Effect of increasing amounts of supplemental progesterone in a timed artificial insemination protocol on fertility of lactating dairy cows

The objectives were to evaluate the effect of supplemental progesterone during a timed artificial insemination (TAI) protocol on pregnancy per insemination and pregnancy loss. Lactating dairy cows from 2 dairy herds were presynchronized with 2 injections of PGF_2α 14 d apart, and cows observed in estrus following the second PGF_2α injection were inseminated (n = 1,301). Cows not inseminated by 11 d after the end of the presynchronization were submitted to the TAI protocol (d 0 GnRH, d 7 PGF_2α, d 8 estradiol cypionate, and d 10 TAI). On the day of the GnRH of the TAI protocol (study d 0), cows were assigned randomly to receive no exogenous progesterone (control = 432), one controlled internal drug-release (CIDR) insert (CIDR1 = 440), or 2 CIDR inserts (CIDR2 = 440) containing 1.38 g of progesterone each from study d 0 to 7. Blood was sampled on study d 0 before insertion of CIDR for determination of progesterone concentration in plasma, and cows with concentration <1.0 ng/mL were classified as low progesterone (LP) and those with concentration ≥1.0 ng/mL were classified as high progesterone (HP). From a subgroup of 240 cows, blood was sampled on study d 3, 7, 17 and 24 and ovaries were examined by ultrasonography on study d 0 and 7. Pregnancy was diagnosed at 38 ± 3 and 66 ± 3 d after AI. Data were analyzed including only cows randomly assigned to treatments and excluding cows that were inseminated after the second PGF_2α injection. The proportion of cows classified as HP at the beginning of the TAI protocol was similar among treatments, but differed between herds. Concentrations of progesterone in plasma during the TAI protocol increased linearly with number of CIDR used, and the increment was 0.9 ng/mL per CIDR. The proportion of cows with plasma progesterone ≥1.0 ng/mL on study d 17 was not affected by treatment, but a greater proportion of control than CIDR-treated cows had asynchronous estrous cycles following the TAI protocol. Treatment with CIDR inserts, however, did not affect pregnancy at 38 ± 3 and 66 ± 3 d after AI or pregnancy loss.     

Supplemental progesterone and timing of resynchronization on pregnancy outcomes in lactating dairy cows

The objective was to determine the effect of exogenous progesterone (P₄) in a timed artificial insemination (TAI) protocol initiated at 2 different times post-AI on pregnancies per AI (P/AI) in lactating dairy cows. Cows (n = 1,982) in 5 dairy herds were assigned randomly at a nonpregnancy diagnosis 32 ± 3 d post-AI to 1 of 4 resynchronization (RES) treatments arranged in a 2 × 2 factorial design using the Ovsynch-56 (GnRH, 7 d later PGF_2α, 56 h later GnRH, 16 h later TAI) protocol. Treatments were as follows: cows initiating RES 32 ± 3 d after AI with no supplemental P₄ (d 32 RES-CON; n = 516); same as d 32 RES-CON plus a controlled internal drug release (CIDR) insert containing P₄ at the onset of Ovsynch-56 (d 32 RES-CIDR; n = 503); cows initiating RES 39 ± 3 d after AI (d 39 RES-CON; n = 494); and same as d 39 RES-CON plus a CIDR (d 39 RES-CIDR; n = 491). Cows were inseminated if observed in estrus before TAI. The P/AI was determined 32 and 60 d after TAI. In a subgroup of cows (n = 1,152), blood samples were collected and ovarian structures examined by ultrasonography on the days of the first GnRH (G1) and PGF_2α of Ovsynch-56. Percentage of cows with a corpus luteum (CL) at G1 was unaffected by timing of treatments, but percentage of cows with a CL at PGF_2α was greater for d 32 than for d 39 cows (87.9 vs. 79.4%). In addition, percentage of cows with P₄ ≥1 ng/mL at G1 was unaffected by timing of treatments, but was increased for d 32 compared with d 39 RES cows on the day of the PGF_2α of the RES protocols (86.5 vs. 74.3%). Treatment did not affect ovulation to G1 or P/AI 32 d after RES TAI (d 32 RES-CON = 30.1%, d 32 RES-CIDR = 28.8%, d 39 RES-CON = 27.5%, d 39 RES-CIDR = 30.5%). A greater percentage of d 39 RES cows underwent premature luteolysis during the RES protocol compared with d 32 RES cows. An interaction was detected between day of RES initiation and CIDR treatment, in which the CIDR increased P/AI 60 d after TAI for d 39 (CON = 23.7% vs. CIDR = 28.0%), but not for d 32 (CON = 26.9% and CIDR = 24.2%) cows. Pregnancy loss was unaffected by treatment. In addition, cows had improved P/AI 60 d after TAI when they received a CIDR and did not have a CL (CON-CL = 28.2%, CON-No CL = 19.2%, CIDR-CL = 27.0%, and CIDR-No CL = 26.5%) or had P₄ <1 ng/mL (CON-High P₄ = 27.8%, CON-Low P₄ = 15.0%, CIDR-High P₄ = 25.0%, and CIDR-Low P₄ = 29.4%) at G1, but not if a CL was present or P₄ was ≥1 ng/mL at G1. In conclusion, addition of a CIDR insert to supplement P₄ during the RES protocol increased P/AI for cows initiating RES 39 ± 3 d after AI but not 32 ± 3 d after AI.     

