Haematology and Serum Characteristics of African Catfish ( Clarias gariepinus Burchell) Fed Graded Levels of Tigernut Based Diet

The chronic effect of feeding tigernut based diets was investigated on African catfish ( Clarias garerpinus ). 225 African catfish were randomly allotted to five experimental diets (CP=40%) in which tiger nut replaced maize at 0%, 25%, 50%, 75% and 100% respectively and fed at 3% body weight daily for a period of 20 weeks. Other water quality parameters were maintained throughout the duration of the study. Blood samples were collected from fish in replicates and analyzed for haematological and serum parameters. Results of the haematology showed no significant differences among the parameters except haemoglobin and Packed cell volume (p<0.05). Similar observation was recorded for the serum biochemistry (p>0.05). This trial indicated that tigernut meal can replace maize wholly in diets of African catfish without any deleterious effect on the physiology and/or health status of the fish.


INTRODUCTION
Fish contributes 22% of animal protein supply in sub-Sahara Africa and 40% of animal protein consumption in Nigeria [1]. Nigeria aquaculture industry is currently faced with the problem of inadequate supply and exorbitant cost of quality fish feeds often imported [2]. Many researchers have been reported to increasing the attempts to develop practical diets for farmed fish in Nigeria by utilizing non-conventional feedstuffs with some encouragements [3,4,5,6,7]. However, some of these feedstuffs contained inherent anti-nutritional inhibitors which may be harmful to the animals fed such ingredients.
African catfish is the largest group of cultured species on the world after Carp, Salmonids and Tilapia. Its net production was estimated to be between 10.0 -15.0t/ha/yr, varying from dominated polyculture and monoculture systems. This productivity is increased with simultaneous stocking of surface feeders such as Silver carp and Catla (Catlacatla) as reported byMokhelsur and Imre [8].
Since blood tissue truly reflects the physical and chemical changes occurring in organisms, detailed information can be obtained therefore, on the general metabolism and physiological status of fish in different groups of age and habitat. Nevertheless, current reality on the use of alternative feed resources mainly to reduce cost of feed and fish has made it imperative to study the effect of feeding non-conventional feedstuff such as tigernut (Cyperus esculentus) often reported to contain some anti-nutrients such as alkaloids, saponins, Trypsin inhibitors, Tannin and phytate on the performance and/or physiological status of the fish. This experiment therefore, evaluated the haematology and serum biochemistry of African catfish fed graded levels of tigernut meal.

Locality
The experiment was carried out at the fish farm complex of Federal Polytechnic, Nekede, Owerri, Nigeria.

Experimental Fish and Management
Two hundred and twenty-five Clarias gariepinus with mean weight 5.0 ± 1.0g were purchased from African Regional Aquaculture Centre (ARAC), Aluu, River state, Nigeria. They were acclimated for a week and feed control diet before assigning them randomly to five treatment diets at 45 fish per treatment which was replicated trice at 15 fish each in hapanet measuring 1.5m x 1.0m x 1.0m in an outdoor cistern. The experimental fish were fed the test diets (Table 3) for 20 weeks at 3% body weight daily. Stale water was often drained off pond and re-filled from the bore-hole water at the farm complex. Water chemistry was monitored and maintained as outline by Boyd [9].

Haematological Evaluation
At the end of the feeding trial, two fish were taken from each of the replicates and put in water in separate bowls and labeled. Fish were tranquilized with 150mg/litre of tricane methane sulphonate (MS222) according to Osuigwe et al. [10]. Blood samples were collected by severing the caudal peduncle of the fish using heparinized tubes, but samples for blood plasma was obtained by centrifuging 5ml of the whole blood for 3 minutes and then the supernatant plasma was collected and stored in plastic tubes at -20ºC for analysis.
Haemoglobin (Hb) concentration was determined by the Cyanmethaemoglobin method by Dacie and Lewis [11] while the parked cell volume and total plasma protein were determined according to the procedure described Siwicki and Anderson [12]. The red and white blood cell counts were determined using Neubauer chamber. Mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH) were obtained according to the method of Dacie and Lewis [11]. Glucose and Urea were determined using UV spectrophotometer (Schimatxu UV-1200) following the procedure of Henry [13] and Bergmeyer [14].

RESULTS
Results of haemotological characteristics of trial fish is shown in Table1.

Haemoglobin (g/dl)
The highest value of 13.4 was recorded from the control group while the least value of 11.3% was obtained from 75% tigernut based diet. There was a significant difference between the control group and those fed the tigernut based diets (p<0.05).

Red Blood Cell (10 6 /mm 3 )
The values ranged from 2.15 in control group to 1.75 in dietary treatment with 75% tigernut inclusion. There was no significant difference among the treatments (p>0.05).

White Blood Cell (10 6 µl)
The highest value of 9850 was recorded from fish fed 75% tigernut diet while the least value of 8410 was recorded from catfish fed 25% tigernut diet. There was no significant differences (p>0.05) among the treatments.

Monocyte (%)
The lymphocyte values was highest in control (0%) group with value of 1.9% while least value of 1.2% was recorded from catfish fed 50% tigernut diet. There was no significant difference between value obtained from the control (0%) group and those fed tigernut based diets (p>0.05).

DISCUSSIONS
The haemoglobin concentration ranged between 11.3-13.4g/dl. These values were slightly above the highest value of 9.60g/100ml recorded by Omitoyin [18] for African catfish juvenile fed poultry litter and 10.62g/100ml reported by Osigwe et al. [10] who fed Clarias gariepinus with Jackbean meal based diets but in agreement with findings of Adeyemo [19].
The packed cell volume (PVC) was highest in the control group (44.7%) while the least value of 38.0% was recorded in catfish group fed tigernut at 75% dietary inclusion (P>0.05). These values were above 36.0% reported by Adeyemo [19], Erondu et al. [20]; Musa and Omoregie [21] who reported a range of 27.58 -35.50% but is within the normal range of 50% for fish (Clark et al. [22]).
The leucocytes values were similar in all treatments (p>0.05). The highest value of 9850 x 10 6 µl was obtained from catfish fed 50% tigernut based diet while the lowest value was 8410 x 10 6 µl catfish group on 25% dietary treatment. These values were similar to finding of Dada and Ikuerowo [17]. Nevertheless, the mean cell haemoglobin concentration (MCHC) reported in this study (29.9 ± 0.2%) is slightly below the value of 33.97% recorded by Adeyemo [19] and Docan et al. [23] for African catfish and Silurus glanis (European catfish) juvenile. This may be due to species differences and age of the fishes that greatly influences value of blood profile and/or haematological indices (Docan et al. [23]).
The serum biochemistry of the African catfish fed tigernut based diets (Table 2) were similar in all indices. The catfish fed test ingredients have similar values with control fish (p>0.05). This perhaps was among the reasons why there was relatively no significant differences in the nutrients utilization among treatments. Blood composition is usually altered during diseases or malnutrition conditions as documented by Feist et al. [24].       Aletor and Egberongbe [25] reported that red blood cell counts and PCV are mostly affected by dietary treatment. Under normal conditions, the blood profile is reasonably constant for any species with changes falling with fairly narrow limit as observed in this study [26]. Based on this experimental observation, the improved utilization of tigernut by the trial fish when compared with broilers [27] may be due to the medium where fish lives hence encouraging leaching of phenols and other anti-nutrients thereby allowing proper utilization/growth of fish without compromising the health status.

CONCLUSION
The result of this study has indicated that tigernut meal can replace maize wholly in diets of African catfish without any deleterious effect on the physiology and/or health status of the fish.