M. Masello

Reproductive management strategies to improve the fertility of cows with a suboptimal response to resynchronization of ovulation

The objective was to compare the reproductive performance of lactating Holstein cows managed with a strategy that included the Ovsynch protocol with exogenous progesterone (P4) supplementation or presynchronization with GnRH 7d before Ovsynch to treat cows without a corpus luteum (CL), a CL <15 mm, or cystic at the time of the PGF2α injection of Resynch (GnRH-7 d-PGF2α-56 h-GnRH-16 to 20 h-TAI). In a preliminary study, blood collection and transrectal ovarian ultrasonography were conducted (n=555) at the PGF2α of Resynch [coincident with nonpregnancy diagnosis (NPD)] to define a cutoff value for CL size that better predicted fertility after timed artificial insemination (TAI). A CL size of 15 mm was selected based on statistical differences in pregnancies per AI (P/AI) [33.2 vs. 10.3 P/AI for CL ≥15 mm (n=497) vs. no CL ≥15 mm (n=58; no CL, CL <15 mm, or cystic)]. Subsequently, in a completely randomized experiment, cows were enrolled in a management strategy that used Ovsynch with P4 supplementation [Ovsynch+P4; GnRH and controlled internal drug release device (CIDR)-7 d-PGF2α and CIDR removal-56 h-GnRH-16 to 20 h-TAI] or a PreG-Ovsynch protocol [PreG-Ovsynch; GnRH-7 d-GnRH-7 d-PGF2α-56 h-GnRH-16 to 20 h-TAI] to treat cows without a CL, a CL <15 mm, or cystic at NPD and the PGF2α of Resynch. Cows with a CL ≥15 mm at the PGF2α of Resynch completed the protocol and received TAI. Data were available from 212, 192, and 1,797 AI services after Ovsynch+P4, PreG-Ovsynch, and Resynch, respectively. At 39d after AI, P/AI tended to be greater for Ovsynch+P4 and PreG-Ovsynch combined (35.1%) than for Resynch cows (31.1%), whereas P/AI were similar for Ovsynch+P4 (34.4%) and PreG-Ovsynch (35.9%). The hazard of pregnancy for cows that received the experimental treatments at least once was similar for cows in the Ovsynch+P4 (n=124) and the PreG-Ovsynch (n=132) group (hazard ratio 1.15; 95% confidence interval: 0.87 to 1.53). Median days to pregnancy were 52 and 59 for cows in the Ovsynch+P4 and the PreG-Ovsynch groups, respectively. The presynchronizing GnRH injection of PreG-Ovsynch induced ovulation in 86.0% of the cows. At the first GnRH of Ovsynch, the proportion of cows with a CL based on ultrasound (86.6 vs. 15.0%), P4 >1 ng/mL (82.8 vs. 31.8%), a follicle ≥ 10 mm (98.0 vs. 84.4%), and P4 concentrations (3.7 vs. 1.1 ng/mL) was greater in PreG-Ovsynch than in Ovsynch+P4. Conversely, more cows ovulated in response to the first GnRH of Ovsynch in Ovsynch+P4 (71.9%) than PreG-Ovsynch (58.3%). At the PGF2α before TAI, more cows had a CL based on ultrasound (92.1 vs. 77.0%) and P4 concentrations were greater in PreG-Ovsynch than in Ovsynch+P4 (4.1 vs. 2.6 ng/mL); however, a similar proportion of cows had P4 >1 ng/mL (79.1 vs. 82.7%). We conclude that the Ovsynch+P4 and PreG-Ovsynch treatments for cows without a CL, a CL <15 mm, or cystic at the PGF2α injection of Resynch led to P/AI similar to that of cows with a CL ≥15 mm, and that both management strategies resulted in similar time to pregnancy.

