Efficacy of Co-synch Protocol on Normal Cyclic Dairy Cows with or Without Corpora Lutea.

Improving reproductive efficiency, estrus synchronization and controlled breeding protocols are efficient management techniques in dairy cows. Therefore, the present study was designed to compare the efficacy of Cosynch protocol in the cows carrying corpora lutea (CL), without CL or with unexamined ovarian structure. Fifty-six cows were divided into 4 groups; control group1 (n=12) and Co-synch treated groups; group2: cows with unexamined ovarian structure group (n=9), group3: cows having only follicles without mature Cl (n=16) and group4: cows having mature Cl (n=19). Ultrasonography was performed before and after gonadotropin (GnRH) injection. Blood was collected for analysis of progesterone (P4) and estradiol 17-ß. Reproductive data was obtained regarding 1^st service conception rate (1^st SCR), number of services/conception (s/c) and days open. Ultrasonography revealed luteinization in cows without mature CL. While those having mature CL showed increase in the size of the CL or formation of accessory CL. Results revealed significant decrease in serum P4 before GnRH treatment in cows having no mature CL. Significant increase in serum P4 levels in all groups was recorded after GnRH treatment. Besides, the highest P4 level was assessed in cows having mature CL. Estradiol 17-ß was significantly decreased in cows having mature CL before and after treatment. Cows having mature CL revealed significant upgrade in the percentage of 1^st SCR, decrease in s/c and shortening in days open as compared with other groups. In conclusion, applying Co-synch to the cows carrying CL is beneficial and promises protocol to improve reproductive performance in dairy cows. [ABSTRACT FROM AUTHOR]