| Livestock Research for Rural Development 31 (7) 2019 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
A feeding trial was conducted in concrete tank conditions to evaluate the effect of feeding regime on growth performance of Oreochromis niloticus. Twelve experimental tanks each of 4.5 m 2 area were divided into 4 feeding groups each with three replicates. Fish (10.42 ± 0.09 g average initial weight) were stocked at the rate of 10 fishes per tank. Experimental diet was prepared to contain 30% protein using housefly maggot meal as main source of protein. Four different feeding schedules were implemented: Low-ration (L) at constant rate of 2.5% body weight (BW), high-ration (H) at constant rate of 5% BW, 1 day low-ration followed by 1 day high-ration (1L/1H) and 2 days low-ration followed by 2 days high-ration (2L/2H). The fish were fed twice daily. Highest growth rate of O. niloticus was achieved in feeding schedule 1L/1H, and the lowest with L. The AFCR values ranged from 1.17 to 2.12, with L showed the best AFCR. Hence there is a need of developing a more appropriate feeding strategy basing on daily alternation of low and high rations of a single diet to optimize profitability in O. niloticus farming.
Key words: feeding schedules, growth responses, proximate, ration
Tilapia farming requires less labour input compared to other agricultural practices such as livestock husbandry, and the profit margin achieved is usually higher (Kaliba et al 2006). However, fish feeds is the major stumbling block, since it is the highest variable cost in fish farming operations (Ali et al 2005; Ferket et al 2011). Thus, feeding fish with proper amount of feed is very important in order to avoid challenges, which can arise from overfeeding, underfeeding or continuous feeding. Overfeeding is costly, wastes feed, and can cause water quality problems which lead to stress and disease (Riche et al 2004). In addition, overfeeding leads to shortage of oxygen especially in hot weather and increases biological oxygen demand (Ferket et al 2011). According to El-Saidy and Gaber (2005) good feeding management, including appropriate frequency, can reduce overfeeding and maximize efficiency. Underfeeding, on the other hand, is a cause for stunted growth and high fish mortalities which are the loss in fish farming enterprise (El-Saidy and Gaber 2005; Riche et al 2004). Furthermore, insufficient feeding limits growth potential of fish and also decreases feed conversion ratio (Abou-Zied and Ali 2015). Continuous feeding of fish with the same feed amount and feeding frequency is also an uneconomical since fish do not have the same daily feed intake because of the existing rhythmic metabolic activities (Riche et al 2004). Therefore, development of appropriate feeding management strategies is imperative in order to optimize feed efficiency by reducing feed wastage and deterioration of water quality and ensure profitability. To achieve this, the present investigation aimed at developing a feeding regime by evaluating the effect of alternating daily rations (2.5% vs. 5% body weight) and feeding frequency (daily feeding vs. alternate day feeding) on the growth, feed utilization and production costs of O. niloticus reared in tank environment.
The present experiment was carried out in round outdoor concrete tanks of the Aquaculture Research Facility belonging to the Department of Animal, Aquaculture and Range Sciences (DAARS) of Sokoine University of Agriculture (SUA) in Morogoro region of Tanzania. SUA lies at the foot of Uluguru Mountains at an altitude of about 500 - 600 m above sea level. Twelve tanks were used, each of 4.5 m2 area. Before the experiment start, all tanks were drained completely and were exposed to sun rays for 7 days till complete dryness. Tanks were then refilled maintaining water level at 1m deep throughout the experimental period of 84 days. The tanks received neither supplemental aeration nor fertilization.
