Prostaglandin F2α and gonadotropin-releasing hormone administration improve progesterone status, luteal number, and proportion of ovular and anovular dairy cows with corpora lutea before a timed artificial insemination program.

The objective of this research was to increase the proportion of cows with at least 1 functional corpus luteum (CL) and elevated progesterone at the onset of the timed artificial insemination (TAI) protocol. Postpartum Holstein cows in one herd were stratified by lactation number at calving (September 2009 through August 2010) and assigned randomly to 2 treatments: 1) Presynch-10 (n=105): two 25-mg injections of PGF(2α) (PG) 14 d apart (Presynch); and 2) PG-3-G (n=105): one 25-mg injection of PG 3 d before 100-μg GnRH (Pre-GnRH) injection, with the PG injection administered at the same time as the second PG injection in the Presynch-10 treatment. Cows were enrolled in a TAI protocol [Ovsynch; injection of GnRH 7 d before (GnRH-1) and 56 h after (GnRH-2) PG injection with AI 16 to 18 h after GnRH-2] 10 d after the second or only PG injection. Blood samples for progesterone or estradiol analyses were collected on median days in milk (DIM): 36, 39, 50, 53 (Pre-GnRH), 60 (GnRH-1), 67 (PG), 69 (GnRH-2), and 70 (TAI). Ovarian structures were measured by ultrasonography on median DIM 53, 60, 67, 69, and 6 d post-TAI to determine follicle diameters, ovulation response to GnRH, or both. Although progesterone concentration did not differ between treatments before Pre-GnRH injection, the proportion of cows with at least 1 CL tended to be greater for PG-3-G than Presynch-10 cows, and more PG-3-G cows ovulated after Pre-GnRH injection than ovulated spontaneously in Presynch-10. Further, the diameter of follicles that ovulated tended to be smaller in PG-3-G than in Presynch-10 cows after Pre-GnRH injection. At GnRH-1, the proportion of cows with progesterone ≥1 ng/mL, the number of CL per cow, and the proportion of cows with at least 1 CL were greater for PG-3-G than Presynch-10. Neither follicle diameter nor percentage of cows ovulating after GnRH-1 differed between treatments. At PG injection during the week of TAI, progesterone concentration and the proportion of cows with progesterone ≥1 ng/mL tended to be greater for PG-3-G than Presynch-10, and PG-3-G had more CL per cow than Presynch-10. No ovarian characteristics differed between treatments after GnRH-2, including progesterone concentration, number of CL per cow, and total luteal volume 7 d after GnRH-2. Many of the previous ovarian traits were improved in both ovular and anovular cows after PG-3-G compared with Presynch-10. Pregnancies per AI at d 32 and 60 were only numerically greater for PG-3-G than for Presynch-10 cows, largely because of differences detected during months without heat stress. We concluded that the PG-3-G treatment increased ovulation rate and luteal function 7 d before the onset of Ovsynch, resulting in improved follicular synchrony and predisposing potentially greater pregnancies per AI in lactating dairy cows.

Stevenson JS ，Pulley SL ，Mellieon HI Jr 《-》

Pregnancy per artificial insemination after presynchronizing estrous cycles with the Presynch-10 protocol or prostaglandin F2α injection followed by gonadotropin-releasing hormone before Ovsynch-56 in 4 dairy herds of lactating dairy cows.

