To determine whether an anti-Salmonella bacterium is involved in control of pathogen load in persistently infected cattle herds. 24 Holstein calves experimentally infected and 39 Holstein cows naturally infected with Salmonella spp. An Escherichia coli (designated as P8E5) that possessed anti-Salmonella activity was isolated from Salmonella-negative bovine feces obtained from a herd with endemic Salmonella infection. In vitro analysis involved enumerating Salmonella enterica serovar Typhimurium coincubated with E coli P8E5. In vivo analysis involved coadministration of Salmonella spp and E coli P8E5 or an E coli control strain to neonatal Holstein calves. Fecal samples were collected on multiple days after inoculation, and quantitative PCR assay was performed by use of Salmonella-specific primers. E coli P8E5 reduced viability of Salmonella spp in vitro. Shedding of Salmonella organisms was diminished in calves administered E coli P8E5, whereas the control strain of E coli had no effect on shedding of Salmonella organisms. In this study, an E coli strain was identified that possessed bacteriocin-like activity and was able to decrease viability of Salmonella organisms in vitro and in vivo. Therefore, it is possible that this organism could be representative of native microbiota that dampen Salmonella spp in persistently infected cattle herds.

An effort to demonstrate the mechanism of homeostatic alteration of high-producing cows at the period of increasing milking capacity and peculiar features of its changing in the conditions of introduction into cattle diets of carbohydrate containing and carbohydrate compensative additives was realized in the conditions of the Republic of Belarus. In course of the experiment there were used white-and-black breed cows of 3-4 lactations with body weight of 700 kg and milk yield over the last lactation of 7000-8000 kg of milk. Experimental cows in two weeks before the supposed calving were administrated with 50 ml of propylene glycol, 6 g of niacin and 50 ml of glycerin; and in course of 60 days after calving the administration of the additives was realized in doses of 125 ml; 6 g; 50 ml, respectively. Research results showed that application of mentioned above additives rendered the positive effect on cow liver that was proved by the improved hemic function of experimental cows: increasing of quantity of erythrocytes, hemoglobin, and hematocrit