Dietary supplementation with goat weed leaf (Ageratum conyzoides) improves growth performance, haematological parameters and attenuates pathological-induced stress in African catfish (Clarias gariepinus) fingerlings

Oluyemi K Gbadamosi and Olamide S Olanipekun¹

Fisheries and Aquaculture Technology Department, School of Agriculture and Agricultural Technology, Federal Univrsity of Technology, Akure, Ondo State, Nigeria
¹ Fisheries and Aquaculture Technology Department, Federal Polytechnic, Ile Oluji, Ondo State, Nigeria
ejayemi@gmail.com

Abstract

The effects of goat weed leaf, Ageratum conyzoides as a phyto-additive on the growth performance, basic haematology and stress responses of African catfish Clarias gariepinus fingerlings were measured. One hundred and fifty C. gariepinus fingerlings of average weight 8.98±1.4 g were randomly selected and distributed into fifteen plastic tanks (40x30x35cm) at the rate of 10 fish per tank representing five treatments in triplicate. Five isonitrogenous diets containing 40% crude protein were formulated and A. conyzoides leaf was supplemented per 100g of feed at 0%, (control) (Ac0), 0.5 % (Ac0.5), 1.0 % (Ac1.0), 1.5 % (Ac1.5), and 2.0 % (Ac2.0) respectively. The fingerlings were fed twice daily at 08.00-09.00h and 4.00-5.00h for a period of fifty-six days. After the feeding trial, fish were challenged with a pathogenic strain of Aeromonas hydrophila. Feed intake decreased almost linearly as the level of Ac in the diet was increased. In contrast, weight gain and feed conversion responded with curvilinear trends. There were improvements in both criteria as the level of Ac was increased to 1% in the diet, followed by negative responses when the Ac level was increased to 2% of the diet. Red and white blood cells in C. gariepinus were higher in fish fed A. conyzoides supplemented diets. The best supplementation level of A. conyzoides was 1.0g/100g of feed.

Keywords: phyto-additives, stress, aquafeed, nutraceuticals

Introduction

The Food and Agriculture Organization (2014) defined aquaculture as the farming of aquatic organisms including fish, molluscs, crustaceans , algae and aquatic plants with some sort of intervention in the rearing process to enhance production, such as regular stocking, feeding and protection from predators. From a humble beginning, aquaculture has spread all over the world gradually transforming from a traditional practice into science. It is now the fastest growing animal producing sector with an average growth rate of 8.8% since 1970 outpacing capture fisheries (1.2%) and terrestrial farmed meat production (2.8%) (FAO 2017). In Nigeria the current demand for fish is about four times the level of local production. The demand for fish by humans stems from its content of protein. More than 60% of the world supply of protein, especially in the developing countries comes from fish (FAO 2017). Fish protein has a high nutritional value due to a well-balanced amino acid profile, ample amount of polyunsaturated fatty acids (PUFA) as well as a number of vitamins and minerals (Edwards 1997). Due to this, the rearing of fish which is a part of aquaculture has become a widely practiced occupation in Africa especially in Nigeria. The African catfish (Clarias gariepinus) is the most reared in Nigeria due to its ability of surviving under harsh environment condition and resistance to diseases. It is also of high market value as it is generally accepted by the young and old (Gbadamosi and Osungbemiro 2016). Aquaculture of African Catfish (C. gariepinus) is a viable means of augmenting the diminishing returns from the wild.

One of the goals of Aquaculture industry is to produce high quality and disease-free fish that are safe for human consumption. Fish feed on wide varieties of diet and plant materials of different types have been formulated to form diets for C. gariepinus juveniles (Dong-toon et al 2012). Aside from the fact that these plant materials provide nutrients, some of them also help in improving the immune system of the fish. The primary effects of plant-based additives are to improve feed efficiency and daily weight gain. The use of these plant-based additives allows fish farmers to maximize performance through improvement in health, weight gain, reproductive rate and feed efficiency. In recent years, some of the herbal substances added to the feed of fish have been reported to contain hepatogenic, hepato-protective and growth stimulating properties which tones efficiency of feed utilization (Bhasker et al 2003).

