Comparative studies on the effect of alternative and some traditional growth promoters on growth performance, body composition, and nutrient digestibility in Tilapia Nilotica fingerlings

     The present study was carried out to evaluate the comparative effects of alternative growth promoters as REE and some traditional growth promoters as Bactocell "probiotic" and oxytetracycline "antibiotics" on growth performance, body composition, feed efficiency and nutrient digestibility of Tilapia Nilotica fingerlings. A total of 200 fish were nearly of the same size with mean body weight (34.48 gm), the fish were divided into equal 4 duplicate groups, each replicate contain 25 fish in cages in artificial concrete ponds with good source of water. Fish groups were fed on 4 isocaloric, isonitrogenous diets (C.P. 36.43%) as follows:- Group (1) fed on diet free from any additives (control group), group (2) fed on diet contained 300mg/kg diet REE, group (3) fed on diet contained 0.6gm/kg diet oxytetracycline and group (4) fed on diet contained 1gm/kg diet Bactocell. The fish were fed the experimental diets at rate of 2-3% of the body weight, for 18 weeks followed by 3 weeks for digestibility trials.

Results of this study revealed that Fish group which fed on diets contained REE (300mg/kg diet) gave higher growth performance than other fish groups. High efficiency of feed utilization (low values of FCR) and protein utilization were observed in groups fed diets contained REE.

 Also, increased condition factor and length gain (cm) with diets contained REE in comparison with other fish groups. Increasing dry matter, crude protein, ether extract and ash content of fish at the end of experiment in diet contained REE in comparison with other fish groups. Increased the digestibility of dry matter, crude protein and fat in diet  contained REE than other groups.

 From this study, we can be concluded that fish diets contained REE gave the best growth performance, feed and protein efficiency, and increased digestibility of nutrients in comparison with other groups which contained Bactocell "probiotic" and oxytetracycline "antibiotics". 

                     Growth promoters or performance enhancers are used in world wide in animal production, where these substances are added to the diets for improving digestion, absorption, feed conversion ratio and body gain. In the European Union, most of these feed antibiotics are forbidden now, were banned since the end of 2005. World wide there is an increase demand for food which can only be achieved by an increased meat production.

            Lynch, (1999) stated that antibacterial growth promoters affect post-weaning health and performance. Wenk , (2003 ) stated that there is a strong need for alternative growth promoters such as pro-and prebiotics, enzymes, organic acids as well as herb extracts. 

            Khan, (2004) reported that these alternatives have to be efficient, safe and they should not harm the environment.

            In China for more than 40 Years, special mineral salts called Rare earth element (REE) or lanthanides are used as feed additives in animal production. Rare earth element are 17 elements which include Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu), Yttrium (Y), Scandium (Sc).

Yang et al., (2005)reported thatgrowth performanceenhancing effects due to dietary supplementation of REE at low concentrations are described for nearly all categories of farming animals, including beef cattle, sheep, pigs, rabbits, ducks, chickens, shrimps and fish. Venkat et al. (2004) reported that Lactobacillus acidophilus and L. sporogenes have an inhibitory effect on the harmless gram negative bacteria present in the gut micro flora of Macro brachium rosen bergii post-larvae.

Abd-El Hamid et al. (2000) found that the combination of dried live Yeast (DLY) and lactobacillus Saccharomyces (LS) led to significant positive effects on fish weight, total length, relative growth rate, condition factor, feed conversion and nutrients utilization.  Ismail et al. (1990)studied the oxytetracycline residues when therapeutic dose (75 mg/kg fish daily) was used in diseased Oreochromus Niloticus. Residues were detected in muscles up to 15 days, in kidney, gills, and gonads up to 19 days while in liver up to 22days after treatment. However, the same dose used in the healthy O.niloticus fish residues were detected in the muscles up to 10days and in kidney, gills, and gonads up to 15 days while in liver up to 19 days.

A total of 200 fish procured from Fish Research Center, Faculty of vet. Medicine, Zagazig University. The fish were nearly of the same size with approximately body weight 34.48gm. The fish were divided into equal 4 duplicate groups (each replicate contained 25 fish) and kept in cages in the artificial concrete pond for two weeks to be acclimatized before the start of the experiment. The fish were fed on iso nitrogenous, isocaloric experimental diet for 18 weeks. The fish in were located in artificial concrete ponds, each replicate of the groups were stocked in a cage made from plastic meshed material, with 80cm x 80cm x 80cm dimensions. The cages were located above the bottom of the pond. The pond had 3 net partitions which divided it into 4 equal parts. They were supplied with de chlorinated water and air supplied by a large air compressor.

