Effect of probiotic feed additive on physiological and biochemical parameters of horses

. Studies were conducted to study the effect of the feed additive ProVetin on the physiological and biochemical parameters of horses. The beneficial effect of the feed additive on the hematological and biochemical profile of the blood of horses was noted. Depending on the dose of the feed additive, the activation of the body's defense mechanisms and energy metabolism is established. In the group of animals receiving a feed additive at a dose of 20 g per head, 45 days after the start of administration, an increase in the level of hemoglobin and erythrocytes relative to the initial level was noted – by 1.6% (142.4 ±13.9 g / l, P < 0.05) and 6.9% (9.3± 0.8 x1012 / l, P < 0.05) accordingly. In horses treated with ProVetin at a dose of 30 g per head, after 1.5 months, hemoglobin increased by 1% (146.9±12.2 g/l, P < 0.05), the number of red blood cells by 2.1% (9.0±1.4x1012/l), total protein by 16% (76.6±6.0 g/ll, P ≤ 0.05), albumins by 19% (38.4±2.6 g/l, P ≤ 0.05) .


Introduction
To date, the development of horse breeding is becoming increasingly important.This industry is an important reserve in the production of environmentally friendly products, mainly for children's and dietary nutrition.Horse meat, unlike the meat of other animals, contains little cholesterol, which is one of the factors determining its dietary value [1][2][3].
Feeding has a significant impact on the productivity of animals.Inadequate feeding is the main reason for the decline in productivity and efficiency of animal husbandry.The manifestation of the genetic potential of productivity depends on the level and type of feeding, its usefulness, which determines the growth energy, live weight and size of the animal, its exterior and physique, quantitative and qualitative indicators of productivity [4][5][6][7][8][9].Therefore, in the further increase in the production of environmentally friendly horse breeding products, the use of high-quality feed and environmentally friendly feed additives is of great importance.
Currently, biologically active additives containing probiotics, prebiotics or synbiotics are increasingly used in veterinary medicine.Probiotic drugs are increasingly being evaluated not only by their antimicrobial effect, but also by the peculiarities of their impact on the body and its microbiota during the development of allergic reactions, autoimmune processes, and the need to strengthen the immune response [10][11][12][13].
One of these means is the feed additive ProVetin, containing bacteria of the strains Bacillus subtilis, Saccharomyces cerevisiae, Trichoderma reesei.The total number of viable cells in 1 g of probiotic is not less than 1*10 9 CFU.
To assess the safety and effectiveness of the use of the feed additive ProVetin in the cultivation of horses, the following tasks were identified: -determine the optimal dose of the feed additive ProVetin; -to establish the effect of the feed additive ProVetin on the dynamics of morphobiochemical parameters of the blood of horses.

Materials and methods of research
Experiments to establish the optimal dose of the probiotic feed additive ProVetin were carried out on horses at enterprises of various forms of ownership of the Moscow region.
The studies were conducted on adult horses, of which 3 groups of 8 horses were formed in each group, taking into account the breed, age and live weight by the method of paired analogues.The first group was a control group, where the feed additive was not used.The horses of groups 2 and 3 received in addition to the main diet the feed additive ProVetin for 45 days: Group 2 -20 g per head per day, group 3 -30 g per head per day.
The groups were formed according to the principle of analogues (taking into account gender, breed, age, body weight, identity of the physiological state).
The rations were made taking into account detailed feeding norms.
The maintenance of animals and their maintenance was the same in all groups and corresponded to the internal regulations adopted in the farm.Sanitary and hygienic, zootechnical and veterinary requirements were met during the experiments.The horses were kept in standard stables, one in a stall, with a daily walk in the brews.The horses were kept in conditions corresponding to veterinary and zootechnical requirements, received a household ration in accordance with generally accepted norms [14].
Blood for research was taken from the jugular vein of horses of each group in the morning before feeding before the start of the experiment and after 45 days of the trial period [15].
Hematological studies of whole blood were performed using an automatic hematological analyzer Abacus Junior 5 Vet.Biochemical blood tests were performed using a semi-automatic biochemical blood analyzer StatFax 1904+ using standardized reagents Vital Diagnostics Spb.