Phytogenic products have also been reported to promote various activities like anti-stress, growth promotion, appetite stimulation and immune stimulation in aquaculture practices (Citarasu et al 2017). Plants are natural sources of safer and cheaper additives (Dong-Hoon et al 2012), which are non-toxic, biodegradable, and biocompatible. Therefore there is a need for fortification of the diet with supplements that can improve the health of fish (Diab 2006). Many plant extracts have been investigated for antimicrobial activity in fish and have been found to have therapeutic potential.

Goat weed, Ageratum conyzoides grows freely and it is even considered as an invasive plant. It is available at “no cost” at all except for the effort made in its collection. In Sub-Saharan Africa, it is used by people for curative purpose but in some cultures, it is delicacy for domestic guinea pigs, horses and cattle (Ebochonu et al 2017), qualifying it as a pasture or fodder. Despite the fact that several plants have been investigated as phyto-additive in fish nutrition there is paucity of information on the use of Goat weed as a dietary supplement in African catfish. Hence the current research was aimed at examining the effects of Goat weed leaves as a phyto-additive on the growth performance, nutrient utilization and health of African catfish.

Materials and methods

Experimental Site

This research was conducted at the Fisheries and Aquaculture Technology Department Teaching and Research farm, Federal University of Technology (FUTA), Akure, Ondo State, Nigeria. C. gariepinus juveniles were collected from FUTA fish Farm. One hundred and fifty C. gariepinus of average weight (8.98±1.4) were randomly selected and distributed into fifteen plastic tanks (40x30x35) cm at the rate of 10 fish per tank representing five treatments in triplicates for a period of fifty-six days. One group serves as control and four groups represent the various levels of the A. conyzoides, 0.0% for control (Ac0), 0.5 % (Ac0.5), 1.0 % (Ac1.0), 1.5% (Ac1.5) and 2.0 % (Ac2.0) respectively.

Preparation of Ageratum conyzoides powder

Fresh leaves of Ageratum conyzoides were collected from Federal University of Technology Akure, Teaching and Research farm and identified at the Department of Crop, Soil and Pest. Federal University of Technology Akure, Ondo State. The leaves were sun-dried and milled into fine powder using Binatone electric blender (model BLG 402).

Formulation of experimental diets

The feed ingredient were purchased at Oja-oba market in Akure, Ondo state. Five (5) experimental diets were prepared to contain 40% crude protein. The ingredients were ground into small particle size. A. conyzoides powder was supplemented at 0.0 (control), 0.5, 1.0, 1.5 and 2.0g/100g. Ingredients (Table 1) were mixed and pelleted to obtain a homogenous mass; cassava starch was added as a binder. The diets produced were sun- dried after pelleting.

Feeding

The fingerlings were acclimatized for a week prior to the commencement of the experiment to reduce stress. They were fed between 08.00 and 09,00h and 16.00 and 17.00h. The water in the plastic tanks was siphoned and changed twice per week. During the experimental period, fish were weighed and feeds were adjusted based on change in body weights every two weeks, Mortalities were recorded. The feeding experiment lasted for 56 days.

Analytical procedure

The chemical analysis of the diets (Table 2) was according to the procedure of AOAC (1990).

Water quality and fish performance

The physical assessment of culture water was carried out weekly and included: temperature, pH, and dissolved oxygen (DO).The water was maintained at 27 - 30 ^oC, dissolved oxygen at 6.5-8.3 mg/L and pH 6.0 - 8.5. Growth performance parameters were measured using the following indices (Gbadamosi 2019): Weight gain (MWG), MWG =W_F-W _I. Where; W_F = Final weight, W_I= Initial weight. Feed Conversion Ratio (FCR), FCR = Total Feed Intake/ Total Weight Gain.