Timed artificial insemination programs during the summer in lactating dairy cows: Comparison of the 5-d Cosynch protocol with an estrogen/progesterone-based protocol

The objective of this study was to compare a GnRH-based to an estrogen/progesterone (E2/P4)-based protocol for estrous cycle synchronization and fixed timed artificial insemination (TAI), both designed for synchronization of ovulation and to reduce the period from follicular emergence until ovulation in cows with a synchronized follicular wave. A total of 1,190 lactating Holstein cows (primiparous: n = 685 and multiparous: n = 505) yielding 26.5 ± 0.30 kg of milk/d at 177 ± 5.02 d in milk were randomly assigned to receive one of the following programs: 5-d Cosynch protocol [d −8: controlled internal drug release (CIDR) + GnRH; d −3: CIDR removal + PGF_2α; d −2: PGF_2α; d 0: TAI + GnRH] or E2/P4 protocol (d −10: CIDR + estradiol benzoate; d −3: PGF_2α; d −2: CIDR removal + estradiol cypionate; d 0: TAI). Rectal temperature and circulating progesterone (P4) were measured on d −3, −2, 0 (TAI), and 7. The estrous cycle was considered to be synchronized when P4 was ≥1.0 ng/mL on d 7 in cows that had luteolysis (P4 ≤0.4 ng/mL on d 0). To evaluate the effects of heat stress, cows were classified by number of heat stress events: 0, 1, and 2-or-more measurements of elevated body temperature (≥39.1°C). Pregnancy success (pregnancy per artificial insemination, P/AI) was determined at d 32 and 60 after TAI. The cows in the 5-d Cosynch protocol had increased circulating P4 at the time of PGF_2α injection (2.66 ± 0.13 vs. 1.66 ± 0.13 ng/mL). The cows in the E2/P4 protocol were more likely to be detected in estrus (62.8 vs. 43.4%) compared with the cows in the 5-d Cosynch protocol, and expression of estrus improved P/AI in both treatments. The cows in the 5-d Cosynch protocol had greater percentage of synchronized estrous cycle (78.2%), compared with cows in the E2/P4 protocol (70.7%). On d 60, the E2/P4 protocol tended to improve P/AI (20.7 vs. 16.7%) and reduced pregnancy loss from 32 to 60 d (11.0 vs. 19.6%), compared with the 5-d Cosynch protocol. In cows withtheir estrous cycle synchronized, the E2/P4 protocol had greater P/AI (25.6 vs. 17.7%) on d 60 and lower pregnancy loss from 32 to 60 d (6.7 vs. 21.7%) compared with cows in the 5-d Cosynch protocol. Follicle diameter affected pregnancy loss from 32 to 60 d only in the cows in the 5-d Cosynch protocol, with smaller follicles resulting in greater pregnancy loss. Pregnancy per AI at d 60 was different between protocols in the cows with 2 or more measurements of heat stress (5-d Cosynch = 12.2% vs. E2/P4 = 22.8%), but not in the cows without or with 1 heat stress measurement. In conclusion, the 5-d Cosynch protocol apparently produced better estrous cycle synchronization than the E2/P4 protocol but did not improve P/AI. The potential explanation for these results is that increased E2 concentrations during the periovulatory period can improve pregnancy success and pregnancy maintenance, and this effect appears to be greatest in heat-stressed cows when circulating E2 may be reduced.     

Presynchronization using a modified Ovsynch protocol or a single gonadotropin-releasing hormone injection 7 d before an Ovsynch-56 protocol for submission of lactating dairy cows to first timed artificial insemination

Presynchronization strategies, such as Presynch-Ovsynch and Double-Ovsynch, increase fertility to timed artificial insemination (TAI) compared with Ovsynch alone; however, simpler presynchronization strategies could reduce costs and simplify reproductive management. Lactating Holstein cows (n = 601) were randomly assigned to 1 of 2 presynchronization treatments before beginning an Ovsynch-56 protocol (GnRH at 70 ± 3 DIM, PGF_2α 7 d later, GnRH 56 h after PGF_2α, and TAI 16 h later at 80 ± 3 DIM) for first TAI. Cows (n = 306) in the first treatment (Double-Ovsynch; DO) were presynchronized using a modified Ovsynch protocol (GnRH at 53 ± 3 DIM, 7 d later PGF_2α, and GnRH 3 d later) ending 7 d before the first GnRH injection (G1) of an Ovsynch-56 protocol. Cows (n = 295) in the second treatment (GGPG) were presynchronized using a single injection of GnRH 7 d before G1 of an Ovsynch-56 protocol at 63 ± 3 DIM. Blood samples were collected at G1 and the PGF_2α injections of the Ovsynch-56 protocol to determine progesterone (P4) concentrations. Pregnancy diagnosis was performed using ultrasonography 32 d after TAI, and pregnant cows were reexamined 46 and 70 d after TAI. Overall, DO cows had more pregnancies per artificial insemination (P/AI) compared with GGPG cows 32 d after TAI (53 vs. 43%). Overall, P/AI did not differ by parity (primiparous vs. multiparous), and pregnancy loss did not differ between treatments or parities. More DO cows had P4 in a medium range (>0.5 to <4 ng/mL) at G1 of the Ovsynch-56 protocol compared with GGPG cows (82 vs. 50%), and more DO cows had high P4 (>4 ng/mL) at the PGF_2α injection of the Ovsynch-56 protocol compared with GGPG cows (67 vs. 36%). Thus, presynchronization with a modified Ovsynch protocol increased P/AI after TAI at first AI by increasing synchrony to the Ovsynch-56 protocol compared with presynchronization using a single injection of GnRH.     

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 PGF_2α 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 PGF_2α 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) PGF_2α with TAI administered 72 h after PGF_2α). 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.     

Increasing length of an estradiol and progesterone timed artificial insemination protocol decreases pregnancy losses in lactating dairy cows

