Response of Asian seabass, Lates calcarifer juvenile fed with different seaweed-based diets

Abstract

The purpose of this study was to evaluate the effects of three seaweeds Kappaphycus alvarezii (KA), Eucheuma denticulatum (ED) and Sargassum polycystum (SP) meal as dietary ingredients in the diets of Asian seabass juvenile on growth performance, feed utilization efficiency and body composition of Asian seabass, Lates calcarifer juveniles. A total of four experimental diets were formulated with 5% inclusion of KA, ED and SP. A diet without inclusion of any seaweed was used as a control diet. Experimental diets were fed to triplicate group of 20 Asian seabass juveniles with initial body weight of 9.73 g ± 0.60 g in an 8-week feeding trial. Growth performance and feed conversion ratio were not significantly affected by the seaweed inclusion in the fish diet; however, the total feed intake was significantly improved (P < 0.05) in fish fed with SP-Diet. Fish carcass composition varied among treatments, with fish fed with control diet demonstrated significantly higher protein and lipid contents. Whereas, fish fed with SP-Diet exhibited significantly higher ash content compared to other dietary treatments. KA-Diet proved that it was the most stable feed among all dietary treatments. On the other hand, the stability of SP-Diet was comparable to the Control-Diet. This indicates that the tested seaweed is able to replace commercial feed binder in the diet formulation. Considering the good performance of K. alvarezii, E. denticulatum and S. polycystum in the present study and the local availability of the seaweed, they can be considered as potential ingredients in the diets for Asian seabass juveniles.

Keywords:

• seaweed
• Kappaphycus alvarezii
• Eucheuma denticulatum
• Sargassum polycystum
• Asian seabass
• Lates calcarifer

Introduction

Seaweed plays important ecological and economic roles in many parts of the world. In recent years, the increasing trend of seaweed production is an indication of rapid utilization in different industries globally. Seaweeds are commonly utilized for food production and extraction of hydrocolloids, and now more interest to diversify the usage. Asian countries are the largest producer by contributing around 20.8 million tonnes (99.1%) from total world algae production. Seaweed industry in Malaysia has shown development since 2001 (18,863 million tonnes) and among the top 10 world algae producers in 2011 by contributing 207,892 million tonnes (Sade et al. 2006). Globally, some species are intensively cultivated, such as brown seaweed, Laminaria sp. and Undaria sp.; red seaweed, Porphyra sp., Eucheuma sp., Kappaphycus sp. and Gracilaria sp.; green seaweed, Monostrome sp. and Enteromorpha sp. (Lüning & Pang 2003). Other seaweed species such as Sargassum sp. are abundantly available in the coastal waters.

Unlike other alternative aquaculture feed ingredients, limited studies were conducted to investigate the potential of seaweed meal in the diets of cultured fish. Several studies reported the use of seaweed meal as an ingredient in formulated fish feed such as in European seabass, Dicentrarchus labrax (Wassef et al. 2013), Tilapia (El-Tawil 2010), snakehead, Channa striatus (Hashim & Mat Saat 1992), shrimp, Litopenaeus vannamei (Maurinho-Soriano et al. 2007) and tiger prawn, Penaeus monodon (Peñaflorida & Golez 1996) with promising findings. In view of the rising feed cost due to the dependency on certain feed ingredients only, more effort should be taken to evaluate the performance of seaweed meal in different aquaculture species. In the present study, three different types of seaweed meals which are Kappaphycus alvarezii, Eucheuma denticulatum and Sargassum polycystum were incorporated in the practical diets for Asian seabass, Lates calcarifer juvenile at 5% inclusion level in order to evaluate the effects on growth performance, survival, feed utilization and body composition.

Materials and methods

K. alvarezii was purchased from Kota Kinabalu local market, E. denticulatum was obtained from Semporna Island and S. polycystum was collected from coastal water nearby Borneo Marine Research Institute (BMRI), Universiti Malaysia Sabah (UMS). The seaweeds were washed thoroughly to clear them from any dirt, sun-dried for about 12 hours and then oven-dried at 60°C for about 6 hours until it was completely dried. After that, the dried seaweeds were ground to a fine homogenous powder by using a laboratory grinder and stored in an airtight container. Four experimental diets were formulated to be isonitrogenous (45% protein) and isolipidic (15% crude lipid) using different type of seaweed meals at 5% inclusion level. Carboxymethyl cellulose, CMC, was included at 2% in the control diet, following the common practice in fish feed formulation. All the dry ingredients were mixed together followed by fish oil and water. The dough was screw-pressed through a 3 mm die, and the finishing feed strands were dried in an oven at 40°C for 6 hours. Proximate composition analysis was done following the methods described in AOAC (1997) (Table 1).

