Neonatal mortality in small ruminant production is a significant economic challenge for farmers, requiring techniques to improve survival rates among newborn lambs. This study focused on mitigating neonatal lamb mortality and enhancing growth rates under semi-intensive farming conditions in the Eastern Mediterranean Region. The study used 320 sheep of two breed types, Awassi and Awassi × Chios (F1) cross-breeds, with each breed type divided into an experimental and a control group. Lambs received immediate umbilical cord care and were subjected to a birth protocol. The experimental groups received an oral feed additive daily from birth until five days of age and from weaning until three days after weaning. This additive aimed to improve the health of the intestinal microbiome and immune function, and included electrolytes and vitamins. The reproductive performances of the ewes and the growth and mortality rates of the lambs were monitored. The study found significant impacts of both genotype and the feed additive on newborn lamb viability. In addition, the weaning weights of lambs of both genotypes improved with the use of the feed additive. The study concludes that administering the recommended feed additive during critical periods from birth to weaning reduces mortality rates and positively influences the growth and development of newborn lambs.