Resynchronization of ovulation protocols for dairy cows including or not including gonadotropin-releasing hormone to induce a new follicular wave: Effects on re-insemination pattern, ovarian responses, and pregnancy outcomes

Our objectives were to evaluate the pattern of re-insemination, ovarian responses, and pregnancy per artificial insemination (P/AI) of cows submitted to different resynchronization of ovulation protocols. The base protocol started at 25 ± 3 d after artificial insemination (AI) and was as follows: GnRH, 7 and 8 d later PGF2α, GnRH 32 h after second PGF2α, and fixed timed AI (TAI) 16 to 18 h after GnRH. At 18 ± 3 d after AI, cows were randomly assigned to the G25 (n = 1,100) or NoG25 (n = 1,098) treatments. The protocol for G25 and NoG25 was the same, except that cows in NoG25 did not receive GnRH 25 ± 3 d after AI. At nonpregnancy diagnosis (NPD), 32 ± 3 d after AI, cows from G25 and NoG25 with a corpus luteum (CL) ≥15 mm in diameter and a follicle ≥10 mm completed the protocol (G25 CL = 272, NoG25 CL = 194), whereas cows from both treatments that did not meet these criteria received a modified Ovsynch protocol with P4 supplementation [controlled internal drug release insert plus GnRH, controlled internal drug release insert removal, and PGF2α 7 and 8 d later, GnRH 32 h after second PGF2α, and TAI 16 to 18 h after GnRH (G25 NoCL = 53, NoG25 NoCL = 78)]. Serum concentrations of progesterone (P4) were determined and ovarian ultrasonography was performed thrice weekly from 18 ± 3 d after AI until 1 d after TAI (G25 = 46, NoG25 = 44 cows). A greater percentage of NoG25 cows were re-inseminated at detected estrus (NoG25 = 53.5%, G25 = 44.6%), whereas more cows had a CL at NPD in G25 than NoG25 (83.7 and 71.3%). At 32 d after AI, P/AI was similar for G25 and NoG25 for inseminations at detected estrus (38.4 and 42.9%), TAI services for cows with no CL (40.4 and 36.7%), and for all services combined (39.6 and 39.0%). However, P/AI were greater for cows with a CL in G25 than NoG25 (40.6 and 32.8%) that received TAI. More cows ovulated spontaneously or in response to GnRH for the G25 than the NoG25 treatment (70 and 36%) but a similar proportion had an active follicle at NPD (G25 = 91% and NoG25 = 96%). The largest follicle diameter at NPD (G25 = 15.0 ± 0.4 mm, NoG25 = 16.5 ± 0.6 mm) and days since it reached ≥10 mm (G25 = 4.0 ± 0.3 d, NoG25 = 5.8 ± 0.6 d) were greater for the NoG25 than G25 treatment. For cows with a CL at NPD, CL regression after NPD, ovulation after TAI, and ovulatory follicle diameter did not differ. In conclusion, removing the first GnRH of a modified Resynch-25 protocol for cows with a CL at NPD and a modified Ovsynch protocol with P4 supplementation for cows without a CL at NPD resulted in a greater percentage of cows re-inseminated at detected estrus and a similar proportion of cows pregnant in spite of reduced P/AI for cows with a CL at NPD.

Extending the duration of the voluntary waiting period from 60 to 88 days in cows that received timed artificial insemination after the Double-Ovsynch protocol affected the reproductive performance, herd exit dynamics, and lactation performance of dairy cows

