Enhancing the Productive Performance of Broiler Chickens by Adding Spirulina platensis Compared with Probiotic, Prebiotics, and Oxytetracycline

This study was conducted in order to find out the effect of Spirulina platensis (S. platensis) algae mixed with drinking water (2%) on the production performance of broiler chickens infected with or without Enterococcus faecalis (E. faecalis) and compare it with the effects of probiotics (containing Lactobacillus acidophilus, L. casi, L. reuteri, and Bacillus subtillis), prebiotics (containing antioxidants and a group of vitamins) as well as oxytetracycline. The experiment included 350 one day old (Ross-308) broiler chicks, randomly divided into 7 groups by 50 chicks per group for 35 days. The groups were divided as follows: T1: infected experimentally with E. faecalis only, T2: treated with S. platensis, T3: infected experimentally with E. faecalis and treated with 2% S. platensis, T4: infected experimentally with E. faecalis and treated with probiotic, T5: infected experimentally with E. faecalis and treated with prebiotic, T6: infected experimentally with E. faecalis and treated with oxytetracycline. T7: control group without any addition. Weekly live body weight and weekly body weight gain were measured as well as weekly feed intake and feed conversion rate for broiler chickens were estimated. The current study proved that S. platensis algae added to drinking water (2%) in T2 and T3 groups had caused a significant increase (P<0.05) in the weekly live body weight and weekly body weight gain, Spirulina also caused a significant decrease (P<0.05) in weekly feed intake and feed conversion rate for broiler chickens. Therefore, S. platensis could be a suitable alternative to some feed additives such as probiotics, prebiotics, and antibiotics in addition to the ability of Spirulina to reduce the symptoms of E. faecalis.


INTRODUCTION
nterococcus faecalis (E. faecalis) is Gram-positive bacteria and facultative anaerobic constitute the natural microflora of intestinal tract in mammals and birds (1). E. faecalis is an opportunistic pathogenic bacterium that causes many infections in poultry including septicemia, endocarditis, central nervous system infections, salpingitis and amyloidosis (2). Antibiotics are used as growth promoters for poultry at low doses than therapeutic doses and the mechanics of antibiotic action is by interaction with intestinal bacterial mass (3)(4)(5). As a result of excessive use of antibiotics, they caused the appearance of new bacterial strains resistant to antibiotics (6). Significantly, E. faecalis antibiotic-resistant bacteria will develop rapidly (7)(8)(9). Resistance genes may be transmitted from animals to

A B S T R A C T
This study was conducted in order to find out the effect of Spirulina platensis (S. platensis) algae mixed with drinking water (2%) on the production performance of broiler chickens infected with or without Enterococcus faecalis (E. faecalis) and compare it with the effects of probiotics (containing Lactobacillus acidophilus, L. casi, L. reuteri, and Bacillus subtillis), prebiotics (containing antioxidants and a group of vitamins) as well as oxytetracycline. The experiment included 350 one day old (Ross-308) broiler chicks, randomly divided into 7 groups by 50 chicks per group for 35 days. The groups were divided as follows: T1: infected experimentally with E. faecalis only, T2: treated with S. platensis, T3: infected experimentally with E. faecalis and treated with 2% S. platensis, T4: infected experimentally with E. faecalis and treated with probiotic, T5: infected experimentally with E. faecalis and treated with prebiotic, T6: infected experimentally with E. faecalis and treated with oxytetracycline. T7: control group without any addition. Weekly live body weight and weekly body weight gain were measured as well as weekly feed intake and feed conversion rate for broiler chickens were estimated. The current study proved that S. platensis algae added to drinking water (2%) in T2 and T3 groups had caused a significant increase (P<0.05) in the weekly live body weight and weekly body weight gain, Spirulina also caused a significant decrease (P<0.05) in weekly feed intake and feed conversion rate for broiler chickens. Therefore, S. platensis could be a suitable alternative to some feed additives such as probiotics, prebiotics, and antibiotics in addition to the ability of Spirulina to reduce the symptoms of E. faecalis. humans through the food chain (10). E. faecalis bacteria may cause important infection and diseases to humans, such as endocarditis, bacteremia, inflammation of the urinary tract and central nervous system infections (11,12).
When the use of antibiotics was banned in many countries of the world, it became necessary to search for feed additives of natural origin for poultry that would be safer and more acceptable for consumers (13). Phytogenic feed additives have been widely employed in the poultry industry to improve the health status and increase growth and productive performance (14).
Spirulina platensis (S. platensis) is a cyanobacteria (bluegreen algae), which is considered as a rich protein food in addition to many vitamins and minerals (15). S. platensis has antioxidant and anti-bacterial properties as well as enhancing the immune system (16). S. platensis algae is considered as one of the most promising diets in the development of the poultry industry, and future research work must be done to exploit it for the purpose of increasing production at the lowest economic cost (17).
The experiment aims to determine the effectiveness of nutritional Spirulina algae as a natural component on the production performance of broiler chickens.

