Effect of CIDR-based (CIDR-synch) protocol, fortimed artificial inseminations, and on the conceptionrate of dairy cows

The objective of this study was to compare the conception rate in dairy lactating Holstein cows to fixed timedartificial insemination among Ovsynch and Ovsynch plus CIDR protocols. One-hundred-and-eighty two Holsteincows with parity ranging from 1 to 4 and post partum period of ≥ 60 days at unknown stages of estrus cycle wererandomly assigned to two treatment groups. Females in the control group (Ovsynch; n = 92) underwent a standardOvsynch protocol (GnRH analogue on Day 0, PGF2alpha analogue on Day 7 and GnRH analogue on Day 9),with timed-AI on Day 10, approximately 18-20 h after the second GnRH treatment. Cows in the Ovsynch + CIDRgroup (n = 90) received a standard Ovsynch protocol plus a CIDR for 7 days (starting on Day 0) were inseminated at the same time using frozen semen. The animals being studied were under nutritional and environmentalconditions and experiment was carried out in different herds with the definite numbers. Pregnancy diagnosis ofanimals under experiment and insemination were performed 45 days later after insemination via rectal touching.The conception rate tended to be greater in the Ovsynch + CIDR group (64.4%, P < 0.05) than in the Ovsynchgroup (46.7%). These results revealed that a CIDR-based protocols for timed-AI improved conception rate in earlypostpartum suckled cows relative to the Ovsynch protocol. Treatment with a CIDR may prevent early maturationof follicles observed in non-pregnant cows treated with the Ovsynch protocol, by maintaining elevated blood progesterone concentrations until PGF2alpha treatment