Aeromonas hydrophila challenge

At the end of the feeding trial, the fish were exposed to a mildly pathogenic strain of Aeromonas hydrophila (MPSTR 2143) This isolate was grown in brain-heart infusion broth (EM Science, Darmstadt, Germany) in a shaking bath at 27⁰C overnight. The concentration of bacterial suspension was determined by the serial plate count method and diluted to 9.3x10⁵CFU (Colony forming unit)/ml in fresh well water. Fish from each dietary treatment were immersed in the bacterial suspension for 5 hours. After exposure, the fish were fed with their respective diets for a further 2 weeks.

Haemotological analysis

Five ml of blood were collected from the fish by a cardiac puncture using disposable heparinized syringes. The sample was put in an EDTA bottle and used to determine the number of red blood cells (RBC) and white blood cells (WBC) by means of a haemocytometer slide (Improved Neubauer type) at a magnification of x400. Haematocrit (Hct) was determined by the microhematocrit method. Haemoglobin (Hb) concentration was measured by the cyanohaemoglobin method (Stoskopf 1993). Whole blood was mixed with 5 ml of Drabkin’s solution (Sigma-Aldrich) in a test tube before allowing to stand for at least 15 min at room temperature. The haemoglobin concentration was calculated from a curve prepared from known standards. Mean corpuscular volume (MCV: Fl), mean corpuscular hemoglobin (MCH: pg) and mean corpuscular hemoglobin concentration (MCHC: %) were calculated using routine techniques.

Statistical analysis

Data were subjected to one-way analysis of variance (ANOVA) using Statistical Package for Social Sciences (SPSS 2006, version 22).

Results and discussion

Feed intake decreased almost linearly as the level of Ac in the diet was increased (Table 3; Figure 1). In contrast, weight gain and feed conversion responded with curvilinear trends (Figures 2 and 3). There were improvements in both criteria as the level of Ac was increased to 1% in the diet, followed by negative responses when the Ac level was increased to 2% of the diet.

These responses are similar to those reported by Gbadamosi and Osungbemiro (2016) in which the inclusion of low levels of Moringa oleifera in the diets of C. gariepinus improved the growth performance and feed utilisation up to an optimum level and subsequently declined (Ritchter et al 2003; Ebochou et al 2017). The highest survival rates of 93.33% were recorded in treatments Ac1.0 and Ac1.5 after Aeromonas hydrophila induced stress. The survival rate of the experimental fish slightly increased with increase in dosage of A. conyzoides powder after pathogenic-induced stress and this might be due to the claims thatA. conyzoides has some medicinal properties (Ebochou et al 2017).

Figure 1. Response in feed intake of catfish supplemented with A. conyzoides leaf meal	Figure 2. Curvilinear response in growth rate of catfish supplemented with A. conyzoides leaf meal
Figure 3. Curvilinear response in feed conversion of catfish supplemented with A. conyzoides leaf meal

The white blood cells followed a curvilinear trend (Table 4, Figure 4) while for the red cells the effect was linear and positive (Figure 5). For the other criteria only the PCV values showed a consistent trend to increase with level of the Ac (Table 4).

Figure 4. Response in concentration of white blood cells in catfish supplemented with A. conyzoides leaf meal	Figure 5. Response in concentration of red blood cells in catfish supplemented with A. conyzoides leaf meal
Figure 6. Response in PCV concentration in blood of catfish supplemented with A. conyzoides leaf meal

Conclusions

• Feed intake decreased almost linearly as the level of Ageratum conyzoidesin the diet was increased. In contrast, weight gain and feed conversion responded with curvilinear trends. There were improvements in both criteria as the level of Ageratum conyzoides was increased to 1% in the diet, followed by negative responses when the additive was increased to 2% of the diet.
  
  
• Red and white blood cells in C. gariepinus were higher when the fish were fed A conyzoides supplemented diets. PCV values showed a consistent trend to increase with level of the Ac.
  
  
• The best supplementation level of A. conyzoides was 1.0g/100g of feed.

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Received 21 March 2020; Accepted 2 June 2020; Published 1 July 2020

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