European field trials
After introduction within the European market several commercial (field) trials were performed in cooperation with feed manufacturers or integrators. Several of these trials are permitted to publish and an overview of these trials is shown in Table 2 (feed conversion corrected to 1500 grams body weight; FCRc1500) and 3 (average daily gain; ADG). Four trials were performed in The Netherlands. Due to practical implications for some of these trials, control parameters were obtained from historical data. In some of the trials Bacillus subtilis C-3102 had to be supplied on top of other feed additives such as medium chain fatty acids or essential oils, in these cases both control group as the Bacillus subtilis treated groups were fed with these additives. In one Dutch trial, two stables of birds fed on Bacillus subtilis were compared to one control stable in which the results between stables differed very much, these are reported separately. Two trials were performed in France, in both these trials the control group was fed with a positive control diet containing essential oils, whereas the other group was fed on Bacillus subtilis without essential oils. In these trials Bacillus subtilis clearly outperformed essential oils. One of these trials consisted of a large field trial with 60 different poultry farms, of which 30 were supplied with diets containing essential oils and the other 30 received Bacillus subtilis, totalling up to 1.500.000 broilers in the complete trial. Overall results in this trial showed that Bacillus subtilis improved economical index by more than 2% outperforming essential oils. Within the UK a trial on a commercial farm took place. Compared to the other trials ADG seems very high and FCRc1500 grams fairly low. The reason for this is the high final body weights, birds were slaughtered at an age of 48 days with final weights of 3.266 kg and FCR of 1.939 for Bacillus subtilis fed birds versus 3.228 kg body weight and 1.986 FCR for control treatment. The trial performed in Poland had small numbers of birds; this contained a pen caged trial in experimental facilities. On average over 8 trials an improvement of 2.3% on FCRc1500 was seen. From the same trials results are given for ADG, which improved on average with 2.7%. These trials were all performed with inclusion rates of Bacillus subtilis*of 50 ppm (50 grams/Mt feed).
Experiences from USA
Whereas European registration was obtained late 2006, Bacillus subtilis* has had a long history of use in animal feed elsewhere in the world. Starting with commercial sales in the Japanese feed market as early as 1987. Later markets have developed in other Asian countries, South and Latin America and in the United States. In the last years many trials were performed and published within the United States. In table 4 an overview reported by Hooge (2008b) is given, in which a meta-analysis is described over data from 9 different trials to measure the overall effects of Bacillus subtilis inclusion. These trials were performed with a dosage as low as 30 ppm. None of the diets contained antimicrobial growth promoters. Trials performed by Fritts et al (2000)10 were performed at University of Arkansas, Poultry Department. The trial was repeated and results on body weight and feed conversion were either numerically or significantly improved. Besides these effects, measurements on carcass microbiology were performed in which significant reductions of aerobic plate counts, coliforms (non-E. coli) and campylobacter were observed. Results of three broiler trials performed at a commercial integrator facility were reported29 and showed improvements in performance parameters. Unpublished trial works (2007) 22 were performed at Virgina Diversified Research Corp. In these trials the birds were infected with Salmonella typhimurium. In 2004 also a trial with multi-stressed birds was performed and reported by Hooge22. Meta-analysis was done both including as well as excluding this specific trial with multi-stressed birds. Overall significant improvement in body weight as well as improved FCR was found.
Bacillus subtilis C-3102* has a long history of usage across the world. Latest insights show that under practical conditions within Europe, similar results on performance parameters are obtained as were found under more conditioned environments in research institutes for registration trials. Bacillus subtilis can be used effectively to improve broiler performance. Consistent results are shown with different inclusion rates ranging from 30 ppm to 100 ppm, but clearly results improve with higher dosages of Bacillus subtilis. Positive results were obtained in birds growing under optimal conditions, for example for European registration dossier at 50 ppm birds reached a final weight of 2.641 kg in 42 days with FCRc1500 of 1.394. But also under suboptimal conditions positive results were obtained, e.g. multi-stressed birds trial reported by Hooge. In the field trial with 60 farms in France and totalling 1,500,000 broilers, farms were also divided in groups based on historical production to see if differences between high and low producing farms occurred. This trial clearly showed that overall birds fed on Bacillus subtilis improved economical index by more than 2%, but best results were obtained in low producing farms. Therefore using Bacillus subtilis as a feed additive can be seen as an insurance. Positive effects on best performing farms can be expected giving good returns on investment. For less producing farms, expected improvements due to Bacillus subtilis are even higher, which will eventually also lead to more uniform results between farms. Although improved growth and feed conversion should be considered as most important effects of using Bacillus subtilis, effects of reducing pathogenic bacteria should definitely not be denied. Improved microbial balance might not only lead to positive effects within one cycle, but trials running for as long as four years (26 cycles), showed consequent improvement by the use of Bacillus subtilis, which could be explained by a carry-over effect due to improved microbial balance in the stables. Reductions of several pathogenic bacteria have not only been found in intestinal microflora, but were also reported to lead to less microbial pollution of broiler carcasses9. Regarding food borne diseases related to chicken meat, in the past great effort has been made on reducing Salmonella, which is still not tackled in all countries. But for the near future also other pathogenic bacteria, such as Campylobacter, will be more and more important. Bacillus subtilis could be a solution assisting in obtaining goals set for Salmonella reduction. For Campylobacter reduction indications are present that Bacillus subtilis as feed additive could be interesting as well, although more research in that area is wished for.
References are available on request