Expression of estrus improves fertility and decreases pregnancy losses in lactating dairy cows that receive artificial insemination or embryo transfer

Treatment alternatives to induce follicular wave emergence for timed-AI in lactating dairy Cows

Two experiments evaluated the effect of different hormonal treatments to synchronize follicle wave emergence on follicle dynamics and pregnancies per AI (P/AI) in estradiol (E2)/progesterone (P4) timed-AI (TAI) protocols in lactating dairy cows. In Experiment 1, lactating, primiparous Holstein cows (n = 36) received a P4 releasing device (Day 0) and were allocated at random to one of the following three treatment groups: Group EB received 2 mg E2 benzoate (EB) intramuscularly (i.m.), Group EB + GnRH received 2 mg EB+20 μg buserelin (GnRH) i.m., or Group EB + P4 received 2 mg EB + 100 mg of injectable P4 (iP4) in oil i.m. All cows received 0.150 mg D-Cloprostenol on Days 7 and 8 followed by P4 device removal, 400 IU eCG and 1 mg ECP on Day 8. Daily ultrasound examinations revealed that although the interval from P4 device removal to ovulation was not affected by treatment, cows that received EB + GnRH had an earlier (P < 0.05) emergence of the new follicular wave (Day 2.6 ± 0.2) than the other two treatment groups (Days 3.5 ± 0.3 and 6.1 ± 0.3, for EB and EB + P4, respectively). In Experiment 2, 808 lactating cows were assigned randomly to the three treatments evaluated in Experiment 1, and all the cows were TAI to determine P/AI. Cows in the EB + GnRH group had greater P/AI (57.4 %, P < 0.01) than those in the EB (44.6 %) or EB + P4 (45.7 %) groups. In conclusion, the administration of GnRH, but not iP4, on the day of insertion of a P4 device improves P/AI in lactating dairy cows synchronized for TAI with an estradiol/P4-based protocol.

Comparison of gonadotropin-releasing hormone and estradiol benzoate plus gonadotropin-releasing hormone to initiate a progesterone-based timed artificial insemination resynchronization protocol in lactating dairy cows

The present study compared 2 strategies to initiate a progesterone (P4)-based timed artificial insemination (TAI) protocol for lactating dairy cows: only GnRH or estradiol benzoate (EB) plus GnRH (EB+GnRH). Lactating Holstein cows (n = 487; 184 primiparous and 303 multiparous) from 2 commercial dairy herds were used for their second or greater services postpartum. Each week, cows that were nonpregnant at the pregnancy diagnosis 32 d after a previous AI were randomly assigned to 1 of 2 experimental groups that differed only in the strategy to initiate (d 0) the TAI protocol. On d 0, every cow received a 2.0-g P4 implant; in the EB+GnRH group, cows were treated with 2.0 mg i.m. of EB and 16.8 µg i.m. of the GnRH analog buserelin acetate, whereas in the GnRH group, cows received only 16.8 µg i.m. of GnRH. On d 7 after the initial treatment, 0.530 mg i.m. of cloprostenol sodium (PGF) was administered in all cows, followed by a second dose on d 8, concomitant with 1.0 mg i.m. of estradiol cypionate and P4 implant withdrawal. The TAI was performed on d 10 (48 h after P4 device withdrawal) in both experimental groups. Only conventional Holstein semen was used throughout the study. The percentage of cows with corpus luteum (CL) on d 0 (73%) and overall ovulation rate after d 0 (54%) did not differ between groups. The CL regression between d 0 and the first PGF treatment was greater in the EB+GnRH group than the GnRH group (42% vs. 31%). Consequently, the proportion of cows with CL at PGF was greater when only GnRH was used on d 0 compared with EB+GnRH (86% vs. 82%), and the mean number of CL at PGF was greater (1.23 vs. 1.11). The expression of estrus near TAI was greater in GnRH group (84% vs. 77%), and cows showing estrus had greater (44% vs. 10%) pregnancy per AI (P/AI) on d 32 for both treatments. We found no effect of the presence of CL on d 0 or at PGF, nor of ovulation after d 0 or CL regression between d 0 and d 7 on fertility. However, fertility was critically impaired when cows did not have CL at both times, d 0 and at PGF treatment. We did not observe any interaction between treatment and other variables, and the P/AI was similar in cows receiving EB+GnRH or only GnRH on d 0 (37.8% vs. 36.6%). In summary, although there was no detectable difference in P/AI between treatments, this study demonstrated potential negative physiological outcomes caused by EB treatment on d 0 (greater incidence of luteolysis after d 0 and fewer cows with CL at PGF treatment). Overall, we found no benefit of adding EB at the initiation of a P4-based TAI protocol on fertility compared with using GnRH alone, despite differences in ovarian dynamics and expression of estrus.

Early induction of luteolysis in a timed AI protocol increases reproductive performance in beef cows

The aim of this study was to produce a longer proestrus by early administration of prostaglandin F2α (PGF) in a timed artificial insemination (TAI) protocol in non-suckling Bos taurus (Angus crossbreed) beef cows. On day 0, cows (n = 489) were treated with an intravaginal 1 g progesterone (P4) device and 2 mg of estradiol benzoate. On day 7, cows were randomized into two groups: PGF7(n = 244; 500 µg of sodium cloprostenol 24 h before P4 device removal) or PFG8 (n = 245; 500 µg of sodium cloprostenol at P4 device removal). On day 8, P4 device was removed and cows received 0.5 mg of estradiol cypionate. All cows were submitted to TAI on day 10 (48-50 hours after P4 device removal). Cows treated with PGF on day 7 had greater expression of estrus (91.3 vs 79.1 %; P = 0.0011), regardless of CL presence at beginning of the protocol. Cows from PGF7 group had lower circulating P4 concentrations on day 8 in comparison with PGF8 treated cows (1.86 vs 2.99 ng/mL; P < 0.001). However, preovulatory follicle diameter did not differ among treatments at TAI (11.9 vs 11.8 mm; P = 0.7881). Pregnancy per TAI (P/TAI) was greater for PGF7 (63.9 vs 50.6 %; P = 0.0114) than PGF8 treated cows. In cows with follicles <8.5 mm at TAI, expression of estrus (33.3 vs 26.6 %; P = 0.6427) and P/TAI (40 vs 26.6 %; P = 0.3657) were low in both PGF7 and PGF8 treated cows, respectively. In cows with medium follicle size (8.5 to 11.9 mm) PGF7 treated cows had greater expression of estrus (90.5 vs 80 %; P = 0.033) and P/TAI (62.2 vs 49 %; P = 0.053). In cows with follicles >12 mm, expression of estrus was greater for PGF7 than PGF8 treated cows (99.1 vs 93.3 %; P = 0.045), however P/TAI did not differ (68.2 vs 59 %; P = 0.149). In cows with P4 < 1.99 ng/mL on day 8, expression of estrus was similar between PGF7 and PGF8 treated cows (92.6 vs 90.4 %; P = 0.53), and P/TAI tended to be greater for PGF7 than PGF8 treated cows (63 vs 52.1 % P = 0.076). However, in cows with P4 > 2 ng/mL PGF7 cows had higher expression of estrus (89 vs 67.5 %; P = 0.0005) and P/TAI (64.8 vs 48.7 %; P = 0.021) than PGF8. Thus, increasing the proestrous period by inducing luteolysis 24 hours earlier than removing the P4 intravaginal device enhanced fertility in non-suckling cyclic beef cows by increasing expression of estrus and P/TAI.

In vitro reminiscence: uterine programming in vivo affects respective luminal epithelial cells function in vitro†

In cattle, the endometrium during diestrus and early pregnancy displays cellular responses that are consequences of prior, transient stimuli. Goal was to establish a model to study cellular memory in the endometrium. The hypothesis is that stimuli given to endometrium in vivo are retained as a cellular memory that remains after bovine uterine epithelial cells (BUECs) are isolated, cultured, and further stimulated in vitro. Objectives were to measure BUEC proliferation/migration and responsiveness to recombinant bovine Interferon-tau (rbIFNT) in vitro: among cows that showed estrus (experiment 1 [Exp1]), cows that became or not pregnant to artificial insemination (Exp2), cows that received or not supplemental progesterone (P4; Exp3) and cows that received or not a COX-1/2 inhibitor (Exp4). Only cows that displayed estrus were included in studies. For all experiments endometrial cytology was collected 4 days after estrus, BUECs were cultured, propagated, and submitted to rbIFNT treatment and an in vitro scratch assay. In Exp1, different cows spontaneously grouped according to proliferative/migratory capacity and responsiveness to rbIFNT of their respective BUECs. In Exp2, BUECs from pregnant cows showed greater rbIFNT responsiveness and cellular proliferation. In Exp3, BUECs from cows supplemented with P4 presented inhibited proliferation and increased expression of RSAD2. In Exp4, Flunixin Meglumine modified rbIFNT responsiveness of BUECs in an IFN-signaling pathway-specific manner. In conclusion, physiological and pharmacological stimuli received by the endometrium in vivo were retained as cellular memory in BUECs, persisted in culture, and changed BUEC proliferation/migration and responsiveness to rbIFNT, which are characteristics associated with fertility in cattle.

Effect of postpartum body condition score change on the pregnancy outcomes of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after a synchronized estrus versus a synchronized ovulation

Our objective was to compare insemination rate and pregnancies per artificial insemination (P/AI) of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after submission to a Double-Ovsynch protocol for timed artificial insemination (TAI) versus a protocol to synchronize estrus at similar days in milk (DIM). Secondary objectives were to determine the effect of protocol synchrony and postpartum body condition score (BCS) change on P/AI. Lactating Jersey cows (n = 1,272) were allocated by odd versus even ear tag number, which was randomly allocated within the herd, within parity and semen type for submission to a Double-Ovsynch protocol (DO; n = 707) or a protocol to synchronize estrus (ED; n = 565). All ED cows detected in estrus were inseminated (EDAI; n = 424), with undetected cows receiving TAI after an Ovsynch protocol (EDTAI; n = 141). There was a treatment by parity interaction on insemination rate with 100% of DO cows receiving TAI, but a tendency for fewer primiparous ED cows to be detected in estrus and AI than multiparous cows (69.5% ± 0.04% vs. 77.1% ± 0.02%, respectively). For cows inseminated with sexed Jersey or conventional beef semen, DO cows tended to have and had more P/AI than EDAI cows (sexed, 49.2% ± 0.03% vs. 43.6% ± 0.03%; beef, 64.2% ± 0.04% vs. 56.3% ± 0.05%, respectively) and had more P/AI than EDAI+EDTAI cows (sexed, 49.1% ± 0.03% vs. 40.6% ± 0.03%; beef, 65.5% ± 0.04% vs. 56.2% ± 0.04%, respectively). Overall, 29.1% of DO cows expressed estrus with 5.0% and 24.2% of cows detected in estrus ≥24 h before and at TAI, respectively, and there was no difference in P/AI 61 ± 4 d after AI based on expression of estrus at TAI. The synchronization rate was greater for DO than EDAI cows (92.1% ± 0.01% vs. 79.2% ± 0.02%, respectively); however, synchronized DO cows had more P/AI than synchronized EDAI cows (55.0% ± 0.02% vs. 49.2% ± 0.03%, respectively). There was an interaction between BCS change from 7 to 39 ± 2 DIM and treatment on P/AI 61 ± 4 d after AI with no difference between DO and EDAI cows that lost = 0.25 (49.8% ± 0.04% vs. 51.0% ± 0.05%, respectively) or maintained or gained (55.6% ± 0.04% vs. 50.8% ± 0.05%, respectively) BCS, but within cows that lost ≥0.5 BCS, DO cows had more P/AI than EDAI cows (54.1% ± 0.04% vs. 36.1% ± 0.04%, respectively). In conclusion, submission of lactating Jersey cows to a Double-Ovsynch protocol for first insemination increased insemination rate and fertility to first insemination compared with AI after a detected estrus regardless of semen type and expression of estrus, particularly for cows with excessive postpartum BCS loss.

