Effects of feeding double strain spores as a probiotics with or without antibiotic growth promoter on broiler performance

The objectives of the study were to investigate the effects of feeding probiotics supplemented diets with or without antibiotic growth promoter on growth performance, carcass characteristics and costeffectiveness of commercial broilers. A gable type open sided house was used for experimental purpose. Three hundred twenty Cobb-500 oneday-old straight run chicks were randomly distributed into four dietary groups having five replications. The number of birds in each replication was 16. Four diets were considered: diet 1: control; diet 2: antibiotic growth promoter (AGP) at a dose of 15g/100kg; diet 3: probiotics (PB) at a dose of 250g/100kg and diet 4: AGP plus PB (15g/100kg+250g/100kg). Birds were vaccinated against common viral diseases as a part of disease prevention program. The records were kept of body weight, feed intake and mortality while weight gain, feed conversion ratio (FCR) and survivability were calculated. Both performance and carcass yield were statistically analyzed for interpretation. Broiler chicks that received PB showed significant improvement in performance (P<0.01) over control with respect to body weight gain, FCR, carcass yield and cost-effectiveness. Feeding AGP alone had comparatively less weight gain, net profit and almost similar feed efficiency compared with PB and AGP+PB groups but its performance was much better than that of control group. The PB fed group showed better meat yield traits. The PB alone group was also more cost effective over control. Feeding PB may be practiced in broiler diet as an alternative to AGP.


Introduction
The term probiotics derived from Greek word "pro bios" which means "in favor of life" (Coppola and Turnes, 2004). According to the definition by FAO/WHO, probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host (Fuller et al., 1989). Currently, probiotics seem to be good alternatives to the use of antibiotics as growth promoters (Tomasik and Tomasik, 2003), which have been used on poultry and livestock in an attempt to increase mean weight gain (Tannock et al., 1999). Probiotics are responsible for the production of vitamin B complex and digestive enzymes, and for stimulation of intestinal immunity, increasing protection against toxins produced by pathogenic microorganisms (Alexopoulos et al., 2004). Several microorganisms have been considered or used as probiotics including fungi particularly mushroom and yeast, bacteria and mixed cultures comprising of various microbes. In broiler nutrition, probiotic species such as Lactobacillus, Streptococcus, Bacillus, Bifidobacterium, Enterococcus, Aspergillus, Candida, and Saccharomyces are widely used to prevent poultry pathogens and diseases and improve broiler's growth performance (Timmerman et. al, 2006;Mountzouris et al., 2007;Awad et al., 2009). Bacteria are more commonly reported as probiotics than fungi. Two genera of bacteria are mostly reported including lactic acid bacteria of the genus Lactobacllus (Sato et. al., 2009;Taheri et. al., 2009) and Bifodobacteria (Patterson and Burkholder, 2003). A widely used probiotics strain, combination of Bacillus subtilis and Bacilluslicheniformis are considered one of the most health-boosting bacteria because they have demonstrated a positive effect in breast, thigh, drumstick, wing and back. Finally, every cut-up part was weighed and recorded for male and female broiler of all replications.

Methods of cost benefit analysis
Cost of production was calculated based on some specific items such as chicks, feed, vaccine, test ingredients and casual labor. Cost of heads was widely varied due to fluctuating market price. The total production cost per bird and per kg bird was calculated. The additional cost incurred for test ingredients was also taken into consideration for calculating cost benefit. The profit or loss was calculated by deducting the production cost per kg broiler and market price of per kg broiler.

Data collection
All data of body weight, feed consumption, feed conversion ratio and survivability were recorded on days 7, 14, 21, 28 and 35. At the end of the trial, carcass measurements data were also collected. During the experimental period, the temperature and relative humidity of the experimental house were recorded four times in a day (6.00 AM, 2.00 PM, 6.00 PM, 11.00 PM) with the help of an automatic thermo-hygrometer. At the end of the experiment the dressing percentage of the broiler was calculated as the dressed weight divided by final body weight of the broiler.

Data analysis
Data of body weight, body weight gain, feed consumption, feed conversion ratio (FCR), livability and edible meat characteristics of male and female broilers were subjected to analysis of variance (ANOVA) in a completely randomized design (CRD) employing SAS (2008, version 9.1) statistical computer package programme.

Growth performance
Productive performance of broiler receiving feed supplemented with probiotics or antibiotic or their combination are shown in Figure. At the end of 35 days of age, the highest FLW (2014.50g/b) was found in broilers fed with both antibiotic growth promoter and probiotics (AGP+PB). This was followed by broiler belonging to probiotics (1913.06g/b), antibiotic (1848.25g/b) and control group (1707.20g/b) respectively. However, broiler receiving either probiotics or antibiotic or both weighed significantly higher than that of control (P<0.01). The difference with regard to live weight and live weight gain among AGP, PB and AGP + PB were also significant (P<0.01) ( Figure 1). The average FI pattern of the broilers of different treatment groups which was differed significantly (P<0.01). Highest amount of feed was consumed by AGP+PB fed group and lowest amount of feed was consumed by AGP fed group. Both AGP and PB containing groups consumed similar amounts of feed and there was no significant difference between them but they are significantly (P<0.01) differed from control and AGP+PB supplemented diet ( Figure 2). Differences in cumulative feed conversion ratio of broiler of different dietary groups differed significantly (P<0.01). The lowest value was obtained for birds that received probiotics ( Figure 3). PB, AGP+PB and AGP supplemented groups showed almost similar but improved efficiency that differed from control group (P<0.01). AGP, PB and AGP+PB receiving groups had 100% survivability while the survivability of the control group was 97.33%.

