Animal Science

Productive performance of Clarias gariepinus small fish, feeding with reduced protein and similar energy concentration

0000-0002-6687-8284J. E. Llanes^{1  *}  , 0000-0002-2641-1815Magaly Herrera² 

¹Empresa de Desarrollo de Tecnologías Acuícolas. Carretera Central km 20 ½, Loma de Tierra, Cotorro. La Habana, Cuba

²Instituto de Ciencia Animal. Apartado Postal 24, San José de las Lajas. Mayabeque, Cuba

ABSTRACT

The productive performance of Clarias gariepinus small fish, feeding with reduced protein and similar energy concentration was evaluated. A total of 360 animals were random distributed according to a one-way model in three treatments, with three repetitions. The experimental treatments were: D1 control) 60 % of fish meal (47.89 % CP and 14.04 MJ/kg DE), D2) 51 % of fish meal (44.71 % CP and 13.62 MJ/kg) and D3) 42 % of fish meal (41.08 % CP and 13.54 MJ/kg DE), supplied at 10 % of body weight for 40 days. There were differences in the supply of crude protein (8.25, 7.56 and 6.67 g), which only affected the final weight of the fish in the D3 treatment (14.89, 14.61 and 13.46 g). However, feed conversion (1.24, 1.25 and 1.29) and survival (89.17, 86.67 and 85.83%) did not differ between treatments and protein efficiency improved (1.69, 1.80 and 1.87). The economic analysis showed monetary savings for feeding of $US 162.09 and 268.00 /t, by reducing the concentrations of crude protein in the rations. It is concluded that the productive performance of Clarias gariepinus small fish, feeding with reduced protein and similar energy concentration, is not compromised and has a positive economic effect.

Key words: feeding; catfish; nutrition; nutritional requirements

Since its introduction in 2000 from Thailand, the catfish Clarias gariepinus has become the main intensively farmed species in Cuba. As part of the culture biotechnics, there is the small fish that is carried out, mainly, in cement or fiberglass pools in a super-intensive way, to obtain animals of 10.0 g of average weight in 35 - 40 d. Initially, it started with imported feed (41.02 % of crude protein, CP and 11.80 MJ/kg of digestible energy, DE), but the dependence on this market caused destabilization in the successful development of the technology, so it was necessary a national formulation.

^{Llanes et al. (2009)} carried out a comparative study between the imported food and another of national production with 60 % fish meal, FM (47.89 % CP and 14.04 MJ/kg DE), with which they achieved better productive and economic results. This formulation is the one used today. The difficult economic situation that Cuba is going through and the low availability of FM in the market makes it necessary to reduce its inclusion percentage, without disfavoring the productive indicators.

The decrease in FM leads to a reduction in the CP level, since other ingredients with similar CP values are not available, such as poultry by-product meal, poultry viscera, blood, hydrolyzed feathers, among others. A possible solution would be to maintain the energy concentration of the ration and, therefore, make a fitment of the CP/DE ratio to maximize the use of CP for body growth (protein--sparing), and reduce the release of nitrogenous compounds by water (^{Campeche et al. 2018} and ^{Rodríguez-Avella 2019}). The objective of this study was to evaluate the productive performance of Clarias gariepinus small fish with reduced protein and similar energy concentration.

Materials and Methods

The research was carried out in the Fish Nutrition Laboratory from Empresa de Desarrollo de Tecnologías Acuícolas (EDTA) in Havana, Cuba. The enterprise has circular cement tanks, with a capacity of 68 L, with constant water flow (replacement of 100 % daily).

The animals were acclimatized in the experimental facilities for one week. After this time, a total of 360 small fish of 0.86 ± 0.03 g of initial weight were selected. The experimental treatments consisted of three diets: D1 control) 60 % FM, which corresponds to the commercial feed for claria small fish, D2) 51 % FM and D3) 42 % FM (table 1). Each had three repetitions and 40 fish per tank. The tank was the experimental unit.