Interval from Oestrus to Ovulation in Dairy Cows-A Key Factor for Insemination Time: A Review

This review describes the oestrus-to-ovulation interval, the possibility of predicting the time of ovulation, and the optimum time for insemination relative to oestrus in dairy cows. The duration of oestrus in dairy cows is approximately 8-20 h, with differences possibly related to the methods of oestrus detection and the frequency of observations. Most cows ovulate approximately 24-33 h after the onset of oestrus and 15-22 h after the end of oestrus. The interval from the preovulatory luteinising hormone (LH) surge to ovulation is approximately 4-30 h. Ovulation occurs when follicle diameter averages 18-20 mm. When it is possible to correctly determine the beginning of oestrus, artificial insemination can be performed utilizing the "a.m.-p.m. rule", and only one insemination may be applied. In cows with too long or too short oestrus-to-ovulation intervals, fertility can be compromised. One important factor that can alter the oestrus-to-ovulation interval is acute or chronic heat stress during the warm season. When there is a risk that insemination may occur too early or too late with respect to the time of ovulation, GnRH administration can be considered.

Fertility in seasonal-calving pasture-based lactating dairy cows following timed artificial insemination or timed embryo transfer with fresh or frozen in vitro-produced embryos

The objective was to compare pregnancy per service event (P/S) in lactating dairy cows following timed artificial insemination (AI) or timed embryo transfer (ET) using either fresh or frozen in vitro-produced embryos. Oocytes were collected once per week for up to 9 wk using transvaginal ovum pick-up from elite dairy donors (ET-DAIRY; n = 40; Holstein-Friesian and Jersey) and elite beef donors (ET-ELITE-BEEF; n = 21; Angus). Both ET-DAIRY and ET-ELITE-BEEF donors consisted of heifers and cows. In addition, oocytes were collected from the ovaries of beef heifers of known pedigree following slaughter at a commercial abattoir (ET-COMM-BEEF; n = 119). Following in vitro maturation and fertilization, presumptive zygotes were cultured in vitro to the blastocyst stage. Grade 1 blastocysts were either transferred fresh or frozen for on-farm thawing and direct transfer. A total of 1,106 recipient cows (all lactating, predominantly Holstein-Friesian) located on 16 herdlets were blocked based on parity, calving date, and Economic Breeding Index, and randomly assigned to receive AI (n = 243) or ET (n = 863) after estrous synchronization with a 10-d Progesterone-synch protocol. Cows assigned to ET were further randomized to receive fresh (n = 187) or frozen (n = 178) ET-ELITE-BEEF embryos, fresh (n = 169) or frozen (n = 162) ET-DAIRY embryos, or fresh (n = 80) or frozen (n = 87) ET-COMM-BEEF embryos. Pregnancy was diagnosed using transrectal ultrasound on d 32 to 35 after synchronized ovulation and confirmed on d 62 to 65, at which time fetal sex was determined. Pregnancy per service event at d 32 was not different between AI (48.8%) and ET (48.9%) and did not differ between dairy and beef embryos (50.3% vs. 48.1%, respectively). However, P/S was less on d 32 following transfer of frozen embryos (41.6%) compared with fresh embryos (56.1%). Pregnancy loss between d 32 and 62 was greater for ET (15.1%) compared with AI (4.7%), with greater losses observed for frozen beef (18.5%), fresh beef (17.3%), and frozen dairy (19.2%) compared with fresh dairy (6.0%) embryos. Serum progesterone (P4) concentration on d 7 was associated with P/S at d 32 and 62. Cows in the quartile with the least serum P4 concentrations (quartile 1) had less probability of being pregnant on d 32 (33.4%) compared with cows in the 3 upper quartiles for serum P4 (45.7%, 55.6%, and 61.2% for quartile 2, quartile 3, and quartile 4, respectively). Sex ratio (male:female) at d 62 was skewed toward more male fetuses following ET (61.1:38.9) compared with AI (43.2:56.8) and was consistent with the sex ratio among in vitro blastocysts (61.2:38.8). In conclusion, P/S was similar for AI and ET, although pregnancy loss between d 32 and 62 was greater for ET than for AI.

Impact of the Sire on Pregnancy Loss

For over a century, scientists have attempted to develop techniques to accurately predict the fertility potential of a male's semen sample. In most livestock species, the sire is responsible for multiple pregnancies per year and up to hundreds of thousands of pregnancies if used for artificial insemination. Use of subfertile or infertile sires can have devastating impacts in regard to the reproductive efficiency of a cow herd. Despite the rapid expansion of fertility studies through advancements in molecular, genomic, and computer techniques, our understanding of male fertility is still far from complete. This article will provide an overview of the impact of the sire in pregnancy loss.

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.

Characterizing pregnancy losses in Bos indicus beef females receiving a fixed-timed artificial insemination protocol

This experiment evaluated pregnancy losses from day 30 of gestation to calving in Bos indicus females, and evaluated if serum haptoglobin concentrations during early gestation impacts subsequent pregnancy losses. A total of 4926 Nelore females were used, being 1802 nulliparous heifers inseminated as yearlings (precocious heifers), 1356 nulliparous heifers inseminated at 24 months of age (conventional heifers), 887 suckling primiparous cows, and 881 suckling multiparous cows. Cows were assigned to an ovulation synchronization + fixed-time artificial insemination (FTAI) protocol from day -11 to 0 of the experiment. Pregnancy status was verified using transrectal ultrasonography on days 30 and 60 after FTAI, via transrectal palpation on day 150 after FTAI, and according to calf birth. Blood samples were collected from all animals diagnosed pregnant on day 30 after FTAI, and analyzed for serum concentrations of haptoglobin and pregnancy associated glycoproteins (PAG). Pregnancy loss was greater (P < 0.01) from day 60-150 of gestation (10.2 %) compared with day 30-60 of gestation (6.0 %) and with day 150 of gestation to calving (7.4 %), and differed (P = 0.04) between these latter two periods. Pregnancy loss from day 30-60 of gestation did not differ (P = 0.26) among parities, whereas total pregnancy losses (day 30 to calving) were greater (P < 0.01) in precocious (28.4 %) and conventional (27.1 %) heifers compared with primiparous (16.4 %) and multiparous (13.0 %) cows. Serum PAG concentrations on day 30 after FTAI were less (P ≤ 0.03) in cows that lost the pregnancy (5.63 ng/mL) from day 30-60 of gestation, as well as those that lost the pregnancy from day 30 to calving (8.59 ng/mL) compared with cohorts that maintained the pregnancy (9.39 and 9.32 ng/mL, respectively). No differences in serum PAG concentrations on day 30 after FTAI were noted (P ≥ 0.23) according to pregnancy losses from day 60 to calving. Serum haptoglobin concentration on day 30 after FTAI also did not differ (P ≥ 0.48) between cows that maintained or lost the pregnancy. This experiment provides novel information about pregnancy losses after day 30 of gestation in B. indicus cattle, with most losses occurring as fetal mortality and not affected by systemic inflammation during early gestation. Pregnancy losses were nearly doubled in precocious and conventional heifers compared with parous cows, demonstrating the relevance of this reproductive failure to B. indicus replacement heifers.

Intensity of estrus expression - valuable obvious determinant of fertility in Bos indicus cows

This study aimed to characterize estrus response and to establish relationships between intensity of estrus, preovulatory follicle (POF) size and estradiol (E2) concentrations on day of AI, luteal profiles and pregnancy outcome in lactating Hariana breed of cows. 200 cyclic cows were subjected to Ovsynch (n = 54) and Pre-OV treatment (n = 146). Ovsynch: Buserelin acetate (BA; 10 µg), Cloprostenol (500 µg) and BA (10 µg) were injected i.m. on day 0, 7 and 9, respectively, irrespective of treatment. Pre-OV: BA (10 µg) and Cloprostenol (500 µg) was also injected i.m. simultaneously 7 days prior to initiate Ovsynch. On the basis of estrus behavior, the cows were classified into three groups: weak, moderate and intense. Artificial insemination performed at 18-24 hours after 2nd BA of Ovsynch in both treatments. The average duration of estrus did not differ (p > 0.05) between Ovsynch and Pre-OV treatment. A positive correlation was observed between estrus response and POF size, concentration of E2 on day of AI and luteal profiles on day 12 post-AI. First service conception rate was higher in cows exhibited intense (45.46%) and moderate (42.56%) estrus response than weak (28.57%) estrus response. In conclusion, intensity of estrus expression could be considered as important determinant for deciding pregnancy outcomes in Bos indicus cows.

Effects of estradiol cypionate dosage and body condition on reproductive performance of Nellore cattle synchronized for timed-artificial insemination

This experiment was designed to evaluate the effects of increasing doses of estradiol cypionate (ECP) and different body condition score (BCS) on reproductive performance of Bos indicus beef females assigned to a timed-artificial insemination (TAI) management. In this experiment, 1683 Bos indicus Nellore cows were blocked by parity and assigned to receive 1) an intravaginal P4 device (1.9 g of P4) and 2.0 mg of estradiol benzoate on day -11, 12.5 mg (i.m.) of dinoprost tromethamine, 300 IU (i.m.) of equine chorionic gonadotrophin, 0.6 mg (i.m.) of estradiol cypionate and CIDR withdrawal on day -2, followed by TAI on day 0 (n = 849; 0.6ECP) or 2) the same synchronization protocol with 1.0 mg of ECP on day -2 (n = 834; 1.0ECP). In both treatments, estrus expression was measured between days -2 and 0. Body condition score (BCS) was evaluated on days -11, 31, and 71 of the experiment and the BCS variation (Δ) was also determined between these timepoints. Transrectal ultrasonography was performed on days 31, 71, and 111 for pregnancy rate determination. All binary data were analyzed using cow as the experimental unit with GLIMMIX, whereas continuous variables were analyzed with the MIXED procedure of SAS. No treatment effects were observed on estrus expression rate. Treatment × BCS interactions were observed for pregnancy rates in all time points (days 31, 71, and 111), as 1.0ECP cows with a LOW BCS also had a greater P/AI than cows assigned to 0.6ECP. In summary, increasing the dose of ECP benefited the reproductive performance of Nellore beef cows with a reduced BCS (≤2.75), whereas no benefits were seen when the BCS was considered adequate (>2.75).