Our hypothesis was that increasing the length of an estradiol and progesterone (P4) timed artificial insemination (TAI) protocol would improve pregnancy per artificial insemination (P/AI). Lactating Holstein cows (n = 759) yielding 31 ± 0.30 kg of milk/d with a detectable corpus luteum (CL) at d −11 were randomly assigned to receive TAI (d 0) following 1 of 2 treatments: (8d) d −10 = controlled internal drug release (CIDR) and 2.0 mg of estradiol benzoate, d −3 = PGF_2α(25 mg of dinoprost tromethamine), d −2 = CIDR removal and 1.0 mg of estradiol cypionate, d 0 = TAI; or (9d) d −11 = CIDR and estradiol benzoate, d −4 = PGF_2α, d −2 CIDR removal and estradiol cypionate, d 0 TAI. Cows were considered to have their estrous cycle synchronized in response to the protocol by the absence of a CL at artificial insemination (d 0) and presence of a CL on d 7. Pregnancy diagnoses were performed on d 32 and 60. The ovulatory follicle diameter at TAI (d 0) did not differ between treatments (14.7 ± 0.39 vs. 15.0 ± 0.40 mm for 8 and 9 d, respectively). The 9d cows tended to have greater P4 concentrations on d 7 in synchronized cows (3.14 ± 0.18 ng/mL) than the 8d cows (3.05 ± 0.18 ng/mL). Although the P/AI at d 32 [45 (175/385) vs. 43.9% (166/374) for 8d and 9d, respectively] and 60 [38.1 (150/385) vs. 40.4% (154/374) for 8d and 9d, respectively] was not different, the 9d cows had lower pregnancy losses [7.6% (12/166)] than 8d cows [14.7% (25/175)]. The cows in the 9d program were more likely to be detected in estrus [72.0% (269/374)] compared with 8d cows [62% (240/385)]. Expression of estrus improved synchronization [97.4 (489/501) vs. 81% (202/248)], P4 concentrations at d 7 (3.22 ± 0.16 vs. 2.77 ± 0.17 ng/mL), P/AI at d 32 [51.2 (252/489) vs. 39.4% (81/202)], P/AI at d 60 [46.3 (230/489) vs. 31.1% (66/202)], and decreased pregnancy loss [9.3 (22/252) vs. 19.8% (15/81)] compared with cows that did not show estrus, respectively. Cows not detected in estrus with small (<11 mm) or large follicles (>17 mm) had greater pregnancy loss; however, in cows detected in estrus, no effect of follicle diameter on pregnancy loss was observed. In conclusion, increasing the length of the protocol for TAI increased the percentage of cows detected in estrus and decreased pregnancy loss.     

Application of one injection of prostaglandin F2α in the five-day Co-Synch + CIDR protocol for estrous synchronization and resynchronization of dairy heifers

The objective was to determine if the 5-d Co-Synch + CIDR (controlled internal drug releasing insert) protocol can be used in dairy heifers for a synchronized timed artificial insemination (TAI) with one injection of PGF_2α for first and second services. In experiment 1, heifers were assigned randomly to receive 1 (n = 295) or 2 (n = 298) injections of PGF_2α in the 5-d Co-Synch + CIDR protocol. Corpus luteum (CL) regression was measured in one replicate (n = 218). No difference in pregnancy per TAI (P/TAI; 46.1 and 48.6%) or CL regression (86.9 and 92.8%) was detected for 1 versus 2 injections of PGF_2α, respectively. In experiment 2, nonpregnant heifers (n = 86) were assigned to a resynchronized 5-d Co-Synch + CIDR with 1 PGF_2α/TAI or insemination at detected estrus. There was no difference in P/TAI (52.2 and 55%) between groups. In experiment 3, nonpregnant heifers (n = 110) were assigned randomly to receive a CIDR (n = 54) or no CIDR insert (n = 56) in the 5-d Co-Synch protocol for resynchronization of TAI. Pregnancy per TAI was lower without the CIDR device (39.3 vs. 51.8%). In a commercial field evaluation, 416 heifers were synchronized for the first and resynchronized TAI with the 5-d Co-Synch + CIDR protocol with 1 injection of PGF_2α. Pregnancy per TAI on d 60 was 58.2 and 47.5% for first and second TAI, respectively; there was a sire effect to the second TAI. In conclusion, the 5-d Co-Synch + CIDR protocol with 1 injection of PGF_2α is an effective reproductive management program for first and second TAI in dairy heifers.     

Resynchronization strategies to improve fertility in lactating dairy cows utilizing a presynchronization injection of GnRH or supplemental progesterone: I. Pregnancy rates and ovarian responses

Objectives were to evaluate 3 resynchronization protocols for lactating dairy cows. At 32 ± 3 d after pre-enrollment artificial insemination (AI; study d −7), 1 wk before pregnancy diagnosis, cows from 2 farms were enrolled and randomly assigned to 1 of 3 resynchronization protocols after balancing for parity, days in milk, and number of previous AI. All cows were examined for pregnancy at 39 ± 3 d after pre-enrollment AI (study d 0). Cows enrolled as controls (n = 386) diagnosed not pregnant were submitted to a resynchronization protocol (d 0-GnRH, d 7-PGF_2α, and d 10-GnRH and AI) on the same day. Cows enrolled in the GGPG (GnRH-GnRH-PGF_2α-GnRH) treatment (n = 357) received a GnRH injection at enrollment (d −7) and if diagnosed not pregnant were submitted to the resynchronization protocol for control cows on d 0. Cows enrolled in CIDR treatment (n = 316) diagnosed not pregnant received the resynchronization protocol described for control cows with addition of a controlled internal drug release (CIDR) insert containing progesterone (P₄) from d 0 to 7. In a subgroup of cows, ovaries were scanned and blood was sampled for P₄ concentration on d 0 and 7. After resynchronized AI, cows were diagnosed for pregnancy at 39 ± 3 and 67 ± 3 d (California herds) or 120 ± 3 d (Arizona herds). Cows in the GGPG treatment had more corpora lutea than CIDR and control cows on d 0 (1.30 ± 0.11, 1.05 ± 0.11, and 1.05 ± 0.11, respectively) and d 7 (1.41 ± 0.14, 0.97 ± 0.13, and 1.03 ± 0.14, respectively). A greater percentage of GGPG cows ovulated to GnRH given on d 0 compared with CIDR and control cows (48.4, 29.6, and 36.6%, respectively), but CIDR and control did not differ. At 39 ± 3 d after resynchronized AI, pregnancy per AI (P/AI) was increased in GGPG (33.6%) and CIDR (31.3%) cows compared with control (24.6%) cows. At 67 or 120 ± 3 d after resynchronized AI, P/AI of GGPG and CIDR cows was increased compared with control cows (31.2, 29.5, and 22.1%, respectively). Presynchronizing the estrous cycle of lactating dairy cows with a GnRH 7 d before the start of the resynchronization protocol or use of a CIDR insert within the resynchronization protocol resulted in greater P/AI after resynchronized AI compared with control cows.     

