Hormonal responses and pregnancy outcomes after five-day ovulation synchronization and presynchronization programs in lactating dairy cows

Doctor of PhilosophyDepartment of Animal Sciences and IndustryJeffrey S. StevensonTwo experiments assessed pregnancy outcomes (pregnancy per AI; P/AI) after 5-d Ovsynch-56 Resynch (RES; GnRH injection 5 d before [GnRH-1; d 0] and 56 h (GnRH-2) after the last PGF2α [PGF] injection on d 6 given 24 h after first PGF injection on d 5, and TAI on d 8) with and without a 5-d progesterone insert. In Exp. 1, only 76% of 1,023 nonpregnant cows enrolled on d 34 post-AI had high (≥1 ng/mL) progesterone. The RES-CIDR cows with low progesterone at treatment initiation had greater P/AI than RES-CON (37.7 vs. 29.4%), whereas RES-CIDR cows with high progesterone had lesser P/AI than RES-CON (27.4 vs. 34.3%) suggesting that supplemental progesterone is progesterone-dependent. In Exp. 2, 381 cows were enrolled in similar treatments on d 31 with RES on d 41post-AI plus a third treatment including PG-3-G (Pre-PGF on d 31, Pre-GnRH on d 34, and RES on d 41. The P/AI was similar among treatments but was greater in cows starting RES on d 41 when progesterone was low (44%) than high (33%).Experiment 3 determined LH and ovulatory responses in cows enrolled in two treatments before AI: 1) Pre10 (n = 37): PGF-1 and PGF-2 given 14 d apart (Presynch); or PG3G (n = 33): PGF given concurrent with the PGF-2, 3 d before GnRH-1 followed in 7 d by Ovsynch [injection of GnRH (GnRH-2) 7 d before PGF (PGF-3) and GnRH-3 at either 56 or 72 h after PGF-3] that was initiated 10 d after PGF-2 for Pre10 or 7 d after GnRH-1 of PG3G. The GnRH- 1 increased incidences of LH surges and ovulation in PG3G compared with Pre10. The LH in serum of Pre10 was greater than that of cows receiving PG3G after GnRH-2. Following GnRH- 3, cows receiving GnRH at 72 h had increased incidence of spontaneous LH surges before GnRH-3. The P/AI for PG3G vs. Pre10 and for 56 vs. 72 h was similar, but the Pre10-72 h treatment combination was less than all other treatment combinations. Release of LH is protocol dependent and flexibility of GnRH timing is an advantage for PG3G before first-service TAI

Luteolysis and pregnancy outcomes after change in dose delivery of prostaglandin F2α in a 5-day timed artificial insemination program in dairy cows

Dairy Research, 2014 is known as Dairy Day, 2014Three experiments were conducted to determine if a larger dose of prostaglandin F2α (PG) administered on day 6 of a 5-day Ovsynch timed artificial insemination (AI) program would induce regression of the corpus luteum to facilitate AI and pregnancy outcomes similar to a traditional 5-day program with two doses of PG. When applying a 5-day program, cows that ovulate in response to the first GnRH injection have a new corpus luteum (CL) that is 2 days younger when PG is administered in a 5- versus 7-day program. To regress successfully the younger CL, a second injection of PG must be given 24 hours after the first PG injection to prevent reduced pregnancy rate after the timed AI. These experiments demonstrated that administering 50 mg PG (10 mL Lutalyse) on day 6 produced luteolysis as efficiently as 25 mg PG (5 mL Lutalyse) administered on days 5 and 6 when the cut point for progesterone was 1 ng/mL 72 hours after the first PG injection or 48 hours after the larger PG dose. In contrast, when the cut point was 0.5 ng/mL, the larger dose of PG was less effective. Pregnancy outcomes in cows did not differ between treatment doses except in one herd (Exp. 3). Although pregnancy outcomes were reduced only in one herd with the larger PG dose, this difference may be confounded with the earlier injection of the second GnRH injection 16 hours before timed AI, rather than failure of luteolysis in response to the larger dose of PG. Delaying the timing of AI, injection of the second GnRH, or both may be warranted to allow sufficient time for progesterone to decrease to basal concentrations in response to a larger dose of PG on day 6 to prevent a reduction in fertility

