Research site and duration of the study
The culture trial was carried out at the Fisheries and Aquaculture Department Research Farm, while measurements and hematologic analysis were conducted at the department laboratory located in the premises of Dennis Osadebay University Anwai, Asaba, Delta State Nigeria.
The research lasted for a period of 56 days from April to June 2023.
Collection of the test ingredient
Fresh goat weed leaves were identified using a chart provided by a plant expert from the Crop science Department and harvested from the reserve vegetation of the Crop Science Department. The harvested leaves were carefully removed and cleaned, then properly dried at room temperature and blended to powder form with the aid of an electric vegetable blender (model BLG 403) (Fig. 1). A proximate and phhytochemical analysis was performed on the leaf (Table 1), before inclusion at varying levels to formulate the test diets. Analysis was carried out using the methods described by Tewelde and Mulubrhan (2019). The relative composition analysis was determined using a mixture of methods namely extraction, Kjeldahl, and near-infrared reflectance spectroscopy (NIR), while the digestibility test was carried out using both the siphoning and stripping methods. Then the formula used to calculate the level of digestibility was;
Digestibility (%) = 100 - (100 x (marker concentration in food/marker concentration in faeces) x (nutrient concentration in faeces/nutrient concentration in the test ingredient or diet)).
Table 1
Proximate compositions and phytochemical constituents of goat weed leaf
Parameters (%) | GWLM |
Moisture | 7.82 ± 0.97 |
Crude protein | 14.64 ± 0.64 |
Crude fibre | 11.87 ± 0.45 |
Ether extract | 5.80 ± 0.08 |
Ash content | 8.98 ± 1.13 |
Nitrogen free extract | 49.72 ± 0.51 |
Anti-nutritional factors (g) | |
Alkaloids | 26.98 ± 0.27 |
Tannins | 7.36 ± 0.19 |
Saponins | 62.03 ± 0.28 |
Flavonoids | 20.74 ± 0.51 |
Phenol | 6.26 ± 0.72 |
Ascorbic acids | 12.35 ± 0.21 |
Anthraquinones | 10.42 ± 0.13 |
Anthocyanin | 15.58 ± 0.49 |
Cardiac glycosides | - |
Trypsin inhibitor | 4.23 ± 0.04 |
Oxalate | 5.12 ± 0.09 |
Phytate | 2.61 ± 0.05 |
Diet formulation and feeding trial
A total of five (5) different diets with varying levels of dietary inclusion (0%, 2%, 4%, 6% and 8%) of goat weed leaf meal (GWLM) as a partial replacement for maize were formulated to contain a minimum of 40% crude protein level (Table 2). The conventional ingredients (maize, soya bean, fishmeal, starch as binder and salt) were sourced from a notable market (Abraka market) in Asaba, Delta State, while vitamin premix, lysine and methionine were purchased from an approved seller. The feed ingredients were mixed with the text ingredient (at varying levels of dietary inclusion) and used to produce 2-mm pellet diets using a locally fabricated pelletizer with a 2-mm die. The various 2 mm feeds produced were further separated in different well-labelled containers (Fig. 2).
Table 2
Percentage composition of diets
Ingredients | GWLM 0% | GWLM 2% | GWLM 4% | GWLM 6% | GWLM 8% |
Maize | 25.80 | 25.28 | 24.77 | 24.25 | 23.74 |
Fish meal | 26.50 | 26.50 | 26.50 | 26.50 | 26.50 |
Soya beans | 34.20 | 34.20 | 34.20 | 34.20 | 34.20 |
GWLM | 0.00 | 0.52 | 1.03 | 1.55 | 2.06 |
Vitamin premix | 2.50 | 2.50 | 2.00 | 2.00 | 2.00 |
Lysine | 2.00 | 2.00 | 2.00 | 2.00 | 2.00 |
Methionine | 2.00 | 2.00 | 2.00 | 2.00 | 2.00 |
Salt | 1.50 | 1.50 | 1.50 | 1.50 | 1.50 |
Binder | 2.50 | 2.50 | 2.50 | 2.50 | 2.50 |
A total of 500 African catfish (C. gariepinus) juveniles collected from Fisheries and Aquaculture Research Farm were used for the feeding trial. Prior to the beginning of the feeding trial, the healthy juveniles were individually weighed to ensure the weight difference was minimal (average 13.7 g). After sterilizing in a mixture of potassium permanganate and water to reduce stress, a one-week acclimatization period was ensured using commercial feed (2 mm). Subsequently, they were randomly stocked in quadruplets of 25 fish per culture tank measuring 1.2 m x 1.2 m x 0.9 m each (labelled Ai-iv, Bi-iv, Ci-iv, Di-iv, and Ei-iv) based on the diet fed (Fig. 3). The test diets were administered twice daily (7:00 hrs. and 18:00 hrs.) and the sampled fish were adequately fed (5% body weight) with proper follow-up to monitor feeding behavior.
