Fig. 6. pH in the control, chicken M, cattle M and chicken-cattle M groups ranged from 6.56 to 8.27, 6.61 to 8.28, 6.93 to 8.27 and 7.04 to 8.27, respectively. pH in all the groups conformed to Water Quality Standard for Fishery GB 11607-89 (China), however, pH had a decrease trend in all groups. DO in the control, chicken M, cattle M and chicken-cattle M groups ranged from 3.13 to 6.77 mg/L, 2.09 to 6.77 mg/L, 0.40 to 6.77 mg/L and 0.20 to 6.77 mg/L, respectively. DO in the control group conformed to Water Quality Standard for Fishery GB 11607-89 (China) and was higher than that in the manure treatment groups; and DO in the chicken M, cattle M and chicken-cattle M groups at 40 d didnt conform to Water Quality Standard for Fishery GB 11607-89 (China). SD in the control, chicken M, cattle M and chicken-cattle M groups ranged from 7 to 62 cm, 9 to 62 cm, 8 to 62 cm and 6 to 62 cm, respectively. SD in manure treatment groups was higher than that in the control. And SD in all groups decreased with the test time delaying. Agricultural Biotechnology2019
TAN in the control, chicken M, cattle M and chicken-cattle M groups ranged from 0.33 to 9.13 mg/L, 0.33 to 2.63 mg/L, 0.33 to 6.40 mg/L and 0.33 to 5.97 mg/L, respectively. TAN in the control was higher than that in the chicken M, cattle M and chicken-cattle M groups, following the order of control>cattle M>chicken-cattle M>chicken M. NO-2-N in the control, chicken M, cattle M and chicken-cattle M groups ranged from 0.010 to 6.109 mg/L, 0.010 to 3.570 mg/L, 0.010 to 2.426 mg/L and 0.010 to 2.081 mg/L, respectively. NO-2-N in the control was higher than that in the chicken M, cattle M and chicken-cattle M groups, following the order of control>chicken M>cattle M>chicken-cattle M. NO-3-N in the control, chicken M, cattle M and chicken-cattle M groups ranged from 1.548 to 12.133 mg/L, 1.548 to 7.343 mg/L, 1.548 to 1.835 mg/L and 1.548 to 1.835 mg/L, respectively. NO-3-N in the control was higher than that in the chicken M, cattle M and chicken-cattle M groups, but no regularity could be found between different manure treatment groups. TN in the control, chicken M, cattle M, chicken-cattle M groups ranged from 2.08 to 28.48 mg/L, 2.08 to 21.33 mg/L, 2.08 to 13.98 mg/L and 2.08 to 12.68 mg/L, respectively. TN in the control was higher than that in the chicken M, cattle M and chicken-cattle M groups, following the order of control>chicken M>cattle M>chicken-cattle M. NO-2-N, NO-3-N and TN in all groups increased with the test time delaying; and TAN in all groups increased with the test time delaying during the first 40 d, but decreased at 60 d.
PO3-4-P in the control, chicken M, cattle M and chicken-cattle M groups ranged from 0.017 to 0.730 mg/L, 0.017 to 2.970 mg/L, 0.017 to 12.270 mg/L and 0.017 to 3.640 mg/L, respectively. TP in the control, chicken M, cattle M and chicken-cattle M groups ranged from 2.075 to 11.007 mg/L, 2.075 to 11.786 mg/L, 2.075 to 12.770 mg/L and 2.075 to 11.794 mg/L, respectively. PO3-4-P and TP in the control were all lower than that in the chicken M, cattle M and chicken-cattle M groups, following the order of cattle M>chicken-cattle M>chicken M>control. PO3-4-P and TP in all groups increased with the test time delaying.
