Using Wastes of Opuntia ficus-indica in Diets of Nile Tilapia

Introduction

Much information is given (Willem Van Cotthem, 2012) on Opuntia ficus-indicaasan aloes. In Arabic is called Sabr, Teen Shoky, Teen Barbary, Hendy, Hendia, or Barshomy. It could be used commercially and industrially in treatment of some diseases (eyes, face, bone, prostate, colon, stomach, and intestine) and in cosmetic manufactures. It is a permanent plant grows in arid zones and tolerates drought and salt for its leaves that are filled with water. It is planted also as fence surrounding the building for protection. Its origin is North America, but outspread from Europe to other countries. Its fruits are delicious, sweetly, nutritious, and moist; therefore, it is a food and a drug for peoples and animals live in deserts. The fruits are containing about 85% moisture, 10% sugars, 1.5% proteins, besides huge amounts of vitamins A and C, and different amounts of organic acids (citric, oxalic,…etc.) and minerals (P & Ca). Therefore the aim of the present study was evaluating the possibility of using powders of either fruits' skins or leaves of the Egyptian Teen Shoky in diets on fish performance. Also, this is an attempt to ameliorate feed costs by substituting such costless wastes in fish diets to replace somewhat imported dietary ingredients to save foreign money.

Using Wastes of Opuntia ficus-indica in Diets of Nile Tilapia - Image 1

Materials and Methods

Experimental animals and their management:

Hundred all-males mono-sex Nile tilapia fingerlings weighed on average 17 g and a total length of 9.2 cm purchased from a private fish hatchery (Al-Emam) at Tolompat 7 (Kafer El-Sheikh Governorate) were transferred in plastic bags to Sakha Aquaculture Research Unit. Then, the experimental fish were adapted in a plastic tank of 1³meter on the experimental Lab. conditions for one week. Thereafter, these fish were randomly divided into 10 glass aquaria at a stocking rate of 10 fish/aquarium that had dimensions of 70x35x40cm and filled with 65 liter of fresh water each. The feeding trial duration was 75 days (from 10/7/2017 till 25/9/2017); during which, each two aquaria (replicates) were singed to each treatment. The experimented fish were initially weighed and biweekly thereafter to readjust the feed quantity must be offered per each aquarium according to the actual body weight changes, maintaining the daily feeding rate at 3% of the biomass. The aquaria water was partially changed via syphoning five times weekly and once totally every week. The rearing water was dechlorinated tap water, since fresh tap water was aerated in a large tank to remove chlorine before be used. Some quality criteria of fish rearing water were measured periodically throughout the experimental duration. The source of light in the experimental lab. was naturally about 10 hours light and 14 hours darkness. Fish rearing water temperature was kept constant via heaters with thermometers.

Experimental diets:

Five experimental diets were formulated to replace 25 and 50% of dietary corn by fig skins and fig leaves in diets (D) No. 2, 3, 4, and 5, respectively besides the control one (diet No. 1) as shown in Table 1. All dietary ingredients were purchased from the local market (Makka Factory for fish diets, Kafr El-Sheikh). Fig fruit skins, as well as fig plant leaves, were collected and separately sun-dried then ground. All experimental diets were formulated by hand mixing all ground ingredients then pressed and pelleted into sinking diets with an average pellets diameter and length of 1 and 2 mm, respectively using an electric pelleting machine. Diets were offered to fish 6 days a week at 2 meals (8 am and 2 pm) daily.

Using Wastes of Opuntia ficus-indica in Diets of Nile Tilapia - Image 2

Measurements of the evaluation:

Besides biweekly body weight, fish total length was measured at the start and at the end of the experiment. Feed consumption was also measured. Growth rates, condition factor, and feed conversion ratio were calculated (Froese, 2006 and Abdelhamid, 2009); where:

Specific growth rate (SGR, %/day) = 100 [In W2 – In W1] / period, days

Relative growth rate (RGR, %) = 100 [W2 – W1] / W1

Condition factor (KF, %) = 100 (Fish weight, g / fish length, cm³)

Feed conversion ratio (FCR) = Consumed food, g / fish body gain, g

Mortality rate (MR, %) = No. of die fish / No. of fish at the experiment begin x 100.

Some measurements in fish rearing water were carried out to determine the suitability of water quality for the experimental fish rearing according to Abdelhamid (1996). Proximate analysis was carried out for the tested dietary ingredients, diets, and whole fish body (in 5 fish per aquarium) according to AOAC (2000).

Statistical analysis:

The obtained numerical results were statistically analyzed using SAS (2006) and Duncan (1955) for statistical differentiation between treatment's' means.

Results and Discussion:

Some fish rearing water quality criteria:

Table 2 shows that there were no marketable effects of the dietary treatments on the water quality criteria measured, and the registered values are within the suitable ranges required for rearing Nile tilapia cited by Abdelhamid (1996) and Abdelhakim et al. (2002).

Experimental diets composition:

Both tested materials were chemically analyzed (Table 3). Teen Shoky fruit skin (peel) (TSFS) contains less dry matter, crude fiber and silica than Teen Shoky leaves (TSL). However, both materials are to some extent chemically similar (Table 2), except the higher levels of crude fiber, ash, and silica in leaves than the fruit skins but the last contains higher fat and nitrogen free extract than the leaves. That perhaps means that the fruit skin may be more nutritious than the leaves.