Table 1 Percentage and proximal composition of the experimental diets, g /100 g 

Ingredients	D1 (60% FM)	D2 (51% FM)	D3 (42% FM)
Fish meal	60	51	42
Soybean meal	15	20	24
Wheat	20	24	28
Soybean oil	4	4	5
Vitamins and minerals premixture*	1	1	1
Total	100	100	100
Calculated analysis, %
Dry matter	91.68	90.46	90.23
Crude protein	47.89	44.71	41.08
Fat	9.96	9.24	9.51
Crude fiber	2.21	2.58	2.88
Ashes	13.08	11.75	10.36
Digestible energy (MJ/kg)	14.04	13.62	13.54
CP/DE (g/MJ) ratio	34.11	32.82	30.34

* Vitamin-mineral mixture(kg of diet): vitamin A, 500IU; D, 100IU; E, 75 000 mg; K, 20 000 mg; B₁, 10 000 mg; B_3, 30 000 mg; B_6, 20 000 mg; B_12, 100 mg; D, 60 000 mg; niacin, 200 000 mg; folic acid, 500 mg; biotin, 0.235 mg; selenium, 0.2 g; iron, 80 g; manganese, 100g; zinc, 80 g; copper, 15g; potassium chloride, 4g; manganese oxide, 0.6g; sodium bicarbonate , 1.5g; iodine, 1.0g; cobalt, 0.25g.

To prepare the diets, the meals were milled in a Creole hammer mill at 250 µm and mixed in a mixer (HOBART MC-600®, Canada) for 3 min. Later, the oil and the vitamin and mineral premixture were added and mixing was continued for 3 min. Pelletization was carried out in a meat mill (JAVAR 32, Colombia) at a diameter of 1 mm and dried in an oven (Selecta, Spain) at 60 ^oC for 24 h. The food was offered in broken pellets the first 15 d and later of 1 mm. The feeding rate was 10 % of body weight/d, supplied in two portions for 40 d, and was fitted every 15 d. The bromatological analyzes were carried out on the ingredients, according to the methods described by ^{AOAC (2016)}, and the digestible energy (DE) was calculated with the caloric coefficients referred by ^{Toledo et al. (2015)}.

Every day the values of temperature and dissolved oxygen were taken with a portable digital oximeter (HANNA^®, Romania). At the end of the bioassay, an individual weighing of the fish was carried out to calculate the following productive indicators:

• Food supplied / fish = food added / number of final animals

• Protein supplied / fish = protein added / number of final animals

• Final average weight

• Daily weight gain = biomass gain / culture days

• Feed conversion factor (FCF) = food added / weight gain

• Protein efficiency = biomass gain / protein supplied

• Survival (S) = number of final animals/ number of initial animals x 100

Statistical analysis. For the analysis of the results, the statistical package InfoStat, version 2012 (^{Di Rienzo et al. 2012}) was used. The mean values were compared using ^{Duncan (1955)} test in the necessary cases.

An analysis of variance was performed, according to a one-way model. The theoretical assumptions of the analysis of variance were verified for all the variables based on the ^{Shapiro and Wilk (1965)} tests for the normality of the errors, and the ^{Levene (1960)} test for the variance homogeneity. The variables fulfill the theoretical assumptions of the ANOVA. Chi-square proportions analysis was used for survival and the ^{Fisher-Yates (1958)} (p<0.05) test was applied for comparison.

Economic analysis. It was carried out by ^{Toledo et al. (2015)} procedure. The costs of the rations were calculated from the international prices of raw materials for November 2021, reported by ^{Indexmundi (2021)} (table 2). The costs of the rations were calculated from the international prices of raw matters for November 2021, reported by ^{Indexmundi (2021)} (table 2). To the results was added 50 % of the total cost of raw matters for additional expenses (transportation, maquila and administrative) for Cuba. These values were multiplied by the FCF obtained in this study to know feeding costs.

Table 2 Prices of raw matters used in the experimental diets, $US/t 

Raw matters	Prices, $ US /t
Fish meal	1 442.75
Soybean meal	442.42
Wheat	317.44
Corn	248.72
Vegetable oil	1 439.57
Dicalcium phosphate	533.24
Vitamin- mineral mixture	1 975.11

Results and Discussion

During the experimental period, water circulation was efficiently controlled to guarantee 100 % of daily turnover. The temperature and dissolved oxygen in the water from the tanks ranged between 26.6 and 23.4 ^oC and from 5.54 to 5.96 mg/L, respectively. Only the temperature values are considered slightly below for the comfort of the species (^{Toledo et al. 2015}).

