Effects of varying dietary protein levels on the breeding performance of Clarias gariepinus broodstocks and fry growth rate

A O Sotolu

Nasarawa State University Keffi, Department of Forestry, Wildlife and Fisheries Shabu-Lafia Campus, Lafia, Nigeria
sotoluola@yahoo.com

Abstract

Breeding performance of Clarias gariepinus under different dietary crude protein (CP) levels 30%, 35%, 40% and a broodstock diet (imported feed) as the control. Female broodstocks were subsequently induced for breeding and were stripped after 11 hours latency period.

Weight of eggs stripped increased with increase in dietary protein levels and no broodstock mortality was recorded. Hatchability rate was highest in fish fed 40% C.P (90.33± 0.44%) which was only marginally different from fish fed 35% CP (89.42± 0.01%) while fish fed 30% CP diet had the least hatchability rate (84.70± 0.12%). Advanced frys were monitored for 3 weeks under intensive feeding and frys from fish fed 40% CP dietary level had superior mean weight gain, specific growth rate, feed conversion ratio and protein efficiency ratio indicating sufficient level of nutrient for gonad development while fry from fish fed 35% CP diet only had marginally different specific growth rate compared with the former (p>0.05).

This study revealed that dietary protein level at 35% CP was able to ensure fish growth maintenance, while 40% CP diet sustained the fish further to ensure proper gonadal development and maturation and consequently, superior performance of the hatchlings.

Key words: Advanced frys, breeding performance, Clarias gariepinus, gonad development, hatchability rate

Introduction

Fish seed production efficiency of many fish farms' hatcheries throughout sub-Saharan African countries or developing countries such as is mostly unsuccessful due to poor nutrition. Nutrition is known to play a major role in the reproductive performance of fish (Manissery et al 2001; Muchlisin et al 2006). Several studies have shown that the nutritional requirements of broodstock during gonadal development vary from those of young fish (NRC 1983; Izquierdo et al 2001). It was reported that increased protein levels from 30 up to 40% C.P in the diets of freshwater fish species resulted in enlarged ovary size and weight of fish followed by high rate of fry hatchability (Pathmasothy 1985; Shim et al 1989). Clarias gariepinus is presently the most widely cultured fish species in Nigeria and many hatcheries in the country are facing the problem of poor spawning and low hatchability rates. The study was therefore carried out to examine the effects of varying dietary crude protein levels on reproductive performance of catfish broodstock.

Materials and methods 

Preparation of experimental diets

This study involved the use of three levels of dietary protein (30, 35 and 40%) as test diets. The protein sources used in formulating the feeds include fishmeal, blood meal and soyabean meal (Table 1).

In addition to the three formulated diets an imported brood fish diet was used as the control making a total of four test diets (Table 2).

All formulated diets were made into pellets of 6mm diameter after homogenous mixing in a Hobart mixer. Thirty six catfish female broodstocks of 883.22± 0.15g average weight were evenly distributed in twelve concrete tanks and are allowed to acclimatize for two days before the commencement of the experiment. All test diets, fish carcass and eggs were chemical analyzed for their crude protein, crude fibre, crude lipid, nitrogen free extract, ash and moisture according to AOAC (2000). Fish were fed ad libitum daily at two feeding regimes between 08:30 – 09:00 hours and 16:30 – 17:00 hours. Feeding of fish per treatment was done in triplicates for eight weeks. Water quality parameters which include dissolved oxygen, pH and ammonia were kept within the range of 6.7-6.9 (mg/l), 7.2-7.8 and 0.16-0.18 (mg/l) respectively and were considered favourable in fish culture tanks according to Boyd (1990).

Preparation of broodstock fish for breeding

At the end of the feeding trials three fish were selected for breeding from each tank. They were injected hormone (Ovaprim ^TM) intramuscularly at an angle of 30 – 45^o of the dorsal fin to artificially induce them for spawning at the rate of 0.5ml/kg of fish. Injected fish were kept in separate tanks and a latency period of eleven hours was allowed before the eggs were stripped. Eggs were stripped into dry plastic bowls, weighed and fertilized with the milt of male fish from the same treatment. Within two to three minutes after fertilization, eggs were evenly spread on “Kakaban” (egg receiver) that was laid inside a (2 x 1.2 x 0.3) m rectangular plastic tank for incubation.

