Evaluation of effectiveness of probiotic feed additive in experiment on laying hens

The paper represents the impact of a probiotic feed supplement on the clinical and biochemical parameters of laying hens in an amateur private farm setting for organic product production. The experiment was conducted on laying hens aged 160 days (n=200) of the Leghorn breed of egg production, floor-housed on deep litter, weighing 1500-1600 g. Before the experiment, the birds were categorised into groups of 100 based on the principle of analogues. Following a 14-day acclimatisation period, a probiotic feed additive (L. casei, L. delbrueckii, B. licheniformis, B. subtilis at a concentration of 10^6 CFU/mL each) was incorporated into the diet of the experimental group in addition to the complete diet at a dosage of 1.0 cm³ per kg of feed for 30 days. The control group of poultry got a full meal according to the standards for laying hens. Before administering the medications, and on 15th and 30th days post-initiation of probiotic feeding, the birds were slaughted under preparatory inhalation chloroform anaesthesia (n=10). Blood samples, together with tissue and organ specimens, were collected for microbiological and biochemical analyses. The results suggest that the use of probiotic feed additives did not significantly alter the quantitative composition of indicator microflora. However, there was a tendency (on the 30th day of the experiment) to increase the content of Lactobacillus spp. and Bacillus spp. by 14.6% and 8.7%, respectively; a tendency to decrease the content of potential pathogenic microorganisms was also detected - Staphylococcus spp. 19.5%, Candida spp. 15.2%, Enterococcus spp. 1.47%, E. coli 13.0%. Administration of probiotics to laying hens resulted in a significant increase in serum immunoglobulin G levels throughout the experiment, with the peak IgG concentration in the experimental group observed on the 30th day, demonstrating an increase of 11.3% (p˂0.05). On the 30th day of the trial, immunoglobulin M and A levels rose by 14.6% and 10.2% (p˂0.05), respectively, while circulating immune complexes increased by 26.3%. The nonspecific resistance indicators in the experimental group of hens exhibited an upward trend: the phagocytic index, bactericidal activity, and lysozyme activity rose by 11.5%, 12.0%, and 13.9%, respectively. The clinical and biochemical findings of the trial indicate that the suggested composition of probiotic bacteria is non-harmful to laying hens. The observational data demonstrate no adverse effect on egg production.