Housefly maggots used for maggot meal were produced in the Aquaculture Research Facility of the DAARS of Sokoine University of Agriculture, Morogoro - Tanzania, using wet poultry manure as described by Hezron et al (2019). Experimental diet (sinking type) with nominal 30% protein content was formulated with housefly maggot meal as main source of protein and other locally available ingredients viz. fishmeal, maize meal and wheat flour. Ingredients and proximate composition of the experimental diet are shown in Table 1. Fishmeal, maize meal, wheat flour, mineral and vitamin premix were purchased from TANFEEDS International Ltd, Morogoro, Tanzania. Appropriate quantities of ingredients in the diet were weighed and thoroughly mixed using hands in a plastic basin. Wheat flour was gelatinized before it was added to the basal mixture of the rest of the ingredients. The resulting dough was extruded through a 2 mm die using Kenwood MG450 powered meat grinder (Kenwood Appliances Ltd, UK). The pellets were sun-dried for two days and stored at cool temperature between 10 - 12˚C until used. Proximate analyses of maggot meal, fishmeal, maize meal and the compounded diet were carried out using the methods of AOAC (2005). Protein (N x 6.25) was analyzed using a Kjeltec System (Tecator), and crude fat using a Soxtec System HT (Tecator) with petroleum ether as the solvent. Ash was determined by incinerating samples in a muffle furnace at 550˚C for 3 hours.
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Table 1. Formulation of diet and its proximate composition (% dry matter basis) |
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Ingredients |
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Housefly maggot meal1 |
45 |
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Fishmeal2 |
5 |
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Maize meal3 |
46 |
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Wheat flour |
2 |
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Vitamin/mineral premix* |
2 |
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Proximate composition |
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Dry matter |
94.8 |
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Crude protein |
30.3 |
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Crude fibre |
9.17 |
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Lipid |
11.8 |
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Ash |
10.1 |
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*
Vitamin A 25 500 000IU, Vitamin D3 5 000 000IU, Vitamin E 5
050IU, Vitamin B2 4 750 mg, Vitamin B6 2 750 mg, Vitamin B12
11 750 mg, Vitamin K3 4 850 mg, CAL PAN 5 750 mg,
Niacinamide 16 500 mg, Vitamin C 10 000 mg, Iron 5 250 mg,
Manganese 12 760 mg, Copper 13 250 mg, Zinc 13 250 mg,
Sodium Chloride 48 750 mg, Magnesium 12 750 mg Potassium
Acetate 73 750 mg, Lysine 15 000 mg, Methionine 12 000 mg,
Antioxidant and Anticaking qsf 1kg.
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At the beginning of experiment, twelve tanks were stocked with monosex O. niloticus averaging 10.42 ± 0.09 g, at a density of 10 fishes per tank in triplicate following a completely randomized design. Two levels of feeding: 2.5% vs. 5% body weight (BW) and two feeding regimes: daily feeding vs. alternate day feeding were used. Alternate feeding schedules were achieved by alternating the presentation of a low feeding level/ration of 2.5% BW/day with a high feeding level/ration of 5% BW/day. Four different feeding schedules were employed as follows: continuously low-ration (L) at a constant rate of 2.5% BW/day and continuously high-ration (H) at a constant rate of 5% BW/day, served as control feeding schedules; alternate day feeding of 1 day low-ration followed by 1 day high-ration (1L/1H); and alternate day feeding of 2 days low-ration followed by 2 days high-ration (2L/2H). Where L refers to the low-ration (2.5% BW/day) and H refers to the high-ration (5% BW/day), and the numerical value refers to the number of days that a particular ration was offered to fish. The quantity of food was adjusted every fourteenth when the weight measurement was taken using electronic weighing balance. Daily feed rations were divided into two equal amounts given at 1000 h and 1700 h to all tanks. At the end of the experiment, all fish were harvested and individually weighed to obtain total fish yield per feeding schedule.
Parameters measured were body weights at the start of the experiment and then at 2 weeks intervals. Growth performances of the experimental fish were computed as follows:
Weight gain (WTG) = final weight (g/tank) - initial weight (g/tank).
Average daily weight gain (ADG) = weight gain (g)/time (days).
Food conversion ratio (FCR) = weight of food given (g/tank)/live weight gain (g/tank).
Protein efficiency ratio (PER) = wet weight gain (g/tank)/amount of protein intake (g/tank).
