Abstract
Poor estrus detection is the greatest limiting factor for reproductive performance in dairy cows. The study aimed to compare the reproductive performance by assessing the fertility rate (FR) between cows inseminated after detected estrus and those inseminated after synchronized ovulation with the Short Synch protocol. A total of 138 primi- and multi-parous dairy cows from 5 dairy farms in North Macedonia were included in the study. At day 65±3 postpartum, an ovarian ultrasound examination was performed for presence of corpus luteum (CL), and body condition scoring (BCS) was made (scale from 1-emaciated to 5-obese). Cows with a CL (n=92) were submitted to two synchronization protocols and grouped accordingly: SPG (n=46) synchronized with a single PGF2α injection, and SSG (n=46) synchronized with a Short Sync protocol (PGF2α–24h–PGF2α–32h–GnRH–16h–TAI). Cows were followed up to the second insemination. Pregnancy diagnosis was done at d30 and d60 after each insemination. Eleven cows (n=11) from the SPG didn’t show estrus signs and were excluded from further analysis. Overall, a higher FR (p=0.0008) was observed in the SSG (71.74%, 33/46) compared to the SPG (34.29%, 12/35). Cows in the SSG with BCS>2.75 (76.19%, 16/21) had a higher FR (p=0.0016) than cows in the SPG with BCS>2.75. No differences were observed (p=0.1242) between both groups that had BCS≤2.75 (68.00%, 17/25; 43.75%, 7/16, respectively). Multiparous cows in the SSG had a higher FR (p=0.0021, 71.43%, 25/35) than their counterparts from the SPG (30.43%, 7/23). No significant differences were observed among the primiparous cows. The results indicate that Short Synch protocol might increase the fertility rate in dairy farms.