This experiment evaluated the reproductive performance, herd exit dynamics, and lactation performance of dairy cows managed with a voluntary waiting period (VWP) of 60 or 88 d. Secondary objectives were evaluating VWP effect on cyclicity status, uterine health, systemic inflammation, and body condition score (BCS) before first service. Lactating Holstein cows from 3 commercial farms in New York State cows were blocked by parity group and total milk yield in their previous lactation and then randomly assigned to VWP of 60 (VWP60; n = 1,352) or 88 (VWP88; n = 1,359) days in milk (DIM). All cows received the Double-Ovsynch protocol (GnRH-7 d-PGF2α-3 d-GnRH-7 d-GnRH-7 d-PGF2α-56 h-GnRH-16 to 20 h-timed artificial insemination; TAI) for synchronization of ovulation and TAI. For second and greater artificial insemination (AI), cows received AI after detection of estrus or the Ovsynch protocol (GnRH-7 d-PGF2α-56 h-GnRH-16 to 20 h-TAI) initiated 32 ± 3 d after AI for cows not re-inseminated at detected estrus. Cyclicity status (progesterone concentration), uterine health (vaginal discharge and uterine cytology), BCS, and systemic inflammation (haptoglobin concentration) were evaluated at baseline (33 ± 3 DIM for both treatments), beginning of the Double-Ovsynch protocol, and 10 d before TAI. Effects of treatments were assessed with multivariable statistical methods relevant for each outcome variable. Extending duration of VWP from 60 to 88 DIM increased pregnancies per AI (P/AI) to first service (VWP60 = 41%; VWP88 = 47%). Nonetheless, the greatest benefit of extending VWP on first-service P/AI was for primiparous cows (VWP60 = 46%; VWP88 = 55%), as P/AI did not differ within the multiparous cow group (VWP60 = 36%; VWP88 = 40%). Physiological status more conducive to pregnancy-characterized by improved uterine health, greater BCS, reduced systemic inflammation, and to a lesser extent more time to resume ovarian cyclicity-explained the increment in P/AI to first service. Our data also indicated that despite having greater P/AI to first service, cows with the longer VWP had delayed time to pregnancy during lactation (hazard ratio = 0.72; 95% confidence interval 0.69-0.98) and greater risk of leaving the herd, particularly for multiparous cows (hazard ratio = 1.34; 95% confidence interval 1.23-1.47). This shift in pregnancy timing led to an overall extension of the lactation length (+13 d), which resulted in greater total milk yield per lactation (+491 kg) but not greater milk yield per day of lactation. In conclusion, data from this experiment highlight the importance of considering the complex interactions between reproductive performance, herd exit dynamics, and lactation performance as well as the effects of parity at the time of defining the duration of the VWP for lactating dairy cows.

Effect of extending the interval from Presynch to initiation of Ovsynch in a Presynch-Ovsynch protocol on fertility of timed artificial insemination services in lactating dairy cows

The specific objective of this study was to determine if increasing the interval between the Presynch and Ovsynch portion of the Presynch-Ovsynch protocol (Presynch: PGF2α-14 d-PGF2α and Ovsynch: GnRH-7 d-PGF2α-56 h-GnRH-16-20 h-timed artificial insemination) from 12 to 14 d would reduce the fertility of lactating dairy cows not detected in estrus after Presynch that receive timed artificial insemination (TAI). Cows from 4 commercial dairy farms (n=3,165) were blocked by parity (primiparous vs. multiparous) and randomly assigned to a 12 (PSOv14-12; n=1,566) or 14 d (PSOv14-14; n=1,599) interval between the second PGF2α (PGF) injection of Presynch (P2) and the beginning of Ovsynch. Cows detected in estrus any time between P2 and the day of the TAI were inseminated (AIED group). From a subgroup of cows (177 and 150 in PSOv14-12 and PSOv14-14, respectively), ovarian parameters and ovulation were evaluated through determination of concentrations of progesterone (P4) in blood and transrectal ultrasonography at the time of the first GnRH (GnRH1) and the PGF injection of Ovsynch. Overall, 52.8% (n=1,671) of the cows were AIED, whereas 47.2% (n=1,494) received TAI. For cows that received TAI, pregnancies per artificial insemination 39 d after artificial insemination were similar for PSOv14-12 (36.3%) and PSOv14-14 (36.0%) but were greater for primiparous (41.5%) than multiparous cows (33.6%). Pregnancy loss from 39 to 105 d after artificial insemination was similar for PSOv14-12 (4.8%) and PSOv14-14 (8.6%), for primiparous (6.4%) and multiparous cows (7.0%), but a tendency for a treatment by parity interaction was observed. Both treatments had a similar proportion of cows with a follicle ≥ 10 mm and similar follicle size at GnRH1; however, the ovulatory response to GnRH was greater for PSOv14-12 (62.2%) than PSOv14-14 (46.4%). A greater proportion of cows with a functional corpus luteum (75.3 vs. 65.6%) and greater concentrations of P4 (3.9 vs. 3.3 ng/mL) at GnRH1 in PSOv14-14 than PSOv14-12 may have compensated for the reduction in fertility expected due to reduced ovulatory response to GnRH1. We concluded that extending the interval from Presynch to Ovsynch from 12 to 14 reduced ovulatory response to GnRH1 but did not reduce the fertility of cows that received TAI when cows were inseminated in estrus after presynchronization. Thus, farms that combine AIED and TAI during the Presynch-Ovsynch protocol may use a 14-d interval between Presynch and Ovsynch to simplify their management without reducing fertility of cows receiving TAI.