Pregnancy per artificial insemination in lactating dairy cows subjected to 2 different intervals from presynchronization to initiation of Ovsynch protocol

A protocol for presynchronization of ovarian status with 2 injections of PGF_2α given 14 d apart, with the last PGF_2α injection given 12 or 14 d before Ovsynch increases pregnancy per artificial insemination (P/AI) in dairy cows. We determined the efficacy of reducing the interval from the last PGF_2α injection (500 μg of cloprostenol) of presynchronization to initiation of Ovsynch on response to treatment and P/AI. Lactating dairy cows were assigned to an Ovsynch protocol, with the initial injection of GnRH given either 9 (PRE-9; n = 135) or 12 d (PRE-12; n = 135) after the second PGF_2α injection of presynchronization. The Ovsynch protocol consisted of 2 injections of 100 μg of GnRH given 9 d apart and 1 injection of PGF_2α given 7 d after the initial GnRH injection, and cows were subjected to timed artificial insemination (TAI; 70 ± 3.5 DIM) approximately 16 h after the second GnRH injection. Body condition score (1–5 scale) was recorded at TAI. Blood samples were taken for progesterone determination at the PGF_2α injection of Ovsynch, at TAI, and at 11 d after TAI. Ultrasonographic examinations were done in all cows at the second PGF_2α injection of presynchronization, initial GnRH injection, PGF_2α injection of Ovsynch, at TAI, and 24 h after TAI for cyclicity status and ovarian responses to treatments, and at 32 and 60 d after TAI for confirmation of pregnancy. Overall, 29 cows (10.7%) were determined acyclic or cystic and excluded from the study. The percentage of cows responding to initial GnRH injection (62.2 vs. 61.5%) did not differ between PRE-9 and PRE-12 but more cows in the PRE-9 group failed to respond to PGF_2α treatment of Ovsynch compared with PRE-12 (22.7 vs. 10.7%). Body condition score at TAI (2.9 ± 0.02) and mean ovulatory follicle diameter (16.4 ± 0.2 mm) were not different between treatments. Overall P/AI at 32 d was reduced in PRE-9 (33.6%) compared with PRE-12 (44.3%) but pregnancy losses (5.0 vs. 3.7%) did not differ between treatments. Primiparous cows in the PRE-12 group had higher mean progesterone concentration 11 d after TAI and greater P/AI 32 after TAI than primiparous cows in the PRE-9 group (6.4 ± 0.5 vs. 4.6 ± 0.5 ng/mL and 55.8 vs. 30.0%, respectively). In conclusion, reducing the interval from the last PGF_2α injection of the presynchronization treatment to initiation of Ovsynch (from 12 to 9 d) did not affect ovulatory response to initial GnRH injection but reduced response to PGF_2α injection of Ovsynch and P/AI at 32 and 60 d after TAI. The reduction in P/AI was particularly evident in primiparous cows of the PRE-9 group.     

Reproductive performance of lactating dairy cows managed for first service using timed artificial insemination with or without detection of estrus using an activity-monitoring system

Lactating dairy cows (n = 1,025) on a commercial dairy farm were randomly assigned at 10 ± 3 d in milk (DIM) to 1 of 3 treatments for submitting cows to first artificial insemination (AI) and were fitted with activity-monitoring tags (Heatime; SCR Engineers Ltd., Netanya, Israel) at 24 ± 3 DIM. Cows (n = 339) in treatment 1 were inseminated based on increased activity from the end of the voluntary waiting period (50 DIM) until submission to an Ovsynch protocol; cows without increased activity from 21 to 65 DIM began an Ovsynch protocol at 65 ± 3 DIM, whereas cows without increased activity from 21 to 50 DIM but not from 51 to 79 DIM began an Ovsynch protocol at 79 ± 3 DIM. Cows (n = 340) in treatment 2 were inseminated based on activity after the second PGF_2α injection of a Presynch-Ovsynch protocol at 50 DIM, and cows without increased activity began an Ovsynch protocol at 65 ± 3 DIM. Cows (n = 346) in treatment 3 were monitored for activity after the second PGF_2α injection of a Presynch-Ovsynch protocol, but all cows received timed AI (TAI) at 75 ± 3 DIM after completing the Presynch-Ovsynch protocol. The activity-monitoring system detected increased activity in 56, 69, and 70% of cows in treatments 1, 2, and 3, respectively. Treatment-2 cows had the fewest average days to first AI (62.5), treatment-3 cows had the most average days to first AI (74.9), and treatment-1 cows had intermediate average days to first AI (67.4). Treatment-1 and -2 cows in which inseminations occurred as a combination between increased activity and TAI had fewer overall pregnancies per AI (P/AI) 35 d after AI (32% for both treatments) compared with treatment-3 cows, all of which received TAI after completing the Presynch-Ovsynch protocol (40%). Based on survival analysis, although the rate at which cows were inseminated differed among treatments, treatment did not affect the proportion of cows pregnant by 300 DIM. Thus, use of an activity-monitoring system to inseminate cows based on activity reduced days to first AI, whereas cows receiving 100% TAI after completing a Presynch-Ovsynch protocol had more P/AI. The trade-off between AI service rate and P/AI in the rate at which cows became pregnant was supported by an economic analysis in which the net present value ($/cow per year) differed by only $4 to $8 among treatments. We conclude that a variety of strategies using a combination of AI based on increased activity using an activity-monitoring system and synchronization of ovulation and TAI can be used to submit cows for first AI.     