Evaluation of pregnancy per artificial insemination of dairy animals detected in estrus during the synchronization protocol and assigned to conventional or sexed semen

Three experiments were designed to evaluate the effects of conventional and sexed-semen on reproductive performance of dairy females detected in estrus. In Exp. 1, 978 lactating Holstein cows and 116 Holstein heifers were used. Cows or heifers were randomly assigned to receive conventional (CONV) or sexed (SEXD) semen on day 0 of a TAI protocol. The TAI was performed using commercial CONV or SEXD frozen-thawed semen from the same 6 Holstein bulls, and SEXD semen was sexed through fluorescence cytometry. In Exp. 2, 390 lactating Holstein × Gir dairy cows and 344 Holstein × Gir heifers were used. Cows and heifers were randomly assigned to receive CONV or SEXD semen on day 0 with frozen-thawed semen from 5 Holstein × Gir bulls. The SEXD was sorted through the Sexcel™ methodology. In Exp. 3, 789 primiparous lactating Holstein cows were enrolled. Cows were randomly assigned to receive CONV or SEXD semen from 5 Holstein bulls, and the SEXD semen was sexed using the same semen allocation methodology described in Exp. 2. All data were analyzed using SAS. Regardless of the experiment, no treatment × bull interaction was observed for any of the variables analyzed herein (P ≥ 0.20). In Exp. 1, multiparous cows assigned to CONV had a greater P/AI vs. cohorts assigned to SEXD (P < 0.01) and a similar response tended to be observed for secundiparous cows (P = 0.10). No treatment effects were further observed when the effects of semen on day 60 P/AI were stratified by heat stress, milk yield, and CL at the beginning of the protocol. In Exp. 2, no P/AI differences between treatment were detected either on days 32 (P = 0.32) or 60 of pregnancy (P = 0.20). In Exp. 3, cows assigned to SEXD had reduced P/AI on day 32 (P = 0.03) and tended to have a reduced P/AI on day 60 of pregnancy (P = 0.06). No further treatment effects or interactions were observed herein (P ≥ 0.13). Overall P/AI of SEXD semen was 78% of the CONV (P < 0.01), but the variation of these results requires some attention. Moreover, an additional analysis was performed considering the median value of P/AI in bulls assigned to CONV and SEXD, and bulls that had a greater P/AI in CONV also had a greater P/AI in SEXD (P = 0.03). In summary, although not directly comparable, the sexing technologies herein provided similar results in heifers, but not in other categories (primiparous, secundiparous, and multiparous cows). Additionally, the P/AI of a sexed semen is associated to its performance on the conventional semen counterpart. Moreover, in the present experiment, no other parameters were shown to impact fertility of dairy females assigned to conventional or sexed-semen.

Differences in Microbial Community Composition between Uterine Horns Ipsilateral and Contralateral to the Corpus Luteum in Beef Cows on Day 15 of the Estrous Cycle

This study evaluated differences in uterine microbiota composition between uterine horns ipsilateral and contralateral to the corpus luteum of beef cows on day 15 of the estrous cycle. Cows (n = 23) were exposed to an estrus synchronization protocol to exogenously induce synchronized ovulation. Cows were then euthanized on day 15 of the estrous cycle, and individual swabs were collected from uterine horns ipsilateral and contralateral to the corpus luteum using aseptic techniques. DNA was extracted, and the entire (V1-V9 hypervariable regions) 16s rRNA gene was sequenced. Sequences were analyzed, and amplicon sequence variants (ASVs) were determined. Across all samples, 2 bacterial domains, 24 phyla, and 265 genera were identified. Butyribirio, Cutibacterium, BD7-11, Bacteroidales BS11 gut group, Ruminococcus, Bacteroidales RF16 group, and Clostridia UCG-014 differed in relative abundances between uterine horns. Rikenellaceae RC9 gut group, Bacteroidales UCG-001, Lachnospiraceae AC2044 group, Burkholderia-Caballeronia-Paraburkholderia, Psudobutyribibrio, and an unidentified genus of the family Chitinophagaceae and dgA-11 gut group differed between cows that expressed estrus and those that did not. The composition of the microbial community differed between the ipsilateral and contralateral horns and between cows that expressed estrus and cows that failed to express estrus, indicating that the uterine microbiota might play a role in cow fertility.

Predicting Pregnancy Outcome in Dairy Cows: The Role of IGF-1 and Progesterone

The purpose of this study was to determine the link between insulin-like growth factor 1 (IGF-1), progesterone (PROG), non-esterified fatty acids (NEFAs), β-hydroxybutyrate (BHB), and glucose (GLU) and pregnancy probability after the first artificial insemination (AI) and during the first 100 days in milk (DIM), during the critical transition period. We determined levels of serum IGF-1, PROG, NEFA, BHB, and GLU in Holstein dairy cows via ELISA, using blood samples collected 7 days before parturition (DAP) until 21 days postparturition (DPP). The group was split into cows diagnosed pregnant at 100 DIM (PREG) and those that did not conceive at 100 and 150 DIM (NPREG). Serum IGF-1 and PROG median levels at 7 DAP were significantly higher in PREG vs. NPREG (p = 0.029), the only statistically significant differences across the subgroups. At 7 DAP, IGF-1 levels within the initial group showed a strong negative correlation with PROG (r = -0.693; p = 0.006), while for the PREG subgroup, the IGF-1 levels exhibited a very strong positive correlation with GLU (r = 0.860; p = 0.011) and NEFA (r = 0.872; p = 0.013). IGF-1 and PROG levels detected at 7 DAP may be useful to predict pregnancy at 100 DIM. The positive correlation of NEFA and GLU levels during the transition period demonstrates that the initial group is not in NEB; thus, the NEFA level was not a decisive factor for reproduction success.

Association of activity and subsequent fertility of dairy cows after spontaneous estrus or timed artificial insemination

The objective of this observational study was to evaluate the association between increased physical activity at first artificial insemination (AI) and subsequent pregnancy per AI (P/AI) in lactating Holstein cows following spontaneous estrus or a timed AI (TAI) protocol. We also wanted to identify factors associated with the intensity of activity increase (PA) captured by automated activity monitors (AAM) and fertility. Two experiments were conducted, in which cows either were inseminated based on the alert of the AAM system (AAM cows) or received TAI following a 7-d Ovsynch protocol (TAI cows) if not inseminated within a farm-specific period after calving. Experiment 1 included 2,698 AI services from AAM cows and 1,042 AI services from TAI cows equipped with the Smarttag Neck (Nedap Livestock Management) from a dairy farm in Slovakia (farm 1). In the second experiment, 6,517 AI services from AAM cows and 1,226 AI services from TAI cows fitted with Heatime (Heatime Pro; SCR Engineers Ltd.) from 8 dairy farms in Germany (farms 2-9) were included. Pregnancy diagnosis was performed on a weekly basis by transrectal ultrasound (farms 1, 3, 7, 8) or by transrectal palpation (farms 2, 4-6, 9). Estrous intensity was represented by the peak value of the change in activity. In experiment 1, PA was categorized into low (x-factor 0-20) and high (x-factor 21-100) PA, and in experiment 2 into low (activity change = 35-89) and high (activity change = 90-100) PA. In TAI cows from both experiments, PA was additionally categorized into cows with no AAM alert. Data were analyzed separately for AAM and TAI cows using multinomial logistic regression models for PA in TAI cows and logistic regression models for PA in AAM cows and P/AI in both groups. In experiment 1, P/AI of AAM cows was greater for AI services performed with conventional frozen semen (57.6%) compared with sexed semen (47.2%), whereas type of semen only tended to be associated with P/AI in TAI cows (54.4% conventional frozen semen vs. 48.9% sexed semen). In experiment 2, P/AI was greater for fresh semen (AAM cows: 44.4% vs. TAI cows: 44.2%) compared with conventional frozen semen (AAM cows: 37.6% vs. TAI cows: 34.6%). In both experiments, pregnancy outcomes were associated with PA. In experiment 1, AAM cows with high PA (55.1%) had greater P/AI than cows with low PA (49.8%). Within TAI cows, cows with no alert (38.8%) had reduced P/AI compared with cows with low (54.2%) or high PA (61.8%). In experiment 2, AAM cows with high PA (45.8%) had greater P/AI compared with cows with low PA (36.4%). Timed AI cows with no alert (27.4%) had decreased P/AI compared with cows with low (41.1%) or high (50.8%) PA. The greatest risk factors for high PA were parity (experiment 1) and season of AI (except for TAI cows from experiment 1). We conclude that high PA at the time of AI is associated with greater odds of pregnancy for both AAM and TAI cows. In both experiments, about 2 thirds of AAM cows (experiment 1: 69.9% and experiment 2: 70.7%) reached high PA, whereas only approximately one-third or less of TAI cows (experiment 1: 37.3% and experiment 2: 23.6%) showed high PA. Although we observed similar results using 2 different AAM systems for the most part, risk factors for high PA might differ between farms and insemination type (i.e., AAM vs. TAI).

Review: Manipulation of follicle development to improve fertility of cattle in timed-artificial insemination programs

The development of an ovulatory follicle is a fundamental premise for any reproductive management program that aims to optimize fertility in cattle. Controlling follicular development comprises the synchronized emergence of a new follicular wave, selection and growth of the dominant follicle, and synchronized ovulation of a high-quality oocyte. All these follicular events, primarily driven by gonadotropin secretion, occur under a very dynamic hormonal environment. In this sense, controlling follicular development demands essentially a precise manipulation of the hormonal environment to modulate gonadotropin secretion. Furthermore, the effectiveness of hormonal manipulation strategies in the management of follicular development depends on specific particularities of each situation, which can vary widely according to genetic groups (Bos taurus vs Bos indicus), nutritional, metabolic, and reproductive status. In this regard, the constant search for the refined synchrony between the hormonal treatments and reproductive events, considering these distinctions and particularities, have provided valuable information that contributed to the development of efficient reproductive programs. This manuscript discusses the physiological bases behind the development of fine-tuned timed-artificial insemination protocols for beef and dairy cattle that resulted in great improvements in reproductive efficiency of beef and dairy herds.

Review: Some challenges and unrealized opportunities toward widespread use of the in vitro-produced embryo in cattle production

The embryo produced by in vitro oocyte maturation, fertilization, and embryonic development is an important resource for genetic improvement and has the potential to improve female fertility and to be programmed to produce offspring with superior ability for health and production. The cultured embryo is also an important component of several realized and potential technologies such as gene editing, somatic cell nuclear cloning, stem cell technologies and gamete generation in vitro. Full realization of the opportunities afforded by the in vitro-produced embryo will require overcoming some technical obstacles to cost-effective implementation of an embryo transfer program. Among the research goals for improving the penetration of embryo transfer in the cattle industry are development of methods to increase the supply of oocytes from genetically elite females, enhance the proportion of oocytes that become transferrable embryos, improve the fraction of embryos that establish pregnancy after transfer, reduce pregnancy wastage after pregnancy diagnosis, and identify culture conditions to optimize postnatal phenotype.

Supplementing Ca salts of soybean oil via low-moisture molasses-based blocks to improve reproductive performance and overall productivity of beef cows

This experiment evaluated reproductive and productive responses of beef cows receiving self-fed low-moisture blocks (LMB) enriched or not with Ca salts of soybean oil (CSSO) throughout the breeding season. Non-pregnant, suckled multiparous Angus-influenced cows were assigned to a fixed-time artificial insemination (AI) protocol (day -10 to 0) followed by natural service (day 15-70). Cows were managed in 12 groups (46 ± 4 cows/group) maintained in individual pastures, and groups received LMB enriched with 25 % (as-fed basis) of CSSO or ground corn (CON) from day - 10 to 100. Both treatments were designed to yield a daily LMB intake of 0.454 kg/cow (as-fed basis). Cows receiving CSSO had greater (P < 0.01) mean concentrations of ω-6 fatty acids in plasma samples collected on days 0 and 55. Cows receiving CSSO had greater (P = 0.05) pregnancy rate to fixed-time AI (67.2 vs. 59.3 %), whereas final pregnancy rate did not differ (P = 0.92) between treatments. Pregnancy loss was less (P = 0.03) in CSSO cows (4.50 vs. 9.04 %), which also calved earlier during the calving season (treatment × week; P = 0.04). Weaning rate tended to be greater (P = 0.09) in CSSO (84.8 vs. 79.4 %), although calf weaning age and weight did not differ (P ≥ 0.72) between treatments. Kilos of calf weaned/cow exposed was greater (P = 0.04) in CSSO cows (234 vs. 215 kg). Therefore, supplementing CSSO to beef cows via LMB during the breeding season improved their reproductive and overall productivity during a cow-calf cycle.

