Objective: To reduce the cost of hormones used in Heat- synch protocol in dairy cows.
Design: Experimental study.
Animals: 144 Holstein cows, at 50 days postpartum. Cows randomly assigned into 3 groups: (1)40 cows; 7.5.µg luliberin, TM. (2) 45 cows; 15.tg luliberin, IM. Seven days later in both groups, 150j.tg D-cloprostenol, TM 25 hours later 1mg Estradiol Benzoate was injected. Cows observed for 4 hours and inseminated based on standing heat. Cows that did not display estrus were inseminated at 48 hours after estradiol injection. (3) Control: group in=59, did not received any treatment and were inseminated 12 hours after displaying estrus. Pregnancy was diagnosed on day 42 after AT via rectal palpation.
Statistical analysis: Days open and pregnancy rate were analyzed by One-way ANOVA and chi square tests, respectively.
Results: The number of days open did not differ among experimental groups (group one: 104.17±7.76 days, group two: 106.28±6.24 days and the third group: 111.86±2.33 days (P>0.05). Pregnancy rate to the first service was not different among groups (group one: 47.5%, 19/40, group two: 48.88%, 22/45, third group: 32.20%, 19/59) (P>0.05).
Conclusion: In conclusion, reducing the dose of GnRH analogue (Luliberin) to half of the full dose did not affect pregnancy rate and days open. Therefore the cost of Heat- synch program can be reduced by using half dose of Luliberin.