AbstractŠabatková J., I. kumprecht, P. Zobač, P. Suchý, B. Čermák: The Probiotic BioPlus 2B as an Alternative to Antibiotics in Diets for Broiler Chickens. Acta Vet. Brno 2008, 77: 569-574.The main aim of this work was to compare the stimulatory effect of the probiotic BioPlus 2B with that of the antibiotic Avilamycin on the growth and feed conversion in broiler chickens. The growth experiment was performed with one-day-old sexed female and male rOSS 308 hybrid chickens (240 females and 240 males) placed in 24 cages. They were fed the starter diet from Day 1 to Day 14, followed by the grower from Day 15 to Day 35 and the finisher in a loose form from Day 36 to Day 42. Diets and water were available ad libitum. The control slaughter of chickens was performed at the end of the experiment (Day 42) to determine the slaughter yield and the content of inner fat in the final product. The supplementation of the diets used in broiler prefattening and fattening with BioPlus 2B resulted in a 4-5% weight gain (P < 0.01) and in a 4-5% improvement (P < 0.01) in feed conversion. Mean slaughter yields were higher (P < 0.01) in chickens fed diets containing probiotic and antibiotic products compared to the group of chickens fed the diet not supplemented with a growth promotor. The weight of inner fat in chickens under study did not differ significantly either between experimental groups or between sexes.

Poultry diets contain mainly feeds of vegetable origin, such as cereal grains, extracted oilseed meals and cereal by-products. These feed ingredients provide a high proportion of total phosphorus (P), but only 20 to 30% of this P are available to the birds, because it is bound in phytate form. Such non-utilized phytate P is transferred with poultry excreta to soil and water and a�er the release it causes adverse effects on the environment. Enzymatic hydrolysis of phytate by the specific enzyme, phytase, results in release and improved utilization of phytate-bound P in the digestive tract, thus leading to a reduced P ABSTRACT: Two growth trials and a short-term metabolism trial were conducted in broiler chickens in the period of 22 to 42 days of age in order to evaluate the effects of two dietary levels of L-lactic acid (1.03 or 2.06 g/kg) and microbial 6-phytase (750 U/kg), added either separately or in combination, on growth rate, feed conversion, dressing percentage and utilization of selected nutrients. In the first growth trial, six different dietary treatments were added to a basal grower diet containing 19.4% crude protein and a reduced level of dietary phosphorus (P) (5.9 g total and 2.9 g non-phytate P per kg). Single administration of L-lactic acid did not show any positive effect on the growth rate or feed conversion. In contrast, phytase addition to a low-P grower diet resulted in the increased final weight of birds and higher feed conversion. This beneficial effect was markedly stronger when the microbial phytase was added to the diets containing L-lactic acid. Based on two-factor analysis of variance, microbial phytase significantly increased the mean final weight by 6.5% (P < 0.01) and significantly improved feed conversion from 1.877 to 1.829 (P < 0.05).In the second growth trial, the same six dietary treatments were added to a basal diet containing a standard level of dietary P (6.7 g total and 4.0 g non-phytate P per kg), but the level of crude protein was reduced to 17.0%. L-lactic acid alone did not show any positive effects on performance. Phytase supplementation alone resulted in numerical improvement of the final weight (+1.1-2.4%), but a higher effect was observed in the diets containing L-lactic acid. In agreement with the reduced final weights of broilers fed the low-protein diets, markedly higher values of feed/gain ratio were noted. In the metabolism trial, selected dietary treatments were involved to evaluate the effects of L-lactic acid and microbial phytase, added either separately or in combination, on the digestibility of nitrogen (N) and fat as well as on the retention and excretion of N and P. Apparent digestibility of N and fat in the low-P diets was not affected by dietary treatments. Retention and utilization of N were numerically higher in all treatments fed low-P diets when compared to the treatment fed a standard diet, but the differences were not significant. Retention of P was numerically higher in all treatments fed low-P diets. When compared to the standard diet, the c...