CODMn in the control, chicken M, cattle M and chicken-cattle M groups ranged from 3.80 to 77.93 mg/L, 3.80 to 55.61 mg/L, 3.80 to 57.05 mg/L and 3.80 to 61.37 mg/L, respectively. TOC in the control, chicken M, cattle M and chicken-cattle M groups ranged from 2.6 to 86.3 mg/L, 2.6 to 64.5 mg/L, 2.6 to 59.6 mg/L and 2.6 to 57.6 mg/L, respectively. CODMn and TOC in the control were all higher than that in the chicken M, cattle M, chicken-cattle M groups at 40 and 60 d, but no regularity could be found between different manure treatment groups. CODMn and TOC in all groups increased with the test time delaying. Chl. a in the control, chicken M, cattle M and chicken-cattle M groups ranged from 1.21 to 26.95 μg/L, 1.21 to 10.89 μg/L, 1.21 to 45.66 μg/L and 1.21 to 39.31 μg/L, respectively. And no regularity could be found between different treatment groups. However, Chl. a in chicken M was more stable than that in other groups.
TLI(∑) in the control, chicken M, cattle M and chicken-cattle M groups ranged from 59.4 to 104.4, 59.4 to 99.4, 59.4 to 101.9 and 59.4 to 103.0, respectively. TLI(∑) in the chicken M, cattle M and chicken-cattle M groups were higher than that in the control at 20 d, but lower than that in the control at 40 and 60 d. However, no regularity could be found between different manure treatment groups. Chl. a and TLI(∑) in all groups increased with the test time delaying.
Discussion
In this study, the final mean weight of tilapia in the groups followed the order of chicken M>control>chicken-cattle M>cattle M. So it could be concluded that chicken manure was better than cattle manure, and could be used in tilapia farming. Lu et al.［17］found a similar phenomenon when they used chicken manure as fertilizer in tilapia pond, and concluded that chicken manure not only increases plankton production in water, but also could be eaten directly by tilapia. However, Zoccarato et al.［2］found an inversing phenomenon that the fish productions followed the order of feed only group>manure and feed group>manure only group, when they used pig manure as fertilizer in carp culture pond in Northern Italy. Maybe different fish species have different environment adaptation, and tilapia is more eutrophication resistant compared with carp, so they resulted in different results. Therefore, it is important to choose a suitable fish species when using animal manure to culture fish.
DO stands for O2 dissolved in water. DO is necessary to aquatic organisms. If there is no oxygen in water, all the aquatic organisms except anaerobic microorganisms will die. DO can oxidize the organic materials in water and ample DO is necessary to maintain good water quality. In our test, DO in the control group was higher than that in the manure treatment groups, Zoccarato et al.［2］and Chen et al.［18］also found the similar result when they used pig manure as fertilizer in carp culture pond in Northern Italy and used chicken manure as fertilizer in aquaculture pond, respectively. Simultaneously, we found that DO had a decrease trend in all the manure treatment groups, Dai et al.［19］also found the similar result when they used duck manure as fertilizer in aquaculture pond. For there are a lot of organic materials in animal manure, and oxidization process will consume DO, the DO decreased in manure treatment group. The phenomenon suggested that aeration is needed in aquaculture pond used manure as fertilizer, especially in high temperature season, for the temperature would influence the saturated concentration of DO in water, the higher of the temperature the lower of the saturated DO in water［20］. SD means the clarification of water. The more of suspended solid is in water, the lower of transparency. Our results showed that SD in all manure treatment groups decreased with the test time delaying, which revealed the suspended solid increased with the test time delaying. Chen et al.［19］also found the similar result when they used chicken manure as fertilizer in aquaculture pond, and what is more, they found SD in manure treatment groups was lower than that in the control. However, different from Chen et al.［19］, we found SD in manure treatment groups was higher than that in the control, revealing manure could decrease suspended solid in tilapia pond.
