Feed can account for 50 to 80% of operating costs in aquaculture production, and generally protein components account for more than two-thirds of fish feed costs. Therefore, given the declining production of fishmeal worldwide, sustainable alternatives to replace the feed source need to be found and produced. Here we present the results of a successful replacement of fishmeal in diets based on feather meal for tilapia.
Feather meal (FeM) is one of the rendered protein ingredients that is commonly used in fish feeds at levels of 3 – 7%; however, fish feed manufacturers are reluctant to use higher levels of feather meal in their feeds due to significant variability in the quality and nutritive value of different batches of feather meal (Bureau, 2010).
Some academic and commercial-scale trials have reported excellent performance in fish with feeds containing greater than 12% feather meal. However, some trials reported relatively poor performance of feed with high levels of feather meal (Bureau, 2010) and the source of discrepancies among the results of different trials was unclear.
It is of utmost importance to accurately characterize the nutritional value of FeM in order to optimize its use in fish feed. Developing methodological approaches and rapid screening tests to effectively differentiate feather meals of different nutritive values should be a priority for the rendering and aquaculture feed industry.
Notably, feeds can account for 50 to 80% of the operational costs of aquaculture production and Malaysia is very dependent on imported soybean and fishmeal as protein sources in its aquaculture industry. Generally, protein ingredients account for more than two-thirds of the fish diet cost.
“Sustainable alternatives to replace the feed source need to be identified and produced due to the declining global production of fishmeal.”
It is practical and economical to focus on further developing downstream processing and increasing the production of FeM and poultry offal meal as protein sources for the aquaculture industry since there is a highly developed status of poultry production in the country and many poultry processing plants.
Here we present the results of completely replacing fishmeal with hydrolyzed FeM-based diets on the growth performance and feed conversion ratio (FCR) of tilapia, and also the effects on water quality parameters.
Materials and method
A total of 315 red hybrid tilapia (Oreochromis sp) male fingerlings with a mean initial body weight of 37 g were purchased from a hatchery in Selangor. Prior to the feeding trial, the fish were adapted to the experimental system for 2 weeks.
Then, they were randomly divided into 3 treatments and three replications with 35 fish per replication. The fish were fed one of the three treatment (Table 1) diets:
(a) control diet,
(b) 10% inclusion of hydrolyzed feather meal (FeM) and
(c) 15% inclusion of hydrolyzed FeM, replacing 92% and 100% of fishmeal in the diets (Table 1)
The hydrolyzed FeM had nutrient content of 13.8 MJ/kg digestible energy and 606 g/kg digestible crude protein. The experimental diets were formulated to be isoenergetic, 13 MJ/ kg digestible energy (DE) and isonitrogenous, 29% digestible protein (DP).
The nutrient compositions of the diets are tabulated in Table 2. By means of using the National Research Council (NRC) nutrient requirements of fish and shrimp (NRC 2011) as a guide, the least cost formulation diets were formulated to meet the minimum specifications for tilapia.
After the extrusion process, the pellets were coated with the vitamin concentrate (Peterlabs Sdn. Bhd.) mixed in fish oil using a coating machine (TSASB).
The fish were fed the experimental diets with a total of 3% (1st 8 weeks) and 2% (2nd 8 weeks) of the fish biomass twice a day at 9.00 am and 4.00 pm.
Every two weeks, the amount of feed was adjusted according to the last live body weight determined by weighing. The experiment was performed in polyethylene tanks, with total volume of 1 m3 each and equipped with a semi-closed water recirculating aquaculture system (RAS).
The RAS system was equipped with a nitrification unit and a sedimentation unit. Stocking density in fish tanks was 28 L/fish. All experimental tanks were supplied with air through an aeration system. A 30% volume of water in the fish tanks was replaced with clean water weekly. The feeding trial was conducted for 16 weeks.
Results and discussion
Growth performance of fish
A steady increase (Figure 1 and 2) was observed with regards to the growth and feed intake among tilapia over the 16 – week period.
The 10% FeM diet gave the best final fish weight, weight gain, SGR and FCR (p < 0.05) compared to the control and the 15% FeM diets (Table 3 and Table 4).
Also, tilapia that were fed with 15% FeM diet performed better than the control for final fish weight, weight gain, SGR and FCR (p < 0.05). The 15% FeM diet (Table 1) did not include any fishmeal; besides protein from FeM, other major protein sources were from plant sources such as soybean and corn gluten meals.
The significantly better (p < 0.05) growth performance and FCR for the 15% FeM diet compared to the control diet suggested that higher FeM inclusion levels are possible if the deficient amino acids in FeM are substituted for synthetic sources.
Bishop et al. (1996) reported that the growth of Oreochromis niloticus fry was not compromised by replacing 9.9% of the total diet with feather meal. This result is comparable to the findings from Chor et al. (2013). However, Chor et al. (2013) evaluated several levels (9.86, 19.71, 29.57, 39.42 and 49.28%) of FeM to replace Danish fish meal as the sole protein source.
It was revealed that catfish that were fed the control diet had significantly better weight gain, specific growth rate and feed intake than those fed with diets containing FeM. Apart from that, they also reported that FeM supplementation at 9.86% was comparable to the control for survival rate and FCR.
“However, high fish mortality and retarded growth were observed in the 19.71 – 49.28% FeM-supplemented diets. Catfish mortality increased with the increase of FeM inclusion with mortality ranging from 11.1 – 62.2% with FeM supplementation.”
