The aim of this study was to investigate the effectiveness of a new experimental complex in diets of lactating cows. The scientific and economic experiments were conducted in conditions of a large industrial complex for milk production from cows of Holstein breed (Russia). Four groups of Holstein cows (third calving), 20 animals each, were formed to conduct an analog method research. The cows in the control group were fed with a basal diet. The cows in other groups were fed with the experimental complex at various doses. All indices have been determined by wide-known methods, such as extracting, capillary electrophoresis, chromatography, quantitative titrimetry, atomic-emission spectrometry and others. To synthesize milk, the organisms of cows in experimental groups spent more digested nitrogen on the average by 14.85%; nitrogen excreted from the bodies of cows with urine was less on average by 4.13%. The increase in milk production averaged 3.8%. In comparison with the control group, the cows of experimental groups had higher content of dry matter in milk on average by 0.4%; fat by 0.17%; and protein by 0.1% (including α-lactalbumin by 31.8% and β-lactoglobulin by 36.6%). The milk protein in experimental groups contained more essential amino acids on average by 9.83%, and the milk fat contained more unsaturated fatty acids on average by 1.46%. The milk in experimental groups was noted for a high content of vitamins (on average by 16.3%, compared with the control group), in particular B2 by 10.8%, B9 by 28.6% and D3 by 39.8%. In addition, the weight fraction of trace elements in milk has been found to increase, i.e., calcium by 17.3%, iodine by 36.4%, potassium by 20.6%, magnesium by 18.5%, manganese by 66.7%, phosphorus by 20.3% and silicon by 54.2%. The increase in the milk productivity of cows and higher fat content in milk made it possible to increase the sale profit of 1 ton of milk on average by 12% and increase the level of profitability of production by 6.5%. The study performed has reliably proved that the proposed premix promoted nutrient availability and digestibility, improved digestibility of feeds and their effective consumption, improved blood hematology, increased milk production and improved the milk composition, which led to an increase in the profitability of production. Manuscript profile

The article presents the data on a comparative research study of the beef production of Kalmyk steers of compact (Group I), medium (Group II) and tall (Group III) body types. It has been found that the steers of a tall body type had higher pre-slaughter weight at the age of 16 months than steers of compact and medium types by 24.7 and 12.1 kg, respectively; the weight of hot carcasses by 15.9 and 7.6 kg; and the carcass yield was higher by 0.5 and 0.2%. The slaughter yield of steers varied from 58.50 (Group I) to 58.69% (Group III). Boning showed that tall youngsters had higher flesh weight in carcasses by 7.05 and 3.61% compared to their analogs of compact and medium types. The average flesh sample from animals of a tall type contained more protein than their analogs by 0.91 and 0.86%, respectively. The fat content in carcass flesh from steers of compact type was higher than from medium and tall steers by 1.05 and 2.56%, respectively. The longissimus dorsimuscle of tall steers contained more essential amino acid of tryptophan and less non-essential amino acid of hydroxyproline. Furthermore, a tendency of higher values of moisture-retaining ability of meat from steers of a compact type has been revealed. Organoleptic characteristics of meat from all experimental steers differed insignificantly. Manuscript profile