Presynchronizing PGF2α and GnRH injections before timed artificial insemination CO-Synch + CIDR program

Fixed-time artificial insemination is an effective management tool that reduces the labor associated with more conventional artificial insemination programs requiring detection of estrus. The 7-day CO-Synch + controlled internal drug release (CIDR) insert protocol has been shown to effectively initiate estrus and ovulation in cycling and non-cycling suckled beef cows, producing pregnancy rates at or greater than 50% in beef cows. The gonadotropin-releasing hormone (GnRH) injection that begins the CO-Synch + CIDR program initiates ovulation in a large proportion of cows, particularly anestrous cows. The CIDR, which releases progesterone intravaginally, prevents short estrous cycles that usually follow the first postpartum ovulation in beef cows. Our hypothesis was that inducing estrus with a prostaglandin injection followed 3 days later with a GnRH injection, 7 days before applying the 7-day CO-Synch + CIDR protocol, might increase the percentage of cycling cows that would exhibit synchronous follicular waves after the onset of the CO-Synch + CIDR protocol. We also hypothesized that the additional GnRH injection would increase the percentage of anestrous cows that would ovulate, thereby increasing pregnancy outcomes

Ovarian characteristics, serum concentrations, and fertility in lactating dairy cows in response to equine chorionic gonadotropin

Master of ScienceDepartment of Animal Sciences and IndustryJeffrey S. StevensonThe objectives were to evaluate the effects of equine chorionic gonadotropin (eCG) administration on preovulatory follicle diameter, serum estradiol and progesterone concentration, corpus luteum (CL) diameter, estrual activity, and pregnancy rate. Lactating dairy cows were submitted to a Presynch-Ovsynch timed artificial insemination (TAI) protocol. Cows (n = 121) in a single herd were treated with 2 injections of prostaglandin F2α (PGF) 14 d apart (Presynch), with the second injection administered 11 d before the onset of a timed AI protocol (Ovsynch; injection of GnRH 7 d before and 56 h after PGF2α, with TAI administered 16 to 18 h after the second GnRH injection). Cows were assigned randomly to receive either saline or 400 IU eCG concurrent with the PGF2α injection of the Ovsynch protocol (d 0). Blood samples were collected during the study to monitor serum changes in progesterone and estradiol to determine if eCG would facilitate increased estrual activity, improved ovulatory response to GnRH, and enhanced post-ovulatory luteal function. Administration of eCG tended to increase the number of CL and on d 9 and 16 after PGF2α, corresponding to d 6 and 13 post-ovulation. Volume of the post-eCG treatment luteal tissue was increased only on d 16. Timed AI pregnancy rates did not differ between eCG (36.9%) and control cows (41.8%). We concluded that use of eCG provided no profertility advantages to dairy cattle when programmed for a timed insemination at first service

Five-day resynch programs in dairy cows including controlled internal drug release at two stages post-artificial insemination