Survival rate (SR) = 100 x [number of fish at harvest/number of fish at stocking].
Water quality parameters notably dissolved oxygen; pH and temperature were also measured every 2 weeks using HANNA HI9829 Multiparameter pH/ISE/EC/DO/Turbidity/Temperature probe (HANNA Instruments, USA). For survival rate, dead fish were removed, counted and recorded.
Data collected were checked for normality and homogeneity of variances and thereafter subjected to Analysis of Variance (ANOVA) at 5% probability. Duncan’s Multi-Range Test was used for mean separation between the treatment means. The calculations were performed using the SAS statistical computer package (SAS 2000).
Fish growth responses, feed utilization and survival rate
Growth responses, feed utilization and survival of O. niloticus maintained on four different feeding schedules for 84 days are shown in Table 2. Fish maintained on feeding schedule 1L/1H showed significantly highest growth response in terms of mean final body weight (FNWT), body weight gain (WTG) and average daily gain (ADG). Meanwhile, increasing trend in mean final body weight between the different feeding schedules was observed in the course of the experimental duration. The changes in mean fish body weight among the feeding schedules were vivid only from the first fourteen days of the experiment, whereby noticeable change was observed for feeding schedule 1L/1H (Figure 1). The apparent feed conversion ratio (AFCR) was significantly best in feeding schedule L (2.5% BW/day) followed by 1L/1H and 2L/2H whereas feeding schedule H (5% BW/day) had the worst AFCR. In terms of survival rate, no significant difference was observed between the four different feeding schedules. However, fish fed at 5% BW/day showed the highest survival rate, while those at 2.5% BW/day and 2L/2H feeding schedules recorded the lowest comparable survival rates.
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Table 2. Growth response, feed utilization and survival of O. niloticus maintained on different feeding schedules for 84 days in concrete tanks |
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Feeding schedule |
SEM |
p |
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L |
H |
1L/1H |
2L/2H |
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INWT (g/tank) |
324a |
306b |
309b |
312ab |
3.77 |
0.0578 |
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FNWT (g/tank) |
2346b |
2782b |
3044a |
2406b |
183 |
0.0458 |
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WTG (g/tank) |
2022b |
2476b |
2735a |
2094b |
186 |
0.0454 |
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ADG (g/day) |
0.80b |
0.98b |
1.08a |
0.83b |
0.07 |
0.0477 |
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TFI (g/tank) |
2323c |
5244a |
4673a |
3567b |
293 |
0.0017 |
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AFCR |
1.17c |
2.12a |
1.71b |
1.72b |
0.05 |
<.0001 |
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PER |
2.66a |
1.45c |
1.83b |
1.81b |
0.07 |
0.0002 |
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SR (%) |
86.67a |
96.67a |
90.00a |
86.67a |
5.77 |
0.6025 |
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INWT = initial weight, FNWT = final body weight, WTG = body weight gain, ADG = average weight gain, SGR = specific growth rate, TFI = total feed intake, AFCR = apparent feed conversion ratio, PER = protein efficiency ratio, SR = survival rate. Means with the same alphabetical superscript within the same row are not significant different at p<0.05 |
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| Figure 1. The mean daily body weight changes of O. niloticus maintained on different feeding schedules |
Water quality parameters were measured during the study in fish tanks. Mean values of water quality parameters were recorded as follows: pH 7.63±0.1, dissolved oxygen (DO) 7.03±0.3 mg/l and temperature 26.21±0.32oC respectively. Water exchanges every two weeks interval at 75% of water volume were used to maintain water quality. The values of water parameters remained within the acceptable ranges for O. niloticus throughout the feeding experiment.
