DIETARY INTAKE OF OXYTETRACYCLINE INJUVENILE LASED SENEGALENSIS(VALENCCIENNES 1842): EFFECTS ON GROWTHPERFORMANCE AND FEED UTILIZATION

E. OMOREGIE*

Fisheries Research Unit, Department of Zoology, University of Jos, P.MB. 2084, Jos, Nigeria .• E-mail: omoregie@unijos.edu.ng

ABSTRACT

Juvenile Labeo senegalensis (Cyprinidae) mean weight: 0.35 ± 0.02 g, were fed moistisonitrogenous and isocaloric diets incorporated with varying levels of veterinary graded oxytet-racycline; 5,2.5, 1.25, 0.625 and 0% (control) over a 6-week period under laboratory conditions.Survival, growth performance and feed utilization of the fish were studied. Survival in all fishgroups was above 90% with the exception of the group fed 5% oxytetracycline incorporated diet.At incorporation levels of 5, 2.5 and 1.25% oxytetracycline, there was significant (P < 0.05)reduction in growth performance compared to 0.625 and 0%. The feed efficiency and proteinefficiency ratios were adequate (below 0.9 and above 2 respectively) with the exception of fish fedthe 2.5 and 5% incorporated diets. The apparent protein digestibility was above 90% in all diets,with the exception of the 5% incorporated diet which resulted in significant reduction (P < 0.05).Proximate composition of the fish carcass indicated that there was no significant differences (P> 0.05) in the tissue protein and lipid of the control fish and group fed diets incorporated with 1.25and 0.625% oxytetracycline. The implications of this drug in growth performance in Labeosenegalensis are discussed.

Key Words: Antibiotics, Cyprinidae, growth performance and feed utilization.

The cyprinid, Labeo senegalensis is presently becoming a very importantaquaculture species in the tropics. The popularity of this species can be at-tributed to its succulent flesh, fast growth rate, ability to withstand low dis-solved oxygen and its ability to adapt to aquacultural manipulations for en-hancing its culture in ponds (Reed et al., 1967). For improving growth of this

I , new species under intensive culture there is need (in addition to other inves-tigations) to study its responses to various drugs presently being used inaquaculture. The threat of epidemic continues to be one of the main obstaclesin the cost-efficient production of fish and shellfish (Efthimiou, 1996),

J. Aqua. Trop. 16(4) (2001) 323-330© Oxford & IBH Publishing Co. Pvt. Ltd.

324 Journal of Aquaculture in the TropicsNovember2001

Undoubtedly, certain diseases that affect fish necessitate the use oftherapeutants including antibiotics (Tojo et al., 1994). It is also true that thesuccess of aquaculture has been made possible by the introduction and ap-plication of certain drugs. Although, the advantages offered by antibiotics areconsiderable, the possible toxic effects on the cultured fish may be serious(Roberts, 1978) therefore, must not be overlooked. Addition of antibiotics tothe diets of fish is widely practised and where therapy is limited to a shortperiod of time, toxic effects of the drug usually go un-noticed.

Oxytetracycline (Terrarnycin'') is an antibiotic produced by Streptomycesrimosus. Of all antibiotics used in aquaculture, it is the drug of choice forvibriosis and other bacterial infections (Roberts, 1978). Its use in fisherieshas been evaluated extensively and it is usually available as a veterinarypremix. Roberts (1978) recommended a dosage of 7.5 g/100 kg fish/day forfive to fifteen days. Depaola et al. (1995) reported that when carefully admin-istered, oxytetracycline can lead to reduction of bacterial outbreaks in catfishponds.

L. senegalensis is highly susceptible to epidemic outbreaks of infectiousdiseases (Obasoyo, 1997). No study has been conducted to assess the efficacyof the application of antibiotics for controlling bacterial diseases in this particularfish species. This present study was conducted to evaluate the effects of varyinglevels of oxytetracycline on survival, growth performance and feed utilizationof juvenile L. seneaelensis.

MATERIALS AND METHODS

A total of 340 laboratory reared juvenile L. senegalensis (mean weight 0.35 ±0.02 g) of the same brood stock were used for this investigation. The fishwere acclimated in experimental circular plastic tanks (45 cm diameter,10 cm deep and 20 I capacity) for 7 days (indoor) with continuous supply ofdechlorinated municipal tap water. A total of 10 plastic tanks were used. Dur-ing the acclimation period, the fish were fed 6% of their body weight threetimes daily at 0900, 1200 and 1500 h with a commercial fish diet. Feedingwas terminated one day before the commencement of the experiment. Thefish were randomly distributed at 20 fish per experimental tank filled with 15 Iwater.

