In recent years, active researches are being conducted to identify the needs of birds in mineral elements that were previously not considered in the diet, but as shown have a significant impact on the body. Selenium belongs to these elements and their compounds, which attract attention of scientists and specialists in poultry industry, as selenium is recognized as indispensable biotic ultramicroelement.

The results of numerous studies conducted on various kinds of animals and birds found that selenium has antioxidant, immune-stimulating, anticarcinogenic, antimutagenic, adaptogenic, anti-virus and radioprotective properties.

The discovery of the biological properties of selenium was the reason for its wide use in feeding poultry. The inclusion of selenium to the animal mixed fodder improves health, increases egg productivity of industrial and parent stock of birds.

It is known that under the influence of various factors in the digestive system of animals and birds physiological changes are observed. In the scientific literature there are some reports that the introduction as inorganic and organic selenium containing preparations to the animal mixed fodders promotes better growth and development of the digestive system of birds, in particular, weight and length of the intestine and thickness of the intestinal wall. However, investigations were conducted mainly on broiler chickens, laying hens and geese grown for meat.

In the absence of publications on the effect of different levels of selenium in the diet on the development of the gastrointestinal tract in ducklings grown for meat, it was necessary to conduct additional investigations.

The objective of the research – to study the effect of different doses of selenium supplements in mixed fodder on development of the gastrointestinal tract in ducklings grown for meat.

Studies were conducted on Ukrainian ducklings of white breed. Different amounts of selenium, mg / kg were additionally administered to the mixed fodder for birds of the research groups: the second group – 0.2; the third group – 0.4; and the fourth group – 0.6. Ducklings from the first control group did not receive selenium supplement. Sodium selenite was used as a source of selenium.

The results showed that among the ducklings which were fed with mixed fodder with added selenium, the maximum length of intestine was recorded in the third experimental group (221.4 cm), and the lowest – in the second experimental group (217.8 cm). Ducklings from the fourth experimental group took on this indicator intermediate place (220.0 cm). Compared with the control group, in the second experimental group difference was 3.5 % in the third – and the fourth 5.2–4.6 %.

A similar trend was observed as for the length of the small intestine. The length of the small intestine in the ducklings from the research groups was 3.6–5.4 % more than in the birds from the control group (194.5 cm).

The length of the large intestine in the ducklings from the second and the third experimental groups was 2.5 and 3.1 % respectively over, and the fourth – 0.6 % less compared with the control group, where the figure was 15.9 cm.

It should be noted that in poultry from all research groups absolute weight of gut increased by 6.3–10.5 % and relative weight of gut increased by 0.2–0.3 %

The mass of the muscle stomach in the ducklings from the third and the four research groups was respectively 10.8 % and 6.7 % higher compared to the ducklings from the control group (63.0 g). The difference in this indicator between the second experimental group and the control group was 0.3 % for the latter.

Thus, the introduction selenium at doses that were studied to the mixed fodder for ducklings positively influenced to the development of the digestive tract of young animals, in particular, increased the weight and the total length of the intestine as a whole and its parts in particular, as well as muscle mass of the stomach. The best performance of the digestive system had ducklings, which were fed mixed fodder enriched with selenium at a rate of 0.4 mg / kg.

Key words: selenium, dose, mixed fodder, ducklings, stomach, intestines.