Treatment of cycling and noncycling lactating dairy cows with progesterone during Ovsynch

Our objective was to determine whether progesterone (P4) supplementation during an Ovsynch protocol would enhance fertility in lactating dairy cows. Lactating dairy cows (n = 634) at 6 locations were assigned randomly within lactation number and stage of lactation to receive the Ovsynch protocol [OVS; synchronization of ovulation by injecting GnRH 7 d before and 48 h after PGF_2α, followed by one fixed-time AI (TAI) 16 to 20 h after the second GnRH injection] or Ovsynch plus a controlled internal drug release (CIDR) P4-releasing insert for 7 d, beginning at the first GnRH injection (OVS + CIDR). Blood was sampled to quantify P4 10 d before the first GnRH injection, immediately before the first GnRH injection, at the time of CIDR removal, before the PGF_2α injection (1 to 2 h after CIDR insert removal), and 48 h after the PGF_2α injection to determine cyclicity status before initiation of treatment, luteal status at the PGF_2α injection, and incidence of luteal regression. Overall, conception rates at 28 (40 vs. 50%) and 56 d (33 vs. 38%) after TAI differed between OVS and OVS + CIDR, respectively; but a treatment × location interaction was detected. Compared with OVS, pregnancy outcomes were more positive for OVS + CIDR cows at 4 of 6 locations 28 d after TAI and at 3 of 6 locations 56 d after TAI. An interaction of luteal status (high vs. low) before CIDR insert removal and PGF_2α injection with pretreatment cycling status indicated that cows having low P4 at PGF_2α injection benefited most from P4 supplementation (OVS + CIDR = 36% vs. OVS = 18%), regardless of pretreatment cycling status. Pregnancy loss between 28 and 56 d after TAI was greater for noncycling cows (31%) compared with cycling cows (16%). Pregnancy loss for cows receiving P4 (21%) did not differ from that for cows not receiving P4 (21%). Supplementation of P4, pretreatment cycling status, and luteal status before PGF_2α injection altered follicular diameters at the time of the second GnRH injection, but were unrelated to pregnancy outcomes. Incidence of multiple ovulation was greater in noncycling than in cycling cows. Further, cows having multiple ovulations had improved pregnancy outcomes at 28 and 56 d after TAI. In summary, a CIDR insert during the Ovsynch protocol increased fertility in lactating cows having low serum P4 before PGF_2α injection. Improved pregnancy outcomes were observed at some, but not all locations.     

Effect of inseminating cows in estrus following a presynchronization protocol on reproductive and lactation performances

Objectives were to evaluate the effects of inseminating cows observed in estrus following a PGF_2α-based presynchronization protocol on reproductive and lactation performance. Weekly, Holstein cows (260 primiparous and 379 multiparous) were balanced by parity, body condition score at 3 d in milk (DIM), and previous lactation milk yield (multiparous cows) and assigned randomly to either of 2 reproductive programs. All cows received 2 injections of PGF_2α at 35 and 49 DIM and a controlled internal drug release insert containing progesterone from 42 to 49 DIM. Cows assigned to the short voluntary waiting period (SVWP) treatment were inseminated if observed in estrus after the second injection of PGF_2α of the presynchronization protocol, and those not inseminated were submitted to a timed artificial insemination (TAI) protocol (GnRH 62 DIM, PGF_2α 69 DIM, GnRH 71 DIM, and TAI 72 DIM), whereas cows assigned to the long voluntary waiting period (LVWP) were all submitted to the TAI protocol and were TAI at 72 DIM. Plasma progesterone was determined at 35, 49, and 62 DIM for evaluation of interval from parturition to resumption of cyclicity. Pregnancy was diagnosed weekly at 32 and 60 d after first AI and at 42 d after subsequent inseminations. Percentage of SVWP cows inseminated in estrus was 58.9% and the interval from parturition to first AI was shorter for SVWP cows (64.7 ± 0.4 vs. 74.2 ± 0.5 DIM). Cows cyclic by 49 and 62 DIM were more likely to be inseminated in estrus than those anovular by 62 DIM (67.9, 61.0, and 32.8%, respectively) and cyclic cows by 49 and 62 DIM had shorter interval from parturition to first AI than anovular cows (62.6 ± 0.7, 63.1 ± 1.2, and 70.1 ± 1.1 DIM). Treatment did not affect pregnancy per AI after first postpartum AI or the rate at which cows became pregnant. Cows that resumed cyclicity by 49 DIM had greater pregnancy per AI than cows still anovular by 62 DIM and became pregnant at a faster rate than cows that resumed cyclicity by 62 DIM and those still anovular by 62 DIM. Inseminating cows that displayed estrus after the presynchronization protocol did not affect reproductive performance compared with submission of 100% of cows to a TAI protocol.     

Evaluation of progesterone supplementation in a prostaglandin F2alpha-based presynchronization protocol before timed insemination

The objective of the study was to determine the effects of treatment with a controlled internal drug-release (CIDR) insert containing progesterone in a PGF_2α-based presynchronization protocol on pregnancy rates at first service in lactating Holstein cows. A total of 1,318 (656 treatment and 662 control) cows from 5 farms were used in the analysis. Cows received a CIDR insert as part of the presynchronization protocol of 2 PGF_2α injections given 14 d apart. The CIDR insert was applied during 7 d before the second PGF_2α injection, whereas control cows received no CIDR insert. Serum progesterone concentrations were measured in samples collected at 37 ± 3 d in milk (DIM; 7 d after the first PGF_2α injection) and at 58 ± 3 DIM, just before initiation of the Ovsynch protocol. According to serum concentrations of progesterone, cows were classified as having either high (≥1 ng/mL) or low (<1 ng/mL) progesterone. The proportion of cows with low progesterone at 37 ± 3 DIM was similar for cows treated later with the CIDR insert (60.7%; n = 654) and for control cows (59.2%; n = 657). In contrast, use of the CIDR insert resulted in fewer low-progesterone cows (17.4%; n = 402) compared with control cows (30.6%; n = 399) at 58 ± 3 DIM. No significant effect of the CIDR insert was detected on overall pregnancy rates. Pregnancy rates, as measured by the percentage of cows pregnant at 37 ± 3 d post timed artificial insemination, for control cows having high or low progesterone at 58 ± 3 DIM were 46.6 and 22.1%, respectively. For the CIDR group, pregnancy rates were 40.4 and 11.4%, respectively, for high- and low-progesterone cows at 58 ± 3 DIM. Overall pregnancy rates were 36.4 and 34.5% for control cows and cows receiving the CIDR insert, respectively. A significant decreasing trend was observed in the proportion of cows having low progesterone as the body condition score increased, at 37 ± 3 and 58 ± 3 DIM. A significant increasing trend in the pregnancy rate was observed as body condition score increased. In conclusion, incorporation of CIDR inserts into a presynchronization protocol reduced the proportion of cows having low progesterone; however, the pregnancy rate did not differ between control cows and those receiving the CIDR insert. Earlier expression of estrus after the second PGF_2α injection, and consequently improper timing of initiation of the Ovsynch protocol, could have negatively affected fertility in the CIDR-treated cows.     

