Association between genomic daughter pregnancy rate and expected milk production on the resumption of estrus behavior in Holstein cattle.

The objective of this observational study was to evaluate estrous expression at the first estrus occurring between 7 to 30 d in milk (DIM), as detected by an automated activity monitor (AAM), and its association with genomic daughter pregnancy rate (GDPR) and genomic expected milk production (GEM) in lactating dairy cows. A total of 4,119 lactations from 2,602 Holstein cows were included. Cows were enrolled as first lactation (n = 1,168), second lactation (n = 1,525) and third and greater lactation (n = 1,426). Hair samples were collected from the tail switch, and cows were genotyped using an SNP platform (Clarifide, Zoetis, São Paulo, SP, Brazil). Postpartum cows were examined daily by the farm personnel from calving until 10 DIM. Calving was classified as assisted (forced calf extraction) and unassisted (normal calving). Retained fetal membranes (RFM), hyperketonemia (KET), and left displaced abomasum (LDA) were also recorded. Mean GDPR (± SD) was -0.29 ± 1.4, and the intensity and duration of the first estrus event was 15.9 ± 13.1 x-factor (intensity unit measurement) and 11.1 ± 3.8 h, respectively. Cows that had greater GDPR had greater intensity and longer duration of estrus at the alert, independent of parity. Overall resumption of estrous expression, between 7 to 30 DIM, was 41.2% (1,695/4,119), where 58.8% (2,424/4,119) did not have an estrus event, 31.0% (1,274/4,119) of cows had one event of estrus, and 10.2% (421/4,119) of cows had 2 or more events of estrus early postpartum. Mean DIM (± SD) at first estrus event, detected by the AAM, was 19.4 ± 4.4 d. Days in milk at first event for cows with one event was 20.7 ± 1.6 d and 15.9 ± 3.1 d for cows with 2 or more events of estrus. First lactation cows were more likely to have an estrus event early postpartum when compared with second and third and greater lactation cows (45.2 ± 1.4% [530/1168] vs. 41.6 ± 1.3% [636/1525] vs. 37.2 ± 1.3% [529/1426], respectively). There was an interaction of parity and GDPR on the proportion of cows demonstrating an early postpartum estrus. There was no difference in the proportion of cows with an early postpartum estrus between those with assisted or unassisted calving, RFM, or LDA. However, cows that had KET were less likely to have an alert early postpartum when compared with cows that did not have KET. Mean genomic expected milk production (± SD) was 256.8 ± 600.1 kg. There was no interaction between GEM and parity on estrous expression (i.e., intensity and duration). There was no interaction between GEM and GDPR on the proportion of estrus early postpartum.

Effects of additional gonadotropin-releasing hormone and prostaglandin F2α treatment to an estradiol/progesterone-based embryo transfer protocol for recipient lactating dairy cows.