Edible meat yield characteristics
Meat yield data are presented in Table 3. The analyzed data in the table indicates that the treatments had no significant effect (P>0.05) on live weight, dressing percentage, thigh, wing and heart weight of the experimental birds. On the other hand, highly significant (P<0.01) differences were obtained in breast meat, abdominal fat content and head weight among different treatments. Highest and lowest breast meat weight was recorded in PB and control group respectively. There was a tendency of increased breast meat content in both PB and AGP+PB groups which had highly significant (P<0.01) effect compared to control group. Higher abdominal fat was determined in control group while lower was in PB group. Also, significant differences (P<0.05) were found on liver, drumstick, and gizzard weight among the dietary groups.

Cost benefit analysis
The cost benefit analysis of feeding AGP and PB is shown in Table 4. The additional cost was incurred 0.37, 0.114 and 0.484 BDT (Bangladeshi Taka) for AGP, PB and AGP+PB fed group respectively. For per bird, total cost of production was maximum (@BDT 173.19) in AGP+PB group and minimum (@ BDT 164.27) in AGP supplemented group. The total cost of production for per kg body weight was highest (@ BDT 97.54) in control group and lowest (@ BDT 85.75) in AGP+PB group. In terms of per bird and per kg body weight, the profit was maximum in AGP+PB treated group. The supplementation of AGP+PB fed group was more profitable over the control group.

Discussion
The results obtained in this study are consistence with the findings of Bai et al. (2013). They compared the probiotics treated group with a control, an antibiotic and(antibiotic+ probiotics) treated group and found that antibiotic, probiotics and their combination improved average body weight in broilers during growing period (21-42days) compared with control. Other author Sabatkova et al. (2008) compared the efficacy of Avilamycin (AGP) and probiotics (Bacillus subtilis and B. licheniformis) to investigate the performance and slaughter yields. They finally reported that the supplementation of probiotics improved 4-5% weight gain (P < 0.01). Ahmad and Taghi (2006) also found that body weight gain of broiler, fed supplemented with probiotics (Bacillus subtilis and B. licheniformis) were significantly higher during the grower phase (21-42 days) than broiler fed the control diets. Not only that, the finding of this trial is also agreed with Salim et al.  (2006).They also reported that supplementation of probiotics in broiler feed improved body weight and body weight gain significantly. In this study, both the live weight and live weight gain of the broiler of both PB and AGP+PB groups are very close to the Cobb500 commercial broiler's productive performance (Cobb 500 Management Guide, 2010). Comparatively lower feed consumption in probiotics supplemented group was in agreement with the results of Shim et al. (2012). They found that birds fed 10 mg/kg avilamycin consumed more (p<0.05) feed during the finisher and overall periods than birds fed diets containing probiotics without avilamycin while others have found non-significant variation in feed intake between control and probiotics group (Faria et al. 2009;Rada et al., 2013). But the result was consistence with Eseceli and Demir (2010) and Erdogan (2007). They also reported that supplementation of probiotics decreased feed intake significantly (P<0.05) compared to control group. In the present study feed intake of probiotics treated group was significantly lower (P<0.01) than control and AGP+PB treated groups.The significant effect of probiotic on feed conversion ratio (FCR) of broiler was in close agreement with Shim et al. (2012); Ashayerizadeh et al. (2009);Sabatkova et al. (2008) andO'Dea et al. (2006). They found that supplementing with Bacillus subtilis and B. licheniformis improved feed conversion efficiency in broiler. Salim et al. (2013) also reported the lowest feed conversion ratio (FCR) with probiotic compared to antibiotic and control group respectively. This result was almost similar to the present study. Positive effect on livability was observed in this study by feeding probiotic to broiler which was consistence with the observation of Knap et al. (2011) and Zhang RenYi (2010). They also found that feeding probiotics (Bacillus spp.) supplemented diet effectively enhance the resistance of broiler and protect them against the negative growth effects and mortality. But Faria et al. (2009) and Eseceli and Demir (2010) revealed that there was no statistically significant difference (P>0.01) in the livability of birds reared with or without adding probiotics in diet.
The results of present study clearly indicate the effect of dietary probiotics towards some important meat yield characteristics of broiler. This result was particularly similar to the result of Molnar et al. (2013) who reported that Bacillus spp. supplemented group had significantly higher (P<0.05) breast yield and lower thigh meat yield than the control group where the breast weight of this experiment was lowest for control and highest for PB supplemented group respectively. Luiz et al. (2012) compared the efficacy of antibiotic with probiotics in meat yield characteristics of broiler and finally reported that probiotics group have lower abdominal fat content compared to antibiotic and control group respectively which is supported recent findings. The result of this study was also particularly consistent with the findings of Xiaolu et al. (2012), who reported that the supplementation of Bacillus licheniformis resulted in increased protein and free amino acid contents, and decreased fat content in chicken breast fillet (P<0.05). Moreira et al. (2001) found no significant difference in carcass yield between birds that were fed probiotic and control diet. However, the result of this study agreed well with the findings of Lei et al. (2013) and Sabatkova et al. (2008). The present study clearly indicates that feeding of AGP, PB and their combination had beneficial effect on the profitability of broiler. The combination of AGP+PB provided highest profit which is almost similar to PB group but higher than the control and AGP group. This result was particularly similar to the results of Roy et al (2013) who reported that feeding probiotics to broiler was either similar or more profitable than combination of AGP+PB while better than AGP alone.

Conclusions
The AGP+PB and PB containing diet improved growth performance over AGP and control group.The PB containing diet improved breast meat, drumstick meat and reduced abdominal fat percentage whereas, control group had highest abdominal fat percentage. The profit per kg of body weight was higher in PB group compared to control.