The effect of the biologically active substance Baikal EM-2 on the intestines of quails

. 5 groups were formed from quails of the Manchurian breed. The control group - the main diet, and the experimental ones were given 0.25% (1 experimental group (EG)); 0.5% (2EG); 0.75 (3EG) and 1% (4EG) Baikal EM-2 solution at the rate of 3 ml per head. Histological studies were performed at the age of 147 days. Egg production per average laying hen in the experimental groups was on average 11.7% higher compared to the control group, the average live weight of quails in the experimental groups is 1.2% higher. In the duodenum, in all experimental groups, there was a better development of villi by 19.8-58.6% (P≤0.001), and in the skinny, the height of the villi was significantly higher in EG1, EG2, and EG4 by 19%-48%. The crypt layer significantly increased in the duodenum of 4EG by 13.9% (P≤0.05). The muscular elements of the duodenum were better developed in the experimental groups. In the cecum, the size of the layers did not differ. We assume that the experienced bird achieved high zootechnical results due to the better development of the villi of the small intestine.


Introduction
Poultry farming is an intensively developing branch of agriculture, where new technological techniques, schemes for keeping and feeding poultry are actively studied and introduced into production processes [1,2,3,4].The intensification of poultry farming is aimed not only at increasing profitability, but also at improving the health of birds, which is necessary to obtain high-quality products.Among the developments aimed at increasing the productivity of the industry while maintaining a healthy livestock include the search for new feed additives.Currently, the search is underway for feed additives that can replace antibiotics, improve the productive qualities and health of birds.It is recommended to use phytobiotics, probiotics, prebiotics, antioxidants, sorbents, etc.
Probiotic additives are created on the basis of one or several types of microorganisms, various types of microorganisms are used to create them, for example lactic acid, soil, etc.
The use of probiotics in meat poultry farming allows to improve the digestibility of nutrients, which contributes to an increase in live weight gains, poultry safety and a reduction in feed costs [5,6], in egg poultry farming -an increase in egg production, egg quality, resulting in a greater economic effect [7,8].
Humic acid-based additives are used as growth stimulants in poultry farming [9].Humic acids contribute to an increase in zootechnical indicators, while they have a protective effect on the intestines, increase immune properties, and also have an antimicrobial effect [10,11,12,13].Due to the ability to improve digestion and assimilation of trace elements, the meat taste qualities are improved [13,14,15].When studying the influence of feeding and maintenance factors on the effectiveness of poultry rearing, an important aspect is the analysis of the state of internal organs, since this makes it possible to identify or exclude pathological processes.It is suggested that histological indicators can serve as markers of well-being in poultry houses [16].The digestive organs react to seasonal changes in the diet by fluctuations in the size of the muscle membrane, which is associated with a change in the availability of food components [17,18].Certain reactions of the membranes of the digestive tube to the introduced components of the diet were revealed [19,20].
In connection with the above, the purpose of the research was to study the effect of the biologically active substance Baikal EM-2 on some morphometric parameters of the quail intestine.

Materials and Methods
The research was carried out in 2022-2023 on the basis of the educational and production poultry house of the RSAU-MAA named after K.A. Timiryazev (city of Moscow).The objects of the study were quails of the Manchurian breed aged from 4 to 147 days.Using the method of pairs of analogues, 5 groups were formed (1 control and 4 experimental) of 50 heads each.All the birds were clinically healthy and kept in cages under the same conditions: temperature and humidity conditions, temperatures, lighting.The maintenance conditions corresponded to zoohygienic norms.
The quails of the control and experimental groups received the basic ration (BR) with free access to water.During the entire experiment, in addition to the main diet, quails of the 1st, 2nd, 3rd, and 4th experimental groups were soldered with solutions of the biologically active additive Baikal EM-2 in the form of 0.25; 0.5; 0.75, and 1% aqueous solution.Baikal EM-2 is developed on the basis of a complex of probiotic microorganisms, saccharomycites, fulvic acids, humic acids, etc.The daily intake of the test substance solution was 3 ml/head.
During the experiment, the live weight, egg production, and safety of quails were considered.The assessment of zootechnical indicators was carried out according to standard methods.
At the end of the experiment on day 147, a morphological autopsy was performed on 6 heads (3 females and 3 males) from each group.When removing the intestines, the length of each intestine was measured and the organs were fixed in 10% neutral formalin.Dehydration was carried out through alcohols of increasing strength, compaction in xylene and paraffin, poured into paraffin.Sections were made on a rotary microtome and stained with hematoxylin-eosin according to the standard procedure.The structures were measured using an ocular ruler and converted to micrometers using an object micrometer.Statistical data processing was carried out in the Excel program.