This study was designed to evaluate whether the utilization of a second PGF2α treatment at the end of an estradiol/progesterone (E2/P4)-based protocol with or without GnRH at the beginning of the protocol would improve pregnancy rates of lactating Holstein cows assigned to timed embryo transfer. A total of 501 lactating Holstein cows in 5 farms were enrolled in the experiment. Within farm, cows were blocked by parity and, within block, were assigned randomly to (1) insertion of an intravaginal P4 device (controlled internal drug-releasing device; CIDR) and estradiol benzoate on d -11, PGF2α on d -4, CIDR withdrawal and an injection of estradiol cypionate on d -2, and timed embryo transfer on d 7 (1-PGF; n = 164); (2) the same treatments as 1-PGF, but with PGF2α administered on d -4 and -2 (2-PGF; n = 171); and (3) 2-PGF with the addition of a GnRH treatment on d -11 (GnRH+2-PGF; n = 166). Ovaries were scanned by transrectal ultrasonography on d -11, -4, and 7, and blood samples were collected on d -11, -4, 0, and 7 for P4 determination. Treatment comparisons were performed using contrasts. The proportion of cows with a new corpus luteum on d -4 was greater in GnRH+2-PGF cows. Cows in 1-PGF had a greater P4 concentration on d 0 but lesser P4 on d 7 compared with cows in the other groups. Cows assigned to receive 2-PGF (2-PGF and GnRH+2-PGF) had greater estrus expression, and a greater proportion of cows ovulated to estradiol cypionate. No further contrast effects were observed for follicle diameter, double ovulation rate, pregnancy per embryo transfer (P/ET) on d 32 and 60, or pregnancy loss. As P4 concentration on d -4 increased, P/ET on d 60 tended to increase. Cows with P4 ≥3.66 ng/mL on d -4 had greater P/ET on d 32 and 60 than those with P4 below that threshold. Regardless of treatment, cows with P4 concentration ≥3.66 ng/mL also had a greater pregnancy per synchronized protocol (P/SP) on d 60. Also, a P4 concentration on d -4 (low or high) × follicle diameter (continuous) interaction tendency was observed when evaluating P/ET. Although P/ET did not differ among cows with different follicles sizes with reduced P4 concentration on d -4 (<3.66 ng/mL), it increased in cows with larger follicles exposed to increased P4 concentration (≥3.66 ng/mL). When P4 on d 0 was evaluated, P/ET on d 32 and 60 was greater for cows with low (≤0.09 ng/mL) versus high (>0.21 ng/mL) P4; as P4 concentration on d 0 increased, P/ET linearly decreased. In summary, cows with increased P4 concentrations during growth of the ovulatory follicular wave had improved P/ET. Administering a second PGF2α dose reduced P4 concentration on d 0 and increased ovulatory response to the protocol, but no benefits were observed on P/ET or P/SP.

Size and position of the reproductive tract impacts fertility outcomes and pregnancy losses in lactating dairy cows.

There are multiple factors that contribute to reduced fertility in lactating dairy cows. Recently, a reproductive tract size and position score (SPS) system was developed as a management tool to identify dairy cows with decreased fertility. The aim of this study was to evaluate the association between the SPS on fertility outcomes such as ovulation failure, pregnancy per artificial insemination (P/AI), concentration of pregnancy-associated glycoproteins (PAGs), and pregnancy loss in lactating dairy cows. Primiparous and multiparous lactating Holstein cows (n = 869) were enrolled at two locations. Location 1 (Loc. 1) in Minas Gerais, Brazil (n = 613) and location 2 (Loc. 2) in Agassiz, British Columbia, Canada (n = 256). At the time of AI (d 0), cows were classified as SPS (small [SPS1], medium [SPS2], or large [SPS3] sized reproductive tract) and ovulation failure was determined at 48 h and 7 d post-AI via ultrasonography (Loc. 2 only). Blood samples were collected on d 24 and 31 of gestation for quantification of PAGs and pregnancy diagnosis was performed via ultrasonography at d 31 and 60 post-AI (Loc. 1) and at d 31 ± 3 and 60 ± 3 post-AI (Loc. 2). Cows diagnosed pregnant at d 31 post-AI but not pregnant at d 60 were defined to have undergone late embryonic pregnancy loss. Parity was found to impact SPS (P < 0.01), as primiparous cows had a higher frequency of SPS1 and lower frequency of SPS3 when compared with multiparous cows (SPS1: 42.6 vs. 15.0%; SPS3: 7.0 vs. 22.0%, respectively). Cows classified as SPS3 had greater ovulation failure at 48 h (P = 0.04) and 7 d post-AI (P = 0.05). Cows classified as SPS1 had greater P/AI when compared to SPS2 and SPS3 (45.9 ± 3.3 vs. 37.4 ± 2.6 and 29.1 ± 3.5%, respectively; P = 0.004). There was no interaction between parity and SPS on P/AI. Pregnancy loss between 31 and 60 d post-AI was increased in cows classified as SPS3 compared to SPS2 and SPS1 (24.3 ± 0.05 vs. 11.6 ± 0.02 and 9.4 ± 0.02%, respectively; P = 0.04). Cows classified as SPS1 and SPS2 had greater concentrations of PAGs at 31 d post-AI when compared to SPS3 at both Loc.1 (P < 0.01) and Loc. 2 (P < 0.01). There was no interaction between SPS and pregnancy loss on PAGs at 24 and 31 d post- AI for either Loc. 1 (P = 0.75 and P = 0.76, respectively) or Loc. 2 (P = 0.61 and P = 0.81, respectively). In conclusion, cows that were classified as SPS3 had greater ovulation failure, reduced P/AI, similar concentrations of PAG on d 24, but decreased on d 31, and a greater incidence of pregnancy loss. Thus, size and position of the reproductive tract is associated with fertility and this scoring system could be used to make reproductive management decisions on dairy operations.