As compared to the present study, there was no mortality in all the treatments (10 and 15% FeM) and this may be due to the difference in quality of FeM between the studies. The growth, feed efficiency, nitrogen or energy gains of rainbow trout were not affected by the inclusion of up to 15% FeM (Bureau, 2000).
Higher FeM usage was reported by Sulomo et al. (2014) as they observed that FeM inclusion up to 19.8% in Nile tilapia diets did not compromise growth and protein utilization. A very high fishmeal inclusion of 22% was observed and in comparison to the present study, only 0 and 1% of fishmeal inclusion for the FeM-based diets were observed.
Referring to the results presented in Table 5, the mean range values for DO2 (mg/L) for all treatments were within the optimum and not significantly different between treatments (p > 0.05). There were significant differences (p < 0.05) in pH and temperature (Table 5) between treatments.
Nevertheless, the pH and temperature ranges were within the optimum. It is noteworthy that the means and range of values for DO2 , pH and temperature were within the optimal range for tilapia production. Weekly DO2 data (Figure 3) for the treatments during weeks 9, 11 and 12 were below 5.0 mg/L and closer to 3.0 mg/L, although these relatively lower values were still within the acceptable range for tilapia production.
“Unionized ammonia (NH3 ) is the toxic form of ammonia and predominates when pH is high. NH4 + is relatively non-toxic (Hargreaves and Tucker 2004) and predominates when pH is low.”
The mean values for unionized NH3 (Table 5) were within the optimum, ranging from 0.028 – 0.031 mg/L (mean 0.029 mg/L) for treatment A, 0.019 – 0.021 mg/L (mean 0.020 mg/L) for treatment B and 0.020 – 0.026 mg/L (mean 0.023 mg/L) for treatment C.
On comparison, unionized NH3 was significantly higher (p < 0.05) in treatment A than treatments B and C. Weekly NH3 values for weeks 1, 13 and 14 exceeded the optimum range for growth, but recovered and were within the optimum range in the subsequent weeks.
“The increase of NH3 during these weeks may have been due to overall fish growth and more protein waste excretion.”
The declines in weekly feed intake (Figure 2) were due to the NH3 increase during these weeks. When ammonia began to accumulate, fish responded through reduced feeding activity and microorganisms use oxygen for the degradation of undigested feed resulting in lower DO2 levels.
The values for the toxic NH3 for all the treatments were below the lower lethal range 0.6 mg/L and below the 2.0 mg/L level when tilapia began to die. Toxic NH3 made up 1.29, 1.07 and 1.04% (Table 5) of the total NH3 plus NH4 + for treatments A, B and C, respectively, which were well below the proportion of under 10% reported by Hargreaves and Tucker (2004).
Values for ionized NH4 + (Table 5) ranged from 2.10 – 2.30 mg/L (mean 2.22 mg/L) for A, 1.68 – 1.94 mg/L (mean 1.85 mg/L) for B and 1.90 – 2.46 mg/L (mean 2.19 mg/L) for C.
There was a significant difference (p < 0.05) in NH4 + values between treatment A and B. NH4 + is relatively non-toxic and the weekly NH4 + data reflected the weekly NH3 data. No detrimental effects on the water quality in the experimental tanks and on the performance of the fish as no mortality recorded with the inclusion of 10 or 15% hydrolyzed feather meal.
“As regards the tilapia aquaculture in Malaysia, average feeding costs of the surveyed farms made up almost 63% of the production cost, while high production cost was due to the use of commercial tilapia feeds (Ng et al., 2013).”
Thus, cheaper feed ingredients like FeM can help alleviate the cost of aquaculture production. Gatlin et al. (2007) and Tacon and Metian (2008) highlighted on the considerable progress made in finding substitutes to replace the diminishing supply of an increasingly expensive fish meal.
The availability of soybean products (soybean meal and soy protein concentrate) made them viable alternatives to fishmeal, but whether they can effectively replace fishmeal in fish diets is still debatable and more research is required with regards to the issue. Hernandez et al., (2010) reported a complete replacement of fishmeal using animal proteins from porcine and poultry by-product meals in practical diets for fingerling Nile tilapia.
The results showed that FeM can completely replace fishmeal (a declining and unsustainable source) in tilapia diets up to 15% of the total feed, resulting in good growth and feed conversion ratio without adverse effects on water quality parameters.
It is practical and economical to produce FeM as a protein source for the aquaculture industry due to the highly developed status of poultry production and many poultry processing plants in Malaysia (Wong and Mardhati, 2010).
Apart from that, developing rapid screening tests to effectively differentiate feather meals of different nutritive value (Bureau 2010) should be a high priority for both the rendering industry and aquaculture feed industry due to the wide variation in results reported for FeM used in aquaculture feed.
This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “REPLACEMENT OF FISHMEAL IN FEATHER MEAL-BASED DIET AND ITS EFFECTS ON TILAPIA GROWTH PERFORMANCE AND ON WATER QUALITY PARAMETER”
developed by: S.T. YONG1, M. MARDHATI1, I.J. FARAHIYAH1, S. NORAINI1 and H.K. WONG – Animal Science Research Centre, Selangor, Malaysia. The original article, including tables and figures, was published on JANUARY, 2018, through JOURNAL OF TROPICAL AGRICULTURE AND FOOD SCIENCE.
The full version can be accessed online through this link: https://www.researchgate.net/publication/335078554_Replacement_of_fishmeal_in_feather_meal-based_diet_and_its_effects_on_tilapia_growth_performance_and_on_water_quality_paramet