The other dietary ingredients used in the experimental rations were also chemically analyzed (Table 4). Soybean meal is a plant protein source, since it contained 35.41% crude protein (CP); yet, the fish meal used herein as an animal protein source was of low CP content (16.33%). Wheat bran as a carbohydrate source contained lowest percentages of CP, crude fat and ash but the highest crude fibers (CF) and carbohydrates (nitrogen free extract, NFE) among the tested dietary ingredient.

Using Wastes of Opuntia ficus-indica in Diets of Nile Tilapia - Image 5

The tested rations were chemically analyzed too (Table 5). Their moisture and crude fat contents were decreased to some extend by the dietary inclusion of fig wastes, particularly with leaves (TSL) than fruit skin (TSFS) and with increasing the inclusion level from 25 to 50%. The opposite trend was recorded for CP and CF that gradually increased in diets 2, 3, 4, and 5 than D1and in D3 and D5 than D2 and D4. However, carbohydrates content was equal in different diets. These slight variations in chemical composition of the experimental diets are due to the nature (chemical composition, Table 2) and level of the fig wastes used herein (TSFS and TSL). Usually any replacement affects the dietary composition as found by many authors used different dietary replacers (Abdelhamid and Saleh, 2015; Abdelhamid et al., 2016and 2018).

Feed consumption:

The dietary inclusion of fig wastes; particularly with 50% TSFS (D3) and 25% TSL (D4) decreased (P≤0.05) the feed consumption (Table 6) of the experimental diets than the control (D1). That may be attributed to higher contents of CF and ash (Table 2) in fig wastes, particularly in TSL than the corn.

Using Wastes of Opuntia ficus-indica in Diets of Nile Tilapia - Image 7

Growth performance:

Dietary inclusion of TSFS and TSL improved (P≤0.05) either of FBW, TBG, DBG as well as SGR and RGR (Table 7), particularly at 25% TSFS and 50% TSL. On the other side, these substitutes increased the MR of the fish as reported too by Abdelhamid et al. (2018). Table 8 shows that final total length and condition factor of the experimental fish did not affect (P>0.05) by the dietary treatments; although, final body weight was significantly (P≤0.05) affected, since it was the highest with D2 and D5 (Tables 7 and 8). It is proved that increased dietary CP (Table 4) significantly elevate FBW and RGR (Tables 6 and 7) as found by Abdelhamid et al. (2001) and Khalil etal. (2001). Moreover, some replacers significantly improved FBW, FBL, FCF and FCR (Abdelhamid et al., 2000).

Feed Utilization:

Feed utilization expressed as feed conversion ratio (FCR) presented in Table 9 for the experimental fish for the whole period of the feeding trial clears the replacement of corn by fig wastes improved the FCR than on the control diet (D1), particularly it was significantly (P≤0.05) the best with D2 and D5. Abdelhamid et al. (2005) recorded better results with Nile tilapia by a dietary replacement concerning their growth performance, feed utilization and their body CP content.

Fish Body Composition:

The chemical composition of the experimental fish at the start composed of 13.67% protein and 2.95% fat. After 75 days of the experimental feeding period, crude protein increased (17.42 – 19.25%) than at the start of the experiment, since dry matter content naturally increased by age and therefore all nutrients increased too. However, the tested material increased (P≤0.05) both protein and ash contents gradually as the level of these materials increased in the diet from 25 (D2 and D4) to 50% (D3 and D5) and then the control (D1, without fig wastes). The opposite trend was recorded for the fat content that decreased by dietary inclusion of fig wastes (than the control), particularly with increasing the fig waste level (P≤0.05). Generally, the negative correlation between protein and fat percentages is a fact (Ali, 2008; Salem et al., 2008; Saad, 2010 and Farrag et al., 2013). Yet, other researchers found a positive relation between CP and EE contents of fish body (Gaber, 2006; Eweedah et al., 2006 and Soltan et al., 2008). Others did not find effect of dietary treatments on fish body composition (Mohamed and Hanafy, 2002 and Soltan, 2002 and El-Dakar, 2004). Anyhow, some wastes fed to fish may reduce fish body fat content and increase ash content (Hassanen et al., 1995). Also, Kheir and Sweilum (1997) reported that increased dietary CP content led to increase fish body CP and lower its ash content. However, the carbohydrates level is naturally low thus did not affect by the dietary treatments (Table 10) as found too by Abdelhamid et al. (2018).

Dietary replacements may improve FBW, TBG, DBG, RGR, SGR, FCR, and fish body CP (Abdelhamid et al., 2011). So, many authors (Abdelhamid et al., 2015; Abdelhamid and Soliman, 2012; 2013; and Khadr, 2018) recommend replacing conventional feed ingredients with unconventional ones without any harms on fish health and performance. Although, some other replacers from polluted sources could be harmful for fish, thus did not recommend to be used in feeding fish (Abdelhamid et al., 2010a & b).

Conclusion

It is possible to feed fish diets containing fig wastes as replacers for dietary corn, particularly at replacement rates of 25% fig skin and 50% of fig leaves without adverse effects on fish.