The objective was to determine the effect of 2 presynchronization treatments on first-service pregnancy per artificial insemination (P/AI) in 4 dairy herds during warm and cool seasons of the year. Cows with ear tags ending with even digits at calving were enrolled in Presynch-10 (Presynch-10): two 25-mg injections of PGF2α (i.e., PG-1 and PG-2) 14 d apart. Cows with ear tags ending with odd digits were enrolled in PG-3-G: one 25-mg injection of PG (Pre-PG) 3 d before injection of 100μg of GnRH (Pre-GnRH), with the Pre-PG injection administered at the same time as PG-2 in the Presynch-10 treatment. Ten days after PG-2 or Pre-PG, all cows were enrolled in a timed AI protocol (Ovsynch-56; injection of GnRH 7 d before GnRH-1 and 56 h after GnRH-2 PG with AI 16 to 18 h after GnRH-2). Median days in milk (DIM) at scheduled timed AI were 75 d, which did not differ among herds. Cows detected in estrus before the scheduled timed AI were inseminated early (early bred, EB). Pregnancy was diagnosed at d 32 to 38 and at d 60 to 66 after timed AI by transrectal ultrasonography or transrectal palpation. Data were analyzed with herd as a random effect and with fixed effects of treatment (EB, Presynch-10, or PG-3-G), parity (primiparous vs. multiparous), season [hot (June through September) vs. cool-cold (October through May)], DIM, estrus at timed AI (0 vs. 1), and all 2-way interactions with treatment. The P/AI at d 32 to 38 for EB (n=472), Presynch-10 (n=1,247), and PG-3-G (n=1,286) were 31.4, 35.0, and 41.2%, respectively; P/AI at d 60 to 66 was 29.8, 32.2, and 37.3%, respectively. Season significantly influenced P/AI at d 32 to 38 and d 60 to 66, but a treatment by season interaction was not detected. The P/AI for PG-3-G and Presynch-10 treatments did not differ during cool-cold weather (d 32 to 38: 46.8 vs. 44.3%; d 60 to 66: 41.6 vs. 41.1%, respectively), but PG-3-G and Presynch-10 produced more P/AI than EB at d 32 to 38. During the summer, P/AI in PG-3-G was greater than in Presynch-10 (d 32 to 38: 35.9 vs. 26.7% and d 60 to 66: 33.2 vs. 24.4%, respectively), and P/AI in EB cows did not differ from that of Presynch-10 cows. Although pregnancy loss did not differ for EB, Presynch-10, and PG-3-G treatments (4.0, 6.7, and 9.3%, respectively), pregnancy loss from d 32 to 38 and d 60 to 66 was 2-fold greater in thinner cows (<2.5 vs. ≥2.5; 9.0 vs. 4.4%). We concluded that presynchronizing estrous cycles with PG-3-G produced more P/AI than inseminating cows at estrus during cooler weather and was superior to Presynch-10 during the summer.

Stevenson JS ，Pulley SL 《-》

Ovarian characteristics and timed artificial insemination pregnancy risk after presynchronization with gonadotropin-releasing hormone 7 days before PGF2α in dairy cows.

The objective was to determine the benefit of including GnRH and PGF2α (PG) as a part of a presynchronization option before enrolling cows in a timed artificial insemination (AI) program. Holstein cows in one herd were assigned weekly at calving from January 2012 to August 2014 to a completely randomized design consisting of two presynchronization treatments. Cows in the Presynch-11 (n = 290) control were administered two PGF2α injections (Presynch PG-1 and Presynch PG-2) 14 days apart starting at 39 ± 4 days postpartum (study Days 0 and 14). Cows receiving the experimental presynchronization treatment (Gsynch-11, n = 287) were treated with GnRH (pre-GnRH) on study Day 7 and PG (pre-PG) on study Day 14. On study Day 25, all cows were enrolled in the Ovsynch-56 timed AI program: GnRH-1 on study Day 25, PG on study Day 32, GnRH-2 on study Day 34, 56 hours after PG, and timed AI on study Day 35, 16 hours after GnRH-2. In a subsample of 255 cows, ovarian structures were monitored for size and ovulation, and blood samples were collected on study Days 7, 14, 25, 32, 34, and 41 to measure progesterone. Concentrations of progesterone were greater (P < 0.05) in Gsynch-11 than Presynch-11 cows before pre-GnRH was administered (3.3 ± 0.3 vs. 2.1 ± 0.3 ng/mL), respectively, and ovulatory response to the pre-GnRH treatment also was greater (P = 0.008) in Gsynch-11 than Presynch-11 cows (53.2 vs. 35.0%), respectively. One week later, the dominant follicle was larger (P = 0.045) in Presynch-11 than Gsynch-11 cows. Eleven days after completing the presynchronization treatments, ovulatory response to the Ovsynch GnRH-1 treatment was greater (P = 0.016) in Presynch-11 than Gsynch-11 cows (62.2% vs. 45.6%), respectively. At the time of the Ovsynch-PG treatment, more (P = 0.019) Presynch-11 than Gsynch-11 cows had at least one CL. Subsequent luteal regression (>96%), ovulation to GnRH-2 (>90%), and synchronization risk (>88%) did not differ between treatments, but incidence of multiple ovulation after GnRH-2 was larger (P = 0.036) in Presynch-11 than Gsynch-11 cows (28.4% vs. 15.9%), respectively. Pregnancy per AI at 32 days (36.4% vs. 35.1%) and 60 days (30.0% vs. 29.0%) after AI did not differ between Gsynch-11 and Presynch-11 cows, respectively, but was suppressed during summer months in both treatments to less than 70% of the pregnancy per AI of nonsummer months. Because more than 90% of the cows were ovular as treatments were applied, the GnRH treatment of Gsynch-11 could not be assessed for its benefit in anovular cows. The Gsynch-11 presynchronization treatment performed comparably with the standard Presynch-11 program and provides a viable presynchronization option for use before first AI in dairy herds.

