Abstract
Background:
Terminal crossbreeding strategies combine prolific maternal lines with growth-oriented sires to enhance lamb productivity and carcass traits. Lamb meat production sustainability depends on genetic efficiency and seasonal adaptability.

Aim:
This study aimed to evaluate the effect of birth season and maternal genotype on reproductive performance, survival rates, and growth traits in lambs produced by Charollais rams crossed with Romanov × Akkaraman (RA) and Romanov × Morkaraman (RM) F1 ewes.

Methods:
Charollais rams (n = 4) were used to artificially inseminate RA (n = 40) and RM (n = 40) F1 ewes. Reproductive traits, survival rates, and weaning data were recorded. The influence of seasonal lambing (spring vs. summer), hormonal synchronization protocols, and type of parturition on lamb productivity was analyzed. Statistical analyses were conducted to assess the significance of litter size and growth metrics.

Results:
RM ewes showed a 13% higher lamb number at birth, whereas RA ewes had a 4.9% advantage at weaning. The survival rates were 12% higher in lambs from RA ewes. Spring lambing resulted in significantly larger litter sizes than summer lambing (p < 0.01). Lambs born in summer exhibited superior body weights. Hormonal synchronization positively influenced the outcomes of birth and weaning.

Conclusion:
F1 maternal lines derived from Romanov crosses, especially under managed breeding strategies, offer promising results for enhancing lamb production efficiency and productivity under semi-intensive conditions.

Key words: Birth season; Lamb productivity; Maternal genotype; Reproductive performance; Terminal crossbreeding.