A resynchronization of ovulation program based on ovarian structures present at nonpregnancy diagnosis reduced time to pregnancy in lactating dairy cows

Our objective was to evaluate time to pregnancy after the first service postpartum and pregnancy per artificial insemination (P/AI) in dairy cows managed with 2 resynchronization of ovulation programs. After first service, lactating Holstein cows were blocked by parity (primiparous vs. multiparous) and randomly assigned to the d 32 Resynch (R32; n = 1,010) or short Resynch (SR; n = 1,000) treatments. Nonpregnancy diagnosis (NPD) was conducted 32 ± 3 d after AI by transrectal ultrasonography. Nonpregnant cows in R32 received the Ovsynch protocol: GnRH, PGF2α 7 d later, GnRH 56 h later, and timed AI (TAI) 16 to 18 h later. Cows in SR with a corpus luteum (CL) ≥15 mm and a follicle ≥10 mm at NPD received PGF2α, PGF2α 24 h later, GnRH 32 h later, and TAI 16 to 18 h later. Cows in SR without a CL ≥15 mm or a follicle ≥10 mm at NPD received a modified Ovsynch protocol with 2 PGF2α treatments and progesterone (P4) supplementation (GnRH plus CIDR, PGF2α and CIDR removal 7 d later, PGF2α 24 h later, GnRH 32 h later, and TAI 16 to 18 h later). Blood samples were collected from a subgroup of cows at the GnRH before TAI (R32 = 114; SR = 121) to measure P4 concentration. Binomial outcomes were analyzed with logistic regression and hazard of pregnancy (R32 = 485; SR = 462) with Coxs proportional regression in SAS (SAS Institute, Cary, NC). For P/AI analysis, the TAI service was the experimental unit (R32 = 720; SR = 819). Models included treatment and parity as fixed effects and farm as random effect. The hazard of pregnancy was greater for the SR treatment (hazard ratio = 1.18; 95% confidence interval: 1.01-1.37). Median time to pregnancy was 95 and 79 d for the R32 and SR treatments, respectively. At NPD, 71.3 and 71.2% of cows had a CL for the R32 and SR treatments, respectively. Treatment did not affect overall P/AI 32 ± 3 d after AI (R32 = 31.0% vs. SR = 33.9%) or for cows with a CL at NPD (R32 = 32.7% vs. SR = 32.8%). For cows with no CL at NPD, P/AI was greater for the SR treatment (36.9%) than for the R32 treatment (28.6%). Pregnancy loss from 32 to 63 d after AI was similar for all services combined (R32 = 8.3% vs. SR = 10.4%) and for cows with no CL at NPD (R32 = 13.2% vs. SR = 7.2%) but tended to be affected by treatment for cows with a CL at NPD (R32 = 6.8% vs. SR = 11.9%). Treatment affected the proportion of cows with P4 ≤0.5 ng/mL at the GnRH before TAI for all cows (R32 = 68.4% vs. SR = 81.8%), tended to have an effect among cows with a CL (R32 = 70.0% vs. SR = 81.8%), and had no effect for cows with no CL (R32 = 64.7% vs. SR = 81.8%). We concluded that the SR program reduced time to pregnancy because of a reduction of the interbreeding interval for cows with a CL at NPD and greater P/AI in cows with no CL at NPD.