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 PGF_2α 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, PGF_2α 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 PGF_2α 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 PGF_2α 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.

What are the factors associated with pregnancy loss after timed-artificial insemination in Bos indicus cattle?

Pregnancy loss (PL) has important impacts on the profitability of livestock production systems, although it is not widely reported, particularly in Bos indicus cattle. The present study retrospectively evaluated PL after timed-artificial insemination (TAI) in Bos indicus (Nelore) beef cows corresponding to several factors, such as parity, body condition score (BCS), presence of corpus luteum (CL) at the beginning of TAI protocols, expression of estrus, and hormonal manipulations during the TAI protocol. Data from two experiments performed during three breeding seasons (BS) were reanalyzed. Both experiments evaluated adding GnRH treatment at TAI in a 7-d estradiol (E2) plus progesterone (P4)-based protocol, with intravaginal P4 implant removal on Day 7 combined with treatment with 0.5 or 1.0 mg E2 cypionate and 300 IU eCG, and TAI on Day 9. In addition, during BS 2 and 3 (Exp 2), cows were randomized to receive or not a PGF treatment on Day 0 (beginning of the TAI protocol). In all BS, presence of CL and BCS were evaluated at the beginning of TAI protocols, follicle size and expression of estrus were evaluated at TAI. The PL was assessed between the first pregnancy diagnosis (∼35d) and parturition. There were no effects of hormonal manipulations within TAI protocols of different BS on PL. There was no interaction between GnRH treatment at TAI and the other variables within BS, and there was no main effect of GnRH treatment on PL (without = 10.1% [102/1007] vs. with = 10.4% [114/1100]). The addition of PGF on Day 0 had no effect on PL (11.5% [102/886] vs. 10.5% [89/850]), as well as EC dose to induce final ovulation (10.8% [89/827] vs. 11.2% [102/909] for 0.5 and 1.0 mg, respectively). Primiparous had greater PL than multiparous cows (14.0% [77/550] vs. 8.9% [139/1557]), and cows not expressing estrus near TAI had greater PL than those expressing estrus (13.5% [57/422] vs. 9.7% [156/1617]). There was no interaction between follicle size at TAI and GnRH treatment on PL. However, probability of PL decreased linearly as follicle size at TAI increased. There were no effects of service number (first TAI or resynchronization), BCS, or presence of CL on D0 on PL. In addition, PL was not affected by sire within any of the BS. In conclusion, some factors that are known to impact pregnancy per AI also influenced PL, such as parity and expression of estrus, although, other aspects such as BCS, number of services, and presence of CL on D0 did not affect PL. Moreover, commonly implemented treatments to increase fertility (e.g., PGF on Day 0 and increasing EC dose to 1.0 mg) did not affect PL. Finally, the GnRH treatment at TAI had no effect on PL and did not interact with any of the variables, an important result, since GnRH at TAI also increases fertility in Bos indicus beef cows.

Changes in body condition score from calving to first insemination and milk yield, pregnancy per AI, and pregnancy loss in lactating dairy cows: A meta-analysis

We determined the association of body condition score (BCS) at calving, at first postpartum artificial insemination (AI), and change in BCS between calving and first AI on pregnancy per AI (P/AI) at 30-45 d, pregnancy loss to 60-85 d, and milk yield in lactating dairy cows. Outcome data were included from 15 studies and 47 herd-year combinations. Additional variables included season of AI, herd, days in milk at first AI, parity, and of mean daily milk yield within 2 wk of first AI. The BCS scale employed was a standard 1-5 scale (1 = severe under conditioning or emaciated and 5 = severe over conditioning) with 0.25 cut points. Presynchronization treatments that included PGF_2α and GnRH increased (P < 0.05) the proportion of cows with luteal function before AI compared with PGF_2α alone. Compared with no presynchronization treatment those that included PGF_2α or PGF_2α and GnRH increased (P < 0.05) first P/AI. Cows having BCS ≥2.75 at AI had greater (P < 0.01) first P/AI than cows with BCS <2.75. As BCS at first AI increased, P/AI increased in a linear (P = 0.04) fashion and was greater in cows expressing estrus when BCS at AI was <2.50. Presynchronization had no association with P/AI for cows with BCS at calving <3.00 compared with those with BCS ≥3.00. In contrast, multiparous cows tended (P = 0.06) to have greater P/AI when they calved with BCS ≥3.00 compared with <3.00. Increasing BCS at AI was associated with decreased (P = 0.01) pregnancy loss. Pregnancy per AI did not differ among cows according to the magnitude of prebreeding BCS loss, but more multiparous cows losing more than 0.5 units of BCS tended to have greater pregnancy losses in second-parity cows (P = 0.09) and in cows of third or greater (P < 0.001) parity. Daily milk yields at first AI differed among parities as expected, but a parity by BCS at calving interaction was detected (P = 0.008). Daily milk yield at first AI decreased (P < 0.001) linearly as BCS at AI increased, with an exacerbated greater negative effect during summer. More prebreeding loss in BCS was associated with more (P < 0.05) milk yield in first- and second-parity cows. We concluded that greater BCS at first AI was associated with improved P/AI, but magnitude of prebreeding BCS loss was not associated with P/AI. In contrast, more pregnancy loss was associated with more prebreeding BCS loss in multiparous cows. Cow having lesser BCS at AI and greater prebreeding loss in BCS produced more milk than their herd mates of greater BCS and lesser prebreeding loss in BCS, respectively.

Applied Use of Doppler Ultrasonography in Bovine Reproduction

The use of Doppler ultrasonography to quantify blood vascularization in reproductive organs has increased over the past decade. Doppler technology has predominantly been explored in research settings to evaluate uterine blood flow and to assess follicular and luteal blood perfusion. Recent research has also explored the use of Doppler technology in applied reproductive management for both the beef and dairy industries and has focused on the use of luteal color Doppler ultrasonography to evaluate embryo transfer recipients and perform early pregnancy diagnosis. Although significant progress has been made and current literature indicates a strong potential for the applied use of Doppler ultrasonography to increase reproductive efficiency in the cattle industry, uptake of this technology is still currently limited. This review summarizes the recent developments in the applied use of color Doppler ultrasonography for reproductive management in both beef and dairy cattle herds.

Positive relationship of rectal temperature at fixed timed artificial insemination on pregnancy outcomes in beef cattle

The overarching aim was to examine the relationship of rectal temperature at fixed time artificial insemination (FTAI) on pregnancy outcomes in a typical breeding season with expected pregnancy rates approaching 50% using Bos indicus and Bos taurus cattle. This represents a continuum of steps to test the hypothesis that elevated body temperature at or around insemination is functionally important to maximize pregnancy outcomes. Rectal temperature of Bos indicus cattle at FTAI ranged from 37.0 to 40.9 °C; 60.6% were hyperthermic. Positive factors impacting pregnancy outcomes were rectal temperature at FTAI, body condition, and estrus patch scores. Rectal temperature at FTAI was positively associated with pregnancy outcomes (P < 0.0001); per each 1 °C increase pregnancy odds increased 1.9 times (95% CI: 1.4 to 2.6). Highest pregnancy outcomes occurred with rectal temperatures exceeding 40 °C (P = 0.0004). Rectal temperature before FTAI in Bos taurus cattle ranged from 37.8 to 41.8 °C; 43.3% were hyperthermic. Factors impacting pregnancy were rectal temperature at FTAI, estrus activity, parity, and ambient conditions on day of FTAI. Rectal temperature of Bos taurus cattle at FTAI was positively associated with pregnancy (P = 0.0286); odds increased 1.45 times (95% CI: 1.0 to 2.0) per each 1 °C increase. Highest pregnancy outcomes occurred with rectal temperatures at FTAI exceeding 40 °C (P = 0.057). Moreover, positive relationship of rectal temperature at FTAI to pregnancy persisted in estrual females (71.25% of total; P = 0.0408; OR 1.5; 95% CI: 1.0 to 2.2). Mindful that 1) elevated temperatures observed in Bos indicus and Bos taurus cattle directly promote meiotic resumption of the oocyte in vitro and that 2) in vivo hyperthermia alters intrafollicular components which others have shown to potentiate ovulation and promote meiotic resumption, it is biologically plausible that an acute elevation in body temperature at or around time of insemination is functionally important to maximize pregnancy outcomes.

Short Communication: Influence of estrus activity and reproductive tract size and position scores on fertility in Bos indicus and Bos taurus suckled beef cows

The primary objective of this study was to determine if estrus activity and reproductive tract size and position score (SPS) are associated with pregnancy outcomes in Bos indicus (Nelore) and Bos taurus (Angus) beef cows. In study 1, multiparous Nelore cows (n = 1,280) were artificially inseminated at a fixed time (FTAI, day 0) using an estradiol and progesterone (P4)-based estrus synchronization protocol. In study 2, multiparous Angus cows (n = 764) were artificially inseminated at a fixed time (FTAI, day 0) using a gonadotropin-releasing hormone and P4-based estrus synchronization protocol. Estrus activity was assessed using Estrotect heat detector patches and scored on day 0 using the following scoring system: 0 (patch was lost, most likely due to repeated mounting), 1 (<25% activation), 2 (≥25%, <50% activation), 3 (≥50%, <75% activation), or 4 (>75% activation) where patch scores of 1 and 2 signified no or limited estrus activity, whereas scores of 0, 3, and 4 had increased estrus activity. Reproductive tract SPS were assigned on day 0 as SPS1: small and compact resting within the pelvic cavity; SPS2: intermediate, resting partially outside the pelvic cavity; and SPS3: larger and resting outside the pelvic cavity. Pregnancy diagnosis was performed by ultrasound on day 30 and 100 after FTAI. Cows were determined as undergoing pregnancy loss if a viable embryo with heartbeat was detected at day 30 but was no longer present at day 100. Pregnancy rate at day 30 was influenced by estrus activity and SPS in both Nelore (P = 0.004) and Angus (P = 0.009) cows. Specifically, cows with smaller reproductive tracts (SPS1) had greater (P < 0.001) pregnancy rate when estrus was expressed before FTAI. There was no effect of estrus activity nor reproductive tract size on pregnancy loss between day 30 and 100 for both breeds. In summary, estrus activity before FTAI may influence reproductive outcomes differently depending on size and position of the reproductive tract at time of breeding.

Association between genomic daughter pregnancy rates and reproductive parameters in Holstein dairy cattle

The objective of this observational study was to evaluate the relationship between genomic daughter pregnancy rate (GDPR) with reproduction parameters such as pregnancy at first artificial insemination (AI), pregnancy per AI, and pregnancy losses (PL). A total of 12,949 events from 3,499 Holstein cows were included. Cows were enrolled as nulliparous (n = 1,220), primiparous (n = 1,314), or multiparous (n = 965). Cows were bred either after a timed AI protocol, timed embryo transfer (ET), or spontaneous estrus. Most lactating cows were bred following a timed AI protocol based on estradiol and progesterone, and most nulliparous were artificially inseminated following estrus detection. Hair samples were collected from the tail switch and cows were genotyped using a SNP platform (Clarifide, Zoetis). Cows that were bred by timed AI were evaluated for estrous behavior using tail chalk. Tail chalk was applied on the head of the tail 2 d before timed AI and the chalk was evaluated at AI (no estrus: 100% of chalk remaining or ≥50% of chalk remaining; Estrus: <50% of chalk remaining). Pregnancy diagnosis was performed at d 32 and 60 after AI using ultrasonography, and the presence of a heartbeat was considered a positive diagnosis. Pregnancy loss was defined as a pregnant cow on d 32 that was nonpregnant on d 60. As GDPR increased, the odds of pregnancy at first AI increased [odds ratio (OR) = 1.28, 95% CI = 1.20-1.35], the odds of pregnancy per AI increased (OR = 1.31, 95% CI = 1.25-1.36), and the odds of PL decreased (OR = 0.66, 95% CI = 0.60-0.72). Most cows that were bred on the day of the timed AI demonstrated estrus (n = 6,075; 92.9%). The odds of demonstrating estrus on the day of timed AI increased as GDPR increased (OR = 1.31, 95% CI = 1.17-1.48). There was no interaction between GDPR and parity or breeding management for pregnancy at first AI, pregnancy per AI, and PL. In conclusion, the odds of pregnancy at first AI and pregnancy per AI increased as GDPR increased. Moreover, the odds of PL increased as GDPR decreased. Greater GDPR was also associated with greater occurrence of estrus on the day of timed AI. These results suggest that selecting for higher GDPR could result in better reproductive performance, but this would need to be assessed with additional research.