Water temperature, dissolved oxygen, PH, ammonium (NH4), nitrite(NO₂),and nitrate (NO₃) were measured three times during the experiment and found to be 27-33⁰C±2⁰C, 5.3 mg/L, 8.1, 0.4 mg/L, 0.14 mg/L, 25 mg /L Respectively.

Growth promoters used:-

1- Rare Earth Element citrate ''alternative growth promoters" from Germany.

2- Oxytetracycline ''antibiotics " 20 %. Unipharma, universal industrial pharmaceutical Co. El obour City, Cairo, Egypt.

3- Pediococcus acidilactici '' Bactocell '' as probiotics each 1gm contains 10 x 10⁹ CFU. EGAVET, Geiza, Egypt.

Diets and feeding: Four isonitrogenous, isocaloric diet were formulated according to NRC (1993) with addition of (300mg/kg diet) REE, other traditional growth promoters as antibiotics (oxytetracycline) 0.6 gm / kg diet and probiotics (Bactocell) 1 gm / kg diet. The formulation and composition of the experimental diet are shown in table (1).  All fish groups were fed on the diets at the rate of 3% from body weight during the experiment.

Growth performance: The fish of each group were weighed at the beginning of the experiment to obtain initial body weight, then they were weighed every four weeks intervals according (Windell et al. , 1978 and Siddiqui et al. , 1988 ).

 The body length was measured at the beginning and the end of the experiment (15 fish/group) to determine the condition factor according to (Gjedrem and Gunnes, 1978) and taken for body composition.

The growth rate and feed utilization were measured according to (Jauncey and Ross, 1982, Siddiqui et al., 1988).   Protein utilization was calculated according to (Stuart and Hung, 1989, Castle and Tiews, 1980).

For evaluation of health condition of the fish during the experiment, escape, defensive, tail and ocular reflexes were regular observed according to (Lucky 1977). Fish of all groups were observed daily, abnormal behaviors and mortality rate were recorded. The macropathological examination was conducted using the method described by (Amlacher 1982).

Preparation of the diets with chromic oxide:-       The finally ground ingredients of each diet were weighed according its formulation and chromic oxide powder was added at a rate of 5 gm per each kilogram of diet (0.5 %). Each diet was thoroughly mixed and pelleted (1.5 mm diameter).

Fish used and feeding:-        Large individuals of each fish group at the end of experiments were reared in glass aquaria (30 x 40 x 150 cm) which contained aerated water at a water temperature 26 - 29 °c (9 fishes / aquarium) and given diets containing chromic oxide two times daily for one week as adaptation period, then for two weeks as a collection period.

Collection of faeces:- The faeces were collected after giving diets by about 5-6 hours using a fine net; faeces were collected after cleaning the aquaria to ensure no residue of diets was left. The collected faeces from each group were dried at 70 °c for 72 hours then at 105 °c for chromic oxide analysis.

Digestibility calculations:-    Apparent digestibility coefficient of dry matter of each diet was calculated (According to NRC 1993). Also, apparent digestibility coefficient of nutrient of each diet was calculated (According to NRC 1993).

Statistical analysis:- The obtained data in this study were statistically analyzed for variance ANOVA, LSD (Least significant difference) according to (Snedecor and Cochran, 1982). Difference among treatment means were compared using Duncan's multiple range test (Duncan, 1995). Data were presented as mean ± SE and significance was declared at (P < 0.05).

Productive performance:-   Data concerning the average body weight development of fish in different groups every 4 weeks during the experiment are present in fig. (1). The results showed variations in the average body weight of fish groups every 4 weeks. The effect of dietary treatments on average body weight was significant (P<0.05), where fish fed diets supplemented with 300mg REE/kg has significant higher body weight as compared to fish fed diet supplemented either Oytetracycline or Bactocell .

The allover performance data is shown in Table (2)  and Fig.(2). Fish fed diet supplemented with 300mg REE has a significant higher value of final body weight gain(28.78g) and body gain percent(82.93%) as compared to those fed diets supplemented with Oxytetracycline (20.10g and 58.23%) or Bactocell (19.06g and 55.29%). 

Our findings are supported by that of  Shen et al. (1991), Halle et al. (2003) and Rambeck et al. (2004) who concluded that REE as alternative growth promoters can improve the growth performance of all animal categories and fish.

Feed efficiency:-  (a) Feed consumption: - The feed consumption of different fish                   groups decreased as fish size increased. The total feed intake of fish group (2) which fed on diet contained REE consumed the highest amount in comparison to group (3) which fed on diet contained oxytetracycline (antibiotics) and group (4) which fed on diet contained Bactocell (probiotics).