Economic performance of lactating dairy cows submitted for first service timed artificial insemination after a voluntary waiting period of 60 or 88 days

The objective of this study was to evaluate the economic performance of dairy cows managed with a voluntary waiting period (VWP) of 60 or 88 d. A secondary objective was estimating variation in cash flow under different input pricing scenarios through stochastic Monte Carlo simulations. Lactating Holstein cows from 3 commercial farms were blocked by parity group and total milk yield in their previous lactation and then randomly assigned to a VWP of 60 (VWP60; n = 1,352) or 88 d (VWP88; n = 1,359). All cows received timed-artificial insemination (TAI) for first service after synchronization of ovulation with the Double-Ovsynch protocol. For second and greater services, cows received artificial insemination (AI) after detection of estrus or the Ovsynch protocol initiated 32 ± 3 d after AI. Two analyses were performed: (1) cash flow per cow for the calving interval of the experimental lactation and (2) cash flow per slot occupied by each cow enrolled in the experiment for an 18-mo period after calving in the experimental lactation. Extending the VWP from 60 to 88 d delayed time to pregnancy during lactation (∼20 d) and increased the risk of leaving the herd for multiparous cows (hazard ratio = 1.21). As a result, a smaller proportion of multiparous cows calved again and had a subsequent lactation (-6%). The shift in time to pregnancy combined with the herd exit dynamics resulted in longer lactation length for primiparous (22 d) but not multiparous cows. Longer lactations led to greater milk income over feed cost and a tendency for greater cash flow during the experimental lactation for primiparous but not multiparous cows in the VWP88 group. On the other hand, profitability per slot for the 18-mo period was numerically greater (

Reproductive performance and herd exit dynamics of lactating dairy cows managed for first service with the Presynch-Ovsynch or Double-Ovsynch protocol and different duration of the voluntary waiting period

68 slot/18 mo) for primiparous cows but numerically reduced (-

Intravaginal instillation of gonadotropin-releasing hormone analogues with an absorption enhancer induced a surge of luteinizing hormone in lactating dairy cows

85 slot/18 mo) for multiparous cows in the VWP88 treatment. For primiparous cows most of the difference in cash flow was explained by replacement cost, whereas for multiparous cows it was mostly explained by differences in replacement cost and income over feed cost. Under variable input pricing conditions generated through stochastic simulations, the longer VWP treatment always increased cash flow per 18 mo for primiparous and reduced cash flow for multiparous cows. In conclusion, extending the duration of the VWP from 60 to 88 d numerically increased profitability of primiparous cows and reduced profitability of multiparous cows. Such an effect depended mostly on the herd replacement dynamics and milk production efficiency.

1064 Resynchronization of ovulation strategies including or not including GnRH treatment before non-pregnancy diagnosis.

The objective of this experiment was to evaluate the reproductive performance and herd exit dynamics of dairy cows managed for first service with programs varying in method of submission for insemination and voluntary waiting period (VWP) duration. Holstein cows from a commercial farm in New York were randomly allocated to receive timed artificial insemination (TAI) after the Double-Ovsynch protocol (GnRH, 7 d later PGF2α, 3 d later GnRH, 7 d later GnRH, 7 d later PGF2α, 56 h later GnRH, and 16 to 18 h later TAI) at 60 ± 3 d in milk (DIM) (DO60 = 458), TAI after Double-Ovsynch at 88 ± 3 DIM (DO88 = 462), or a combination of AI at detected estrus (starting at 50 ± 3 d in milk) and TAI with the Presynch-Ovsynch protocol (PGF2α, 14 d later PGF2α, 12 d later GnRH, 7 d later PGF2α, 56 h later GnRH, and 16 to 18 h later TAI; PSOv = 450). Subsequent artificial insemination (AI) services were conducted at detected estrus or the Ovsynch protocol (32 ± 3 d after AI GnRH, 7 d later PGF2α, 56 h later GnRH, and 16 to 18 h later TAI) for cows not reinseminated at detected estrus. In a subgroup of cows, cyclicity (based on progesterone concentration), uterine health (vaginal discharge and uterine cytology), and BCS were evaluated at baseline (DO60 and DO88 = 33 ± 3 DIM; PSOv = 34 ± 3 DIM), beginning of the synchronization protocol (DO60 = 33 ± 3 DIM; DO88 = 61 ± 3 DIM; PSOv = 34 ± 3 DIM), and within -5 (PSOv) or -10 d (DO) of the VWP end (DO60 = 50 ± 3 DIM; DO88 = 78 ± 3 DIM; PSOv = 45 ± 3 DIM). Effects of treatments were assessed with multivariable statistical methods relevant for each outcome variable. Cows in the DO88 treatment had delayed time to pregnancy during lactation (DO60 vs. DO88 hazard ratio = 1.53, 95% confidence interval = 1.32 to 1.78; PSOv vs. DO88 hazard ratio = 1.37, 95% confidence interval = 1.19 to 1.61) and, within multiparous cows, the DO88 and PSOv treatments had greater risk of leaving the herd than cows in the DO60 treatment (DO88 vs. DO60 hazard ratio = 1.49, 95% confidence interval = 1.11 to 2.00; PSOv vs. DO60 hazard ratio = 1.39, 95% confidence interval = 1.03 to 1.85). Cows in the DO88 treatment had improved uterine health, greater BCS, and reduced incidence of anovulation than cows in DO60 and PSOv; however, overall pregnancy per AI 39 ± 3 d after AI was similar for the 3 treatment groups. In summary, reproductive management strategies that led to similar average DIM to the first service (∼60 d) through a combination of AI at estrus with TAI (PSOv) or all TAI (DO60) resulted in reduced time to pregnancy after calving when compared with an all TAI program (DO88) with a VWP of 88 d. Within the multiparous cow group, those that received all TAI with a VWP duration of 60 d were less likely to leave the herd than cows in the other treatments.

