Simple SummaryStressful events play a major negative role in the modern technology of weaned piglets. These events include but are not limited to weaning itself, lack of maternal milk, loss of maternal bonding, mixing of different litters, transportation to growing-finishing farms, and housing conditions. Various additives (phenazepam, aminazine, vitamins E and C, the extract Eleutherococcus senticosus, and ultraviolet irradiation) at different doses and combinations with or without ultraviolet irradiation were used to evaluate their effect on the viability and growth rate of piglets after weaning. Content of lipids in the blood and liver, antioxidant activity (AOA) and lipid peroxidation (LPO) significantly decreased or increased with the use of the additives. Feeding a mixture of additives increased survival rate, average daily gain, and live weight at the end of the experiment.AbstractThe purpose of this study was to evaluate the viability and growth rate of piglets after weaning, the content of lipids in the blood and liver, antioxidant activity (AOA) and lipid peroxidation (LPO) when various additives are used in feed. The experiments were performed on two crosses of piglets obtained from Large White breed sows and Landrace breed boars. Twenty to 28 animals were randomly assigned per group. The following additives were tested: the benzodiazepine phenazepam, the neuroleptic aminazine, vitamins E and C, and the extract Eleutherococcus senticosus (Araliaceae). Different doses and combinations of the additives against ultraviolet irradiation were used. The addition of these substances improved the growth rate and viability of piglets. AOA increased under the influence of all factors studied, especially with the addition of extract of Eleutherococcus in feed in combination with aminazine and UV-irradiation (p < 0.01). However, the addition of Eleutherococcus extract and aminazine intensified LPO (p < 0.01), but use of UV irradiation helped to decrease LPO values (p < 0.01). Feeding a mixture of additives per pig per day of 3 mL of Eleutherococcus extract, 80 mg of 25% tocopherol, and 500 mg of ascorbic acid increased survival rate, average daily gain, and live weight at the end of the experiment. Thus, the use of prophylactic antistress and sedative drugs during weaning helps AOA normalize LPO of red blood cells; enhance post weaning growth of the pigs by 4.8% to 24.6% and increases piglet survival rate by 5% to 5.1%.