Effect of an Ovsynch56 protocol initiated at different intervals after insemination with or without a presynchronizing injection of gonadotropin-releasing hormone on fertility in lactating dairy cows

The objectives of this study were to evaluate effects of 2 resynchronization protocols beginning at different intervals after artificial insemination (AI) on the pattern of return to estrus, ovarian responses, and pregnancy per AI (P/AI) to reinsemination. Lactating cows from 2 dairies, located in Texas (n = 2,233) and Minnesota (n = 3,077), were assigned to 1 of 4 timed AI (TAI) protocols 17 ± 3 d after AI. All cows were examined for pregnancy 31 ± 3 d after previous AI. Cows assigned to early Ovsynch56 (E-OV56) or OV56 received the Ovsynch56 protocol starting 24 or 31 d after AI, respectively. Cows assigned to early GnRH-GnRH-PGF_2α-GnRH (E-GGPG) or GGPG received a presynchronizing GnRH injection 17 or 24 d after AI, respectively, 7 d before the start of the Ovsynch56 protocol. Cows observed in estrus after enrollment were inseminated on the same day. Ovaries were examined and blood was sampled for progesterone concentration on the day of first GnRH and PGF_2α injection of the Ovsynch56 protocol. Pregnancy was diagnosed at 31 and 66 d after resynchronized AI. On the day of the first GnRH injection of the TAI, a higher percentage of cows on E-GGPG and GGPG protocols had a corpus luteum (E-GGPG = 83.8, GGPG = 91.2, E-OV56 = 80.4, and OV56 = 75.5%) and progesterone concentration >1 ng/mL (E-GGPG = 62.5, GGPG = 76.0, E-OV56 = 53.6, and OV56 = 60.8%) than cows assigned to other protocols. However, the percentage of cows ovulating to the first GnRH injection of TAI was not affected by treatment. Fewer E-GGPG and more OV56 cows were reinseminated in estrus (E-GGPG = 23.7, GGPG = 49.0, E-OV56 = 41.6, and OV56 = 57.6%). Treatment did not affect P/AI at 31 or 66 d for cows reinseminated in estrus. However, cows reinseminated in estrus had greater P/AI at 31 (40.0 vs. 27.5%) and 66 d (36.0 vs. 23.9%) than cows completing the TAI protocols. Among cows completing the TAI protocols, initiation of GGPG at 24 d after AI increased, whereas initiation of Ovsynch56 at 24 d after AI decreased P/AI at 31 d after reinsemination (E-GGPG = 30.6, GGPG = 28.3.0, E-OV56 = 22.3, and OV56 = 28.7%). Pregnancy per AI did not differ across treatment at 66 d after TAI (E-GGPG = 26.6, GGPG = 24.4, E-OV56 = 20.0, and OV56 = 24.1%). Overall, type of resynchronization protocol and protocol initiation time did not affect P/AI 66 d after reinsemination (E-GGPG = 29.7, GGPG = 30.5, E-OV56 = 26.1, and OV56 = 30.4%). In conclusion, GGPG resynchronization protocols and initiation of resynchronization protocol 24 d after AI reduced the number of cows reinseminated in estrus but neither the timing of initiation of resynchronization nor presynchronization with GnRH affected overall P/AI.     

Treatment with gonadotropin-releasing hormone after first timed artificial insemination improves fertility in noncycling lactating dairy cows

Lactating Holstein cows were assigned randomly to treatments to improve fertility after first postpartum timed artificial insemination (TAI). In Experiment 1, cows received no treatment (control; n = 9), a controlled internal drug releasing (CIDR) insert from 5 to 12 d after TAI (CIDR; n = 9), or 100 μg of GnRH 5 d after TAI (G5; n = 7). Although treatments did not affect circulating progesterone (P₄) concentrations from 5 to 19 d after TAI, there was a tendency for CIDR cows to have greater P₄ compared with control or G5 cows within 24 h after treatment. In 2 field trials, cows received either control (n = 223), CIDR (n = 218), or G5 (n = 227) treatments (Experiment 2), or control (n = 160), G5 (n = 159), or treatment with 100 μg of GnRH 7 d after TAI (G7; n = 163; Experiment 3). Treatment did not affect pregnancies per AI (P/AI) in Experiments 2 or 3; however, when data were combined to compare control (n = 383) and G5 (n = 386) treatments, P/AI tended to be greater for G5 (49.1%) than for control (45.8%) cows. This effect resulted from a GnRH treatment × cyclicity status interaction in which P/AI for noncycling cows receiving G5 was greater than for noncycling control cows (45.5 vs. 31.1%). In conclusion, treatment with CIDR inserts after TAI had no effect on P/AI, whereas treatment with GnRH 5 d after TAI improved P/AI for noncycling, but not for cycling cows.     

Pregnancy rates to timed artificial insemination in Holstein heifers given prostaglandin F2alpha twenty-four hours before or concurrent with removal of an intravaginal progesterone-releasing insert