Results and Discussion
The safety of livestock in 4 experimental groups was 100%, in 1 and 2 -98%, in 3 -96%, and in the control group -94%.The average live weight after the first 40 days of the experiment in the experimental groups was 1.2% higher than in the control group.Egg production per average laying hen in the experimental groups was on average 11.7% higher compared to the control group.
Histological studies of the duodenum of quails of the control group showed that the wall of this department consists of mucosa, muscle, and serous membranes.The serous membrane is poorly identified due to its small size, so it is not represented in further measurements.In the total thickness of the intestinal wall, the main share falls on the mucous membrane, it is about 94.3%.The muscle membrane accounts for only 5.7%.The muscular membrane consists of an inner annular layer and an outer longitudinal layer.The annular layer in the duodenum is much better developed, it is 2.5 times thicker than the longitudinal one.In the mucosa, a layer of villi and a layer of crypts are well expressed, directly under the crypts on the border of the mucosa there is a muscle plate of the mucous membrane.The villi of the mucosa are smooth, leaf-shaped, the height of the villi layer is 5.7 times greater than the crypt layer.
Morphometric studies have shown that the same ratio of layers is observed in all experimental groups as in the control group.The wall thickness of the duodenum is minimal in the control group, and the maximum in the 4 experimental group, it is 47% greater than in the control (Table 1).The total wall thickness in the experimental groups is significantly greater than in the control group, while the wall thickness increases sequentially to the 4th experimental group.In all experimental groups, the wall thickness increases due to a reliably significant increase in the thickness of the villi layer and all muscle elements, and in the 4 experimental group, in addition, also due to a significant increase in the crypt layer.This confirms the data on the increase in the height of the villi in the duodenum when using probiotics [21].The thickness of the villi layer consistently and significantly increases with an increase in the concentration of the complex additive.In experimental groups 1-, 2-, 3-, and 4, this increase is 19.8%, 31.7,57.4,58.6%, respectively.The preparation had a much weaker effect on the crypt layer, a significant increase in this layer was observed only in group 4 receiving a 1% solution of the studied additive.Measuring the length of this part of the intestine in quails did not reveal significant differences between the experimental and control groups.Therefore, with an equal length of the duodenum, a change in the ratio of the thickness of the layer of villi and crypts towards the villi can be regarded as a positive effect of the preparation, since it leads to an increase in the surface area of the mucosa.Similar data on the positive effect of probiotics on increasing the ratio of villi height to crypt height are confirmed by our studies [22].In the duodenum, the processes of abdominal and parietal digestion occur and an increase in the height of the villi may indicate a positive effect of this preparation on the processes of digestion of feed components.Nevertheless, it should be noted that in the first experimental group, the wall thickness increases to a greater extent due to muscle elements, compared with the height of the villi.In the 4 experimental group, there was a significant and maximum increase in both the crypt layer and the villi layer, which suggests that this concentration of the additive is optimal for this part of the intestine.
Histological studies of the jejunum of quails have shown that the wall of this department, as well as the duodenum, consists of the same layers: mucous, muscular, and serous membranes.There are no fundamental differences in the structure, but it should be noted that in the caudal direction there is a decrease in the total height of the intestinal wall, in the control group its height is 502 microns, which is 1.8 times less than in the duodenum (Table 1).The height of the mucous membrane is especially reduced due to the height of the villi and the thickness of the crypt layer.Thus, the height of the villi in the control group is 2 times less than in the duodenum, and the crypt layer is 1.6 times lower.The thickness of the muscle elements, on the contrary, increases in the caudal direction.In the experimental groups, the jejunum wall thickness was significantly greater only in group 4. The minimum value is observed in the control group, the maximum value in the 4 experimental group.In groups 1 and 2, the villi layer was significantly higher by 19% compared to the control group.The thickness of the crypt layer in the 2 experimental group is significantly lower than in the control group.In the 3 experimental group, no significant differences were found compared to the control group.In the 4 experimental group, both the villi layer and the crypt layer were significantly higher by 48% and 20%, respectively.