Impact of GnRH administration at the time of artificial insemination on conception risk and its association with estrous expression

Cows with reduced estrous expression have compromised fertility. The aim of this study was to determine whether the administration of GnRH at the time of artificial insemination (AI) would affect ovulation rates and the fertility of animals expressing estrous behavior of lesser intensity. Cows were enrolled at the time of estrus from 3 farms (n = 2,607 estrus events; farm A: 1,507, farm B: 429, farm C: 671) and randomly assigned to receive GnRH at AI or not (control). The intensity of estrous expression, monitored through leg-mounted activity monitors, was determined using the maximum activity during estrus; estrous expression was categorized as greater or lower relative to the farm median. On farm A, cows were assessed at alert, and 24 h, 48 h, and 7 d post-alert for ovulation using ultrasonography. Pregnancy per AI was confirmed at 35 ± 7 d post-estrus for cows that were inseminated. Differences between treatments were tested using the GLIMMIX procedure of SAS. Treatment with GnRH at the time of AI increased pregnancy per AI (41.3 ± 1.6 vs. 35.7 ± 1.7%). An interaction between treatment and estrous expression on pregnancy per AI was found. Control cows with greater estrous expression had greater pregnancy per AI than those with lesser expression, whereas GnRH administration increased pregnancy per AI for cows with lesser estrous expression but not those with greater expression (GnRH, greater intensity: 43.5 ± 2.1; GnRH, lesser intensity: 37.8 ± 2.2; control, greater intensity: 42.6 ± 2.2; control, lesser intensity: 31.0 ± 2.2%). A higher proportion of cows with greater estrous expression that were administered GnRH at AI were found to ovulate by 48 h and 7 d post-estrus; however, ovulation of cows with lesser estrous expression was unaffected by GnRH administration. In conclusion, fertility of cows with reduced estrous expression may be increased using GnRH at the time of AI; however, increased ovulation rates do not seem to be the direct mechanism behind this relationship.

Administration of PGF2α at the moment of timed-AI using sex-sorted or conventional semen in suckled nelore cows with different intensity of estrus behavior

The aim of this work was to evaluate pregnancy rates (PR) and ovulatory characteristics of Nelore cows receiving PGF2α at the time of AI (artificial insemination) in a progesterone(P4)/estradiol-based timed-AI protocol. We also compared the effects of PGF2α treatment at AI in cows inseminated with conventional or sex-sorted semen, with the absence or expression of estrus. In experiment 1, a total of 701 suckled, multiparous Nelore cows from two commercial beef farms were submitted to the same protocol. All cows received a 12.5 mg (IM) injection of dinoprost tromethamine (Dinoprost; Lutalyse®; PGF treatment) at days 7 and 9 of a timed-AI protocol. Following P4 device removal (day 11; D11), AI was performed 48 h later with conventional or sex-sorted semen from two different sires. At AI, cows received an additional dose of 12.5 mg (IM) of Dinoprost (PGF treatment) or 2.5 mL (IM) of sterile saline (Control). Estrus behavior was determined at D11 by activation of an estrus detection device (Estrotect®). The overall PR was 32.8% (n = 348) at Farm 1 and 42.3% (n = 353) at Farm 2 (P = 0.01). Despite PR differences between farms, the same factors affected PR at Farms 1 and 2. Body condition score (P = 0.02), estrus behavior (P = 0.01), and type of semen (P < 0.001) were factors affecting PR. Conventional semen had a 2.73x greater chance of successful pregnancy than sex-sorted semen. Cows displaying estrus had a 2.5x greater chance of successful pregnancy than cows that did not display estrus. No treatment effect (P = 0.67) was detected in cows receiving conventional or sex-sorted semen. However, there was a tendency (P = 0.08) for an interaction between treatment (PGF or control) and estrus behavior (estrus or no estrus). PGF2α at the time of AI tended to increase PR of cows that did not display estrus (P < 0.10). In experiment 2, 29 suckled, multiparous Nelore cows were compared using B-mode and Doppler ultrasongraphy to assess the ovulatory characteristics of cows receiving the 12.5 mg (IM) injection of Dinoprost (PGF treatment) or saline solution (control) at D11. No significant effects of PGF2α treatment at D11 were observed in follicular characteristics and/or ovulation performance. It was concluded that fertility of sex-sorted semen was lower than conventional semen, regardless of the PGF2α treatment. The 12.5 mg treatment of Dinoprost at AI did not accelerate the occurrence of ovulation; however, it was interesting to note that PGF2α treatment at timed-AI appeared to increase the fertility of cows that did not display estrus, independent of semen type.

Occurrence and greater intensity of estrus in recipient lactating dairy cows improve pregnancy per embryo transfer

The aim of this study was to determine the association between occurrence and intensity of estrous expression with pregnancy success in recipient lactating dairy cows subjected to embryo transfer (ET). Two observational studies were conducted. Holstein cows were synchronized using the same timed ET protocol, based on estradiol and progesterone in both experiments. At 9 d after the end of the timed ET protocol only animals that had ovulated were implanted with a 7-d embryo [experiment 1 (Exp. 1); n = 1,401 ET events from 1,045 cows, and experiment 2 (Exp. 2); n = 1,147 ET events from 657 cows]. Embryos were produced in vivo (Exp. 1 and Exp. 2) and in vitro (only Exp. 2), then transferred to recipient cows as fresh or frozen-thawed. Pregnancy was confirmed at 29 and 58 d after the end of timed ET protocol. In Exp. 1, animals had their estrous expression monitored through a tail chalk applied on the tail head of the cows and evaluated daily for chalk removal (no estrus: 100% of chalk remaining; estrus: <50% of chalk remaining). In Exp. 2, cows were continuously monitored by a leg-mounted automated activity monitor. Estrous expression was quantified using the relative increase in physical activity at estrus in relation to the days before estrus. Estrous expression was classified as no estrus [<100% relative increase in activity (RI)], weak intensity (100-299% RI), and strong intensity (≥300% RI). Data were analyzed by analysis of variance using mixed linear regression models (GLIMMIX) in SAS (SAS Institute Inc.). A total of 65.2% (914/1,401) and 89.2% (1,019/1,142) of cows from Exp. 1 and Exp. 2, respectively, displayed estrus at the end of the ovulation synchronization protocol. In Exp. 1, cows expressing estrus before to ET had greater pregnancy per ET than those that did not [41.0 ± 2.3% (381/914) vs. 31.5 ± 2.9% (151/487), respectively]. Similarly, in Exp. 2, cows classified in the strong intensity group had greater pregnancy per ET compared with cows in the weak intensity and no estrus groups [41.3 ± 2.2% (213/571) vs. 32.7 ± 2.7% (115/353) vs. 11.3 ± 3.5% (26/218), respectively]. There was no effect of ET type on pregnancy per ET in Exp. 1. However, in Exp. 2, cows that received an in vivo-produced embryo, either fresh or frozen, had greater pregnancy per ET compared with cows that received in vitro-produced embryo. Cows receiving embryos in the early blastocyst and blastocyst stage had greater fertility compared with cows receiving embryos in the morula stage. There was an interaction between the occurrence of estrus and the stage of embryo development on pregnancy per ET, cows which displayed estrus and received a morula or early blastocyst had greater pregnancy per ET than cows that did not display estrus. In conclusion, the occurrence and the intensity of estrous expression improved pregnancy per ET in recipient lactating dairy cows and thus could be used as a tool to assist in the decision making of reproduction strategies in dairy farms.

Plasma concentrations of progesterone in the preceding estrous cycle are associated with the intensity of estrus and fertility of Holstein cows

The aim of this study was to determine the association between concentrations of progesterone (P4) during previous the estrous cycle with the intensity of spontaneous or estrogen-induced estrous expression and pregnancy per artificial insemination (P/AI). A total of 1,953 AI events from lactating Holstein cows were used, consisting of 1,289 timed AI events from experiment 1 (Exp. 1) and 664 AI events from experiment 2 (Exp. 2). In Exp. 1, cows were bred after a timed AI protocol based on estradiol and P4. In Exp. 2 animals were bred upon spontaneous estrus detection. In both experiments cows were continuously monitored by an automated activity monitor (AAM), in Exp.1 a relative increase of activity was calculated (i.e., percentage of increase activity at estrus compared to cow's baseline activity) and in Exp.2, activity data from each cow were computed into an index value that ranged from 0 to 100. In Exp.2 duration (hours) of estrus were calculated and defined as the total time above the threshold (35 index). The intensity of estrous expression was determined for each event and classified as either high or low intensity using the median of each experiment. Blood samples were collected for P4 analysis in Exp. 1 at -4 d, 0 d, and 7 d relative to timed AI, and in Exp. 2 immediately following estrus (0 d), 7 d, 14 d, and 21 d post-AI. Concentration of P4 was classified as greater or lower according to the median value in each experiment. Cows with lower concentrations of P4 at AI had greater estrous expression in Exp. 1 (363.6 ± 5.2 vs. 275.9 ± 8.0% relative increase) and Exp. 2 (76.7 ± 1.9 vs. 67.4 ± 4.7 index; and 12.5 ± 0.5 vs. 9.3 ± 1.8 hours). Cows with a greater intensity of estrous expression at timed AI had greater concentrations of P4 at -4 d than cows with lower intensity estrus or no estrous expression (4.6 ± 0.2 vs. 3.6 ± 0.2 vs. 3.7 ± 0.2 ng/mL). Cows with greater concentrations of P4 at -4 d had greater P/AI (32.8 ± 4.4 vs. 22.4 ± 4.5%), whereas cows with lesser concentrations of P4 at d0 for either timed AI (35.2 ± 3.4 vs. 19.6 ± 4.6%) or spontaneous estrus (31.8 ± 2.8 vs. 23.4 ± 3.2%) had greater P/AI. Cows with greater concentrations of P4 7 d post-timed AI had greater P/AI compared with cows that had lower concentration of P4 (39.1 ± 2.9 vs. 24.7 ± 2.6%). Similarly, cows that had lower concentrations of P4 at 7 d, 14 d and 21 d post-spontaneous estrus tended to have lower P/AI when compared with cows with greater concentrations of P4. Overall, concentrations of P4 prior to and at AI were associated with greater estrous intensity and P/AI at both spontaneous and timed AI events.

