Effect of Probiotic Inclusion in the Diet of Broiler Chickens on Performance , Feed Efficiency and Carcass Quality

An experiment was conducted with three hundred and twenty broiler chickens to evaluate the influence of supplementation of probiotic on growth, microbiological status and carcass quality of chickens. The probiotic contained similar proportions of six strains of variable organisms namely Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium bifidum, Aspergillus oryzae, Streptococcus faecium and Torulopsis sps and was fed at 100 mg/kg diet. The body weight and feed conversion of probiotic fed groups were superior (p<0.05) compared to the control group in the 4, 5 and 6 weeks. The chickens fed the diet with probiotic had lower (p<0.05) numbers of coliforms and Campylobacter than chickens fed the control diet. All chickens’ carcasses on the control diet were positive for Salmonella while only 16 of the 40 carcasses were positive from chickens fed diets containing probiotic. The leg and breast meat of probiotic fed chickens were higher (p<0.05) in moisture, protein and ash, and lower in fat as compared to the leg and breast meat of control chickens. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 8 : 1153-1156)


INTRODUCTION
The extensive uses of antibiotics in animal farms to promote growth rate, increasing feed efficiency and prevention of intestinal infections have led to the development of antibiotic-resistant bacteria in the gastrointestinal tract and drug residuals in meat.The use of probiotics in order to competitively exclude the colonization of intestinal pathogens has been proposed for poultry, specially after some countries banned certain antibiotics being frequently included in rations as growth promoters.Probiotics are defined as viable microorganisms (bacteria or yeasts) that exhibit a beneficial effect on the health of the host when they are ingested (Salminen et al., 1998).
Salmonella and campylobacter (jejuni) have often been considered responsible for human gastroenteritis and poultry have often been implicated as source of these human infections.
Intestinal colonization of salmonella, campylobacter and coliforms in the chickens play a role in carcasses contamination at slaughter, thus, reducing salmonella, campylobacter and coliforms colonization in chickens may potentially reduce incidence of infections in humans.Maruta et al. (1996) reported that administering probiotic (Bacillus subtilis C -3102) to chickens reduced the level and incidence of campylobacter and salmonella in the intestinal tract of broilers, however, scanty information are available on the aspects of poultry meat quality influenced by probiotic feeding.The present study was conducted to study the effect of probiotic feeding on performance, microbiological status and carcass quality of broiler chickens.

MATERIALS AND METHODS
Three hundred and twenty day old commercial broiler chickens (Ross), were weighed and distributed randomly into two groups of 160 chickens.Subsequently, the chickens in each group were distributed to 20 replicates of eight chickens and raised on wood shavings litter.
The chickens were allowed to have free access to a starter diet during the first 3 wks and then to a finisher diet during the second 3 wks (Table 1) and free access to water.The control group was fed a basal diet, whereas the experimental group was fed the same basal diet but supplemented with probiotic provide 100 mg per kg diet.The probiotic used in the experiment contained similar proportion of six strains of variable organisms namely Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium bifidum, Aspergillus oryzae, Streptococcus faecium and Torulopsis sps.The room temperature with continuous lighting was maintained at 34°C initially, and then reduced by 3°C/wk until it reached 21°C, at which temperature the room was maintained for the rest of the feeding period.Body weight gain and feed consumption were monitored weekly and feed conversion rate was calculated as feed consumed per unit of weight gain.
At the end of the sixth week, 40 chickens from each

Effect of Probiotic Inclusion in the Diet of Broiler Chickens on Performance, Feed Efficiency and Carcass Quality
group were randomly selected and slaughtered.Proximate composition (AOAC, 1994) and microbiological status of carcasses were determined.Chickens were removed from feed, but not water, for 8 h prior to slaughter, chickens on the control feed were first.After these chickens were processed, scald water was changed, all equipment cleaned and sanitized using a commercial sanitizer, and the treated chickens were then processed.Feed withdrawal times were staggered to account for differences between processing intervals.Pre-chilled carcasses were sampled using the whole carcasses rinse technique of Cox et al. (1983) modified to 400 ml BPD rinse solution.Each sample rinse was evaluated for salmonella incidence (positive/total), coliforms and campylobacter counts by approved methods (FDA, 1992).The data were evaluated by using Student , s test to compare results for control and experimental groups.probability was based on p<0.05.

Performance
The results obtained of chickens performance (Table 2) showed that the live weight of the group receiving probiotic on the 4 th , 5 th and 6 th weeks (respectively; 878 g, 1,300 g and 1,700 g), was higher (p<0.05)than control.No differences were observed in feed intake between groups.
The feed conversion rate (FCR) of the probiotic fed group was superior (p<0.05)compared to the control group on 4 th , 5 th and 6 th weeks.
The data suggest that there is a lag phase of 21 d before the effects of the probiotic preparation are seen.Mohan et al. (1996) also stated that the use of probiotic in feed had a beneficial effect on body weight gain of broiler chicks from 4 th to 6 th week of age.Other studies also report favorable response of inclusion of probiotic in poultry diets.Fritts et al. (2000) noted that inclusion of calsporin (Bacillus subtilis C-3102) in broiler diets resulted in a significant improvement in 42 day body weight and feed conversion during the 21 to 42 d period.Jin et al. (1996) found that inclusion of probiotic (Lactobacilli and Bacillus subtilis) in diet stimulated favorable microbial balance in gut and consequently improved feed efficiency and growth performance in bloilers.Chiang and Hsieh (1995) reported that broilers fed probiotic-supplemented diet had better weight gain and feed efficiency when compared to the broilers fed the unsupplemented diet.

Mortality
The cumulative mortality of chickens on the experimental was 1.8 per cent while 5 per cent of the control group chickens was the case.Cmiljanic et al. (2001) also noted similar findings.

Composition of leg and breast
The mean values for carcass and proximate composition (Moisture %, Protein % and Ash %) of leg and breast meat (Table 3) increased (p<0.05) in probiotic fed chickens, whereas, the fat % of leg and breast meat was lower (p<0.05) in probiotic fed chickens.This indicates a better retention of minerals especially calcium, phosphorus, nitrogen and improved protein efficiency ratio (Nahashon et al., 1992(Nahashon et al., , 1994;;Mohan et al., 1996;Kumprecht and Zobac, 1998) in probiotic fed birds as compared to control birds.Pietras (2001) also reported meat of chickens given probiotic (Lactobacillus acidophilus and streptococcus faecium bacteria) on the whole rearing period had significantly higher protein content, while crude fat and total cholesterol contents tended to decrease.Endo and Nakano (1999) reported that addition probiotic included species of Lactobacillus, Streptococcus, Clostridium, Saccharomyces and Candida to broilers diets, decreased cholesterol concentration in thigh meat and increased linolenic acid and unsaturated fatty acid / saturated fatty acid ratio in pectoral and thigh meat.In contrast, Joy and Samuel (1997) noted that inclusion of Lactobacillus sporogenes in broiler diets did not influence carcass protein, carcass fat and fat pad thickness.

CONCLUSIONS
The supplementation of probiotic to the diet significantly improved the live weight and feed conversion rate on 4 th , 5 th , 6 th weeks indicates a lag time and the chickens carcasses fed the diet with probiotic had lower numbers of coliforms and compylobacter.The leg and breast meat of probiotic fed chickens were higher in moisture, protein, ash and lower fat per cent as compared to the leg and breast meat of control chickens.

Table 2 .
Effect of probiotic on performance of chickens

Table 3 .
Effect of probiotic on microbial status of carcasses meat

Table 4 .
Effect of probiotic on proximat composition of leg andMeans in the same row with no common superscript differ significantly (p<0.05).