Nitrogen and phosphorus are essential for all living things, however, excessive nitrogen and phosphorus, especially higher TAN and NO-2-N, is hazardous to aquatic organism directly or indirectly. The nitrogen and phosphorus in pond water mainly come from feed residual, fish feces, fertilizer; and for nitrogen, the microorganisms are also an important source, such as blue algae, could fix nitrogen from the air. In this study, TAN, NO-2-N, NO-3-N, TN in the control were higher than that in the manure treatment groups, revealing manure could decrease nitrogen concentration in aquaculture water to some extent. However, Lu et al.［17］found an inversing phenomenon in TN when they used chicken manure as fertilizer in tilapia pond. As to PO3-4-P and TP, in this study, PO3-4-P and TP in the control were lower than that in the manure treatment groups. Lu et al.［17］also found the similar result in TP when they used chicken manure as fertilizer in tilapia pond. Furthermore, our results showed TAN, NO-2-N, NO-3-N, TN, PO3-4-P and TP in all test groups increased with the test time delaying, Dai et al.［19］also found the similar result in TP when they used duck manure as fertilizer in aquaculture pond. For the water in all the test groups were not changed during the experiment, so this phenomenon is normal, which revealed the accumulation of TAN, NO-2-N, NO-3-N, TN, PO3-4-P and TP in aquaculture water.
CODMn and TOC are always used as the index standing for organic pollution, and CODMn is also used as the index standing for reductive inorganic pollution, such as nitrite and sulfide. In this study, CODMn and TOC had the similar change trend, and CODMn and TOC in all test groups increased with the test time delaying, Dai et al.［19］also found the similar result in CODMn when they used duck manure as fertilizer in aquaculture pond. As to the concentrations of CODMn and TOC, our result showed that CODMn and TOC in the control were all lower than that in the manure treatment groups for the first 20 d, Lu et al.［17］found a similar phenomenon in CODMn when they used chicken manure as fertilizer in tilapia pond. However, after 20 d, the CODMn and TOC in the control were significant higher than that in the manure treatment groups. It is known that CODMn is the index standing for organic pollution and reductive inorganic pollution. Because a lot of organic manure was put into manure treatment groups, the CODMn in the control was lower than that in the manure treatment groups for the first 20 d, and the result of our experiment that TOC in the control was lower than that in the manure treatment groups demonstrates our conclusion. For TOC was lower and NO-2-N was higher in the control than that in the manure treatment groups for the first 20 d, it might be concluded that the organic material was the main source of CODMn for the first 20 d. And the reason of the phenomenon that CODMn in control was higher than that in the manure treatment groups after 20 d might be that the reductive inorganic materials and organic materials in the control was higher than that in the manure treatment groups, and the results of our experiment that NO-2-N and TOC in control were all significant higher than that in the manure treatment groups demonstrates our conclusion. Chl. a can represent the quantity of phytoplankton to some extent, and the higher Chl. a means the higher quantity of phytoplankton. In this study, Chl. a in chicken M was more stable than that in other groups and there was a violent increase in Chl. a in the control, cattle M and chicken-cattle M groups at the end of the test. The phenomenon showed that phytoplankton structure in chicken M was more stable than that in other groups and there was a violent increase in phytoplankton in the control, cattle M and chicken-cattle M groups at the end of the test.
TLI(∑) is usually used as an index reflecting the trophic level of water body. And the TLI(∑) is calculated according to five parameters, that is total nitrogen (TN), total phosphorus(TP), transparency (SD), chlorophyll a (Chl. a) and permanganate index (CODMn). The higher of TN, TP, SD, Chl. a and CODMn, the larger of TLI(∑), revealing the severer of the trophic level; and the reverse is the same. And according to the value of TLI(∑), the trophic level of water quality can be classified as oligotrophic level (TLI(∑) value is between 0 and 30, mesotrophic level (TLI(∑) value is between 30 and 50 and eutrophic level (TLI(∑) value is higher than 50［16］. In this study, TLI(∑) in the control was lower, for the first 20 d, and was higher, after 20 d, than that in the manure treatment groups, revealing the water quality in the control was better, for the first 20 d, and was worse, after 20 d, than that in the manure treatment groups.
Conclusions
Chicken manure could increase the tilapia production, rather than cattle manure. And the tilapia yields followed the order of Chicken M>control>Chicken-Cattle M>Cattle M, and the tilapia yield in the Chicken M group increased by 12.43% compared with the control.
Adding chicken manure into tilapia pond could make water quality decreased at the beginning 20 d, but could increase water quality after 20 d and stabilize the phytoplankton structure.
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