Evaluation of presynchronization and addition of GnRH at the beginning of an estradiol/progesterone protocol on circulating progesterone and fertility of lactating dairy cows.

The objectives of this study were to determine if the utilization of a presynchronization strategy would improve fertility at first artificial insemination (AI) during an E2/P4 ovulation synchronization protocol with or without GnRH administration at the beginning of the protocol. This experiment was conducted using cows (n = 665) at their first postpartum service and the following breeding treatment: CIDR insertion and 2.0 mg of estradiol benzoate (EB) on day -11; 25 mg dinoprost tromethamine (PG) on day -4; PG, CIDR withdrawal, and 1.0 mg of estradiol cypionate (ECP) on day -2; timed-AI on day 0. At 31 ± 3 days postpartum, cows were randomly allocated to one of three treatments on a weekly basis: 1) -P + GnRH: cows assigned to the breeding protocol with 100 µg of GnRH on day -11, 2) P + GnRH: cows assigned to a presynchronization protocol using CIDR insertion +2 mg EB on day -28, PG + ECP and CIDR withdrawal on day -21, and beginning of the breeding protocol plus GnRH (100 µg) on day -11, and 3) +P-GnRH: cows assigned to a presynchronization protocol and the breeding treatment without GnRH on day -11. No treatment effects were observed on P/AI at the pregnancy diagnoses on days 32 and 60, or for pregnancy losses between days 32 and 60 of pregnancy whether analyses included all cows or only cows that ovulated near TAI. Moreover, milk yield negatively affected P/AI. Cows with greater circulating P4 concentrations on day -4 had greater P/AI on day 60. Cows without CL on day -11 had a reduced P/AI and this effect was more significant in cows not treated with GnRH. Cows assigned to -P + GnRH had the lowest circulating P4 concentration on day -4 (3.4 ± 0.16 ng/mL), followed by + P-GnRH (4.56 ± 0.17 ng/mL), and +P + GnRH (5.08 ± 0.17 ng/mL) cohorts. The data of the current study suggest that the combination of a Presynch and GnRH administration at the beginning of a TAI protocol was the most effective way to increase the % of cows with a functional CL and with elevated circulating P4 concentrations at the time of PG treatment.

Comparison of 2 protocols to increase circulating progesterone concentration before timed artificial insemination in lactating dairy cows with or without elevated body temperature.

Two treatments designed to increase circulating progesterone concentration (P4) during preovulatory follicle development were compared. One treatment used 2 intravaginal P4 implants (controlled internal drug-releasing inserts; CIDR) and the other used a GnRH treatment at beginning of the protocol. Lactating Holstein cows that had been diagnosed as nonpregnant were randomly assigned to receive timed artificial insemination (TAI) following 1 of 2 treatments (n = 1,638 breedings): (1) GnRH: CIDR+ 2 mg of estradiol (E2) benzoate + 100 µg of GnRH on d -11, PGF2α on d -4, CIDR withdrawal + 1.0 mg of E2-cypionate + PGF2α) on d -2, and TAI on d 0; or (2) 2CIDR: 2 CIDR + 2 mg of E2-benzoate on d -11, 1 CIDR withdrawn + PGF2α on d -4, second CIDR withdrawn + 1.0 mg of E2-cypionate + PGF2α on d -2, and TAI on d 0. Milk yield was measured daily between d 0 and d 7. Rectal temperature was measured using a digital thermometer at d 0 and 7, and elevated body temperature was defined as an average rectal temperature ≥39.1°C. Pregnancy diagnoses were performed on d 32 and 60 after TAI. We detected no effect of treatments on pregnancy per AI or pregnancy loss regardless of elevated body temperature, body condition score, parity, milk yield, or presence or absence of a corpus luteum (CL) on d -11 or d -4. Pregnancy per AI at 60 d was reduced [elevated body temperature = 22.8% (162/709), no elevated body temperature 34.1% (279/817)] and pregnancy loss tended to increase [elevated body temperature = 20.2% (41/203), no elevated body temperature 14.4% (47/326)] in cows with elevated body temperature. Various physiological measurements associated with greater fertility were also reduced in cows with elevated body temperature, such as percentage of cows with a CL at PGF2α (decreased 7.9%), ovulatory follicle diameter (decreased 0.51 mm), expression of estrus (decreased 5.1%), and ovulation near TAI (decreased 2.8%) compared with cows without elevated body temperature. A greater proportion of cows (30.2%) had a CL at PGF2α in the GnRH treatment [74.1% (570/763)] than in the 2CIDR treatment [56.9% (434/763)]; however, circulating P4 concentration was greater at the time of PGF2α treatment (d -4) for cows 2CIDR (4.26 ± 0.13 ng/mL) than in cows in GnRH (3.99 ± 0.14 ng/mL). Thus, these 2 protocols yield similar fertility results that might be due to somewhat different physiological alterations. Treatment with GnRH increased the proportion of cows with a CL at PGF2α; however, the 2CIDR protocol increased circulating P4 under all circumstances.

