Comparison of Melengestrol Acetate-Prostaglandin F2α to Syncro-Mate B for estrus synchronization in beef heifers

The effect of timing of administration of oestradiol benzoate on characteristics of oestrus, timing of ovulation and fertility in Bos indicus heifers synchronised with a progesterone releasing intravaginal insert

“…Failure to ovulate has been associated with the treatment of anoestrous heifers with a synchronisation treatment. 17 It is unlikely that the group of heifers treated on Farm B contained many heifers that were anoestrous or prepubertal at the time of commencing the synchronisation treatment as a corpus luteum was detected in >90% of the heifers subjected to ultrasonography during the period in which inserts were in place. This indicated that the majority of heifers on Farm B had ovulated prior to being treated.…”

Progestogen-Based Estrus Synchronization for Beef Replacement Heifers and Cows

“…We propose the general hypothesis that progestogen (MGA) treatment before the GnRH-PGF 2α estrus synchronization protocol will (1) successfully induce ovulation in anestrous postpartum beef cows and peripubertal beef heifers; (2) reduce the incidence of a short luteal phase among anestrous cows induced to ovulate; (3) increase estrus response, synchronized conception, and pregnancy rate; and (4) increase the likelihood of successful fixed-time insemination. 2,7 Current reports indicate that EDR is approximately 32% in lactating cows 4 and 70% in heifers. S ynchronization of ovulation using timed injections of prostaglandin F 2α (PGF 2α ) and gonadotropinreleasing hormone (GnRH)-the Ovsynch program of ovulation management-improves pregnancy rates and reduces days open in lactating dairy cows 1,2 ( Fig.…”

Synchronization of Estrus in Beef Females with the Melengestrol Acetate/Prostaglandin F2αProcedure: Estrus and Efficacy of 72-Hour Timed AI

“…Researchers have utilized the value of MGA and eliminated the negative effects on fertility by feeding MGA for about 14 days and then administering a luteolytic PGFza about 17 days later (Brown et al, 1988: Plugge et al, 1990Jaeger et al, 1992;Patterson and Corah, 1992;Yelich et al, 1995;Patterson et al, 1995). Subsequent to PGFzu treatment in most studies, females have been bred at estrus via the am/pm rule.…”

“…However, administration beyond the normal lifespan of corpora lutea suppresses fertility of the subsequent estrus (DeBois and Bierschwal, 1970;Beal et al, 1988;Anderson and Day, 1994). Therefore, some researchers have taken the approach of administering MGA for about 14 days followed by the administration of the luteolysin prostaglandin F,, (PGF,) about 17 d later so that estrus can be synchronized with normal fertility (Brown et al, 1988;Jaeger et al, 1992). Synchronized pregnancy rates (6-day) to this procedure have been reported to be about 49 to 57% and are similar to pregnancy rates in females that had been bred at non-synchronized estrus.…”