A practical basal diet was supplemented with 0%, 0.625%, 1.25%, 2.50%and 5.00% oxytetracycline at the expense of carboxymethyl cellulose. In ad-dition to the carboxymethyl cellulose, cassava flour also served as a binder inthe various diets. The diets were processed based on methods described byOmoregie and Ogbemudia (1993). The diets were isonitrogenous (mean crudeprotein: 42.86 ± 0.22%) and isocaloric (mean gross energy: 31482.84 ± 0.00Jg-1). Other nutrients; moisture, crude lipid, crude fibre, ash and total carbo-hydrate were all not significantly different (P > 0~05) within the various diets

Journal of Aquaculture in the Tropics November 2001 325

(Table 1). Chromic oxide (0.5%) was used as a marker to evaluate the effectof oxytetracycline on apparent digestibility of protein following the methodssuggested by Furukawa and Tsukahara (1966). Cassava flour used in theformulation was pre-treated as described in Omoregie et al. (1991).

Table 1: Formulation and proximate composition of the control and experimental diets

Diets

OX5 OX2.5 OC1.25 OXO.625 CON

Ingredients (% wet weight)Oxytetracycline 5 2.5 1.25 0.625 0Fishmeal 40 40 40 40 40

Corn oil 5 5 5 5 5

Groundnut meal 35 35 35 35 35

Cassava flour' 10 10 10 10 10

Vitamin premix" 2 2 2 2 2

Mineral premix" 2.5 2.5 2.5 2.5 2.5Carboxymethyl cellulose 0 2.5 3.75 4.375 5Chromic oxide 0.5 0.5 0.5 0.5 0.5

Nutrient contents (% dry weight)

Moisture 4.33 4.25 4.67 4.73 4.08Crude protein 42.57 42.72 42.88 43.01 43.12

Crude lipid 22.19 22.35 22.94 23.27 23.37

Crude fibre 2.34 2.24 2.35 2.69 2.36

Ash 4.90 5.08 5.12 5.14 5.15Total carbohydrate 23.67 23.36 22.04 21.16 21.92

Calculated gross energy (Jg-') 3142.84 3142.84 3142.84 3142.84 3142.84

, Treated as described in Omoregie et al. (1991).'* Composition as in Ufodike and Matty (1983).

The fish were fed with the experimental diets three times daily~Q900, 1200and 1500 h), at a rate of 6% body weight per day. There were 2 replicates foreach diet. The feeding trial lasted for a period of 6 weeks. All fish in each tankwere bulk weighed, to calculate the mean weight gain of fish per tank. Fordigestibility calculation, faecal samples for each treatment were collected dailyby siphoning before the second feed. Faecal samples were also collected bygentle stripping of the fish abdomen. The faeces were over dried at 105°C for24 h and storing in airtight vials under refrigeration (4°C) for subsequent chro-mic oxide and total nitrogen analyses.

At the end of the feeding trials, samples of the fish carcass (5 fish fromeach tank) were taken for proximate analysis using standard methods (AOAC,1984). Gross energy of the diets was calculated using conversion factors asdescribed by New (1987). The following water quality parameters were moni-tored once weekly; temperature, dissolved oxygen, free carbon dioxide,

326 Journal of Aquaculture in the TropicsNovember 2001

alkalinity and pH using standard methods (APHA et al., 1980). Specific growthrate' (SGR) was ca!culated using the formula given by Brown (1957) and thefeed efficiency ratio (FER) was calculated as the ratio of weight gained to thequantity of food consumed (Winberg, 1956). The protein efficiency ratio (PER),the efficiency with which the fish utilize dietary protein, was obtained accord-ing to methods described by Osborne et al. (1919). Apparent net protein uti-lization (ANPU) was calculated according to the methods of Furukawa andTsukahara (1966).

Statistical comparisons were made using a one-way analysis of variance(ANOVA). Mean differences between treatments were tested for significance(P < 0.05) using the Duncan multiple range (Duncan, 1955).

RESULTS

In all the experimental tanks, with the exception of the control, low feedingactivity was observed during the first week. However, during the remaining5 weeks, food was activity consumed; there did not appear to be a differencein feeding activity according to treatments thereafter. The water qualityparameters monitored during the feeding trials (Table 2) were all within theacceptable range for the culture of warm water fish and the incorporation ofoxytetracycline into the diets did not affect the quality of the water (P > 0.05).