Stevenson JS 《-》

Alternative programs to presynchronize estrous cycles in dairy cattle before a timed artificial insemination program.

The objective was to test potential presynchronization programs applied to cows before a timed artificial insemination (TAI) program to increase the percentage of cows ovulating in response to both GnRH injections of a TAI program and having a functional corpus luteum before the first GnRH injection of the TAI program. At calving, cows were blocked by lactation (1 vs. 2+) and assigned randomly to receive 1 of 5 presynchronization treatments. Two variants of the standard Presynch program were tested in which 2 injections of PGF2α were administered 14 d apart with either 14 d (Pre14; n=122), 12 d (Pre12; n=123), or 10 d (Pre10; n=151) intervening before a TAI program was initiated. Two other presynchronization programs consisted of administering a progesterone-releasing controlled internal drug release (CIDR) insert for 7 d plus PGF2α administration at insert removal. Insert removal occurred either 10 d (CIDR10; n=157) or 3 d (CIDR3; n=117) before a TAI program was initiated. The TAI program was a standard Cosynch program [injection of GnRH 7 d before (GnRH-1) and 72 h after (GnRH-2) PGF2α with TAI administered 72 h after PGF2α]. Cosynch served as the control (n=157), and cows were assumed to be starting this program at random stages of the estrous cycle. From a subset of cows per treatment (ranging from 49 to 51 cows each), blood samples were collected from coccygeal vessels by using evacuated tubes at d -28, -14, 0 (onset of TAI program), 7, 9, 14, and 21. Ovarian scans were conducted on d 0, 7, 9, 14, and 21 by transrectal ultrasonography. Diameters of follicles and corpus luteum were measured at each exam, and ovulation was determined on d 7 (response to GnRH-1 on d 0) and d 14 (response to GnRH-2 on d 10). Ovulatory incidence after GnRH-1 (47.1 to 67.3%) and GnRH-2 (78 to 90.2%) varied but did not differ among treatments. Before GnRH-1, progesterone concentrations were less in the CIDR3 treatment than in all other treatments. Before GnRH-2, progesterone was greater in the CIDR3 treatment than in all other treatments. Luteal regression and synchronization rate (successful luteolysis and ovulation after GnRH-2) did not differ among treatments. Pregnancy rate per AI at 32 and 60 d post TAI was less in CIDR3 cows than in cows in all other treatments. None of the Presynch treatments improved key responses (ovulation, luteolysis, and synchronization rate) known to improve fertility compared with a standard Cosynch program without presynchronization.

Stevenson JS 《-》

A modified presynchronization protocol improves fertility to timed artificial insemination in lactating dairy cows.

To compare 2 hormonal protocols for submission of lactating dairy cows for timed artificial insemination (TAI), nonpregnant lactating Holstein cows (n = 269) >60 d in milk were randomly assigned to each of 2 treatments to receive TAI (TAI = d 0). Cows assigned to the first treatment (Ovsynch, n = 134) received 50 microg of GnRH (d -10), 25 mg of PGF2alpha (d -3), and 50 microg of GnRH (d -1) beginning at a random stage of the estrous cycle. Cows assigned to the second treatment (Presynch, n = 135) received Ovsynch but with the addition of 2 PGF2alpha (25 mg) injections administered 14 d apart beginning 28 d (d -38 and -24) before initiation of Ovsynch. All cows received TAI 16 to 18 h after the second GnRH injection. Ovulatory response after each GnRH injection for a subset of cows (n = 109) and pregnancy status 42 d after TAI for all cows were assessed using transrectal ultrasonography. Based on serum progesterone (P4) profiles determined for a subset of cows (n = 109), P4 concentrations decreased for Presynch cows after the first 2 PGF2alpha injections, and Presynch cows had greater P4 concentrations at the PGF2alpha injection on d -3 compared with Ovsynch cows. Although the proportion of cows ovulating after the first and second GnRH injections did not differ statistically between treatments (41.1 and 69.6% vs. 35.9 and 81.1% for Ovsynch vs. Presynch, respectively), pregnancy rate per artificial insemination (PR/AI) at 42 d post TAI was greater for Presynch than for Ovsynch cows (49.6 vs. 37.3%). Parity, DIM, and body condition score (BCS) at TAI did not affect PR/AI to TAI. These data support use of this presynchronization protocol to increase PR/ AI of lactating dairy cows receiving TAI compared with Ovsynch.

Navanukraw C ，Redmer DA ，Reynolds LP ，Kirsch JD ，Grazul-Bilska AT ，Fricke PM ... -  《JOURNAL OF DAIRY SCIENCE》