Table 1. Ingredient composition (g/100 g) and proximate composition (% dry matter basis) of experimental diets.

Ingredient	Control-Diet	KA-Diet	ED-Diet	SP-Diet
Fish meal	45	45	45	45
Soybean meal	20	20	20	20
Dietary lipid	10	10	10	10
Seaweed meal	0	5	5	5
Vitamin premix	3	3	3	3
Mineral premix	1	1	1	1
CMC	2	0	0	0
Tapioca starch	10	10	10	10
α-cellulose	9	6	6	6
Proximate composition (% DM)
Moisture	10.61 ± 0.28	10.59 ± 0.34	10.61 ± 0.36	10.69 ± 0.12
Crude protein	45.45 ± 0.25	45.59 ± 0.14	45.61 ± 0.12	45.75 ± 0.11
Crude lipid	14.54 ± 0.25	14.52 ± 0.21	14.51 ± 0.29	14.57 ± 0.27
Ash	7.05 ± 0.23	14.31 ± 0.07	16.20 ± 0.17	11.48 ± 0.11

CMC, Carboxymethyl cellulose (binder).

Water stability of experimental feed was determined at different time intervals according to Pascual et al. (1978). Triplicate samples of each diet were weighed about 3–4 g, placed in separated 80 µm nylon sack and immersed in a 2 L aquarium filled with aerated seawater for 10, 20, 30, 40 and 60 minutes. The sacks were removed slowly after each test time end. After that, the pellets were placed in a petri dish and oven-dried at 105°C for 2 hours.

L. calcarifer juveniles were obtained from the Hatchery of Fisheries Department in Tuaran, Sabah. The juveniles were acclimatized for about 2 weeks prior to the feeding trial and were fed with diet containing 45% crude protein and 15% crude lipid. A total of 240 juveniles of Asian seabass with initial body weight of 9.73 ± 0.60 g (mean ± SE) were selected and randomly distributed into 12 150 L square fibreglass tank with stocking density of 20 individual per tank. The feeding trial was conducted for 8 weeks.

At the end of the feeding trial, three fish from each tank were sampled for determination of body indices and whole-body proximate composition. The samples of viscera and liver were removed and weighed for calculation of condition factor (CF), viscerosomatic index (VSI) and hepatosomatic index (HSI).

Growth, feed utilization and indices were determined using the following formulas: The data on diet water stability, growth performances, feed utilization, survival, body indices and whole-body proximate analysis were compared by using one-way analysis of variance IBM SPSS Statistics 20 for Windows to determine the significant differences among treatments. Whereas, the multiple comparisons were tested by Duncan’s multiple range test. Significant level was set at P < 0.05.

Results and discussion

In the present study, seaweed was chosen as an ingredient due to its availability in natural water bodies, commercial availability and good nutritional profile. Based on the previous studies, low supplementation of seaweed in fish feed provides beneficial effect to the fish overall performance (Hashim & Mat Saat 1992; Peñaflorida & Golez 1996; Valente et al. 2006; Wassef et al. 2013; Shapawi et al. 2014). However, the response of fish to seaweed inclusion might be species-specific. In the present study, the growth performance and feed utilization of Asian seabass juveniles fed with experimental diets were not statistically different, but there were trends of increased WG and SGR of the fish, indicating the positive role of seaweed in promoting good growth in fish. The final body weight, FBW (28.35 ± 5.20 g), WG (190.84 ± 34.39%) and SGR (1.90 ± 0.22 %/d) of fish fed with S. polycystum (SP-Diet) were slightly higher than the values obtained in other treatments (final weight = 24.81–25.83 g; BWG = 159.54–167.20%; SGR = 1.68–1.75%/d). While highly efficient feed conversion ratio was obtained in all experimental diets which ranged from 1.0 to 1.07. Similarly, PER and NPU were not significantly affected by the seaweed inclusion in the fish diet (Table 2). In addition to the good growth and feed utilization, the fish showed high survival rates with no significant difference (P < 0.05) observed among treatments (98–100%). According to Hashim and Mat Saat (1992), 5% of Ulva spp. in the diet of snakehead, C. striatus resulted in increased growth rate, feed consumption and feed efficiency of the fish. Mustafa et al. (1995) found that 5% of Ascophyllum nodosum, Porphyra yezoensis and Ulva pertusa in red sea bream (Pagrus major) fingerlings helps in increasing body weight, feed utilization and muscle protein deposition of the fish. Meanwhile, the inclusion of 5% of freshwater algae Hydrodictyon reticulatum into Oreochromis niloticus and Tilapia zillii diets has increased growth performance and protein utilization efficiencies (Appler 1985). Many seaweed species including Kappaphycus sp. are excellent sources of minerals, vitamins and omega-3 fatty acids which are beneficial for fish health (Hortado-Ponce et al. 1990; Rupérez 2002; Matanjun et al. 2009). Efficient feed utilization shown in the present study suggests the possible presence of food attractant in these tested seaweed meal which was also reported in other study (Hashim & Mat Saat 1992).