(b) Feed conversion ratio (FCR):- It was observed that FCR values decreased as fish size increased. There was significant difference in FCR between fish groups. Fish fed diet supplemented with 300mg REE has significant lower FCR (2.12) as compared to fish fed diet supplemented with Bactocell (3.09). No significant difference was detected between fish fed diet supplemented with 300mg REE and those fed diet supplemented oxytetracycline (2.81) or the control (2.73).

These findings are in agreement with that of Winfree and Stickney (1981), and Osman (1987) who found that the FCR was higher for large fish than for small fish. Also, these results are in agreement with that of Halle et al. (2003) and Rambeck et al. (2004)who concluded that REE can improve feed intake and feed conversion in different animals.

Protein utilization:-              Table (3) showed that the protein efficiency ratio (PER), protein retention and protein productive value (PPV) at the end of the study were higher values (1.30, 1.42, 6.37) respectively in group (2) which fed on diet contained REE, while group (3) which fed on diet contained oxytetracycline (1.00, 1.03, 5.10) and in group (4) which fed on diet contained Bactocell (0.90, 1.06, 4.94).

From these results, it could be concluded that REE improved the protein utilization in the diets. These findings are in agreement with that of Yeng (1990), Shen et al. (1991), Halle et al. (2003), and Rambeck et al. (2004).

Condition factor and length gain (cm):-    The results of length gain (cm) and condition factor are present in Table (4). The highest values were obtained in group (2) which fed on diet contained REE, while were lowest in group (3) which fed on diet contained oxytetracycline (antibiotics) and group (4) which fed on diet contained Bactocell (probiotics). These results are supported by Gjedrem and Gunnes (1978) who reported that the high condition factor is an indicator of the good nutritional (healthy) state of fish.

Body composition:-   The effect of REE, antibiotic and probiotic supplementation on body composition (including CP, EE and ash) of fish is presented in Table (5). The effect of dietary treatments was not significant (p>0.05). The values of protein content was in the order 300 mg REE > Bactocell > oxytetracycline > control. The ash content of the body followed the same trend, while ether extract was 19% for fish fed diet supplemented with oxytetracycline and 18.5% for fish fed the other dietary treatments. These results are supported by that of Li et al. (1992) and Cheng et al. (1994) and Rambeck et al. (2004).

Digestibility results  :-           The effect of diets contained REE, Bactocell and oxytetracycline on the digestibility coefficient of dry matter; crude protein and fat were shown in Table (6). The results showed that the digestibility coefficient of dry matter was (78.95%) for fish fed on diet contained REE, while the digestibility coefficient of dry matter were 73.57 and 77.45% for fish fed diets supplemented with oxytetracycline and Bactocell respectively. The digestibility coefficient of crude protein and fat for diets supplemented with REE were 89.86% and 97.55% respectively, while for diets contained oxytetracycline were 84.52% and 95.27% respectively, but for diets contained Bactocell were 88.6% and 96.48% respectively.

 These results agree with those reported byLi et al. (1992), Cheng et al. (1994), He et al. (2003) and Rambeck et al. (2004)who found that REE can improve digestibility and utilization of nutrients in the diets in all animal categories. Also, Awaad et al. (2003) reported that Bactocell can improve digestibility and utilization of nutrients in the diets of broilers.

From this investigation, we can be concluded that , addition of REE as feed additives "alternative growth promoters" by small amounts increase the fish production, where at the level of 300mg/kg diet REE gave the highest growth performance and protein utilization as well as digestibility of nutrients in the diets of Tilapia Nilotica fingerlings,      in comparison with other traditional growth promoters as probiotics and antibiotics.

*Vitamin mixture provide(g , mg or I.U/kg diet):- Vit. A 5000 I.U , D3 200 I.U ,  E. 100 mg , K 10 mg ,  C 1000 mg ,  B1 10 mg ,  B2 15 mg ,  B6 7.5 mg ,  B12  0.1mg ,  Biotin  0.2 mg , Folic acid 0.4 mg ,  Choline HCL 1 g  ,  Inositol 3000 mg ,  Pantothenic acid 50 mg , Nicotine 100 mg ,  P-aminobenzonic acid 50 mg.

 ** mineral mixture: each 1000 gm contains: potassium chloride 16gm, sodium chloride 250gm, phosphorous 25gm, iron 10gm, manganese 5gm, magnesium 40gm, zinc 5gm, copper 5gm, iodine 150 gm, nickel 90gm, molybdenum 100gm, cobalt 10gm, selenium 10gm and calcium carbonate till 1000gm.

*** digestible energy calculation based on values of protein 3.5 kcal/gm, fat 8.1 kcal/gm, NFE, 2.5 kcal/gm. (according Santiago, et al., 1982). 

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