New approaches to increasing the immune status of laying hens of highly productive egg crosses under conditions of heat stress

Purpose. Study of the influence of new feed additives on the main production indicators of laying hens of the "Hisex Brown" cross, the morphological and biochemical composition of blood, the safety of the test poultry population under conditions of high summer temperatures in the south of the Lower Volga region, as well as substantiation of the feasibility of using the tested preparations in industrial poultry farming of the egg direction. Materials and Methods. The object of the study were laying hens of the Hisex Brown cross and feed additives. The studies were carried out on three groups of laying hens of 100 heads in each group. The bird of the control group received standard food and plain water for drinking, the bird of experimental group 1 received the feed additive “Yantarnyj holodok” orally with drinking water, at a dose of 0.8 liters per 1000 liters of water, the bird of experimental group 2 received the optimal dose of “Glimalask-Lact” in an amount of 0.5% by weight of the feed. The feed and water consumption of the test laying hens was determined daily by groups by weighing and measuring the feeds and their remains and the water drunk by the hens during the entire period of the experiment. Egg production per 1 laying hen was calculated as the ratio of the number of eggs laid per month to the number of birds in each group. The content of carotenoids in the egg yolk was determined spectrophotometrically, and vitamins A and E were determined by high-performance liquid chromatography. The biochemical parameters of the blood serum of the laying hens were determined using URIT 800 Vet and URIT 3020 Vet analyzers (China). Results. In the experimental groups, significantly more eggs were obtained per 30 days per laying hen: in the 1 experimental group – by 4.18% (P≤0.05), in the 2nd – by 5.17% (P≤0.05), when compared with the control. The digestibility coefficients of feed nutrients in both experimental groups were higher than in the control: organic matter – by 1.26 (P≤0.001) and 1.54% (P≤0.001), crude protein – by 1.54 (P≤0.05) and 1.68% (P≤0.05), calcium – by 2.99 (P≤0.01) and 3.21% (P≤0.01), respectively. The quality of the egg shells of chickens of the first experimental group that consumed the feed additive “Yantarnyj holodok” with water and the chickens of the second experimental group that consumed the test additive “Glimalask-Lact” with food exceeded the quality of the shells of the control group by 3.31% in the 1st experimental group and by 3.55% in the 2nd experimental group. Similarly, the egg fertility of hens of experimental group 1 is 1.84% (P≤0.05) and hens of experimental group 2 is 2.24% (P≤0.05) higher than the control analogue, respectively. The content of carotenoids in the yolk of the eggs of laying hens of the experimental groups was higher in comparison with the similar indicator of the control by 3.0 (P≤0.01) and 5.3% (P≤0.01), vitamin A – by 3.5 (P≤0.05) and 4.7% (P≤0.05), vitamin E – by 1.7 (P≤0.05) and 2.7% (P≤0.05). A decrease in the level of globulins in the blood serum of laying hens of the 1st and 2nd experimental groups relative to the control level by 2.5 (P≤0.05) and 2.6% (P≤0.05) indicates the absence of signs of inflammatory processes in the body of the experimental poultry. Conclusion. Addition of the tested additives to feed and water created the effect of acidifying water in the 1st experimental group and the effect of acidifying feed in the 2nd experimental group, which made it possible to reduce physiological load on the body from exposure to high temperatures, improve feed consumption, digestibility of calcium, phosphorus and vitamins, maintain the level of egg productivity of the cross and the quality of hatching egg, and stimulate immunity.