Azolla A Boon for the Growth of Gift Tilapia, Oreochromis Niloticus (Linnaeus, 1758)

Understanding the nutritional requirements and production of sh feed is essential to the development and sustainability of aquaculture for the matured feed mill practices. Fish feed management includes choosing the right feed, using a correct feeding method, calculating the feeding cost and ensuring the cost effectiveness of sh farm. The purpose of the present study was to feed the shes with four different feeds and assessment of growth performance by length weight relationships. The growth analysis was executed by measuring FCR and related indices in gift tilapia oreochromis niloticus. Four feed composition was selected without any chemical contamination. In the present study shes were collected from the golden farm, Neyyattinkara, Thiruvananthapuram district, South India. Fishes were introduced into four different tanks of well oxygenated good quality water. In each experimental tank, 20 shes were introduced. For each experimental container a specic feed was xed from 4 different diets. Every day feed was given to the shes. They were fed two times for the period of 3 months. They were maintained to assess their growth performance. Four types of feeds used for the present study are control diet, diet 1, diet 2 and diet 3. Measurement of length and weight was measured on every 15 days interval. Based on the length-weight data, growth analysis was carried out by calculating relative growth (RG), relative growth rate (RGR), specic growth rate (SGR), feed conversion ratio (FCR) and the Fulton’s condition factor. The results of mean length in diet3proved the highest length of 6.455 ± 0.46cm and diet one contain lowest length of 5.03 ± 0.68cm. Highest weight of 96.8 ± 0.37g was recorded in diet3 and lowest weight obtained for the control diet (3.645 ± 0.306 g). In growth analysis the relative growth of sh was estimated in diet 3 having high relative growth (11.91). Relative growth rate was elevated in diet 3(1.5597). The upper limit of specic growth rate was 1.9146% observed in diet 3. The feed conversion ratio was maximum in diet 3 (58.06) and minimum in control diet (36). The highest k value in Fulton's condition factor was noticed in diet 3(88.32).All experimental results proved that live Azolla [D3] was a superior feed for the present trials.


Introduction
The raise of human inhabitants has led to the scarcity of animal protein sources all over the globe. It has directed the awareness of sh as the fast and strong compensatory source of high quality animal protein.
Fishes are quite diverse from the other animal food sources because they provide calories with high class proteins which hold all essential amino acids in simply digestible form. So they are the valuable nutrition source. Numerous studies have investigated the probability of optional protein source (Gatlin et al. 2007).
Health promoting aspects of sh in the human diet with Omega 3 fatty acids and other vital ingredients were contributed by aquaculture. Fish meal is a scarce and expensive protein source for commercial sh feeds. This explains the need for the substitute of sh proteins by other sources. Most of these studies showed that the partial replacement of sh meal can be successfully accomplished with respect to nutritional and health aspects.
Supplemental feeding is necessary for the enhancement of sheries to achieve greatest yields from resources of fresh water sh farming. Replacement of improved nutrients can instigate sh growth rapidly and they accomplish maximum weight in shortest possible time. The nutritional content of the feed entail on what species of sh is being cultured and at what stage it is cultured. Fish nourishment has advanced in recent years with the development of latest, balanced, pro table diets that encourage optimal sh growth and health. When shes are reared in high density in indoor systems or con ned cages, they cannot scavenge freely on natural food.  Typically in the formulation of feed, selected parameters were greatly in uenced by the raw material selection by the introduction of alternative nutrition sources. Dietary changes using alternative sources can be utilized in the culture system. Moreover 40 -60 % of the total feed production cost, any negative effects on feed e ciency should be avoided. Finally the quality of the product including its highly bene cial properties for human health should not be compromised.
Due to the demand of sh meat, to overcome the nutrition de cit and to get a good quality sh meat without any chemical contamination; it is necessary to substitute a superior feeding exploration. In the present study, assessment of growth was substantiated by measuring length-weight relationships and by applying statistical factors due to the interpretation of relative growth, relative growth rate, speci c growth rate, feed conversion ratio and Fulton's condition factor. Gift tilapia, Oreochromis niloticus shes were fed by mentioned diets. The present study was framed to assess the growth of shes in three selected feeds with control and comparing them by utilising natural feed ingredients.

COLLECTION OF SAMPLE
For the present study purpose gift tilapia, Oreochromis niloticus was collected from the Golden farm, Neyyatinkara, Thiruvananthapuram district of Kerala. The collected shes were maintained and cultured by using selected feeds.

MAINTENANCE AND CULTURE OF FISHES
In the present study 1cm mean sized shes were introduced into different cement tanks of well oxygenated good quality water. In each experimental container 20 shes were introduced. Four different diets were given to the shes in four different tanks. All the experimental trials were done in triplicates and their average was taken for data analysis. Every day, they were fed two times. For the period of three months they were maintained to analyse different assessments of their growth performance.

