the objective of this study was to determine the best time for artificial insemination in taleshi ewes. one hundred and fifty ewes were randomly allotted to three groups (n=50/per group). estrus was synchronized with intravaginal insertion of controlled internal drug release (cidr) for 14 days. at the time of cidr removal pmsg (300iu) was injected to the ewes. the first (ai28), second (ai40) an...

The present study determined whether a 5-day CO-Synch + controlled internal drug release (CIDR) protocol with two doses of PGF2α would improve timed artificial insemination (AI) pregnancy rate compared with 7-day CO-Synch + CIDR protocol in beef cows. Angus cross beef cows (N = 1817) at 12 locations were randomly assigned to 5-day CO-Synch + CIDR or 7-day CO-Synch + CIDR groups. All cows receiv...

The objectives of this study were to evaluate estrus response and pregnancy rates resulting from timed artificial insemination (AI) following estrus synchronization using CIDR in postpartum beef cattle. A total of 100 cows were randomly divided into three groups. Groups 1, 2 and 3 were artificially inseminated at 48-50 h (n=30), 53-55 h (n=30) and 58-60 h (n=40) after CIDR removal, respectively...

the aim of this study was to determine the effects of ecg, pgf2α and gnrh hormone on improvement of reproduction performance of cidr synchronized zandi ewes in breeding season. 500 ewes with age of 2.5-4 years and same nutritional condition were selected for this study and received cidr for 12 days. then these ewes were assigned to five equal groups. first group received no hormone (control gro...

The success of a fixed-time artificial insemination (FTAI) program depends on a high ovulation rate during a short interval. Equine chorionic gonadotropin (eCG) has been used in FTAI protocols to improve follicular growth and thereby to produce larger, more responsive follicles for ovulation with increased pregnancy rates. The aim of the present study was to evaluate the effects of eCG on concept...

Several effective fixed-time AI (FTAI) protocols have been developed to facilitate AI in beef heifers that circumvent the need for estrus detection. Among these are the 5-d CO-Synch + controlled intravaginal progesterone insert (CIDR) protocol (5dCO), PGF2α (PG) 6-d CIDR protocol (PG-6dCIDR), and 14-d CIDR-PG protocol (14dCIDR-PG). Although each of these protocols varies in duration and approac...

Many estrus synchronization protocols aim to induce a new follicular wave to improve response and enhance pregnancy rate. Our objectives were to determine the effectiveness of GnRH analog administered d 0 and 9 during an extended controlled internal drug release (CIDR) protocol to produce 2 follicular waves, induce cyclicity in anestrus cows, and evaluate the effi cacy of a single 50-mg dose of...

On d 0 of the experiment Bos indicus x Bos taurus (n=130) cows received an injection of GnRH and a progesterone-releasing device called an Eazi-BreedTM CIDR® for 7 d with a prostaglandin F2a injection at CIDR removal. Upon CIDR removal cows were divided into two AI treatments: 1) injection of estradiol cypionate (ECP) 24 h after CIDR removal with AI 8 to 10 h after a detected estrus and timed-A...

Most fixed-time insemination protocols utilize an injection of GnRH at the beginning of the protocol to initiate a new follicular wave. However, the ability of GnRH to initiate a new follicular wave is dependent on the stage of the estrous cycle. We hypothesized that administering PGF(2α) 3 d before initiating a fixed-time AI protocol would improve synchrony of follicular waves and result in gr...