Estimation and determination of broodstock performance

Hatchability rates of eggs were determined based on the method of percentage in hatched eggs as described by Aluko and Ali (2001). Survival rate was determined by the methods of Jensen (1996). Normal healthy hatchlings were estimated on percentage basis of dead and deformed hatchlings and gamete quality in female Clarias gariepinus was determined by fecundity/gonado-somatic index ratio according to Fernandez et al (1998). Separated hatchlings were fed weighted imported feed (Artemia) 3 days after hatching for 10 days ad libitum followed by floating feeds of 0.3mm (Coppens) for 7 days and followed by 0.5mm (Coppens) for another 10 days. Average weights of fish were determined per treatment at 0^th day and 17^th day of feeding (that is, 11^th day and 28^th days of the experiment) using sensitive electronic scale (P.E Balance mx Rady 300g max).

Statistical analysis

All data collected were processed and subjected to ANOVA of the one-way classification and significant mean differences were separated according to Steel et al (1997) 5%.

Results and discussion 

Table 2 shows the proximate composition of test diets. Crude protein contents of all diets were within the range of 30.21% and 40.12% while crude fat ranged between 10.32% and 13.65%. Gross energy was highest in the control diet (30.28.71kcal/kg) and least in diet 2 (2970.16 kcal/kg). These results are in line with the range of values of crude protein formulated for catfish and energy requirement for optimum performance as reported by Faturoti (2000) and corroborated by Fasakin (2007). Table 3 presents the weight differentials between stripped fish and before they were stripped of eggs.

All fish injected with hormone oozed out eggs easily without exerting much pressure which suggests that the recommended dosage of 0.5ml/kg of the hormone (Ovaprim ^TM) by Syndel International Incorporation was adequate at eleven hours latency period. The ease of stripping may be responsible for the zero mortality rates of broodstocks recorded in this study indicating no stress on the fish before and after the stripping exercise as all fish started responding well to feed by 8 hours after the stripping of eggs was carried out. The earlier reports of Aiyelari et al (2007) informed that broodstock mortality after stripping can result due to stress. Hatchability rates of eggs, larva survival and weight of eggs were presented in Table 4.

Mean weight of eggs increased with increase in crude protein content of the diet and the weight of eggs stripped followed the same trend. This observation may be due to availability of more nutrients in the diets as higher protein level seems to favour more egg formation by the ovary. This reason may further be responsible for the significantly higher larval survival rate and good larval quality recorded. Larval survival rate was least in control diet (30% C.P) 84± 70 ± 0.12 and highest in diet 4 (40% CP) 90.33± 0.44 (p<0.05). The importance of broodstock nutrition has been stressed earlier by Cerda et al (1994) while Muchlisin et al (2006) reported that dietary protein levels influenced parameters such as weight gain and proximate composition of brood fish, quantity and quality of eggs and larval viability. Fry growth performance and nutrient utilization assessment was presented in Table 5.

Mean weight of fish and mean weight gain increased with increase in crude protein content of diets. Specific growth rate and protein efficiency ratio also followed the same pattern while feed conversion ratio took the reverse order, which was highest in control diet (2.49) and least in diet 4 (40%CP) 1.70. This observation was in line with the reports of Chong et al (2004) and El-Sayed et al (2003) and they seem to confirm the assertions of Izquierdo et al (2001), that it is desirable to ensure that nutritional requirements of broodstock must be fulfilled to optimize reproductive performance. The extent of larval viability was demonstrated by significant total feed intake by fish fed diet 4 (40% CP) which consequently had direct effect on feed conversion ratio and protein efficiency ratio and specific growth rate. Fish fed the 30% protein diet and the control had the lowest weight of eggs indicating that this level is insufficient to fulfill the requirements of the female catfish broodstock and hence, reduced gonadal development and quality of the hatchlings (high deformed larva and mortality). Similar results have been reported by Al Hafedh et al (1999), stressing the relatively poor fish performance in terms of inferior specific growth rate and fecundity in fish when they were fed diets low in quality. Although studies with tilapia and grass carp showed no relationship between dietary protein and egg size according to Gunasekara et al (1997) and Khan et al (2004) but the reports of Manissery et al (2001) showed that dietary protein level affects common carp egg quality.

Conclusion  

• This study revealed that dietary protein level affect catfish broodstock performance.

  
  

• The higher the protein levels in the diet the higher the hatchability rate.

  
  

• Larval performance at advanced stage however performed marginally different from fish fed 35% CP and those fed 40% C.P diets in terms of specific growth rate.

  
  

• Contrarily, final mean weight and weight gain of fish were significantly affected with variation in the crude protein of fish diets suggesting that 35% CP feed can only be sufficient for fish growth maintenance, while 40% CP diet can further  ensure proper gonad development and maturation of fish and consequently, superior performance of the hatchlings.

References  

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Received 13 December 2009; Accepted 12 February 2010; Published 1 April 2010

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