Comparison of fertility following use of one versus two intravaginal progesterone inserts in dairy cows without a CL during a synchronization protocol before timed AI or timed embryo transfer.

The objective was to evaluate the effect of increased progesterone (P4) during preovulatory follicle growth during timed AI (TAI) or timed embryo transfer (TET) protocols. Lactating dairy cows with no CL and low circulating P4 (≤1.0 ng/mL) were submitted to a protocol using one or two intravaginal P4 implants (controlled intravaginal releasing device [CIDRs]), and were bred to TAI or TET. The low P4 cows for this experiment were identified on nine farms, four utilized TAI (n = 326 of 1160 cows examined), and five utilized TET (n = 445 of 1396). All cows were synchronized by insertion of P4 implant(s) (CIDR[s]) at start of protocol (Day -11) and simultaneous treatment with 2 mg of E2-benzoate. After 7 days, cows were treated with PGF (Day -4) and 2 days later treated with 1.0-mg E2-cypionate and CIDR(s) were removed (Day -2). Cows received TAI on Day 0 or TET on Day 7. Cows were randomly assigned to receive either one or two CIDRs on Day -11 until Day -2 (1CIDR vs. 2CIDR). Presence of CL was determined by ultrasound on Day -11 and Day 7 after protocol (to determine ovulation to protocol), P4 concentrations were determined on a subset of cows (Day -11, Day -4, Day 7), and ovulatory follicle diameter was evaluated on Day 0. Pregnancy success (P/AI or P/ET) was evaluated on Days 32 and 60. The 2CIDR treatment increased circulating P4 by Day -4 (1.77 ± 0.23 vs. 2.18 ± 0.24 ng/mL) but had no effect on ovulation at the end of protocol (83.6 vs. 82.6%) or ovulatory follicle diameter (15.6 ± 0.3 vs. 15.3 ± 0.3 mm). If only cows that ovulated to the protocol were included, 1CIDR tended to have lower P/AI than 2CIDR by Day 32 (42.8 vs. 52.6%; P = 0.10) and Day 60 (37.7 vs. 48.1%; P = 0.08) but there was no effect on pregnancy loss. There was an interaction (P = 0.05) between ovulatory follicle diameter and CIDR treatment on P/AI (Day 60). In cows ovulating larger follicles (≥14 mm), 2CIDR treatment increased P/AI compared with 1CIDR (53.3 vs. 34.9%; P = 0.02) but not in cows ovulating small follicles (<14 mm). There was no effect of treatment on P/ET on Day 32 (30.0% vs. 32.0%) or Day 60 (24.7% vs. 25.6%). Thus, these results add evidence to the concept that increased circulating P4 during preovulatory follicle development may improve P/AI, most likely due to improved oocyte quality in cows that ovulate larger follicles, since improvement was only in cows ovulating larger follicles and no effect of preovulatory P4 was observed in cows that received ET.