Dairy Research, 2013 is known as Dairy Day, 2013Two experiments were conducted to assess pregnancy outcomes after a 5-day Ovsynch-56 Resynch (RES; gonadotropin-releasing hormone injection 5 days before [GnRH-1; d 0] and 56 hours (GnRH-2) after PGF2α [PG] injections on day 5 and 6, timed artificial insemination [TAI] on day 8) with and without a progesterone-releasing intravaginal controlled internal drug release (CIDR) 5-day insert. In Exp. 1, nonpregnant cows were enrolled on day 34 post- AI: day 34 RES-CON (n = 528) or day 34 RES-CIDR (n = 503). Blood was collected for progesterone assay. Pregnancy per AI (P/AI) was diagnosed by uterine palpation per rectum at 34 and 62 days post-TAI. Only 76% of 1,031 cows had high progesterone (≥1 ng/mL) on day 34 at the nonpregnant diagnosis. No differences in P/AI were detected between treatments. The day-34 RES-CIDR cows with low (<1 ng/mL) progesterone, however, had greater (P = 0.036) P/AI than day-34 RES-CON cows (37.7 vs. 29.4%), whereas day-34 RES-CIDR cows with high progesterone had lesser P/AI than day-34 RES-CON (27.4 vs. 34.3%). In Exp. 2, cows were enrolled on day 31 post-AI after a nonpregnant diagnosis: (1) day 31 PG-3-G (n = 102): Pre-PG on day 31, Pre-GnRH on day 34, and RES on day 41 (n = 102); (2) day 41 RES-CON (n = 108) as Exp. 1, but on day 41; and (3) day 41 RES-CIDR (n = 101) as Exp. 2, but on day 41. Blood was collected for progesterone assay and ovarian structures were mapped by ultrasonography on days 31, 34, 41, 46, and 48. Pregnancy was diagnosed by ultrasonography on days 31 and 59 post-TAI. The proportion of cows with high progesterone on day 31 was 70.6%. More (P < 0.001) cows ovulated after Pre-GnRH on day 31 PG-3-G (60.4%) than for day 41 RES-CON (12.5%) or day 41 RES-CIDR (17.1%). More (P < 0.001) PG-3-G cows had luteolysis after Pre-PG on day 31 than other treatments (73.7 vs. < 11%). The proportion of cows with high progesterone on day 41 at GnRH-1 tended (P = 0.10) to be greater for PG-3-G (75.6%) than for other treatments (65 to 70%). The P/AI was greater in cows starting RES on day 41 when progesterone was low (44%) than when it was high (33%), but no treatment differences were detected 31 days after TAI (PG-3-G = 33.3%; d 41 RES-CON = 38.9%; d 41 RES-CIDR = 35.6%). We concluded that improved P/AI for cows initiating the 5-day RES on day 34 without a corpus luteum is progesterone-dependent because addition of the CIDR insert to the RES treatment improved P/AI in cows with low progesterone (Exp. 1). Although day-31 PG-3-G increased luteolysis and produced greater ovulation rates before the onset of RES, no increase in P/AI was detected compared with RES started on day 41 with or without a CIDR insert

Prostaglandin F2α and GnRH administration improved progesterone status, luteal number, and proportion of ovular and anovular dairy cows with corpora lutea before a timed artificial insemination program

Dairy Research, 2011 is known as Dairy Day, 2011The 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) program. Postpartum Holstein cows in 1 herd were stratified by lactation number at calving (September 2009 through August 2010) and assigned randomly to 1 of 2 treatments: (1) Presynch-10 (n = 105): two 25-mg injections of prostaglandin F2α (PG) 14 days apart (Presynch); and (2) PG-3-G (n = 105): one 25-mg injection of PG 3 days before 100 μg gonadotropin- releasing hormone (GnRH; Pre-GnRH), with the PG injection administered at the same time as the second PG in the Presynch-10 treatment. Cows were enrolled in a TAI protocol (Ovsynch; injection of GnRH 7 days before [GnRH-1] and 56 hours after [GnRH-2] PG with AI 16 to 18 hours after GnRH-2) 10 days 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 days 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 than ovulated spontaneously in Presynch-10. Furthermore, diameter of follicles that ovulated tended to be smaller in PG-3-G than Presynch-10 cows after Pre-GnRH. 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 days 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 days 32 and 60 were only numerically greater for PG-3-G vs. 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 days before the onset of Ovsynch, resulting in improved follicular synchrony and predisposing potentially greater pregnancies per AI in lactating dairy cows

Pregnancy per AI after presynchronizing estrous cycles with Presynch-10 or PG-3-g before Ovsynch-56 in four dairy herds of lactating dairy cows