FEED INGREDIENTS
Control Diet Rice, ground nut oil cake, turmeric, corn, Green gram.
Diet 2 Grow n (readymade feed obtained from farm)

Diet 3 Azolla FEED FORMULATION
Different ingredients selected to formulate the feed were separately sun dried and crushed well using a mixer grinder to small particle size. A sieve was used to remove large particles or foreign materials which can damage the machinery. The ingredients were weighed and appropriate quantities were taken for feed preparation.

Control Diet [CD]
The control diet was prepared by adding different amount of ingredients such as 25gm rice our, 25gm ground nut oil cake; 5gm turmeric powder, 20gm corn our and 25gm green gram were taken. The modi ed method of Gull et al. (2005) was adapted. With the help of warm water the dry ingredients were mixed slowly. Good mixing can improve palatability. Water was added and mixed well to form a mash with a cake like consistency. As a general rule, the total moisture content of the mash should be in the range of 45 to 55% to produce good pellets. Pass the feed mash mixture through a pellet machine (mincer) with 1mm diameter. The mash was then steamed in a food steamer for about 10 to 15 minutes.
Later it is cooled and kept in the refrigerator for 48 hours. This mash was then dried in the room temperature and cut the extrusion (which looks like noodles) into similar length to the closest pellet diameter. The moist pellets were then dried to moisture content of 10% or less simply by spreading the pellets under the sun rays.

Diet 1[D1]
This diet was prepared by taking 25gm rice our, 25gm powdered shelled sh, 25gm wheat our, 10gm fenugreek and 15gm corn our and mixed thoroughly to make an emulsion with the help of warm water. Mix with dry ingredients slowly. To improve palatability the contents were mixed well. By the addition of needed water the mash with a cake like consistency was formed. The total moisture content of the mash should be kept in the range of 45 to 55% to produce good pellets. Pass the feed mash mixture through a pellet machine (mincer) having 1mm diameter. The mash is then steamed in a food steamer for about 10 to 15 minutes. Later it is cooled and kept in the refrigerator for 48 hours. This mash is then dried at the room temperature and cut the extrusion (which looks like noodles) into similar length to the closest pellet diameter. The moist pellets were then dried to reduce the moisture content of 10% or less simply by spreading the pellets under the sun rays.

Diet 2[ D2]
Grow out (commercial) feed was bought as a readymade feed from the aquarium to fed the shes in the third tank.

Diet 3[D3]
Azolla (natural feed) were given to the shes in the fourth tank directly without any modi cation of the feed.

FEEDING THE EXPERIMENTAL FISHES
Correct delivery of food is important to reduce feed waste. Underfeeding can result in loss of production while overfeeding results in feed wastage and can lead to deterioration in water quality. A serious decline in water quality can result in loss of stock and the need for corrective measures. The shes were fed twice a day preferably after sunrise (7 to 9 am) and before sunset (4 to 6 pm). 2gm of feed was provided to shes in each container every time.

ESTIMATION OF LENGTH -WEIGHT RELATIONSHIP
The length and weight of the shes (Jisr et al. 2018) from each container were measured at every 15 days to estimate the length -weight relationship. Fish was measured in terms of weight gain and increase in length. Total length (TL) was measured to the nearest 0.1mm using 30cm ruler as the distance from the tip of the anterior most part of the body to the caudal n while weight measurements were taken in gm using 0.01g sensitive weighing balance at an interval of 15days.

Relative growth (RG)
It is used for the comparison of the size of similar organisms. RG is calculated with the formula quoted here.

Relative growth rate (RGR)
RGR is the growth rate relative to the size of the population. It is calculated by the following formula.

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The speci c growth rate is de ned as the rate of increase of biomass of a cell population per unit of biomass concentration. Weight was recorded in grams. It is calculated by using the following formula (Steel et al. 1997).

Feed conversion ratio (FCR)
The success of an aquaculture practice is dependent upon many factors relating to the eld of biology, engineering and economics. The feed conversion ratio is a remarkable tool for understanding the acceptability of given feed (Inayat and Salim, 2005). FCR is calculated using the following equation.
Where F is the weight of food supplied to sh during the study period; W f is the live weight of the sh at the end of the study period; W 0 is the live weight of the sh at the beginning of the study period

Length-weight relationship
The Length -weight (log transformed) relationships were determined by linear regression analysis and scatter diagrams of length-weight were plotted. The length -weight relationship of the experimented sh was worked out as per cube law given by Le Cren (1951).

W= aL b
Where, W= Weight of sh (g), L is observed total length (cm), 'a' is the regression intercept and 'b' is the regression slope.