Table 2. Growth performance, feed utilization and body indices of Asian seabass juvenile fed with different seaweed-based diets for 8 weeks feeding trial.

	Control-Diet	KA-Diet	ED-Diet	SP-Diet
FBW (g)	24.81 ± 2.32	25.83 ± 2.86	25.52 ± 1.76	28.35 ± 5.20
WG (%)	159.54 ± 36.54	167.20 ± 18.75	156.73 ± 15.20	190.84 ± 34.39
SGR (%/day)	1.69 ± 0.26	1.75 ± 0.12	1.68 ± 0.11	1.90 ± 0.22
Survival (%)	98.33 ± 2.89	98.33 ± 2.89	100 ± 0.0	100 ± 0.0
TFI (g/fish)	32.23 ± 0.87^a	33.26 ± 0.50^a	31.03 ± 1.86^a	38.39 ± 1.85^b
FCR	1.01 ± 0.23	1.04 ± 0.10	1.07 ± 0.04	1.0 ± 0.16
PER	0.55 ± 0.06	0.56 ± 0.03	0.55 ± 0.01	0.54 ± 0.05
NPU	49.33 ± 6.80	42.56 ± 5.62	41.12 ± 6.75	41.85 ± 9.96
CF	1.49 ± 0.16	1.48 ± 1.12	1.46 ± 0.04	1.48 ± 0.04
HSI	0.90 ± 0.07^a	1.05 ± 0.08^ab	1.05 ± 0.09^ab	1.22 ± 0.15^b
VSI	9.40 ± 0.18	9.66 ± 0.6	8.68 ± 1.06	10.97 ± 2.31

Note: Mean with different superscripts in the same row are not significant differences among treatments (P < 0.05). Initial body weight = 9.73g ± 0.65.

FBW, final body weight; WG, weight gain; SGR, specific growth rate; TFI, total feed intake; FCR, feed conversion ratio; PER, protein efficiency ratio; NPU, net protein utilization; CF, condition factor; HSI, hepatosomatic index; VSI, viscerosomatic index.

All body indices including CF, VSI and HSI were not significantly influenced by the seaweed inclusion in fish diet (P < 0.05) and showed a normal pattern of body indices. Whole-body proximate composition of fish in the present study was significantly influenced by the experimental diets. In general, diets with seaweed inclusion resulted in higher body moisture. Crude protein and lipid of fish fed with seaweed-based diets were lower than those fed with the control diet. Meanwhile, crude ash was higher in fish fed with the seaweed-based diets (Table 3). Similar trend of moisture and ash contents were also obtained by Valente et al. (2006), where whole-body moisture of European seabass (D. labrax) fed with 5% Gracilaria bursa-pastoris, 5% Ulva rigida and 5% Gracilaria cornea were 69.55%, 68.46% and 67.97%, respectively. The difference in protein content of body composition of fish may greatly influenced by the protein content of the seaweed itself, where low level of protein was determined in the tested seaweed. The higher ash content represents the higher macrominerals and trace elements present in the marine macroalgae (Matanjun et al. 2009).

Table 3. Whole-body proximate composition (% wet weight) of Asian seabass fed with different seaweed-based diets for 8 weeks feeding trial (mean ± SD).