The pellets had good physical constitution and hydrostability. Rapid intake of diets by the animals was observed, which suggests that the palatability of the rations was not affected by the reduction of FM and the increase of vegetable ingredients. The FM is an ingredient that provides high palatability compared to vegetable ingredients, such as soybean meal (SM), and although it was reduced by 18 %, the diets still continued with high inclusion.

^{Rodríguez-Avella (2019)} reported that the amino acids alanine, glutamic acid and serine, present in FM, stimulate appetite and food response in fish, although the mechanisms are unknown. Also, ^{Nascimento et al. (2020)} reported that most plant-derived nutrient sources contain anti-nutritional substances, which are the main cause of poor palatability and can limit their use, mainly in small fishes.

The productive performance of Clarias gariepinus small fish with the experimental diets (table 3) showed that the decrease in FM and, therefore, in dietary protein provided less supply of CP for the animals and a decrease of 1.43 g in the final weight of the fish that intake the D3 (42 % FM). Feed conversion was not disadvantaged between treatments. Similar results reported for the same species ^{Matter et al. (2004)}, by achieving better growth, feed efficiency and carcass composition, with protein levels of 37 % compared to 32 and 28 %.

Table 3 Productive performance of Clarias gariepinus small fish, feeding with the experimental diets 

Indicators	D1 (60 % FM)	D2 (51 % FM)	D3 (42 % FM)	SE (±)	p
Food supplied/fish, g	17.22	16.94	16.23	0.58	0.655
Protein supplied / fish, g	8.25 ^a	7.56 ^ab	6.67 ^b	0.28	0.035
Final weights, g	14.89 ^a ± 0.45	14.61 ^a ± 0.46	13.46 ^b ± 0.43	-	0.022
Daily weight gain, g /d	0.35± 0.01 ^a	0.35± 0.01 ^a	0.32± 0.01^b	-	0.023
Feed conversion	1.24	1.25	1.29	0.02	0.275
Protein efficiency	1.69 ^b	1.80 ^ab	1.87 ^a	0.03	0.015

Different letters in the same row differ at p<0.05, according to ^{Duncan (1955)}

^{De Souza et al. (2017)} in hybrid catfish (Pseudoplatystoma reticulatum x Leiarius marmoratus), feeding with 32 and 40 % CP and similar energy concentration, analyzed the productive performance, carcass yield and visceral fat index and obtained the best results with 40 % CP, although they registered an increase in the accumulation of visceral fat. Also in this same species, different protein: lipid ratios (9.00, 4.60, 3.54 and 1.78) were assessed, in terms of growth, digestive enzymes, metabolic profile and hematological parameters. With 4.60 they achieved the best results, which they attributed to the greater protein saving due to the effect of energy (^{Campeche et al. 2018}).

Another result in catfish was different. ^{Mora et al. (2010)} evaluated diets with 28, 32 and 36 % CP and similar DE (14.29 - 15.25 MJ/kg) in fattening yaque catfish (Leiarius marmoratus) in floating cages, with an initial average weight of 35 g. These authors did not found differences in growth and the best feed conversion was with 28 % CP, which could be related to the omnivorous nature of these fish, size and feeding to satiety, which allows them to grow with lower protein levels.

^{Toledo et al. (2015)} reported that one way to correct diets low in protein and essential amino acids is to supply rations to satiety to compensate for deficiencies and not affect growth, although feed efficiency deteriorates. This strategy can be inconvenient and costly, despite the lower feed price, because the fish can overfeed and waste a lot of food, even with a careful and competent feeder. In addition, a lot of fecal matter is generated which can affect water quality.

In other species, such as chames (Dormitator latifrons), four diets of 30 and 40 % CP, with 8 and 16 % lipids, were evaluated, and there were not discrepancies in the growth and proximal composition of the muscle (^{Badillo et al. 2018}). On the contrary, the best productive results in Carassius auratus (Cyprinidae) were with 40 and 45 % CP and 8 % lipids. Meanwhile, with lower values, the animals had lower performance. From the above, it can be inferred that the levels of nutrients (protein and energy) have effects on the fish growth, but it depends on the species, feeding habits, size, digestibility and palatability of the ingredients that make up the diet, balance of AA, CP/DE ratio, feeding rate, and physical and chemical conditions of the water. In addition, high concentrations of dietary protein do not necessarily result in increased growth and health status of the fish, since it has been shown that in some cases they can limit the regeneration of muscle, skin, blood cells, which causes fatty infiltration of the liver (^{Wang et al. 2013}).