The objective was to compare pregnancy rates in nulliparous Holstein heifers given PGF_2α 24 h before, or concurrent with, removal of an intravaginal progesterone-releasing (CIDR) insert in 3 timed artificial insemination (TAI) protocols. Heifers (from 2 herds) were assigned randomly, over 11 mo, to 1 of 3 modified Ovsynch protocols. On d 0 (without reference to the stage of the estrous cycle), all heifers were given 100 μg of GnRH i.m. and a CIDR insert (containing 1.9 g of progesterone). In the PG-7/P4-8 protocol (n = 99), PGF_2α was given on d 7, and CIDR inserts were removed on d 8. In the PG-7/P4-7 (n = 98) and PG-8/P4-8 (n = 102) protocols, PGF_2α administration and CIDR removal occurred concurrently, on d 7 or 8, respectively. In all 3 protocols, a second GnRH treatment (100 μg) was given 48 h after PGF_2α with TAI 16 to 20 h later. Blood samples were collected (subset of 124 heifers) on d 0, 7, 10 or 11 (i.e., at TAI), and 17. Pregnancy rates (32 d after TAI) for protocols PG-7/P4-8, PG-7/P4-7, and PG-8/P4-8 were 61.8, 55.6, and 54.1%, respectively. Pregnancy rate was higher when synchronization was initiated during diestrus than when initiated at other stages (57.0 versus 34.8%). Although pregnancy rates were not affected by season, there was an interaction between protocol and season; pregnancy rates were significantly lower in summer in heifers subjected to PG-7/P4-7 and PG-8/P4-8, but season did not affect pregnancy rates in heifers subjected to PG-7/P4-8. In summary, giving PGF_2α 24 h before CIDR removal, followed by TAI (PG-7/P4-8 protocol), resulted in consistent pregnancy rates, regardless of season, relative to protocols involving PGF_2α treatment concurrent with CIDR removal.     

Hormonal manipulations in the 5-day timed artificial insemination protocol to optimize estrous cycle synchrony and fertility in dairy heifers

Objectives were to determine the effects of GnRH at the initiation of the 5-d timed artificial insemination (AI) program combined with 2 injections of PGF_2α on ovarian responses and pregnancy per AI (P/AI) in dairy heifers, and the role of progesterone concentrations on LH release and ovulation in response to GnRH. In study 1, heifers received a controlled internal drug release (CIDR) insert containing 1.38 g of progesterone on d 0, an injection of 25 mg of PGF_2α and CIDR removal on d 5, and an injection of 100 μg GnRH concurrently with AI on d 8. Heifers were assigned to receive no additional treatment (control; n = 559) or an injection of GnRH on d 0 and a second injection of PGF_2α on d 6 (G2P; n = 547). In study 2, all heifers were treated as described for the control in study 1, and were allocated to receive no additional treatment (control; n = 723), an injection of PGF_2α on d 6 (NG2P; n = 703), or an injection of GnRH on d 0 and an injection of PGF_2α on d 6 (G2P; n = 718). In study 3, heifers received a CIDR on d 7 after ovulation and were assigned randomly to a low-progesterone (LP; n = 6) treatment in which 2 injections of 25 mg of PGF_2α each were administered 12 h apart, on d 7 and 7.5 after ovulation, or to a high-progesterone (HP; n = 12) treatment in which no PGF_2α was administered. On d 8, heifers received 100 μg of GnRH and blood was sampled at every 15 min from −30 to 180 min relative to the GnRH for assessment of LH concentrations. Additionally, 94 heifers were assigned to LP or HP and ovulation in response to GnRH was evaluated. In study 1, P/AI was greater for G2P than for the control on d 32 (59.4 vs. 53.5%) and 60 after AI (56.6 vs. 51.3%). In study 2, administration of GnRH on d 0 increased the proportion of heifers with a new corpus luteum on d 5 (control = 21.9 vs. NG2P = 20.1 vs. G2P = 34.4%). Administration of a second PGF_2α increased the proportion of heifers with progesterone <0.5 ng/mL at AI (control = 83.1 vs. NG2P = 93.0 and G2P = 87.2%). Pregnancy per AI was greater for G2P than for control and NG2P on d 32 (control = 52.9 vs. NG2P = 55.0 vs. G2P = 61.7%) and 60 (control = 49.0 vs. NG2P = 51.6 vs. G2P = 59.1%). In study 3, HP attenuated LH release and reduced ovulation (19.0 vs. 48.4%) in response to GnRH compared with LP. Combining GnRH and 2 doses of PGF_2α in the 5-d timed AI protocol improved follicle turnover, luteolysis, and P/AI in heifers. Elevated concentrations of progesterone suppressed LH release and are linked with the low ovulatory response to the initial GnRH treatment of the protocol.     

Comparison of responses to Ovsynch between Holstein-Friesian and Swedish Red cows

The Ovsynch protocol was designed to synchronize ovulation, thereby allowing timed artificial insemination (TAI) of all cows without detection of estrus. However, the effectiveness of Ovsynch in different breeds of dairy cows has not been previously compared. The aim of this study was to compare the response to Ovsynch in cycling lactating Holstein-Friesian (HF) and Swedish Red (SR) dairy cows. A total of 495 cyclic cows (n = 347 HF, n = 148 SR) were housed together and treated with Ovsynch (GnRH - 7 d - PGF_2α - 56 h - GnRH - 16 to 18 h - TAI). Ovulatory responses, synchronization rate, maximal follicle size at the time of AI, and percentage of pregnant cows per AI (P/AI at 31 and 62 d after AI) were compared between breeds. Ultrasonography was performed during Ovsynch at first GnRH, PGF_2α, at time of AI, and 7 d after AI. Ovulatory response and synchronization rate were similar in HF versus SR cows (60.2 vs. 62.2%; 88.4 vs. 88.5%, respectively). Cows that ovulated to the first GnRH of Ovsynch had smaller follicle size at AI (15.9 ± 0.1 vs. 16.4 ± 0.2 mm). Maximal follicle size at AI was greater for HF (16.4 ± 2.2 mm) than SR (15.5 ± 2.3 mm) cows. The P/AI was greater for SR than HF cows at the 62-d pregnancy diagnosis (56.1 vs. 46.1%). In addition, pregnancy loss between 31 and 62 d of pregnancy was greater in HF (10.1%) than SR (3.5%) cows. Fertility was less in HF cows during the hot season (57.7 in cold vs. 38.1% in the hot season), whereas such a decrease was not observed in SR (60.0 in cold vs. 53.5% in the hot season) cows. Thus, although the GnRH treatments of Ovsynch were equally effective in SR and HF cows, pregnancy outcomes (P/AI at d 62 and pregnancy survival) were greater in SR than HF cows, and P/AI in SR cows was not compromised during the hot season as was found for HF cows.     