Daily activity measures and milk yield immediately before and after a fertile estrus and during the period of expected return to estrus after insemination in dairy cows

The objective of this study was to characterize changes in milk yield and other physical measures during a 7-d periestrual period encompassing estrus (d 0) and during a 16-d period of expected return to estrus beginning at d 17 after artificial insemination (AI) until pregnancy status was determined on d 32. Lactating dairy cows milked thrice daily were fitted with CowManager SensOor ear tags (Agis) capable of assessing real-time eating, rumination, resting, high activity (estrus), ear-surface temperature, and heat alerts. Data were uploaded to the cloud, downloaded daily into Excel (Microsoft Corp.) spreadsheets, averaged to produce daily means for each activity, and analyzed as repeated measures relative to estrus or to d 17 after AI. Daily milk was unchanged during the periestrual period but was greater in nonpregnant cows that failed to return to estrus (NP-NR) during d 21 through 26 compared with NP cows that returned to estrus (NP-R) and pregnant (PREG) cows during that same period. Daily ear-surface temperature was greater during d 1 to 3 compared with d 0 and averaged 0.6 to 1.7°C greater from d 17 through 32 in NP-NR cows compared with NP-R and PREG cows. Daily rumination and resting times reached nadirs on d 0, with decreases occurring 48 h before estrus. Both rumination and resting times increased by 25 or 81% on the day after estrus, respectively. Rumination and resting times were less in NP-R cows during d 22 through 26 compared with NP-NR and PREG cows. In contrast, daily eating time was greatest on the day of estrus compared with 3 d before and after estrus. The NP-R cows spent more time eating during d 17 through 32 compared with NP-NR and PREG cows. High activity increased by 97% during 48 h before estrus, peaked at estrus, and decreased to a constant level during d 1 through 3. The NP-R cows had greater high activity on d 22 through 26 compared with NP-NR and PREG cows. We conclude that resting and rumination activity decreased to daily nadirs, whereas eating and high activity peaked on the day of estrus. Fertile estrus was associated with 12% greater high activity, 11% less resting time, and 6% less rumination time. In addition, cows that returned to estrus after AI had greater daily eating and high activity times and less rumination and resting time during the period of expected return to estrus after AI compared with pregnant cows and cows failing to return to estrus.

Factors associated with estrous expression and subsequent fertility in lactating dairy cows using automated activity monitoring

The objective of this observational study was to identify factors associated with estrous duration (DU) and intensity measured as the peak of activity (PA) change and subsequent fertility in lactating Holstein cows using a neck-mounted automated activity monitor (Heatime Pro, SCR Engineers Ltd., Netanya, Israel). Ambient temperature and relative humidity were recorded hourly to calculate the temperature-humidity index (THI). A total of 5,933 estrus events from 3,132 cows located on 8 commercial dairy farms in Germany were used for this study. Farms participated in monthly DHIA testing. Pregnancy diagnosis was performed either by transrectal palpation [farm 1: 42 ± 3 d; farm 3: 40 ± 3 d; farms 4 and 8: 38 ± 3 d; farm 5: 43 ± 3 d after artificial insemination (AI)] or transrectal ultrasonography (farms 2, 6, and 7: 30 ± 3 d after AI). Estrous intensity was categorized based on peak activity of estrus into low (35-89 index value), and high (90-100 index value) PA. Overall, 73.5% of estrus events were of high PA. The mean (± standard error of the mean) DU was 14.94 ± 0.06 h. There was a strong correlation between DU and PA (r = 0.67). In the final statistical model, only PA was associated with pregnancy per artificial insemination (P/AI), with 1.35 greater odds of pregnancy for cows with high PA compared with cows with low PA. Increased THI 1 wk before AI was associated with shorter DU, lower PA, and decreased P/AI. A small percentage of cows (4.7%) showed short interestrus intervals (i.e., more than 1 activity peak within 7 d close to the event of estrus), resulting in reduced DU, PA, and P/AI. The change of weighted rumination was associated with DU and PA, as a lower nadir was associated with a greater risk for high PA and long DU. There was no association, however, between the nadir of change of weighted rumination and P/AI. Whereas milk yield and somatic cell count from the DHIA test date before AI were negatively associated with estrous expression, neither milk yield nor somatic cell count was associated with P/AI. Surprisingly, multiparous cows expressed estrus with longer DU (13.15 ± 0.31 h) compared with primiparous cows (12.52 ± 0.32 h), whereas PA did not differ among parities. Pregnancy per AI was greater for primiparous (29.4%) than for multiparous (22.1%) cows. An estrus event with long DU or high PA was more likely later in lactation. Milk fat, milk protein, milk urea nitrogen, and lactose from the DHIA test date closest to AI had no association with estrous expression or P/AI. In conclusion, DU and PA were highly correlated, and cows with high PA were particularly associated with greater odds for pregnancy. A negative association between estrous expression and P/AI was identified for increased THI 1 wk before AI and cows with short interestrus intervals using automated activity monitor.

Factors That Optimize Reproductive Efficiency in Dairy Herds with an Emphasis on Timed Artificial Insemination Programs

Simple Summary

Reproductive efficiency is critical for profitability of dairy operations. The first part of this manuscript discusses the key physiology of dairy cows and how to practically manipulate this reproductive physiology to produce timed artificial insemination (TAI) programs with enhanced fertility. In addition, there are other critical factors that also influence reproductive efficiency of dairy herds such as genetics, management of the transition period, and body condition score changes and improve management and facilities to increase cow comfort and reduce health problems. Using optimized TAI protocols combined with enhancing cow/management factors that impact reproductive efficiency generates dairy herd programs with high reproductive efficiency, while improving health and productivity of the herds.

Abstract

Reproductive efficiency is closely tied to the profitability of dairy herds, and therefore successful dairy operations seek to achieve high 21-day pregnancy rates in order to reduce the calving interval and days in milk of the herd. There are various factors that impact reproductive performance, including the specific reproductive management program, body condition score loss and nutritional management, genetics of the cows, and the cow comfort provided by the facilities and management programs. To achieve high 21-day pregnancy rates, the service rate and pregnancy per artificial insemination (P/AI) should be increased. Currently, there are adjustments in timed artificial insemination (TAI) protocols and use of presynchronization programs that can increase P/AI, even to the point that fertility is higher with some TAI programs as compared with AI after standing estrus. Implementation of a systematic reproductive management program that utilizes efficient TAI programs with optimized management strategies can produce high reproductive indexes combined with healthy cows having high milk production termed “the high fertility cycle”. The scientific results that underlie these concepts are presented in this manuscript along with how these ideas can be practically implemented to improve reproductive efficiency on commercial dairy operations.

Timing of artificial insemination using fresh or frozen semen after automated activity monitoring of estrus in lactating dairy cows

The objective of this observational experiment was to determine the association between the time of artificial insemination (AI) and pregnancy per AI (P/AI) in lactating Holstein cows inseminated with either fresh or frozen semen considering different characteristics of an estrus event (i.e., onset, peak, and end) using an automated activity monitoring system. A total of 3,607 AI services based on the alert of an automated activity monitoring system (Heatime; SCR Engineers Ltd., Netanya, Israel) were evaluated from 4 commercial dairy farms in Germany. Pregnancy diagnosis was performed by transrectal palpation 38 ± 3 d after AI or by transrectal ultrasonography 30 ± 3 d after AI. Estrus intensity was categorized based on peak activity of estrus (PAE) into low (35-89 index value) and high (90-100 index value) intensity. The mean (± standard deviation) duration of an estrus event was 14.3 ± 4.6 h. The mean (± standard deviation) interval from onset of estrus (OE; moment where index value was ≥35) to AI was 16.8 ± 8.0 h, from PAE to AI was 11.9 ± 8.1 h, and from end of estrus (EE; moment where index value returned to <35) to AI was 2.5 ± 8.7 h. Primiparous cows had greater P/AI than multiparous cows, whereas first AI postpartum yielded greater P/AI compared with subsequent AI services. Type of semen was not associated with P/AI. Cows with heat stress 1 wk before AI had decreased P/AI. Cows with low estrus intensity (26.0%) were less fertile compared with cows showing high estrus intensity (32.8%). Cows with intermediate 100-d milk yield had decreased P/AI compared with cows with either low or high 100-d milk yield. There was a quadratic effect of the interval from OE to AI on P/AI. At 38 d after AI, P/AI was greatest for cows inseminated from 7 to 24 h after OE, within 18 h after PAE, or from 5 h before EE to 12 h after EE. There was no interaction between the interval from OE to AI and type of semen. There tended to be an interaction between the intervals from PAE to AI and type of semen and from EE to AI and type of semen. Cows inseminated with fresh semen within 5 h before EE had greater P/AI compared with frozen semen, whereas cows inseminated with frozen semen from 13 to 18 h after EE had greater P/AI compared with fresh semen. In conclusion, inseminating cows from 7 to 24 h after OE or 1 to 18 h after PAE yielded greatest P/AI irrespective of type of semen. In addition, high estrus intensity was positively associated with P/AI.

Progesterone dose during synchronization treatment alters luteinizing hormone receptor and steroidogenic enzyme mRNA abundances in granulosa cells of Nellore heifers

The objective was to investigate effects of progesterone (P₄) dose on abundance of luteinizing hormone receptor (LHCGR), aromatase (CYP19A1), 3β-hydroxysteroid dehydrogenase (HSD3B1), and other steroidogenic mRNA transcripts in granulosa cells from dominant follicles. Nellore heifers were assigned to one of six groups: new, first-use controlled internal drug release device (CIDR1) inserted for 5 days (Large-P₄-dose-D5; n = 7) or 6 days (Large-P₄-dose-D6; n = 8), prostaglandin (PG)F_2α administered on D0 and 1 previously-used CIDR (CIDR3) inserted for 5 days (Small- P₄-dose-D5; n = 8) or 6 days (Small-P₄-dose-D6; n = 8), CIDR1 inserted on D0 and removed plus PGF_2α on D5 (Large-P₄-dose-proestrus (PE); n = 7), and CIDR3 and PGF_2α on D0 and 1, CIDR3 removed plus PGF_2α on D5 (Small-P₄-dose-PE; n = 7). Duration of P₄ treatment (D5 compared to D6) affected abundances of CYP19A1 mRNA transcripts, with there being greater abundances on D6 than D5 (P ≤ 0.05). Heifers treated with the large dose of P₄ had a smaller dominant follicle, less serum and intra-follicular estradiol (E₂) concentrations (P ≤ 0.05) and lesser LHCGR, CYP19A1, and HSD3B1 transcript abundances (P ≤ 0.05). Heifers treated to induce PE had a larger follicle diameter (P = 0.09), greater intra-follicular E₂ concentrations and larger abundances of CYP19A1 mRNA transcript (P ≤ 0.05) than heifers of the D6 group. Overall, treatment with larger doses of P₄ resulted in lesser abundances of LHCGR, HSD3B1, and CYP19A1 mRNA transcripts; thus, potentially leading to development of smaller dominant follicles and lesser E₂ concentrations.

The effect of clitoral stimulation post artificial insemination on pregnancy rates of multiparous Bos indicus beef cows submitted to estradiol/progesterone-based estrus synchronization protocol

Clitoral stimulation after artificial insemination (AI) in beef cattle is a common practice utilized by AI technicians; however, the effect of clitoral stimulation during fixed-time AI (TAI) is still unknown. The objective of the present experiment was to evaluate the effect of clitoral stimulation on temperament responses and pregnancy rates to TAI in Bos indicus beef cows. A total of 1,186 multiparous Nellore cows across three different locations were assigned to an estradiol/progesterone-based estrus synchronization + TAI protocol (day -11 to 0). Cows were randomly assigned to receive either 3 s of clitoral stimulation (n = 602) or no clitoral stimulation (n = 584) immediately after TAI (day 0). Cow body condition score (BCS) was recorded on day -11. Estrus expression was evaluated based on estrus detection visual aid patch activation on day 0 (estrus, ≥50% activated; no estrus, <50% activated). Temperament was assessed by individual chute score based on a 5-point scale before TAI, and individual exit velocity was measured after clitoral stimulation. Pregnancy diagnosis was performed 30 d after TAI via transrectal ultrasonography. Pregnancy rate to TAI was positively affected by BCS (P < 0.01) and estrus expression (P = 0.03). Pregnancy rates of cows receiving clitoral stimulation did not differ (P = 0.39) from cows non-stimulated (47.5 ± 4.6% vs. 44.3 ± 4.6%, respectively). No interaction of clitoral stimulation and estrus expression was observed (P = 0.26). Chute score was positively correlated to exit velocity (P < 0.01; r = 0.29); however, clitoral stimulation did not affect exit velocity (P = 0.86). In summary, pregnancy rates to TAI are influenced by various factors and multiple strategies have the potential to increase the fertility of beef cows submitted to TAI; however, clitoral stimulation of Bos indicus beef cows did not improve TAI pregnancy rate.

