Pregnancy in dairy cows after synchronized ovulation regimens with or without presynchronization and progesterone.

Two experiments examined pregnancy after synchronized ovulation (Ovsynch) with or without progesterone (P4) administered via controlled internal drug release (CIDR) intravaginal inserts. In experiment 1, 262 lactating cows in one herd were in 3 treatments: Ovsynch (n = 91), Ovsynch + CIDR (n = 91), and control (n = 80). The Ovsynch protocol included injections of GnRH 7 d before and 48 h after an injection of PGF20. Timed artificial insemination (TAI; 57 to 77 d postpartum) was 16 to 20 h after the second GnRH injection. Cows in the Ovsynch + CIDR group also received a CIDR (1.9 g of P4) insert for 7 d starting at first GnRH injection. Control cows received A-I when estrus was detected using an electronic estrus detection system. Based on serum P4, 44.1% of cows were cyclic before Ovsynch. Pregnancy rates at 29 d (59.3 vs. 36.3%) and 57 d (45.1 vs. 19.8%) after TAI and embryo survival (75.9 vs. 54.5%) from 29 to 57 d were greater for Ovsynch + CIDR than for Ovsynch alone. In experiment 2, 630 cows in 2 herds received TAI at 59 to 79 d postpartum after 6 treatments. Estrous cycles were either presynchronized (2 injections of PGF2alpha 14 d apart; n = 318) or not presynchronized (n = 312). Within those groups, Ovsynch was initiated 12 d after second presynchronization PGF2alpha, and used alone (n = 318) or with CIDR inserts for 7 d (1.38 g of P4/insert, n = 124 or 1.9 g of P4/insert, n = 188). Before Ovsynch, 80% of cows were cyclic. Presynchronization increased pregnancy (46.8 vs. 37.5%) at 29 d after TAI, but CIDR inserts had no effect on pregnancy in experiment 2. Overall embryonic survival between 29 and 57 d in experiment 2 was 57.7%. Use of CIDR inserts with Ovsynch improved conception and embryo survival in experiment 1 but not in experiment 2, in part due to differing proportions of cyclic cows at the outset. Presynchronization before Ovsynch enhanced pregnancy rate.

Characteristics of estrus before and after first insemination and fertility of heifers after synchronized estrus using GnRH, PGF2alpha, and progesterone.

Our objectives were to determine fertility of heifers after synchronization of estrus using PGF2alpha, preceded by progesterone (P4), GnRH, or both, and to examine the variability of estrual characteristics in heifers before first and second AI. Dairy (n = 247) and beef (n = 193) heifers were assigned randomly to each of three treatments: 1) 50 microg of GnRH (injected i.m.) administered on d -7 followed by 25 mg of PGF2alpha (i.m.) on d -1 (GnRH + PGF; modified Select Synch protocol); 2) placement of an intravaginal progesterone (P4)-releasing insert on d -7, PGF2alpha on d -1, and insert removal on d 0 (P4+PGF); and 3) 50 microg of GnRH plus a P4 insert on d -7, followed by 25 mg of PGF2alpha on d -1, and insert removal on d 0 (P4+GnRH+PGF). Characteristics of estrus were examined before first AI and before the next eligible AI (18 to 26 d later), including duration of estrus, number of standing events, and total and individual duration of standing events. In addition, all heifers were checked visually at least twice daily for estrus. Blood samples were collected on d -7, -1, and 0 for determination of P4, and pregnancy status was diagnosed by ultrasonography 27 to 34 d after AI. Rates of detected estrus were less (P < 0.05) in dairy than in beef heifers, and greater (P < 0.05) in heifers treated with P4. Pattern of conception and pregnancy rates among treatments differed between beef and dairy heifers (treatment x group interaction; P < 0.05). In dairy heifers, conception and pregnancy rates were greatest with P4+PGF, followed by P4+GnRH+PGF and GnRH+PGF, respectively. The opposite was observed among treatments in beef heifers. Administration of P4 without the preceding injection of GnRH produced the lowest pregnancy rates in beefheifers. Ofthe quantified sexual behavioral characteristics during the synchronized estrus, the number of standing events and total duration of standing events were greater (P < 0.01) than those observed during the next eligible estrus before second AI, whereas duration of estrus was unaffected.