Dairy Research, 2012 is known as Dairy Day, 2012The objective was to determine the effect of 2 presynchronization treatments on first-service pregnancy rate 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 with 2, 25-mg injections of prostaglandin F2α (i.e., PG-1 and PG-2) 14 days apart. Cows with ear tags ending with odd digits were enrolled in PG-3-G comprising 1, 25-mg injection of PG (Pre-PG) 3 days before 100 μg gonadotropin-releasing hormone (Pre-GnRH), with the Pre-PG injection administered at the same time as PG-2 in the Presynch-10 treatment in the Presynch-10 treatment. Ten days after PG-2 or Pre-PG, all cows were enrolled in a timed artificial insemination (TAI) protocol (Ovsynch-56; injection of GnRH 7 days before [GnRH-1] and 56 hours after [GnRH-2] PG with AI 16 to 18 hours after GnRH-2). Median days in milk (DIM) at scheduled TAI were 75 days, which did not differ among herds. Cows detected in estrus before the scheduled TAI were inseminated early (early bred; EB). Pregnancy was diagnosed at days 32 to 38 and at days 60 to 66 after TAI by transrectal ultrasonography or transrectal palpation. Data were analyzed with herd as a random effect and with fixed effects of treatment (EB, Presynch-10, PG-3-G), parity (primiparous vs. multiparous), season (hot [June through September] vs. cool-cold [October through May]), DIM, estrus at TAI (0 vs. 1), and all 2-way interactions with treatment. The pregnancy rate at days 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; pregnancy rate at days 60 to 66 was 29.8, 32.2, and 37.3%, respectively. Season significantly influenced pregnancy rate at days 32 to 38 and days 60 to 66, but a treatment by season interaction was not detected. The pregnancy rate for PG-3-G and Presynch-10 treatments did not differ during cool-cold weather (d 32 to 38: 46.8 vs. 44.3%; days 60 to 66: 41.6 vs. 41.1%, respectively), but PG-3-G and Presynch-10 produced a higher pregnancy rate than EB at days 32 to 38. During summer, pregnancy rate in PG-3-G was greater than in Presynch-10 (days 32 to 38: 35.9 vs. 26.7% or days 60 to 66: 33.2 vs. 24.4%, respectively), and pregnancy rate 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 days 32 to 38 and days 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 pregnancies than inseminating cows at estrus during cooler weather and was superior to Presynch-10 during summer

Ovarian characteristics, serum hormone concentrations, and fertility in lactating dairy cows in response to equine chorionic gonadotropin

Dairy Research, 2010 is known as Dairy Day, 2010The objective of this study was to evaluate the effects of equine chorionic gonadotropin (eCG) on various characteristics associated with an effective timed artificial insemination (AI) protocol in lactating dairy cows. Cows (n = 121) in a single herd were treated with 2 injections of prostaglandin F2α (PGF2α) 14 days apart (Presynch), with the second injection administered 11 days before the onset of a timed AI protocol. Cows received either saline or 400 IU eCG concurrent with the PGF2α injection of the Ovsynch protocol (injection of gonadotropinreleasing hormone or GnRH, 7 days before and 48 to 56 hours after PGF2α with insemination occurring 12 to 16 hours after the second GnRH injection). Blood samples were collected during the study to monitor serum changes in progesterone and estradiol in order to determine if eCG would facilitate increased estrual activity, improved ovulatory response, and enhanced postovulatory luteal function. Administration of eCG tended to increase the number of corpora lutea (CL) and on days 9 and 16 after PGF2α, corresponding to days 6 and 13 postovulation, but the volume of the luteal tissue was less than that in the control. Timed AI pregnancy rates did not differ between eCG (36.9%) and control cows (41.8%). We concluded that use of eCG provided no profertility advantages to dairy cattle when programmed for a timed insemination at first service

Concentrations of luteinizing hormone and ovulatory responses in dairy cows before timed artificial insemination