Symposium review: Linking activity-sensor data and physiology to improve dairy cow fertility

Several studies have demonstrated that the intensity of estrous expression is associated with ovulation, ovarian and uterine function, and fertility, and is dependent on social hierarchy and the housing system used. Data from recent studies involving spontaneous and induced estrus have shown that a greater relative increase and longer estrus (captured by different automated activity monitors; AAM) are both associated with improved pregnancy per artificial insemination (AI; around 10 to 14% increase) and decreased pregnancy losses. Intensity and duration of estrus were surprisingly weakly associated with preovulatory follicle diameter and concentrations of plasma estradiol at estrus, whereas ovulation failure was associated with low estrus intensity. Studies have also shown that the display of estrous behavior near AI was associated with the modification of expression of genes related to the immune system, adhesion molecules, and prostaglandin synthesis in the endometrium. Transcripts in leukocytes and in the conceptus tissue associated with maternal recognition of pregnancy as well as conceptus elongation were all associated with differences in the intensity of estrous expression. Most recently, studies from the United States and Canada have demonstrated that reproductive programs emphasizing detection of estrus using AAM can be successful and comparable to intensive timed AI protocol-based programs that incorporate GnRH and PGF_2α treatments. Further, one study concluded that the administration of GnRH at AI for spontaneous estrus events greatly improved pregnancy per AI, but only for cows with reduced intensity of estrous expression, showing the potential to use AAM data as a tool in targeted reproductive programs. Quantitative information from estrus events could be used to improve estrus detection and develop decision-making strategies at the farm level. Future studies in this field should aim to better understand ovarian, conceptus, and endometrial mechanisms associated with either the expression or the intensity of estrus, and to refine the identification of phenotypes related to estrus (relative increase, absolute increase, baseline levels, duration, and repeatability within cow) to improve data usage, estrus detection, and possibly genetic selection.

The incompletely fulfilled promise of embryo transfer in cattle-why aren't pregnancy rates greater and what can we do about it?

Typically, bovine embryos are transferred into recipient females about day 7 after estrus or anticipated ovulation, when the embryo has reached the blastocyst stage of development. All the biological and technical causes for failure of a female to produce a blastocyst 7 d after natural or artificial insemination (AI) are avoided when a blastocyst-stage embryo is transferred into the female. It is reasonable to expect, therefore, that pregnancy success would be higher for embryo transfer (ET) recipients than for inseminated females. This expectation is not usually met unless the recipient is exposed to heat stress or is classified as a repeat-breeder female. Rather, pregnancy success is generally similar for ET and AI. The implication is that either one or more of the technical aspects of ET have not yet been optimized or that underlying female fertility that causes an embryo to die before day 7 also causes it to die later in pregnancy. Improvements in pregnancy success after ET will depend upon making a better embryo, improving uterine receptivity, and forging new tools for production and transfer of embryos. Key to accelerating progress in improving pregnancy rates will be the identification of phenotypes or phenomes that allow the prediction of embryo competence for survival and maternal capacity to support embryonic development.

Increasing the length of an estradiol with progesterone timed artificial insemination protocol with 2 controlled internal drug release devices improves pregnancy per artificial insemination in lactating dairy cows

The objective of this study was to compare the effects of different lengths of ovulation synchronization protocols using 2 controlled internal drug release (CIDR) devices on ovarian dynamics and pregnancy outcomes in lactating dairy cows. Lactating Holstein cows (n = 1,979) were randomly assigned to receive timed artificial insemination (TAI; d 0) following 1 of 2 treatments: (1) 9-d protocol (n = 988; 9D) with 2 intravaginal devices containing 1.9 g of progesterone (CIDR) and 2.0 mg of estradiol benzoate on day -11; 25 mg (i.m.) of dinoprost tromethamine (PG) and withdrawal of 1 CIDR on d -4; 1.0 mg (i.m.) of estradiol cypionate, second CIDR withdrawal, and PG on d -2; and TAI on d 0 and (2) 10-d protocol (n = 991; 10D) with 2 CIDR and 2.0 mg of estradiol benzoate on d -12; 25 mg of PG and withdrawal of 1 CIDR on d -4; 1.0 mg of estradiol, second CIDR withdrawal, and PG on d -2; and TAI on d 0. There was no effect of protocol on estrus detection, whereas a greater percentage of cows from 10D had ovulated close to TAI [no corpus luteum (CL) at AI and a CL at d 7] versus cows assigned to 9D protocol. A protocol × heat stress (average cow temperature ≥39.1°C on day of AI and d 7) interaction was observed in a manner that pregnancy per AI (P/AI) was greater in non-heat-stressed 10D versus 9D cows, whereas P/AI did not differ when cows were under heat stress. Furthermore, 10D protocol did not increase P/AI when all cows that received AI were included in the analysis or in cows that ovulated near TAI. However, animals assigned to 9D without any event of heat stress had a reduced P/AI when compared with cows assigned to 10D without heat stress. A protocol × CL presence at the beginning of the protocol interaction was observed and cows with a CL at the beginning of the protocol had a greater P/AI in 10D versus 9D; meanwhile, in cows without a CL, no differences on P/AI were observed. The protocol × CL presence at the beginning of the protocol interaction on P/AI was also observed for cows that ovulated near TAI. A greater percentage of cows assigned to 9D had follicles of medium size (13-15.9 mm), and greater percentage of cows assigned to 10D had larger follicles (>16 mm). Increasing the length of an estradiol with progesterone-based ovulation synchronization protocol (10D vs. 9D) increased the proportion of cows with larger follicles (>16 mm) and increased P/AI in cows without heat stress and in cows with a CL at beginning of the protocol. Moreover, the 10D protocol increased the proportion of cows with ovulation near TAI, demonstrating the effectiveness of this protocol in improving the reproductive performance of lactating Holstein cows.

Inflammatory diseases in dairy cows: Risk factors and associations with pregnancy after embryo transfer

The objectives of the present prospective cohort study were to identify risk factors for inflammatory diseases in Holstein-Gyr crossbred dairy cows and characterize the associations of those diseases with pregnancy per embryo transfer (ET). Diseases were diagnosed in the first 60 d postpartum in 252 primiparous and 481 multiparous cows. Uterine diseases (UTD) included retained placenta, metritis, clinical endometritis, and subclinical endometritis. Nonuterine diseases (NUTD) included mastitis, lameness, pneumonia, and displaced abomasum. Blood was sampled on d 0, 1, and 2 postpartum and analyzed for concentrations of haptoglobin, fatty acids, total Ca (tCa), P, and Mg, and again on d 8 postpartum and analyzed for concentration of β-hydroxybutyrate. The association between concentrations of metabolites in serum and inflammatory diseases was determined. Cows received a timed ET program starting 28 ± 3 d postpartum with first ET at 46 ± 3 d postpartum using fresh in vitro-produced embryos. Pregnancy was diagnosed on d 31 and 59 of presumptive gestation. Overall, 63.3% of the cows were diagnosed with UTD and 20.6% with NUTD. The risk factors for UTD included season of calving, parity group, calving problems, days with subclinical hypocalcemia, and serum concentrations of haptoglobin and Mg, whereas the risk factors for NUTD were parity group and serum Mg concentration. Cows that developed UTD had increased concentrations of haptoglobin on d 2 and fatty acids on d 1 and 2, and reduced concentrations of tCa on d 1 and 2 and of P and Mg on d 2 postpartum compared with cows without UTD. Cows that developed NUTD had increased concentrations of fatty acids on d 0 to 2 postpartum, and decreased concentrations of tCa and P on d 0 and 1, and of Mg on d 1 and 2 postpartum compared with cows without NUTD. Cows that developed NUTD had a 340-kg reduction in milk yield in the first 60 d postpartum. Inflammatory diseases were associated with lesser body condition score and increased loss of body condition in the first 70 d postpartum. Maintenance of pregnancy after ET was reduced in UTD cows following the first (41.7 vs. 25.4%) or all ET (46.4 vs. 36.2%), whereas maintenance of pregnancy was reduced in NUTD cows only at the second ET (39.0 vs 25.9%). The reduced pregnancy maintenance in UTD cows combined with a reduced 21-d service rate (61.9 vs. 54.8%) decreased the 21-d cycle pregnancy rate (28.6 vs. 19.9%) and the hazard of pregnancy to 300 d postpartum by 35%, resulting in an extra 32 d open. In conclusion, inflammatory diseases depressed fertility in dairy cows receiving ET, with the greatest impact observed in UTD cows. This suggests that local inflammation of the uterus impairs maintenance of pregnancy in dairy cows following ET.

New approaches to diagnose and target reproductive failure in cattle

Reproductive failure and pregnancy loss in cattle are some of the largest economic burdens to cattle producers and one of most perplexing factors influencing management decisions. Pregnancy loss may occur at any point during gestation with the largest percentage of loss occurring in the first 30 days and, subsequently, decreasing as the pregnancy progresses. Losses may be attributed to numerous factors, predisposed issues or environmental conditions such as nutritional stressors or disease. From a research perspective, determining the exact causes of pregnancy loss or embryonic mortality in cattle have been difficult, due to limitations of accurately determining early gestation pregnancy status. Until methods that precisely determine embryo success early in gestation are available, our understanding of in vivo pregnancy loss will lack clarity necessary to develop management strategies to decrease such loss. In this review, we will briefly discuss the pivotal periods of pregnancy loss affecting beef and dairy cattle, methods and technologies to determine pregnancy status and embryo viability and potential opportunities to decrease reproductive failure.