Experimental Design
The experimental design of the study was based on the approval of the Public Health Department at the College of Veterinary Medicine, University of Baghdad, in its session held on February 25, 2019. All procedures carried out in this study were reviewed and accepted in compliance with the ethical principles of animal welfare by the Scientific Committee at the College of Veterinary Medicine, University of Bagdad.
This study was conducted in the poultry fields of the College of Veterinary Medicine, University of Baghdad for the period from November 9, 2019, to December 13, 2019. The experiment included a total of 350 one-day-old straight-Run broiler chicks (Ross-308), which were randomly divided into 7 groups with 50 chicks per group placed in 2×2 m 2 pens for 5 weeks.
The challenge test was pre-performed on 5 groups, each group consisted of 20 chicks (they were challenged with different concentrations of bacteria to choose the concentration that killed half of the experimental animals) to determine the LD50 of bacteria, which was 1×10 8 CFU/mL. Chicks of groups T3, T4, T5 and T6 were infected on the third day of their life, then the clinical symptoms were observed in the chicks in the second week of life (18). T1 = E. faecalis. only, T2= added S. platensis, T3 = E. faecalis. + S. platensis (2%), T4 = E. faecalis. + probiotic (DPP company, USA, contains minimum of 1 x 10 8 CFU/g total Lactobacillus acidophilus, L. casi, L. reuteri, and Bacillus subtillis 3.3 g/20 liters of drinking water), T5= E. faecalis. + prebiotic (produced by Biolink Company, UK, contains extract of beta-glucans as antioxidants and a group of vitamins 7.5 mL in 20 liters of clean drinking water), T6= E. faecalis. + oxytetracycline 2500 mg/L of drinking water, T7: control group without any addition.

Mean Body Weight (g)
The body weights were calculated weekly by weighing chicks individually at day one old and at the end of each week by sensitive balance. Mean body weight was calculated from the weight of all chicks divided on the number of chicks (19).

Weekly Mean Weight Gain (g)
The mean body weight gain (WG) for each group was calculated weekly by recording the weight gain at the beginning of the week and at the end depending on the following equation (20): Weekly WG = BW at end of week − BW at begining of week

Feed Intake
Feed intake (FI) was calculated weekly depending on weighing the remained feed at number of the dead chicks and the number of their feeding days. Feed intake of chicks was calculated according to the equation which was mentioned by (21) as follows: Where, W = quantity of FI through the week (g), L= number of live chicks fed through the week., D = numbers of dead chicks × number of their feeding days.

Feed Conversion Ratio
Feed conversion ratio (FCR)was measured weekly for each group up to the end of experiment. Measurement was done according to the equation below (19):

Statistical Analysis
Statistical Package of Social Sciences (SPSS) version 26 (Inc., Chicago, IL, USA) computer software was used for analysis of the results. The data were analyzed as one-way ANOVA, and significant differences between groups were assessed using Fisher's Least Significant Difference (LSD). Values with P≤0.05 were considered to indicate statistically significance (22). All results are expressed as the mean±SEM.

