A, D va E vitaminlarining parrandalar tuxum mahsuldorligiga ta’siri

Abstract

This thesis analyzes foreign research on the effects of fat-soluble vitamins A, D3, and E on hen egg production, egg weight, eggshell quality, and the nutritional value of egg yolk. The importance of vitamin E in reducing heat stress under the hot summer conditions and sharply continental climate of Karakalpakstan is highlighted, along with the role of vitamin D3 metabolites in maintaining eggshell quality in older laying hens.Vitamin A deficiency causes severe ovarian degeneration, resulting in a significant decline in egg production. Supplementing the diets of heat-stressed hens with 12,000 IU/kg of vitamin A improves egg production and immune response. Increasing dietary vitamin A levels to 10,000–20,000 IU/kg enhances egg weight and eggshell strength, while yolk retinol content increases linearly. However, high doses reduce tocopherol concentrations in the yolk, and at 20,000 IU/kg, lipid oxidation increases. Therefore, excessive vitamin A supplementation may interfere with vitamin E metabolism.The active metabolite of vitamin D3, 25-OH-D3, is particularly effective in improving eggshell quality. Under high stocking-density conditions, supplementation of the diet of 45-week-old Lohmann hens with 69 µg/kg of 25-OH-D3 increased eggshell weight, while the improvement in eggshell thickness was more pronounced under stress conditions. When 25-OH-D3 was supplied throughout the entire laying period, the total number of eggs increased, and eggshell quality improved in hens aged 53–87 weeks. However, supplementation with 25-OH-D3 only during the rearing period improved bone quality but did not significantly affect egg production or eggshell quality.Under chronic heat stress at 32 °C, hens receiving 500 mg/kg of vitamin E achieved an egg production rate of 72.6%, compared with 51.2% in the control group. Egg weight also increased from 63.1 g to 66.6 g. This effect is associated with maintaining the concentration of egg yolk precursors (vitellogenin) in blood plasma. When vitamin E is administered before, during, and after heat stress, a dose of 250 mg/kg is considered optimal. Increasing dietary vitamin E to 400 mg/kg raised the α-tocopherol content in egg yolk from 144 to 477 µg/g, thereby increasing the functional and nutritional value of eggs.