1270 Profitability of dairy cows managed for first service with the Double-Ovsynch or Presynch-Ovsynch protocol and different duration of the voluntary waiting period

Our objectives were to evaluate circulating LH concentrations after intravaginal (IVG) instillation of GnRH analogs in lactating dairy cows. In 2 experiments, lactating Holstein cows (experiment 1: n = 32; experiment 2: n = 47) received the experimental treatments 48 h after the first of 2 PGF2α treatments given 12 h apart and 7 d after a modified Ovsynch protocol (GnRH at -7 d, PGF2α at -24 h, PGF2α at -56 h, GnRH at 0 h). In experiment 1, cows were stratified by parity and randomly allocated to receive the following treatments: 2 mL of saline IVG (SAL, n = 6), 100 µg of gonadorelin (Gon) i.m. (G100-IM, n = 5), and 100 (G100, n = 7), 500 (G500, n = 8), or 1,000 µg of Gon IVG (G1000, n = 7). In experiment 2, treatments were SAL (n = 8), G100-IM (n = 8), G1000 (n = 7), 1,000 µg of Gon plus 10% citric acid (CA) IVG (G1000CA, n = 8), 80 µg of buserelin IVG (B80, n = 8), and 80 µg of buserelin plus 10% CA IVG (B80CA, n = 8). In both experiments, blood was collected every 15 min from -15 min to 4 h, and every 30 min from 4 to 6 h after treatment. Data for area under the curve (AUC), mean LH concentrations, and time to maximum LH concentration were analyzed by ANOVA with (mean LH only) or without repeated measures using PROC MIXED of SAS (version 9.4, SAS Institute Inc., Cary, NC). The proportion of cows with a surge of LH was evaluated with Fishers exact test using PROC FREQ of SAS. In both experiments, LH concentrations were affected by treatment, time, and the treatment by time interaction. In experiment 1, the AUC for LH and maximum LH concentration were greatest for the G100-IM treatment and were greater for the G1000 than for the SAL and G500 treatments. The proportion of cows with an observed surge of LH was 100 and 0% for cows that received Gon i.m. and IVG, respectively. In experiment 2, the AUC and maximum LH concentrations were greater for the G100-IM, G1000CA, and B80CA treatments than for the other IVG treatments. The proportion of cows with a surge of LH differed by treatment (SAL = 0%, G100-IM = 100%, G1000 = 14%, G1000CA = 88%, B80 = 13%, and B80CA = 100%). For the treatments with a surge of LH, time to maximum concentration of LH was the shortest for the G100-IM treatment, intermediate for the G1000CA treatment, and the longest for cows in the B80CA treatment. In conclusion, Gon (up to 1,000 µg) absorption through intact vaginal epithelium after a single IVG instillation was insufficient to elicit a surge of LH of normal magnitude. Conversely, IVG instillation of 1,000 µg of Gon and 80 µg of buserelin with the addition of citric acid as absorption enhancer resulted in a surge of LH of similar characteristics than that induced after i.m. injection of 100 µg of Gon.