Injection of eCG on Day 6 postpartum could enhance early resumption of ovarian activity in Holstein dairy cows. The present study was conducted to investigate the effects of eCG treatment on Day 6 postpartum on reproductive performance of Holstein dairy cows. Holstein dairy cows (n=420) were randomly assigned to two groups. Cows in eCG-treated group (n=220) received an intramuscular injection of eCG (500IU Folligon®) on Day 6 postpartum, while cows in the Control group (n=200) received no treatment. Estrus expression was observed thrice daily, and AI was carried out 12 hours after standing estrus. Data were analyzed using GLM and Genmod procedures, and survival analysis. Days to first service decreased in the eCG-treated (74.4±1.76 days) compared to the Control (84.2±2.79 days) group (P=0.008). Calving to conception interval was shorter in eCG-treated (103.9±3.14 days) vs Control (130.3±5.70 days) group (P=0.0006). Cows treated with eCG were inseminated and conceived earlier than untreated cows (P<0.05). In conclusion, injection of eCG on Day 6 postpartum improved reproductive performance in Holstein dairy cows.
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