Table 2: Mean (n = 14) water quality parameters measured during the experimental period

Parameter Maximum Minimum Mean ± S.ETemperature (OC) 24.25 23:98 24.18 ± 0.10

IDissolved oxygen (mgl-') 7.12 6.71 I 6.90 ± 0.13Free carbon dioxide (mgl-') 4.20 3.39 3.94 ± 0.29Alkalinity (mgl-') 21.45 19.02 20.44 ± 0.83pH 7.20 6.79 I 7.01 ± 0.16

The mortality, growth performance and feed utilization of L.senegalensisfed the control and experimental diets is shown in Table 3. The highest mor-tality was recorded with diets OX5, there was however, no significant differ-ence (P > 0.05) in the survival of the fish fed other diets. The mean growthresponse of L. senegalensis during the 6-week period is shown in Fig. 1. Thehighest growth was obtained with CON (control diet) followed by diets OXO.625and OX1.25. The lowest growth rate was recorded with OX2.

j5 and OX5, which

were significantly lower (P < 0.05) than those obtained with diets CON, OXO.625and OX1.25. The FER and PER were best for the control diJt, these however,were not significantly different (P > 0.05) from those fed di~ts with OXO.625.The apparent protein digestibility was high, with values abbve 90% with theexception of OX5 which had 81.45%. The best apparent protein digestibility(96.13%) was recorded in the fish fed the control diet.

Journal of Aquaculture in the Tropics November 2001 327

4.03.5

---- 3.0on'-'+-' 2.5..con(l) 2.0;3:t: 1.5ro(l):2 1.0

0.50.0

0

--A-OX5'--0-- OX2.5__._- OX1.25

~OXO.625

-a-CON

------,----'" ...•_--,----,------,-._---

2 3 4 5 6

Feeding period (weeks)

Fig. 1. Mean weight gain of Labeo senegalensis fed the control and experimentaldiets for 6 weeks.

Table 3: Mean' (n = 20) survival, growth and feed utilization of Labeo senegalensis fed the. .... control arid experimental diets for 6 weeks

Indices Diets

OX5 OX2.S OX1.2S OXO.625 CONSurvival (%) 81.34b 92.00' 96.20- 98.00' 98.40'Initial body weight (g) 0.33" 0.378 0.358 0.33" 0.36-Final body weight (g) O.SOb 1.23° 3.09d 3.3S- 3.81-Weight gain (%) S1.52b 86.00" 782.86d 915.15- 958.33"SGR (% day:') 1.0Gb 2.86< 5.198 5.52" 5.62"FER 0.96b 0.81° 0.74" 0.71" 0.70"PER 1.07b 1.34< 2.01" 2.08" 2.14-ANPU (%) 81,45b 90.08< 94.36" 94.78" 96.13-

, Values within the same row with same superscripts are not significantly-different at O.OSlevelof probability.

The proximate composition of carcass (% wet weight) of fish fed the ex-perimental diets is shown in Table 4. The moisture content was significantlylowest in CON, this was closely followed by OXO.625. The results indicate aninverse relationship between carcass protein content and levels of oxytetra-cycline in the various diets, with the highest carcass protein content in CON(16.46%) and the lowest (14.98) in OX5. The carcass lipid and ash contentwas observed to follow the same pattern as the carcass protein.

328 Journal of Aquaculture in the Tropics November 2001

Table 4: Mean' (n = 5) carcass composition of Labeo senegalensis fed the control andexperimental diets for 6 weeks

DietsOX5 OX2.5 OX1.25 OXO.625 CON

Moisture 74.80b 74.13b 73.45" 73.09" 73.01"Crude protein 14.94b 15.38e 15.95" 16.01" 16.46"Crude lipid 3.9b" 4.02e 4.13" 4.20" 4.348

Ash 3.12b 3.4ge 4.13" 4.12" 4.588

, Values within the same row with same superscripts are not significantly different at 0.05 levelof probability.

DISCUSSION

The problems of disease outbreak in aquaculture have over the years beentreated with antibiotics. A range of antibiotics are usuallyl available for fishtreatment. Most of these drugs are usually incorporated as veterinary premixeswith varying activity. Roberts (1978) reported that most aJailable antibioticswhen used at certain level tend to pose more problems due to their toxicity.He noted that although conventional sulphonamides have the advantage ofrelatively low cost, but could cause problems due to their renal toxicity. Amajor problem facing aquaculturists is that of dosage, especially with respectto new aquaculture species with no available literature on recommended doses.The cyprinid, L. senegalensis is one such species. Depaola et al. (1995) notedthat some of the antibiotics used for treating fish diseases which are suppos-edly used at safe levels may still affect the fish physiological activities due tocumulative effects.