Stage of cycle, incidence, and timing of ovulation, and pregnancy rates in dairy cattle after three timed breeding protocols.

In experiment 1, 705 cows were assigned to three treatments: 1) the Ovsynch protocol (a GnRH injection given 7 d before and another 48 h after one PGF2alpha injection); 2) PGF2alpha + Ovsynch (one PGF2alpha injection given 12 d (d -22) before initiating Ovsynch (d -10); and 3) 2xPG12 (two PGF2alpha injections 12 d apart; d -15 and -3, followed 48 h later by a GnRH injection. All cows were inseminated (d 0) 16 to 20 h after the GnRH injection on d -1. Cyclic status was estimated by serum progesterone. More cows were in early diestrus at d -10 for PGF2alpha + Ovsynch (36%) and 2 x PG12 (29%) versus Ovsynch (19%). Multiparous cows receiving PGF2alpha + Ovsynch had greater pregnancy rates via ultrasonography at d 28 after AI (42%) than contemporaries after Ovsynch (28%) or 2xPG12 (27%) but did not differ significantly at palpation 10 to 30 d later (28, 19, and 17%, respectively). Pregnancy of first-parity cows was similar across treatments at 28 d (41%) or at palpation (33%). Pregnancy rates for 128 anestrous cows were lower, regardless of treatment. Overall embryo survival from d 28 until palpation was 72% but was only 44% in 2xPG12 cows that were anestrus through d -10. Experiment 2 included the three treatments above plus controls (one GnRH injection 7 d before PGF2alpha and AI after estrus). Preovulatory follicles were 6 to 11% larger near estrus in controls than on d -1 in cows receiving GnRH. More controls ovulated by 32 h after onset of estrus than were treated cows by 32 h after GnRH, but percentages (79 to 94%) were similar by 40 h. In multiparous cows, PGF2alpha before Ovsynch increased pregnancy rates, whereas the 2xPG12 protocol produced similar pregnancy rates as Ovsynch across parities. Ovulation was effectively induced by 40 h after GnRH.

An alternative AI breeding protocol for dairy cows exposed to elevated ambient temperatures before or after calving or both.

Our objective was to determine if a timed artificial insemination (AI) protocol (Ovsynch) might produce greater pregnancy rates than AI after a synchronized, detected estrus during summer. Lactating Holstein cows (n = 425) were grouped into breeding clusters and then assigned randomly to each of two protocols for AI between 50 and 70 days in milk. All cows were treated with GnRH followed 7 d later by PGF2alpha. Ovsynch cows then were treated with a second injection of GnRH 48 h after PGF2alpha and inseminated 16 to 19 h later. Controls received no further treatment after PGF2alpha and were inseminated after detected estrus. Pregnancy was diagnosed once by transrectal ultrasonography (27 to 30 d after AI) and again by palpation (40 to 50 d). Based on concentrations of progesterone in blood collected before each hormonal injection, only 85.4% of 425 cows were considered to be cycling. Although conception rates were not different between protocols at d 27 to 30, AI submission rates and pregnancy rates were greater after Ovsynch (timed AI) than after detected estrus. A temperature-humidity index > or = 72 was associated with fewer controls detected in estrus with lower conception than for controls detected in estrus when index values were < 72, whereas the reverse was true for cows after the Ovsynch protocol. We concluded that a timed AI protocol increased pregnancy rates at d 27 to 30 because its success was independent of either expression or detection of estrus. However, because of poorer embryonic survival in Ovsynch cows during heat stress only (39.5 vs. 69.2% survival for Ovsynch and control, respectively), pregnancy rates were not different by d 40 to 50 after timed AI.