Estrous Synchronization in Rarámuri Criollo Cattle Using 5- and 7-Day Co-Synch + CIDR Protocols

Resumen

Objective: To evaluate the reproductive response of Rarámuri Criollo cows to two estrous synchronization protocols: 5- and 7-day Co-Synch + CIDR.

Design/methodology/approach: Twenty multiparous Rarámuri Criollo cows (6 years old; 238 ± 52 kg; body condition score = 5) were randomly assigned to two treatments in a completely randomized design. In Treatment 1 (T1; n = 10), the Co-Synch + CIDR protocol was applied for 7 days, while in Treatment 2 (T2; n = 10), it was applied for 5 days. Timed artificial insemination (TAI) was performed 48 hours (T1) and 72 hours (T2) after device removal. Body condition score (BCS) was recorded on days 0, 90, and 150. Estrus response, insemination rate, and pregnancy rate were analyzed using logistic regression; time to estrus was assessed using the Kaplan-Meier method; and BCS was analyzed with a mixed model using SAS® at α = 0.05.

Results: Estrus response was 80% in both treatments. Time to estrus onset was shorter in T1 (41.2 ± 2.36 h) than in T2 (60.0 ± 4.96 h). No significant differences were observed in insemination rates (80% in T1 vs. 90% in T2) or pregnancy rates (60% vs. 50%, respectively). Body condition score increased progressively throughout the study.

Limitations/implications: The small sample size limits the generalizability of the findings. Future studies with larger cohorts are recommended to confirm the absence of treatment effects.

Findings/conclusions: Both the 5- and 7-day Co-Synch + CIDR protocols were effective for estrous synchronization in Rarámuri Criollo cows.