One of the most common difficulties observed with antibiotic treatment viadiet is the acceptance of the diet, evidently related to the taste of such formu-lated diet. In this experiment, the acceptance of the diet incorporated withvarying levels of oxytetracycline was low during the first week of feeding,perhaps due to the flavour of the drug in the diets. However, this problemdisappeared after the fish adapted to the new taste. Totten and Jobling (1997)noted similar acceptance of oxytetracycline medicated diet by the Arctic charr,Salvelinus alpinus. In fish species were acceptance of antibiotic medicatedfeed is a problem, Totten and Jobling (1997) suggested the application ofsmall quantities of feeding stimulants such as squid extract to improve dietpalatability. Behaviour of taste response have been reported by other au-thors, including Olvera et al. (1990), Nikl et al. (1993) and Siwicki et al. (1993).

In terms of survival, the fish fed 2.5, 1.25 and 0.625% of oxytetracyclineincorporated diets had over 90% survival, which was significantly not differ-ent from the survival of fish fed the control diet. It can therefore be concludedthat at levels below 2.5% oxytetracycline can be used in the treatment of the

Jormal of Aquaculture in the Tropics November 2001 329

fish, L. senegalensis without resulting in significant mortality of the fish. Thenutritional quality of diets incorporated with oxytetracycline, as determined bygrowth in body weight of the fish was adequate. Although final growth perfor-mance was higher in the control diet, no statistically significant differenceswere detected in the growth rate and feed utilization in the group of fish feddiets incorporated with 0.625% of oxytetracycline. The group of fish fed 5% ofoxytetracycline had the lowest growth and feed utilization. The results indi-cated an apparent deleterious effects of the drug in the fish at levels above2.5% incorporation.

Although the FER was better with the control diet, this parameter wasadequate for all the experimental diets with the exception of the dietincorporated with 5% oxytetracycline. The results for PER and apparent proteindigestibility (used as an indication for protein digestive value) were alsoadequate except in fish fed diet containing 5% oxytetracycline. With theexception of 5% oxytetracycline, the apparent protein digestibililty was above90%, while protein efficiency ratio was above 2 in fish fed diets incorporatedwith 1.25 and 0.625% oxytenacycline. Similar values of apparent proteindigestibility and protein efficiency ratio have been reported when fish werefed with high quality diets (W~tanabe and Pongmaneerat, 1991; Bimbo andCrowther, 1992; Omoregie ahd Ogbemudia,1993; Rodriguez-Serna et al.,1996). Comparison of the pr+ximate composition of the fish indicated thatthere was no significant differences in the nutrient content of fish fed thecontrol diets as compared with those fed 1.25 and 0.625% oxytetracyclinediets.

Results from this investigation show that it is feasible to incorporate appro-priate levels of oxytetracycline into the diet of L. senegalensis without reduc-ing the nutritional quality of the diet. However, at levels above 2.5%, growthperformance was not as encouraging as with lower levels. This indicates someamount of impairment in the physiology of the fish, hence the signifIcantlylower deposition of protein, lipid and ash in the tissues of the fish fed with 5%level. Roberts (1978) had earlier reported renal toxicity in fish fed with higherlevels of sulphonamides. Similarly, Toften and Jobling (1997) reported thatthe addition of oxytetracycline to diets of the Arctic salmon resulted in poorerfeed utilization. Since the main reason of the use of oxytetracycline in aqua-culture is for disease treatment, it is therefore necessary to evaluate the ap-propriate levels needed to effect treatment in L. senegalensis. This is bearingin mind that preliminary results from this investigation revealed that at levelsabove 2.5% in diets, oxytetracycline reduces the growth performance andfeed utilization by the fish. Secondly, at 5%, the drug could lead to significantmortality in the fish. At least pending investigation on the specific level of thedrug that will be effective in treatment of this fish, optimal caution and consid-eration for the fish should be observed during the application of oxytetracy-cline in the treatment of disease outbreaks.

330 Journal of Aquaculture in the Tropics November 2001

ACKNOWLEDGEMENT

Funding for this research was provided by the Faculty of Natural Science,University of Jos, Nigeria via Faculty Research Grant No. UJ/FNS/9S-99/00S.The technical assistance received from Mr. T.O. Ojobe, Miss E. Anwa andMrs. M. Oyebanji is also greatfully appreciated.

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Received 31.01.00Accepted 28.03.01