Evaluation of the Potential for Direct-Fed Microbials to Enhance Utilization of Phosphorus in Broiler Chickens

摘要

Feed accounts for about 60--68% of the total cost of poultry production. Chicken cannot efficiently absorb organic or phytin-bound phosphorus, thus about 70--80% of dietary or plant based phosphorus is excreted in the manure of broiler chickens. The goal of this research was to identify microbes with the potential to improve utilization of a plant source of phosphorus in the gastrointestinal tract (GIT) of broilers.;A total of 8,082 sequences were obtained using a metagenomic approach, with 61% of those sequences representing 5,030 species of various bacterial organisms. The highest proportion of bacteria was Massilia which represented 46% of the total dominant microbial population, Bacteroides (9%), Streptomyces (6%), Bacillus (6%), and 18 different species each constituting less than 5% of these dominant microbes. Three microbes Lactobacillus, Enterococcus, and Bifidobacterium (LEB) with the potential to hydrolyze free phosphorus were isolated and characterized. The isolated microorganisms maintained the ability to grow at all the different pH ranges (1--5), and bile concentrations of 0--3.5%. Also, the ability of the bacteria to hydrolyze free phosphorus was evaluated in-vitro. The effect of the three bacteria on performance of 400 day- old Ross broilers was evaluated during an eight-week period. The results indicated that broiler chickens fed probiotic bacteria at the rate of 100 or 150 mg/kg of feed consumed 12.0% and 17.8% more feed, respectively, and increased body weight gain by 5.9% and 8.4%, respectively, when compared with the control birds. Broiler chickens fed diets containing the probiotics at 100 or 150 mg/kg of feed retained 15.2% and 17.5% of phosphorus as against 8.6 % for the birds on the diets without the bacteria. Except for birds on dietary treatment LEB-150, which had a higher mortality (7.3%), the remaining six dietary treatments had mortality ranging from 2.0--3.3% which was less than that of the controls birds (4.5%).