Efficacy of CIDR in cosynch and oestrus synchronization protocols in lactating cows
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It was aimed to compare efficacy of CIDR in Cosynch and estroussynchronization protocols based on pregnancy rates following the firstservice at 45–160 days postpartum in lactating cows. In Group I(Cosynch-CIDR, n = 100), CIDRÒ(progesterone, 1.38 g) wasinserted intravaginally concurrently with GnRH injection (ReceptalÒ,buserelin acetate, 0.02 mg, i.m.). Seven days later CIDR was removedand PGF2a(DinolyticÒ, dinoprost tromethamine; 25 mg, i.m.) wasinjected followed by timed artificial insemination (TAI) and GnRHinjection 56 h later. In Group II (Control-CIDR, n = 81), CIDR wasadministered for 7 days. One day before CIDR removal, PGF2awasadministered. During 5 days following CIDR removal, artificialinsemination (AI) was performed following heat detection based onAM/PM rule. Pregnancies were diagnosed with transrectal ultraso-nography 40–45 days after AI or TAI. Pregnancy rates did not differbetween Cosynch-CIDR (35%; 35/100) and Control-CIDR (38.3%;31/81) groups. Submission rate for AI was higher (p < 0.01) inCosynch-CIDR group (100%; 100/100) compared to Control-CIDRgroup (82.7%, 67/81). In Control-CIDR group, frequencies of cowsdetected in heat following 1, 2, 3, 4, 5 days after CIDR removal were19.8% (16/81), 37.0% (30/81), 17.3% (14/81), 7.4% (6/81), 1.2% (1/81); respectively. Whereas, 17.3% (14/81) of cows were not detected inestrus during 5 days after CIDR removal in Group II. In conclusion,use of CIDR in Cosynch protocol provides similar pregnancy rates buthigher submission rate compared to CIDR based estrous synchroni-zation protocol in lactating cows.