The present results suggest that alternate day feeding schedules through manipulation of low and high feeding rations support better growth rate of O. niloticus and enhance feed utilization as reflected by improved FNWT, WTG and AFCR. One of the best observed performances was that of weight gain of fish maintained on feeding schedule 1L/1H which was higher by almost 21% and 15% than the daily low-ration (2.5% BW/day) and the daily high-ration (5% BW/day), respectively. The optimal amount of feed offered to fish could explain the improved performances for feeding schedule 1L/1H used in the growth trial. Consequently WTG and TFI values were higher with the apparent FCR values remained within the range of 1.17 - 2.12 recorded in different feeding trials with Nile tilapia by Ogunji and Wirth (2000), El-Saidy and Gaber (2005) and El-Sayed (2002). Another reason for observed high weight gain and improved feed utilization could be linked to reduced feed waste through consumption of available feed. The results supported the findings that when fish maintained on certain mixed feeding schedules performed better than or equally well as those fish maintained regularly on high ration (Abel-Hakim et al 2009; Bolivar et al 2006).This agreed with Patel and Yakupitiyage (2003) who observed a better performance of Nile tilapia maintained on alternate day feeding schedule of 1 day 1.5% BW followed by 1 day 2.3% BW over those fed continuously at 1.5% BW and 2.3% BW. On the other hand, the observed low total feed intake in this study was probably one of the important reasons for low FNWT and WTG of fish maintained on L (2.5% BW/day). Poor growth performance of fish fed regularly at 2.5% BW was also attributed to competition for food and/or social hierarchy as the result of reduced ration size (Bolivar et al 2006). In general, alternate day feeding schedules had superior influence on fish growth performance compared to the continuous low and high ration feeding schedules as observed in earlier studies by Joshua et al (2017) and Kumar et al (2017).
The least apparent feed conversion ratio (AFCR) recorded in fish maintained on 2.5% BW/day could be explained by reduced ration size which supplied all the essential nutrients to fish. Nevertheless, the higher PER of fish fed regularly at 2.5% BW/day compared to others, suggests the efficient utilization of the small quantity of feed protein provided for growth. Insufficient feeding as the result of reduced ration size led to increased competition between the fish, stunted growth and in turn resulted in poor feed conversion ratio (El-Sayed 2002; Abel-Hakim et al 2006). Similarly, the poorest feeding efficiencies were reported in common carp (Sardar et al 2011) and hybrid striped bass (Adakili and Taşbozan, 2015) when the amounts of feeds supplying all the essential nutrients were reduced. The AFCR recorded amongst the four different feeding schedules tested were, however, in line with the values reported by El-Saidy and Gaber (2005) who studied the effect of dietary protein levels (25 and 30%) and feeding rates of 1, 2 and 3% BW/day on growth performance, production traits and body composition of Nile tilapia cultured in concrete tanks.
Fish survival was reasonably good for all four different feeding schedules tested and ranged from 86.6 to 96.7%. The present results were in line to the values reported by El-Saidy and Gaber (2005) but higher than the 65.4 to 78.1% reported by Abel-Hakim et al (2009) who maintained O. niloticus on feeding levels of 1, 2.5, 3 and 4.5% BW/day. Moreover, the results suggest that feeding schedules may have limited effects on fish survival. Thus, the comparable high fish mortalities recorded at feeding schedules L (2.5% BW/day) and 2L/2H could be attributed to reduced ration size which led to increased competition for food and in turn resulted in cannibalism. Similar observations have been reported by El-Sayed (2002) for O. niloticus and Joshua et al (2017) for tilapia hybrids. The authors pointed out that cannibalism could be one of the main factors responsible for fish mortalities when the ration is insufficient.
This study was supported in full by the graduate scholarship provided to the first author by the project titled A Sustainable Development of Tilapia Culture in Tanzania under the AquaFish Innovative Lab (AIL) supported by the U.S. Agency for International Development (USAID). Assistance of the laboratory staff of the Department of Animal, Aquaculture and Range Sciences of Sokoine University of Agriculture in feed analyses during the study period is highly appreciated.
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Received 4 May 2019; Accepted 9 June 2019; Published 2 July 2019