ESTIMATION OF LENGTH AND WEIGHT RELATIONSHIP
In the present investigation, an average length and weight of freshwater sh gift tilapia 'Oreochromis niloticus' was studied for a period of 90days. The length was measured in centimetres and weight was estimated in grams. The maximum length of O.niloticus was 7.   Growth of sh depends on a wide range of positive or negative impact factors. Many studies are evidences for the growth of shes in aquaculture. They mainly proved that increase in size of organisms directly proportional to feed consumption and quality of diets.

Relative growth
In the present study gure 1 showed the relative growth of shes. The RG of the gift tilapia O.niloticus was high in the diet 3 (11.91) and less in the control diet (7.73).

Relative growth rate
The control diet having relative growth rate 0.1031in CD and the diet1 has the RGR of 0.5385. The relative growth rate of 1.1182 was noticed in diet 2. The maximum RGR was 1.5587 in D3 [ gure 2].

Speci c growth rate
The speci c growth rate of the O.niloticus was maximum in the diet 3 (1.9146) and minimum growth rate in control diet (0.8024). Figure 3 showed the results of SGR.

4.Feed conversion ratio>
The feed conversion ratio of the control diet was 36. Diet 3 have the feed conversion ratio of 58.06 and diet1 and diet2 ratio were 42.86 and 47.

Length weight relationship
The relationship between the length and weight of the control diet was 0.2931×L 1.5235 , diet1 was 0.002×L 4.483 . The diet 2 interpreted was 1.9503×L 0.3608 and diet 3 showed the length weight relationship of 4.7025×L 0.110 .

Fulton's condition factor
The Fulton's condition factor for control diet 1 was 64.80 and diet 1 was 66.67.The diet 2 and diet 3 having the Fulton's condition factor of 72.96 and 88.32. This also indicates the changes in food reserves Discussion Unique set of water chemistry needs is indispensable to a healthy balanced and practical aquaculture system (Delong et al. 2009).The growth of different sh species was ideal, which were in uenced by diverse choice of water quality features(Nailor et al. 2021). Organisms generally augment in size (length, weight) during development. The key factors that in uence the growth of sh are the amount of food, the number of sh utilizing same food, temperature, oxygen and other water quality factors. Besides these the size, age and sexual maturity of the sh also plays well. The rapport between the applied length and weight gained signi cance, because every animal gained growth by length and weight in its life. In the present investigation, an average weight of O.niloticus was studied for a period of 90days. Maximum mean length 7.1±0.725cm was noticed in diet 3, minimum length found was 0.96±0.212cm in diet 1 and the moderate length was 5.03±0.6840cm in diet 2. Similar study carried out by Anene (2005)  of the gift tilapia O.niloticus was high in the diet 3 (11.91) and less in the control diet (7.73).The relative growth rate was higher in the diet 3 (1.558) and lesser in the control diet (0.1031). The speci c growth rate of the O.niloticus was high in the diet 3 (1.9146) and minimum in control diet (0.8024). Similar study carried out by Makori et al. (2017) proved that the speci c growth rate of the O.niloticus in earthen ponds were recorded the same growth rate of 3.7%/day SGR. When compared with these studies, our study reported moderate SGR. The length weight relationship of sh is important for estimation of growth observations. The relationship between length and weight of the control diet was 0.2931x L^1.5235, the diet 1 having 1.9503×L^4.483, the diet 2 having 4.7025×L^0.110. Similar study was carried out by shahabuddin et al. (2015). They proved that the length and weight relationships of the juveniles of Nile tilapia, oreochromis niloticus showed the allometric increase of growth. Khallaf (2003) reported differences in length weight relationship of O.niloticus in a polluted canal compared with those of other authors in different localities and times. These differences were attributed to the effect of eutrophication and pollution on growth and other biological aspects. The Fulton'scondition factor for O.niloticus was estimated in the range of 64.80, 66.67, 72.68 and 88.32 respectively. Further the highest amount was recorded in diet 3 (82.32) and the lowest amount was noticed in the control diet. The condition factor is an important factor to determine the relative degree of robustness and nourishment in sh (Mortuza and AI-Minsed, 2013). This factor might be in uenced by sex, age, maturity and environmental condition (Anyanwu and Okoro, 2007). The condition factor obtained in the present experiment showed sh above average condition which indicated good health condition during the experiment and indicated an isometric growth, which is the desirable factor in sh farm. All the results of the present study proved that there was a signi cant increase in the body size of shes reared in azolla [D3]. So from the present results exposed that O.niloticus will grow well in azolla fed tanks.

Declarations Funding
No funding was received

Con icts of interest/Competing interests
There are no con icts of interest to declare.

Ethics approval
The Department of science, Southern Region has approved this research.

Contribution Description
LGB conceived and designed research. MR conducted experiments and generated data. LGB and MR analyzed data. MR wrote the manuscript and LGB corrected and edited the whole contents. All authors read and approved the manuscript.