Comparison of reproductive management programs for submission of Holstein heifers for first insemination with conventional or sexed semen based on expression of estrus,pregnancy outcomes,and cost per pregnancy

Our objective was to evaluate reproductive management programs for submission of Holstein heifers for first insemination with conventional or sexed semen. In experiment 1, nulliparous Holstein heifers (n = 462) were submitted to a 5-d progesterone-releasing intravaginal device (PRID)-Synch protocol [d 0, GnRH + PRID; d 5, PGF_2α − PRID; d 6, PGF_2α; d 8, GnRH + TAI] and were randomly assigned for PRID removal on d 5 or 6 of the protocol followed by timed artificial insemination (TAI) with conventional semen. Delaying PRID removal decreased early expression of estrus before scheduled TAI (0.9 vs. 12.2%), and pregnancies per AI (P/AI) did not differ between treatments. In experiment 2, nulliparous Holstein heifers (n = 736) from 3 commercial farms were randomized within farm to 1 of 3 treatments for first AI with sexed semen: (1) CIDR5 [d −6, GnRH + controlled internal drug release (CIDR); d −1, PGF_2α − CIDR; d 0, PGF_2α; d 2, GnRH + TAI]; (2) CIDR6 (d −6, GnRH + CIDR; d −1, PGF_2α; d 0, PGF_2α − CIDR; d 2, GnRH + TAI); and (3) EDAI (PGF_2α on d 0 followed by once-daily estrous detection and AI). Delaying CIDR removal decreased early expression of estrus before scheduled TAI (0.004 vs. 27.8%); however, CIDR5 heifers tended to have more P/AI at 35 (53 vs. 45 vs. 46%) and 64 (52 vs. 45 vs. 45%) days after AI than CIDR6 and EDAI heifers, respectively. Overall, CIDR5 and CIDR6 heifers had fewer days to first AI and pregnancy than EDAI heifers which resulted in less feed costs than EDAI heifers due to fewer days on feed until pregnancy. Despite greater hormonal treatment costs for CIDR5 heifers, costs per pregnancy were $16.66 less for CIDR5 than for EDAI heifers. In conclusion, delaying PRID removal by 24 h within a 5-d PRID-Synch protocol in experiment 1 suppressed early expression of estrus before TAI, and P/AI for heifers inseminated with conventional semen did not differ between treatments. By contrast, although delaying CIDR removal by 24 h within a 5-CIDR-Synch protocol in experiment 2 suppressed early expression of estrus before TAI, delaying CIDR removal by 24 h tended to decrease P/AI for heifers inseminated with sexed semen. Further, submission of heifers to a 5-d CIDR-Synch protocol for first AI tended to increase P/AI and decrease the cost per pregnancy compared with EDAI heifers.     

Effects of resynchronization programs on pregnancy per artificial insemination, progesterone, and pregnancy-associated glycoproteins in plasma of lactating dairy cows

Objectives were to develop a timed artificial insemination (TAI) resynchronization program to improve pregnancy per AI and to evaluate responses of circulating progesterone and pregnancy-associated glycoproteins in lactating cows. Cows (n = 1,578) were presynchronized with 2 injections of PGF_2α, given 14 d apart starting on d 45 ± 3 postpartum, followed by Ovsynch [2 injections of GnRH 7 d before and 56 h after injection of PGF_2α, TAI 16 h after second injection (d 0)]. The Resynch-treated cows received an intravaginal progesterone insert from d 18 to 25, GnRH on d 25, and pregnancy diagnosis on d 32, and nonpregnant cows received PGF_2α., GnRH 56 h later, and TAI 16 h later (d 35). The control cows were diagnosed for pregnancy on d 32 and nonpregnant cows received GnRH, PGF_2α 39 d after TAI, GnRH 56 h later, and TAI 16 h later (d 42). Pregnancy was reconfirmed on d 60 after AI. Ovarian structures were examined in a subset of cows at the time of GnRH and PGF_2α injections. Blood samples for analyses of progesterone and pregnancy-associated glycoproteins were collected every 2 d from d 18 to 30 in 100 cows, and collection continued weekly to d 60 for pregnant cows (n = 43). Preenrollment pregnancies per AI on d 32 did not differ for cows subsequently treated as Resynch (45.8%, n = 814) and control (45.9%, n = 764), and pregnancy losses on d 60 were 6.7 and 4.0%, respectively. Resynchronized service pregnancy per AI (36%, n = 441; 39.5%, n = 412) and pregnancy losses (6.3 and 6.7%) did not differ for Resynch and control treatments, respectively. Days open for pregnant cows after 2 TAI were less for the Resynch treatment than for the control treatment (96.2 ± 0.82 vs. 99.5 ± 0.83 d). Cows in the Resynch treatment had more large follicles at the time of GnRH. The number of corpora lutea did not differ between treatments at the time of PGF_2α. Plasma progesterone for pregnant cows was greater for Resynch cows than for control cows (18-60 d; 6.6 vs. 5.3 ng/mL), and plasma concentrations of progesterone on d 18 were greater for pregnant cows than for nonpregnant cows (5.3 vs. 4.3 ng/mL). Plasma pregnancy-associated glycoproteins during pregnancy were lower for cows in the Resynch treatment compared with control cows on d 39 (2.8 vs. 4.1 ng/mL) and 46 (1.3 vs. 3.0 ng/mL). Cows pregnant on d 32 that lost pregnancy by d 60 (n = 7) had lower plasma concentrations of pregnancy-associated glycoproteins on d 30 than cows that maintained pregnancy (n = 36; 2.9 vs. 5.0 ng/mL). Pregnancy-associated glycoproteins on d 30 (>0.33 ng/mL) were predictive of a positive d 32 pregnancy diagnosis (sensitivity = 100%; specificity = 90.6%). In conclusion, Resynch and control protocols had comparable pregnancy per AI for first and second TAI services, but pregnancy occurred 3.2 d earlier in the Resynch group because inseminations in the Resynch treatment began 7 d before those in the control treatment. Administration of an intravaginal progesterone insert, or GnRH, or both increased progesterone during pregnancy. Dynamics of pregnancy-associated glycoproteins were indicative of pregnancy status and pregnancy loss.