In general, in omnivorous fish, the decrease in fish meal is replaced with SM, considered one of the best profiles of amino acids (AA) and cost-effectiveness, compared to other vegetable sources (^{Toledo et al. 2015}). The SM has high levels of CP (from 38 to 48 %), but the sulfurized AA are lower in relation to the quantitative requirements of most fish species, which is reflected in poor feed efficiency and reduced growth (^{Chen et al. 2018} and ^{Rodríguez-Avella 2019}). However, in C. gariepinus, it was shown that crystalline methionine supplementation alleviated these deficiencies (^{Elesho et al. 2021}).

Protein efficiency is another aspect that should be highlighted in the production indicators. In this study, it improved by reducing the supply of CP (table 3), because less protein was used, and weight gain was not affected. This shows that fish feeding with lower levels of protein use dietary protein more efficiently. Therefore, it is necessary to fit the energy level to maximize the use of protein for body growth purposes, so that less energy will be required for its oxidation. ^{Zaminhan-Hassemer et al. (2020)} reported that the efficient use of dietary protein depends on the content and balance of amino acids, an important aspect in order not to compromise fish growth, reduce nitrogen excretion and the environmental impact on fish production.

The results of the survival rates are shown in table 4. There were not differences between the diets. This indicates that there was no cannibalism, by reducing the concentration of CP. These results were higher than those achieved under productive conditions (40 %).

Table 4 Survival results of Clarias gariepinus small fish, feeding with the experimental diets, % 

Indicators	D1 (60 % FM)		D2 (51 % FM)		D3 (42 % FM)		SE (±)	p
Survival	No.	%	No.	%	No.	%	2.99	0.809
	107	89.16	106	88.33	103	85.83

Regarding the economic analysis (table 5), the indicators clearly show that the use of less amount of FM and protein content, leads to a lower cost of food due to its lower price (less protein). In this sense, and since there are no differences in feed conversion, and survival is not impaired between treatments, it is consistent that the economic benefit with the use of feed D2 (51 % FM) and D3 (42 % FM) is higher to the control (60 % FM), with higher protein content and cost. The 18 % reduction in FM leads to using 180 kg less per ton of feed. This represents US$ 259.70 and the possibility of producing one ton of food for every 2.33 t of control feed, even more when a significant amount of the budget is used to import raw matters to guarantee the sustainability of crop.

Table 5 Economic analysis of Clarias gariepinus small fish with commercial feed, USD /t 

Indicators	D1 (60 % FM)	D2 (51 % FM)	D3 (42 % FM)
Feed cost	1 609.25	1 466.71	1 339.12
Feeding cost	1 995.47	1 833.39	1 727.47
Saving	-	162.09	268.00

Feeding cost = Feed cost x feed conversion

Restricted feeding with differences in dietary protein levels between treatments predicted differences in protein intake. Therefore, variations in growth will only result from differences in metabolic efficiency (^{Rodríguez-Avella 2019}). Also, total food intake can improve the use of available nutrients and increase feed efficiency (^{Toledo et al. 2015}). Hence, the reduction of CP with a similar energy concentration was feasible to reduce the FM percentage, since the final weight was only affected by 1.43 g. This may not be visible at 35 d, since the goal with this food was to reach 10.0 g final weight. Thus, feed efficiency and feeding costs were improved. It is concluded that in Clarias gariepinus small fish, feeding with protein reduction and similar energy concentration, the productive performance is not compromised and a positive economic effect is achieved.

Acknowledgments

Thanks to the Centro Nacional de Producción de Animales de Laboratorio (CENPALAB) for the support provided in the acquisition of raw matters for the preparation of experimental diets.

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Received: February 26, 2022; Accepted: June 07, 2022

^*Email: [e-mail]

Conflict of interests: The authors declare that there is no conflict of interest between them.

Author’s contribution: J. E. Llanes: Conceptualization, Investigation. Magaly Herrera: Formal analysis.