Análisis de registros reproductivos del núcleo de selección merino australiano de la Estación Experimental de la Facultad de Agronomía Salto

Reproductive efficiency is a fundamental pillar of sheep production systems, as it determines the number of lambs produced, flock replacement rates, and the flock’s overall productivity progress. The objective of this study was to analyze the effects of age at lambing, body condition, live weight, type of artificial insemination, insemination protocol, and the year of breeding (during the 2018–2025 period) on key reproductive efficiency indicators: fertility, prolificacy, and fecundity. The analysis utilized a database containing historical records from the Australian Merino selection nucleus at the Faculty of Agronomy’s Experimental Farm (Estación Experimental de la Facultad de Agronomía Salto). The results showed a significant effect of the breeding year on all evaluated indicators (p < 0.05) for both fixed-time artificial insemination (FTAI) and ram mating (follow-up mating) reflecting the influence of environmental conditions on reproductive performance. Fertility showed significant year-to-year variation, with the lowest values ​​recorded in 2019–2020 and the highest in 2022; generally, fertility was higher in ram mating groups compared to FTAI groups. Ewe age had a differential impact depending on the breeding method: fertility declined with age in FTAI groups but increased in ram mating groups. Additionally, intrauterine insemination yielded higher fertility rates than intracervical insemination, although this varied by year. Prolificacy and fecundity were also affected by the breeding year, showing variations linked to environmental conditions. Prolificacy increased with age up to the adult category, whereas total fecundity peaked in middle-aged ewes before declining. The synchronization method influenced fertility but had no observed effect on prolificacy. Body condition and live weight were influenced by age and year, helping to explain some of the variability observed in the reproductive indicators. The results confirm that the system’s reproductive efficiency is determined by the interaction among individual ewe factors, reproductive management practices, and environmental conditions, highlighting the importance of comprehensive management to optimize productive performance in sheep selection systems.