Growth Performance and Feed Utilization
The growth parameters and feed utilization indices (body weight gain, final weight, initial weight, specific growth rate, survival rate, feed intake, and feed conversion ratio) of the sampled fish were measured biweekly using an Anid@ weighing balance (product of A&D Technology Trading (Shanghai) Co., Ltd. (Shanghai, China)) to measure body weight (BWT), meter rule, and calliper for standard length (SL) and total length (TL) of the fish. Survival rates (SR) and feed conversion rate (FCR) were evaluated using the methods described by Irabor et al. (2022a). The changes in weight and length observed as recorded were calculated using the modified methods of Garca-Ortega et al. (2016) and Irabor et al. (2016).
Body weight gained (g) = final weight - initial weight
The specific growth rate was calculated with\(\frac{ \text{L}\text{i}\text{n} \left(\text{f}\text{i}\text{n}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t}\right) - \text{L}\text{i}\text{n}\left(\text{i}\text{n}\text{i}\text{t}\text{i}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t}\right)}{\text{N}\text{u}\text{m}\text{b}\text{e}\text{r} \text{o}\text{f} \text{c}\text{u}\text{l}\text{t}\text{u}\text{r}\text{e} \text{d}\text{a}\text{y}\text{s}}\) x 100
Daily feed intake was determined by = weight of leftover feed - weight of the total feed given.
The feed conversion ratio (FCR) is expressed as the quotient of food intake and weight gained:
$$\frac{ \text{T}\text{o}\text{t}\text{a}\text{l} \text{f}\text{e}\text{e}\text{d} \text{c}\text{o}\text{n}\text{s}\text{u}\text{m}\text{e}\text{d} }{\text{T}\text{o}\text{t}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t} \text{g}\text{a}\text{i}\text{n}\text{e}\text{d}}$$
Survival rate was expressed as the difference between total fish stock and quantity harvested:
\(\frac{\text{N}\text{u}\text{m}\text{b}\text{e}\text{r} \text{o}\text{f} \text{f}\text{i}\text{s}\text{h} \text{h}\text{a}\text{r}\text{v}\text{e}\text{s}\text{t}\text{e}\text{d} }{\text{N}\text{u}\text{m}\text{b}\text{e}\text{r} \text{o}\text{f} \text{f}\text{i}\text{s}\text{h} \text{s}\text{t}\text{o}\text{c}\text{k}\text{e}\text{d}}\) × 100
Water Quality Analysis
Basic water quality parameters as inferred by Boyd (2001); dissolved oxygen, hydrogen, and hydroxyl ion concentration (pH) and temperature were monitored with the aid of the YSI (556 mps) meter model, while the APHA (1998) method was used to measure ammonia concentration in the holding receptacle.
Haematological and serological analysis
The blood profile of the sampled fish was evaluated at the end of the feeding trial (56 days) to determine the effect of the test ingredient. This was done by collecting blood samples from ten (10) randomly selected fish each from the various culture tanks using the procedure described by Gbadamosi and Olanikpekun (2020). Using sterile needles and syringes (1ml), blood was drawn from each of the fish through the lateral line close to the tail region and placed in sterile vials containing ethylenediaminetetraacetic acid (EDTA). The technique outlined by Amenyogbe et al. (2022) and Witeska et al. (2022) was used to calculate white blood cell (WBC), red blood cell (RBC), packed cell volume (PCV), haemoglobin concentration (Hb), total leukocyte counts, and erythrocyte counts. The following methods were also used to calculate the mean corpuscular volume (MCV) of the blood constants, the mean corpuscular haemoglobin (MCH), and the mean corpuscular haemoglobin concentration (MCHC):
White blood cell (WBC) counting area: The 4 huge squares at the edges of Neubauer's compartment are utilized to count white blood cells.
Red blood cells (RBCs) are counted in the 5 squares of the central square (which is separated into 25 squares, each one is then split further into 16 squares).
Haemoglobin (Hb) = MCV x RBC divided by 29.8.
Mean corpuscular volume (MCV %) = \(\frac{\text{P}\text{C}\text{V}}{\text{R}\text{B}\text{C}}\) X 10
Mean corpuscular haemoglobin (MCH %) = \(\frac{\text{H}\text{b}}{\text{R}\text{B}\text{C}}\) X 10
Mean corpuscular haemoglobin concentration (MCHC %) = Hb (g/dL) × 100/Hct.
Serum was extracted from the blood samples collected by centrifuging some volume of the blood samples separated into well-labelled red top tubes for 5 minutes at 5000 g and 4 ° C in fresh sterile microtubes. After being thoroughly separated, the supernatant was stored at -20 ° C for additional examination using methods described by Rashidian et al. (2021).
Data Analysis
The data collected from the research were subjected to a One-way Analysis of variance (ANOVA) using the SPSS version 23 analysis package. Furthermore, a Duncan multiple range test was employed to separate the means.