The muscle plate in all experimental groups is significantly lower than in the control group.In the 1 and 2 experimental groups, all layers of the muscle membrane are significantly lower, especially in the 2nd experimental group: by 25% in the ring layer and by 50% in the longitudinal layer.Such a decrease in the thickness of the muscular membrane compensates for a significant increase in the mucous membrane and leads to the fact that the thickness of the intestinal wall does not change.In the experimental group 3, no significant effects of the additive on the mucosa components were found.In this group, , 020 (2024) BIO Web of Conferences MSNBAS2023 https://doi.org/10.1051/bioconf/2024820200909 82 the effect of the additive is observed in the muscle elements, thus, the muscle plate of the mucous membrane is 1.5 times smaller and in the ring layer of the muscle membrane -it is 1.3 times smaller compared to the control group.The best results were obtained in the experimental group 4, this is evidenced by a reliably significant increase in all components of the mucous membrane.Thus, the thickness of the villi layer is 1.5 times greater, and the crypt layer is 1.2 times greater than in the control group.It can be said that this preparation dosage causes positive changes in the structure of the jejunum wall, increasing the mucosa surface and improving the absorption of nutrients in the jejunum.The large intestine of birds undergoes reduction and the caecum remains fully developed.In the cecum structure, the tendency to decrease the wall thickness continues, in the control group its thickness is 2.6 times less than in the jejunum and 4.6 times less than the duodenum wall (Table 2).On the contrary, the number of muscle elements increases.The ring layer of the muscular membrane in the cecum of quails is on average 1.7 times thicker than in the small intestine.The longitudinal layer of the muscular membrane is 3-4 times thicker than in the small intestine.The main reduction of the wall occurs due to changes in the mucosa structure: villi disappear, the number of crypts decreases, the muscle plate is reduced.This leads to a decrease in the processes of digestion and absorption of nutrients in this department.
This complex additive had no effect on the preservation of the epithelium of the villi throughout the intestinal tube, which confirms some data [23].At the same time, a number of studies have noted the protective effects of humic acids [11,13,14] and probiotics [24] on the intestinal mucosa, which consist in reducing pathological manifestations.It is possible that the combined use of these additives reduces the effectiveness of the protective action of each of them.
As is known, probiotics have their effect in the gastrointestinal tract, positively affecting the intestinal microflora, which improves digestion and increases the absorption of nutrients from the feed.The maximum effect of these preparations is observed in the initial part of the digestive tract, which confirms the data of other studies.This is evidenced by an increase in the height of the villi in the duodenum, especially in the experimental group 4. It is noted that the use of probiotics causes an increase in the height of the villi in the duodenum and jejunum [23,24].Nevertheless, in our studies in the caudal direction, there is a slight decrease in the preparation activity, especially in the experimental group 3. A stable positive effect on the structure of the jejunum mucosa is observed in the , 020 (2024) BIO Web of Conferences MSNBAS2023 https://doi.org/10.1051/bioconf/2024820200909 82 experimental group 4, as evidenced by a significant increase in all mucosal structures.At lower preparation concentrations, such a significant effect is not observed in groups 1 and 2 of the experimental groups, although in these groups the ratio of the height of the villi to the height of the crypts increases.
The effect of this preparation in the distal parts of the digestive tube is not observed.In this department, the use of the preparation negatively affects the mucosa in the experimental group 1, in other groups the preparation does not have a significant effect on the mucosa structures.In the muscle membrane, the preparation affects the structures in different ways.There is a significant increase in the ring layer of musculature in 3 and 4 experimental groups and a significant decrease in the longitudinal layer in all experimental groups, which indicates the depressing effect of the preparation on the muscular components of the cecum wall.
Lymphoid tissue is somewhat better developed in the stroma of the villi in the duodenum in the experimental groups.It can be said that there is no effect on the development of lymphoid tissue in the jejunum and caecum.

Conclusion
Based on the conducted studies, it can be concluded that the histological structure of the quail intestine along the entire length of the intestinal tube was different.The intestinal wall thickness and the height of the villi decreased in the caudal direction.The wall thickness and the height of the villi were maximal in the duodenum and were, respectively, 1335.6 and 1145.6 microns, the minimum wall thickness in the caecum was 156.7 microns.The muscular membrane increased distally.
Biologically active substance Baikal EM-2 with the use of all tested dosages had a positive effect on all parts of the intestine.The most effective was the evaporation of Baikal EM-2 in the form of a 1.0% solution and allowed to increase the wall thickness of the duodenum by 47.5%, the jejunum -by 36.4%, the cecum -by 30.4%.
It is possible that an increase in the mucous membrane of the small intestine contributed to an increase in live weight and egg production in quails of the experimental groups.
Thus, the data obtained as a result of the study allow to conclude that the use of the biologically active substance Baikal EM-2 soldered in the form of a 1.0% aqueous solution is the most effective for improving the structure of the gastrointestinal tract of quails.

Table 1 .
Morphometry of the small intestine of quails, microns.

Table 3 .
Morphometry of the cecum, microns