Inducing ovulation with oestradiol cypionate allows flexibility in the timing of insemination and removes the need for gonadotrophin-releasing hormone in timed AI protocols for dairy cows.

The effects of addition of gonadotrophin-releasing hormone (GnRH) to a progesterone plus oestradiol-based protocol and timing of insemination in Holstein cows treated for timed AI (TAI) were evaluated. Cows (n=481) received a progesterone device and 2mg oestradiol benzoate. After 8 days, the device was removed and 25mg dinoprost was administered. Cows were allocated to one of three (Study 1; n=57) or four (Study 2; n=424) groups, accordingly to ovulation inducer alone (Study 1; oestradiol cypionate (EC), GnRH or both) or ovulation inducer (EC alone or combined with GnRH) and timing of insemination (48 or 54h after device removal; Study 2). In Study 1, the diameter of the ovulatory follicle was greater for GnRH than EC. Oestrus and ovulation rates were similar regardless of ovulatory stimuli. However, time to ovulation was delayed when GnRH only was used. In Study 2, cows treated with GnRH or not had similar pregnancy per AI (P/AI) 30 days (41.5% vs 37.3%; P=0.28) and 60 days (35.9% vs 33.0%; P=0.61) after TAI. TAI 48 and 54h after device removal resulted similar P/AI at 30 days (40.3% vs 38.5%; P=0.63) and 60 days (33.8% vs 35.1%; P=0.72). Thus, adding GnRH at TAI does not improve pregnancy rates in dairy cows receiving EC. The flexibility of time to insemination enables TAI of a large number of cows using the same protocol and splitting the time of AI.

Timing of prostaglandin F2α treatment in an estrogen-based protocol for timed artificial insemination or timed embryo transfer in lactating dairy cows.

Objectives were to investigate progesterone concentrations and fertility comparing 2 different intervals from PGF(2α) treatment and induced ovulation in an estrogen-based ovulation synchronization protocol for timed artificial insemination (TAI) or timed embryo transfer (TET) in lactating dairy cows. A total of 1,058 lactating Holstein cows [primiparous (n=371) and multiparous (n=687)], yielding 34.1 ± 0.33 kg of milk/d at various days in milk were randomly assigned to receive treatment with PGF(2α) on either d 7 or 8 of the following protocol: d 0: 2mg of estradiol benzoate + controlled internal drug release device; d 8: controlled internal drug release device removal + 1.0mg of estradiol cypionate; d 10: TAI or d 17: TET. Only cows with a corpus luteum at d 17 received an embryo and all cows received GnRH at TET. Pregnancy diagnoses were performed by detection (transrectal ultrasonography) of an embryo on d 28 or a fetus on d 60. Fertility [pregnancy per artificial insemination (P/AI) or pregnancy per embryo transfer (P/ET)] was affected by breeding technique (AI vs. ET) and time of PGF(2α) treatment (d 7 vs. 8) at the 28-d pregnancy diagnosis for TAI [32.9% (238) vs. 20.6% (168)] and TET cows [47% (243) vs. 40.7% (244)] and at the 60-d pregnancy diagnosis for TAI [30% (238) vs. 19.2% (168)] and TET cows [37.9% (243) vs. 33.5% (244)]. The progesterone (P4) concentration at d 10 altered fertility in TAI cows, with higher P/AI in cows with P4 concentration <0.1 ng/mL compared with cows with P4 concentration ≥ 0.1 ng/mL, and in ET cows, with higher P/ET in cows with P4 concentration <0.22 ng/mL compared with cows with P4 concentration ≥ 0.22 ng/mL. Prostaglandin F(2α) treatment at d 7 increased the percentage of cows with P4 <0.1 ng/mL on d 10 [39.4 (85) vs. 23.2 (54)]. Reducing the period between PGF(2α) and TAI from 72 to 48 h in dairy cows resulted in a clear reduction in fertility in cows bred by TAI and a subtle negative effect in cows that received TET. The earlier PGF(2α) treatment benefits are most likely mediated through gamete transport, fertilization, or early embryo development and a more subtle effect of earlier PGF(2α) treatment that may be mediated through changes in the uterine or hormonal environment that manifests itself after ET on d 7.