Fixed-time inseminaton of suckled beef cows. 2. Cosynch and progesterone

The Cosynch protocol (GnRH 7 days before and again 48 h after PGF2 with AI at the second GnRH injection) produced pregnancy rates in suckled beef cows that exceeded 50% without heat detection and with only three handlings of all cows. The addition of an intravaginal progesterone insert to the Cosynch protocol improved pregnancy rates in two of the three breeds of cows studied

Fixed-time inseminaton of suckled beef cows. 2. Cosynch and progesterone

The Cosynch protocol (GnRH 7 days before and again 48 h after PGF2" with AI at the second GnRH injection) produced pregnancy rates in suckled beef cows that exceeded 50% without heat detection and with only three handlings of all cows. The addition of an intravaginal progesterone insert to the Cosynch protocol improved pregnancy rates in two of the three breeds of cows studied

Fertility of heifers after synchronization of estrus using GnRH, PGF2α, and progesterone (CIDR)

Our objectives were to determine fertility of heifers after estrus synchronization using PGF2α preceded by either progesterone, GnRH, or both. Beef (n = 193) and dairy (n = 246) heifers were assigned randomly to three treatments: 1) 50 μg of GnRH and a used intravaginal progesterone-releasing insert were administered on day −7, followed by 25 mg of PGF2α on day −1, and CIDR removal on day 0 (CIDR + GnRH + PGF); 2) the same as 1) but without the GnRH (CIDR + PGF); and 3) the same as 1) but without the CIDR (GnRH + PGF; modified Select Synch). Rates of estrus detection were lower in dairy than in beef heifers, and greater in heifers treated with the CIDR. In dairy heifers, conception and pregnancy rates were greatest in the CIDR + PGF treatment, followed by the CIDR + GnRH + PGF and GnRH + PGF treatments. The opposite trend was observed among treatments in beef heifers. All estrus-synchronization treatments produced acceptable estrus detection and pregnancy rates

Synchronizing estrus in replacement beef heifers using select synch, MGA, AND PGF2

The Select Synch protocol (GnRH at day - 7, PGF2 at day 0, AI at detected heat) was compared to protocols using either MGA + prostaglandin (Colorado system) or two injections of prostaglandin to synchronize estrus in replacement heifers at three locations. Percentage of heifers detected in heat before, during, or after the target breeding week was not different among treatments but varied in percentages among locations. Overall conception rates ranged from 64 to 69%. Pregnancy rates varied from 46 to 56% and tended to be greatest in the MGA + PGF2" treatment. Costs of these treatments ranged from $3.50 to$8 and were lowest for the MGA + PGF2 protocol

Supplemental progestin increases pregnancy rates in suckled beef cows

In two experiments, combining a source of progestin with the ovulation synchronization protocol using gonadotropin-releasing hormone plus prostaglandin F2a (GnRH + PGF2a) tended to increase or statistically increase pregnancy rates in suckled cows compared to GnRH + PGF2a alone. These improvements were accomplished without any detected estrus when cows were inseminated and received a second injection of GnRH at 48 hr after PGF2a

Ovulation synchronization with progestins prior to a Cosynch protocol in beef cows

A multi-location study was conducted using suckled beef cows in Minnesota and Kansas to test the benefit of adding a source of progestin to the Cosynch ovulation synchronization protocol (injections of GnRH, 7 days before and 48 hr after an injection of PGF2", with a fixed-time artificial insemination (AI) administered at the same time as the second GnRH injection). Feeding melengestrol acetate (MGA) for 14 days followed in 12 days by the Cosynch protocol was compared to the Cosynch protocol with the addition of a progesterone-impregnated insert (CIDR) placed in the vagina for 7 days concurrent with the first GnRH injection. Pregnancy rates after the first AI (timed AI) were 22% greater with the CIDR insert, whereas conception rates for those cows returning to estrus were greater for cows previously fed MGA. Total pregnant cows after two inseminations were 64% for CIDR cows and 59% for MGA cows

Resynchronization of estrus with progesterone and estrogen in previously inseminated beef cows

A study was conducted in 609 beef cows to determine whether or not estrus might be resynchronized in previously inseminated beef cows to accommodate a second artificial insemination (AI) early in the breeding season. Previously inseminated cows were treated for 7 days with progesterone (via a previously used intravaginal progesterone-releasing insert [CIDR]) beginning 13 days after AI. In addition, injections of estrogen (estradiol benzoate [EB] or estradiol cypionate [ECP]) were given at insertion and removal of the CIDR insert. Rates of return to estrus and total pregnancy rates were increased after treatments with progesterone and estrogen compared with controls. No harm to pregnancies occurred in pregnant cows and a second AI period was facilitated by the end of the first 23 days of the breeding season

Fertility after timed breeding using GnRH, PGF2, and norgestomet

At the KSU Purebred Unit, 164 purebred Angus, Hereford, and Simmental cows were used to test a new estrus-synchronization program using GnRH, PGF2, and norgestomet. Cows were inseminated after detected estrus, or in the absence of estrus, inseminations were made at one fixed time after a second injection of GnRH. The treatment consisted of a 100 µg injection of GnRH plus a 6-mg ear implant of norgestomet. Seven days later, the ear implant was removed, and 25-mg of PG F2% was injected. In the absence of estrus, the time-bred group received a second injection of GnRH 48 h after PGF2% and was inseminated 16 h later. The treatment induced 10 of 36 anestrous cows to ovulate. Conception rates tended (P<.09) to be greater in Angus (72.2%) than Hereford cows (52.8%) , with conception rates in Simmental cows (51.5%) being similar to those in Hereford. Overall, pregnancy rates were similar between the time-bred group (59.3%) and the estrus-bred group (53.8%). We conclude that using GnRH, PG F2%, and norgestomet in a timed breeding program ca n eliminate the necessity of heat detection. In addition, the treatment induced estrus in 28% of the noncycling cows