RESULTS AND DISCUSSION
The nutritional analysis of Spirulina algae for every 100 g is shown in Table 1.
The results showed significant differences in the body weight of chicks in the first week of the experiment, where group T2 recorded a significant increase in body weight over the control group (P<0.05), while the other groups recorded a significant decrease compared with the control group (P<0.05). Group T2 in all five weeks of the experiment recorded a significant increase over the control group (P<0.05). The other groups, on the contrary, recorded a decrease from the control group (P<0.05), this is also clearly shown in Table 2.
The results showed significant differences (P<0.05) between the treatment groups and the control group in weekly weight gain, where the weight gain for groups T2 and T7 was significantly more than the rest of the groups. The weight gain of the experimentally affected group T3 increased significantly (P<0.05) more than the affected groups T4, T5 and T6 as shown in Table 3. It was observed that there was a significant decrease in the amount of feed intake by the chicks in group T1 compared to the rest of the experiment groups in all the study weeks (P<0.05). While T2 recorded a significant increase in the proportion of feed intake at P<0.05. The increase in the feed intake for group T3 was more than for groups T4, T5, and T6 when comparing the experimentally infected groups as shown in Table 4.
The results of the current study recorded a significant increase in the feed conversion rate in groups T1 and T6 (P<0.05) more than the other groups. Whereas the group experimentally infected with pathogenic bacteria T3 recorded a significant decrease in F.C.R (P<0.05) when compared to the infected groups T4 and T5 as shown in Table 5.

DISCUSSION
Probiotics (Lactobacillus acidophilus, L. casi, L. reuteri and Bacillus subtillis) and prebiotics (contains extract of beta-glucans as antioxidants and a group of vitamins) work to stimulate the immune system of chicks and increase their ability to resist bacterial infections as well as stimulate the production of digestive enzymes in addition to containing vitamins that positively affect the health of birds (23).
Spirulina platensis is a multicellular, photosynthetic prokaryotic algae that contains a very high amount of proteins (55-70%) of the dry weight, vitamins and minerals (24,25) which play an essential and important role in increasing the productive performance of broiler chickens (17,26). It has been demonstrated by (27) that up to 10% of the total nutritional content from microalgae can be used safely as a partial diet substitute for traditional protein sources in poultry feeding. Spirulina in food increases the Lactobacillus population and enhances the absorption of vitamins (28).
The results of the current study showed that there was a significant increase at the level of P<0.05 in live body weight, as well as in the weekly weight gain for groups T2 and T3 (from the affected groups) during all weeks of the experiment compared with the control group. Group T3 was among the groups experimentally infected with E. faecalis and treated with the addition of 2% of S. platensis powder to chicks drinking water, this addition caused a significant increase in the growth of chicks and improved health status due to its high protein ratio including important amino acids present in Spirulina and antioxidants content. In addition to improving the digestive ability of poultry, Spirulina also helped in strengthening the immune system and reduced the need for antibiotics, medications, and multivitamin supplementation, this is in agreement with the results of (29, 30) who indicated the possibility of improving chicken immunity response and substituting Spirulina instead of antibiotics. These improvements may be because of the synergetic effect of the chemical components (total phenolic and flavonoid contents and total antioxidant) found in Spirulina; these chemical constituents had antioxidant action (31,32).
The current study showed a significant increase at the level of P<0.05 in feed intake in group T2 compared to control group, while there was a significant increase and a lesser percentage in the groups T3 and T4 in comparison with experimentally infected groups. On the other hand, the study indicated a significant decrease in the feed conversion rate at P<0.05 in group T2, as well as significant decrease in group T3 for infected groups at P <0.05. These results are in agreement with (29,33) who have also proven that adding Spirulina algae works to reduce food conversion ratio.
Overall, Adding of Spirulina platensis to drinking water at a percentage 2% led to a significant increase in the productive performance as well as improving the immunity