Feed	Control-Diet	KA-Diet	ED-Diet	SP-Diet
Moisture (%)	65.61 ± 0.79^a	67.78 ± 0.26^b	70.18 ± 1.15^c	68.55 ± 0.07^b
Crude protein (%)	22.0 ± 0.93^c	20.13 ± 0.30^b	18.59 ± 0.72^a	19.22 ± 0.27^ab
Crude lipid (%)	6.70 ± 0.15^c	6.15 ± 0.26^b	5.24 ± 0.26^a	5.55 ± 0.15^a
Ash (%)	5.51 ± 0.16^a	6.15 ± 0.29^b	6.0 ± 0.35^b	7.31 ± 0.17^c

Note: Initial whole-body moisture composition was 70.14 ± 0.30, crude protein 18.81 ± 0.21, crude lipid 4.93 ± 0.08 and ash 4.26 ± 0.04. Different superscripted letters in each row indicate significant differences (P < 0.05) among treatments.

Water stability of feed decreased slightly with time. After 60 minutes, only 1.69% of weight loss was observed from the least stable diet which is SP-Diet. KA-Diet had the greatest water stability of 98.56% after 60 minutes in the water. Among the tested diets, KA-Diet, which contains K. alvarezii, was the most stable diet followed by ED-Diet (E. denticulatum), Control-Diet (Fish Meal-Based Diet) and SP-Diet (S. polycystum). Feed with inclusion of E. denticulatum and S. polycystum resulted in comparable stability with the control diet (Table 4). Even though the binding properties of the tested seaweed in the present study were not analysed, Kappaphycus sp., Eucheuma sp. and Sargassum sp. are well known for their high content of carrageenan, agar and alginate, respectively (Trono & Ganzon-Fortes 1988). In the present study, the diet which contains carrageenan (KA-Diet) was proved as the most stable feed compared to the diets containing agar (ED-Diet), alginate (SP-Diet) and also commercial binder CMC (Control-Diet). From this result, we can conclude that there is a great potential of using carrageenan in replacing the commercial binder. The small differences in water stability among the diets containing carrageenan, alginate and agar still suggest that low-level inclusion of seaweed in the diet at about 5% is sufficient to form strongly bound feeds. Thus, the use of natural and pure binders in fish feeds should be re-evaluated as it is neither necessary nor cost-effective (Hashim & Mat Saat 1992).

Table 4. Water stability (%) of four experimental diets (mean ± SD) within tested time.

Diet	10 min	20 min	30 min	40 min	60 min
Control-Diet	98.67 ± 0.11	98.72 ± 0.06^ab	98.54 ± 0.10^ab	98.52 ± 0.09^ab	98.32 ± 0.10^a
KA-Diet	98.88 ± 0.11	98.85 ± 0.13^b	98.79 ± 0.03^c	98.77 ± 0.10^c	98.56 ± 0.08^b
ED-Diet	98.86 ± 0.13	98.75 ± 0.05^ab	98.64 ± 0.13^bc	98.63 ± 0.09^bc	98.34 ± 0.11^a
SP-Diet	98.84 ± 0.11	98.57 ± 0.12^a	98.45 ± 0.10^a	98.35 ± 0.08^a	98.31 ± 0.04^a

Note: Different superscripted letters in each row indicate significant differences (P < 0.05) among treatments.

Based on this study, it is clearly shown that the marine macroalgae such as K. alvarezii, E. denticulatum and S. polycystum have high potential to be alternative ingredients in the diets for Asian seabass juveniles at 5% inclusion level without any deleterious effect on growth performance, survival, feed utilization and body composition of the fish. In term of growth performance and feed utilization, SP-Diet was better than other diets, followed by KA-Diet, Control-Diet and SP-Diet. From the water stability point of view, the KA-Diet demonstrated good water stability profile, followed by ED-Diet, Control-Diet and SP-Diet. Among the three different types of seaweed, S. polycystum is the most recommended seaweed to be included into fish diet considering its natural availability in the coastal waters. As a conclusion, the seaweed used in this study helped promote good growth performance, feed utilization and survival of fish apart from serving as a feed binder.

Acknowledgement

The authors would like to thank the staff of Fish Hatchery, Borneo Marine Research Institute, UMS for their technical assistance and the Fisheries Department of Sabah for supplying the Asian seabass seeds.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by a research grant from Ministry of Rural and Regional Development Malaysia [grant number R951015].