Dairy Research, 2013 is known as Dairy Day, 2013The objective of this study was to determine the incidence of spontaneous and gonadotropinreleasing hormone (GnRH)-induced surges of luteinizing hormone (LH) and ovulatory responses in lactating dairy cows enrolled in a timed artificial insemination (TAI) protocol. Cows (n = 70) in a single herd were assigned to one of two presynchronization protocols: Pre- 10 or PG-3-G. Cows assigned to the Pre-10 treatment received 2 injections of prostaglandin F2α (PGF2α) 14 days apart (Presynch), with the second injection administered 10 days before the onset of a TAI protocol. Cows assigned to the PG-3-G treatment received an injection of prostaglandin F2α (PGF2α), then 3 days later an injection of GnRH (GnRH-1) 7 days before the onset of a TAI protocol. All cows received the first GnRH injection (GnRH-2) of the Ovsynch protocol and a PGF2α injection 7 days later, then cows received the breeding injection of GnRH (GnRH-3) at either 56 or 72 hours after PGF2α, with insemination occurring 12 to 16 hours after the second GnRH injection. Blood samples were collected during the study to monitor serum changes in LH, progesterone, and estradiol to determine why ovulatory responses to GnRH-induced LH release did not approach 100% when follicle dominance and adequate follicle size was achieved. Presynchronization administration of GnRH-1 increased the incidence of LH surges and ovulation rates in cows presynchronized with PG-3-G compared with Pre-10. Incidence of ovulation and occurrence of LH surges did not differ after GnRH-2, but more LH was released in Pre-10 than PG-3-G cows. Luteolysis, LH surge incidence, and ovulation rates were similar among the 4 treatment-time combinations after GnRH-3. Pregnancy per TAI was decreased in Pre-10 at 56 hours compared with Pre-10 at 72 hours and PG-3-G at 56 and 72 hours. We concluded that administration of GnRH 56 hours before breeding decreased pregnancy per TAI compared with administration of GnRH at 72 hours when cows were presynchronized with Pre-10. Presynchronization with PG-3-G resulted in acceptable pregnancy per TAI with GnRH administration occurring at either 56 or 72 hours before TAI. The flexibility of GnRH timing with the PG-3-G presynchronization protocol may be an advantage compared with the Pre-10 protocol for dairy cattle when programmed for a TAI at first service

Evaluation of the 5- vs. 7-day CIDR program in dairy heifers before timed artificial insemination

Dairy Research, 2011 is known as Dairy Day, 2011Our objectives were to determine: (1) the effectiveness of an injection of PGF2α to regress the corpus luteum before initiating an timed artificial insemination (TAI) program, (2) ovulation response to gonadotropin-releasing hormone (GnRH), and (3) pregnancy outcomes in dairy heifers inseminated with conventional and gender-biased semen. Heifers (n = 545) from 3 locations (Florida, Kansas, and Mississippi) were assigned randomly to 1 of 2 treatments: (1) 25-mg prostaglandin F2α (PGF2α) injection and controlled internal drug release (CIDR) insert on day −7 followed by 100 μg of GnRH administered on day −5, and a 25-mg PGF2α injection at CIDR insert removal (7D) on day 0; or (2) 100 μg of GnRH and insertion of previously used autoclaved CIDR on day −5 and a 25-mg PGF2α injection at CIDR removal (5D) on day 0. Artificial insemination occurred after detected estrus from days 0 to 3. Those heifers not detected in estrus were inseminated on day 3 (72 hours after PGF2α) and given a second 100-μg dose of GnRH (72 hours after CIDR removal). Blood collected on days −7 and −5 was assayed to determine concentrations of progesterone and presence of a CL (progesterone ≥1 ng/mL) on d −7. Blood progesterone concentrations on days 0 and 3 were used to determine if luteolysis occurred in all heifers. Pregnancy was determined on days 32 and 60 and intervening pregnancy loss was calculated. Of those heifers in the 7D treatment having progesterone ≥1 ng/mL on day −7, the proportion having progesterone <1 ng/mL 2 days later (luteolysis) was greater (P < 0.05) than that in the 5D treatment (43.0 vs. 22.9%), respectively. A treatment by location interaction was detected for pregnancies per AI. The Kansas location had no detectable treatment differences. In contrast, the 7D treatment produced more (P < 0.05) pregnancies in the first replicate of the Florida location and at the Mississippi location. We concluded that the 5D protocol was not more effective in producing acceptable luteolysis, pregnancy, and ovulation rates compared with the modified 7D protocol