Research results and their discussion
When examining the blood of horses at the beginning of the experiment, moderate leukocytosis was found in all groups (table 1).The number of leukocytes ranged from 14.0±0.9×109 /l to 15.1±1.2×10 9 /l.In the study of the leukocyte formula, there was a slight increase in the number of lymphocytes in horses of the control group (7.8±0.7×10 9 /l) and the 1st experimental group (8.0±0.5×10 9 /l).Such indicators as the content of erythrocytes, hemoglobin, hematocrit, platelet levels were within the physiological norm for this type of animal.The use of the feed additive ProVetin had a positive effect on the hematological parameters of the blood of horses.After 45 days of using the feed additive, the animals of the experimental groups showed normalization of the level of leukocytes relative to the initially obtained data.So, in 1st experimental group, the number of leukocytes was 11.2±1.5×10 9/l, in the 2nd group -10.6±1.8×10 9 /l.In the control group, moderate leukocytosis remained in horses -the number of leukocytes was 14.8±1.8×10 9/l.When analyzing the leukoformules of animals of all groups, the content of granulocytes and agranulocytes were in the reference ranges of the physiological norm.There was a tendency to increase the level of hemoglobin and erythrocytes in horses of experimental groups treated with ProVetin.An analysis of the indicators characterizing the biochemical status of the blood of the studied horses (Tables 3, 4) showed that before the experiment and the introduction of a feed additive into the diet, the total protein content in the blood serum of horses of all groups corresponded to the normative values of the lower limit without significant intergroup differences.After 45 days of the experimental period, there was a tendency to a slight decrease in the amount of total protein in the blood serum of horses of the control group by 7% (60.9 ± 7.2 g/l).In the horses of the 2nd experimental group, who received the feed additive ProVetin at a dose of 20 g per head, the amount of total protein practically did not change.In animals of the 3rd experimental group receiving ProVetin at a dose of 30 g per head, after a month of the experimental period, there was a tendency to increase the level of total protein in the blood serum (by 16%), mainly due to the content of albumins (by 19%).The content of globulins in the blood of horses of all groups before the start of the experiment corresponded to the lower limits of the norm for this type of animal.After 45 days of the experimental period, the animals of the experimental groups showed an increase in the level of globulins as an adequate response to the introduction of the feed additive ProVetin (in the 1st experimental group by 9.6%, in the 2nd group -by 13.4%).
Since the globulin fraction proteins are mainly represented by compounds with a protective function, it can be assumed that the introduction of the ProVetin feed additive into the diet caused an increase in the protective mechanisms of the equine body, more effectively in the 3rd experimental group, where ProVetin was used at a dose of 30 g per animal.The level of urea in the blood of horses of all groups at the beginning of the studies corresponded to the normative values without significant intergroup differences.After 45 days of the experimental period, there was a tendency to decrease the content of this metabolite in the blood of horses of the experimental and control groups, more pronounced in animals of the 2nd experimental group, which correlates with an increase in the level of total protein in the blood serum and, apparently, indirectly indicates the use of amino groups not for the synthesis of urea, but for the synthesis of amino acids, and in the futureprotein.Probably, the decrease in the level of urea concentration in the blood is an adaptive mechanism aimed at preserving nitrogen for protein synthesis.The blood glucose content in horses of all groups corresponded to the normative values without significant differences.After 45 days of the experimental period, there was a tendency to a slight increase in blood content in horses of the control group by 3.7%, and in animals of the 1st and 2nd groups -by 5.5 and 7%, respectively.Consequently, the introduction of a feed additive for 45 days contributed to the optimization of energy metabolism, which was more pronounced in the 2nd experimental group of horses receiving ProVetin at a dose of 30 g per head.
The level of ALT and triglycerides in horses of the control and experimental groups before the start of the study and 45 days after the introduction of the feed additive was within the values of the physiological norm for this type of animal.The AST content for the entire study period in animals of the control and experimental groups was also within the limits of the reference level, but after 45 days the AST level of horses of the control group increased by 11.5%, and in animals of the experimental groups decreased slightly relative to the initial indicators.The cholesterol level in the analysis of the blood serum of horses of the 1st and 2nd experimental groups shows a significant decrease in comparison with the control group -3.1± 0.3 mmol/l and 3.2± 0.3 mmol/l (P < 0.05).

Conclusion
Based on the conducted studies, it was found that the use of the feed additive ProVetin to horses, bacteria of the strains Bacillus subtilis, Saccharomyces cerevisiae, Trichoderma reesei, had a positive effect on the hematological and biochemical profile of the blood of horses.Depending on the dose of the feed additive ProVetin, activation of the body's defense mechanisms and energy metabolism has been established.In the group of animals receiving a feed additive at a dose of 20 g per head, 45 days after the start of administration, an increase in the level of hemoglobin and erythrocytes relative to the initial level was noted -by 1.6% and 6.9%, respectively.In horses treated with ProVetin at a dose of 30 g per head, after 1.5 months, hemoglobin increased by 1% (146.9±12.2g/l, P≤0.05), the number of red blood cells by 2.1% (9.0±1.4x10 12 /l), total protein by 16% (76.6±6.0 g/l, P≤0.05), albumins by 19% (38.4±2.6 g/l, P≤0.05).Also, in the experimental groups of animals, the normalization of the level of leukocytes relative to the initial values was noted -in the 1st group, the number of leukocytes was 11.2±1.5×10 9/l, in the 2nd group -10.6±1.8×10 9 /l.In the biochemical profile of horses of the experimental groups, an increase in globulins was noted, which most likely indicates the activation of the immune system and normalization of immunostructural homeostasis.
Based on the above, it should be noted that the results of the study allow us to recommend the use of adult horses of the feed additive ProVetin in a dose of 20-30 g per head per day for 45 days.

Table 1 .
Hematological blood parameters of horses before the introduction of the feed additive ProVetin

Table 2 .
Hematological blood parameters of horses 45 days after the introduction of the feed additive ProVetin

Table 3 .
Biochemical parameters of the blood of horses before the introduction of the feed additive ProVetin

Table 4 .
Biochemical blood parameters of horses 45 days after the introduction of the feed additive ProVetin