Effect of estrus expression or treatment with GnRH on pregnancies per embryo transfer and pregnancy losses in beef recipients synchronized with estradiol/progesterone-based protocols

Two experiments were designed to determine the effect of expression of estrus or GnRH treatment on pregnancies per embryo transfer (P/ET) and pregnancy losses in beef recipients that were synchronized with estradiol/progesterone based protocols for fixed-time embryo transfer (FTET). Experiment 1 evaluated the effect of expression of estrus and GnRH treatment in the absence of estrus on P/ET. Beef cows (n = 729) were treated with 2 mg estradiol benzoate (EB) and an intravaginal device containing 0.5 g of progesterone. Devices were removed 8 d later and all cows received prostaglandin F2α (PGF2α), 400 IU eCG, and 0.5 mg estradiol cypionate (ECP) at that time. Expression of estrus was determined at 48 and 56 h after device removal using tail-paint and cows that did not show positive signs of estrus by 48 h received GnRH or no treatment at random. The overall estrus rate was 76.0% (554/729); 68.0% had positive signs of estrus by 48 h after progesterone device removal and 28.0% of those not in estrus by 48 h showed estrus by 56 h. The proportion of recipients receiving in vivo-derived (IVD) or in vitro-produced (IVP) embryos and P/ET were greater in recipients that showed estrus by 48 and 56 h (94.0% and 48.4%, respectively) than in those that did not show estrus 41.0% and 29.0%, respectively; P < 0.01). However, GnRH treatment of recipients not showing estrus by 48 h did not improve P/ET. Experiment 2 evaluated the effect of expression of estrus on P/ET and pregnancy loses up to parturition in recipients synchronized with two estradiol-based protocols. Beef cows (n = 403) were divided at random to receive the same synchronization protocol as in Experiment 1 (ECP) or a J-Synch protocol (device removal on day 6 and without using estradiol cypionate to induce ovulation). In this experiment, pregnancy was determined at 30 and 60 d by ultrasonography, and all pregnant recipients were followed until parturition to determine pregnancy losses during gestation. Although the number of recipients receiving IVP embryos was greater in the ECP group (90.5% vs. 83.5%; P = 0.03), P/ET did not differ (ECP: 37.0% and J-Synch: 39.0%; P = 0.43). Overall, 88.0% (357/407) of the recipients synchronized showed estrus and a greater P/ET (P = 0.05) was found in the recipients that showed estrus (39.0%) vs. those that did not show estrus (26.0%), regardless of treatment group. Pregnancy losses were lower (P = 0.004) and the calving rate was higher (P = 0.01) in recipients that showed estrus (25.0% and 29.3%, respectively) than in those that did not (88.8% and 2.9%, respectively). In summary, expression of estrus was associated with a greater P/ET in recipients treated with two different estradiol/P4-based synchronization protocols. The expression of estrus was associated with a greater proportion of recipients receiving embryos, P/ET and calving rate. Treatment with GnRH did not improve P/ET in the recipients that did not show estrus, questioning the its use in recipients synchronized with estradiol/progesterone based FTET protocols.

Reproductive performance following a modified Presynch-Ovsynch, Double-Ovsynch, or conventional reproductive management program in Korean dairy herds

We aimed to compare the reproductive performance of dairy cattle following a modified Presynch-Ovsynch, Double-Ovsynch, or conventional reproductive management program (CRMP). On Day 30 (±5) after calving (calving = Day 0), 960 lactating cows were assigned randomly to one of two presynchronization treatments, before the synchronization of ovulation (Ovsynch) or CRMP without presynchronization. Cows were administered prostaglandin F_2α (PGF_2α) on Days 38 (±5) and 52, and gonadotropin-releasing hormone (GnRH) on Day 55 (Presynch-G-Ovsynch group, n = 333); or GnRH on Day 45 (±5), PGF_2α on Day 52, and GnRH again on Day 55 (Double-Ovsynch group, n = 307). Thereafter, each cow underwent Ovsynch 7 days later: GnRH on Day 62, PGF_2α on Day 69, and GnRH again 56 h later, followed by timed artificial insemination (AI) 16 h later. The remaining cows underwent AI when estrus was detected or Ovsynch (CRMP group, n = 320). In a subset of cows (each n = 40) in the two presynchronization groups, blood collections and ovarian ultrasonography were performed on Days 30 (±4), 52, 62, and 69, and uterine cytology on Days 30 (±4) and 52. The probabilities of pregnancy per AI 32 and 60 days after the first AI were higher in the Presynch-G-Ovsynch (odds ratio [OR]: 1.89 and 1.81, P < 0.01) and Double-Ovsynch (OR: 1.63 and 1.60, P < 0.05) groups than in the CRMP group. The likelihood of pregnancy by 210 days postpartum was higher (P < 0.05) in Presynch-G-Ovsynch (hazard ratio [HR]: 1.29) and Double-Ovsynch (HR: 1.31) groups than in the CRMP group, whereas the least square mean number of inseminations per conception was lower (P < 0.05) in Presynch-G-Ovsynch (1.8) and Double-Ovsynch (1.8) groups than in the CRMP group (2.1). The percentages of cows with serum progesterone concentrations ≥1.0 ng/mL or with a corpus luteum (CL) did not differ between the groups (P > 0.1) on Days 30, 62, and 69, but were lower (P < 0.05) on Day 52 in the Presynch-G-Ovsynch than in the Double-Ovsynch groups. However, the diameter of the dominant follicles, the proportion of neutrophils in uterine cytological samples, and the prevalence of an accessory CL on Day 69 did not differ (P > 0.1) between the two groups. In conclusion, both the Presynch-G-Ovsynch and Double-Ovsynch programs improved reproductive performance vs. CRMP in smallholder Korean dairy herds, and there were no differences in the ovarian endocrine and structural dynamics, or uterine health, between the two programs involving presynchronization.

Optimization of a 5-day fixed-time embryo transfer (FTET) protocol in heifers I. Manipulation of circulating progesterone through reutilization of intravaginal progesterone devices during FTET

The objectives of the present study were to: 1) compare the reproductive efficiency of embryo transfer (ET) recipients after synchronization of estrus or a 5-day synchronization of ovulation protocol for fixed time ET (FTET), and 2) determine the effect of reutilization of intravaginal P4 devices (CIDRs), up to four times, in a 5-day FTET protocol. In Experiment 1, 817 dairy heifers were assigned to one of three groups: PGF + estrus detection, 5-d FTET protocol with new (1.38 g P4) or 2nd use CIDR (previously used once for 5 d). Fresh in vitro produced embryos were transferred 7 ± 1 day after estrus (PGF + estrus) or GnRH (5-day FTET). Utilization rate (transferred/treated) was greater (P < 0.001) in heifers submitted to FTET compared to ET after estrus, however pregnancies per ET (P/ET) were not different (P > 0.10). As a result, pregnancy per treated (P/treated) recipient was greater (P < 0.05) in heifers in the 5-day FTET protocol. In Experiment 2, 40 dairy heifers without a corpus luteum (CL) were randomly allocated into one of four groups using new, 2nd use, 3rd use (previously used twice for 5 d/each), or 4th use (previously used thrice for 5 d/each) CIDRs. Circulating P4 was reduced (P < 0.01) with each reutilization. In Experiment 3, ovarian follicular dynamics were evaluated in 238 dairy heifers submitted to a 5-day protocol with either new, 2nd use, 3rd use or 4th use CIDRs at random stages of the estrous cycle. Prostaglandin F2α (PGF) was administered at CIDR removal and again 24 h later. Ovulation was induced by GnRH treatment 72 h after CIDR removal. Preovulatory follicle diameter increased (P < 0.001) progressively with increasing CIDR reutilization. Ovulation rate did not differ between treatments, however, interval from CIDR removal to ovulation decreased (P < 0.001) in heifers receiving 3rd and 4th use CIDRs compared to new or 2nd use. Finally, in Experiments 4 and 5, 1203 heifers submitted to a 5-day FTET protocol were randomly assigned to receive either a new CIDR, a 3rd use CIDR (Experiment 4) or a 4th use CIDR (Experiment 5). Despite the increase in CL volume on D5 in heifers treated with 3rd use (P = 0.03) or 4th use CIDRs (P < 0.01), there were no differences (P > 0.05) in utilization rate, P/ET, or P/treated. Thus, use of a 5-day FTET synchronization protocol improves reproductive efficiency by increasing recipient utilization, and reutilization of CIDRs up to four times in recipient dairy heifers does not compromise reproductive performance.

Prostaglandin F2α influences pre-ovulatory follicle characteristics and pregnancy per AI in anovular dairy cows

Objectives were to determine the effects of a dose of PGF_2α administered 2 days before timed artificial insemination (AI) on LH pulsatility, characteristics of the pre-ovulatory follicle, and pregnancy per artificial insemination (P/AI) in anovular dairy cows, particularly in cows not subjected to hyperthermia. In experiment 1, 2,011 lactating Holstein cows had ovaries scanned by ultrasound to determine corpus luteum (CL) presence and only those without a CL in two consecutive exams were enrolled (n = 437). Cows had the estrous cycle synchronized with an estradiol-progesterone based protocol starting on experiment Day -11 and timed AI on Day 0. Cows were assigned randomly to receive a single dose of 25 mg of PGF_2α as dinoprost on Day -4 (1PGF, n = 222) or two doses of 25 mg each of PGF_2α, one on Day -4 and one on Day -2 (2PGF, n = 215). Rectal temperatures were evaluated on the day of AI and 7 days later and cows were classified as being normothermic (<39.1 °C) or hyperthermic (≥39.1 °C). Ovulatory responses and P/AI were determined. In experiment 2, cows with regressed CL were exposed to low concentrations of progesterone and then randomly assigned to the same estrous synchronization protocol and treatments, 1PGF (n = 28) and 2PGF (n = 28). Blood was sampled and analyzed for concentrations of progesterone, and for concentrations of LH and 13,14-dihydro-15-keto-PGF_2α metabolite (PGFM) every 15 min starting 1 h before to 6 h after treatments and then every 2 h from 12 to 59 h after treatments. The pre-ovulatory follicle was aspirated 44 h after treatments and concentrations of estradiol quantified. In experiment 1, treatment of anovular cows with a second dose of PGF_2α increased P/AI in normothermic cows (19.8 [18/91] vs. 38.8% [31/80]), but not in hyperthermic cows. Synchronization was not affected by treatment, but it was greater for normothermic than hyperthermic cows (87.1 [149/171] vs. 77.8% [207/266]). When only synchronized cows were evaluated, the same responses were observed; treatment with 2PGF increased P/AI compared with 1PGF in normothermic cows (23.1 [18/78] vs. 43.7% [31/71]), but not in hyperthermic cows. In experiment 2, administration of 25 mg of dinoprost in 2PGF resulted in concentrations of PGFM 26-fold greater than 1PGF in the first 6 h after treatment (48 vs. 1,242 pg/mL). Cows receiving 2PGF had smaller basal LH concentration (0.57 vs. 0.46 ng/mL) and less frequent LH pulses (4.5 vs. 3.9 pulses/6 h), but duration of the LH surge was longer for 2PGF than 1PGF (13.1 vs. 15.5 h). Treatment with 2PGF increased the diameter and volume of the pre-ovulatory follicle, and concentration of estradiol (115 vs. 262 ng/mL) and total follicular estradiol content (124 vs. 505 ng) compared with 1PGF. Collectively, these results suggest that PGF_2α has a role in fertility of anovular cows that is unrelated to its luteolytic effect.

Short communication: Greater intensity of estrous expression is associated with improved embryo viability from superovulated Holstein heifers

The aim of this study was to determine the association between estrous expression, measured using a breeding indicator and an automated activity monitor (AAM), and the success of embryo collection after superovulation. Holstein heifers (n = 51; 10.5 to 14.5 mo, and 325.0 ± 21.1 kg of body weight) were superovulated (n = 69 events) for the collection of embryos using a protocol based on sequential administration of FSH for follicle superstimulation and GnRH to induce ovulation. Artificial insemination (AI) was performed twice, once at the moment of GnRH administration and again 12 h later, using thawed, sexed semen. Ovaries were scanned via ultrasonography on the day of the first AI to count the total number of preovulatory follicles and 7 d later for the total number of corpora lutea present. Embryos were collected 7 d post-AI, counted, and assessed for viability. A breeding indicator (Estrotect, Rockway Inc., Spring Valley, WI) and a collar-mounted AAM (CowScout Activity Monitoring System, GEA, Dusseldorf, Germany) were used to measure standing mounts and an algorithmic estimate of estrous expression, respectively. A score for the breeding indicator was given as follows: score 1 = 100% of the indicator was intact; score 2 = 50% of the indicator was rubbed off; score 3 = greater than 50% of the indicator was rubbed off. Estrous expression detected by the AAM was quantified through the relative increase in physical activity and duration of time spent above a set threshold. Data were analyzed by ANOVA using the MIXED procedures of SAS (SAS Institute Inc., Cary, NC). The number of follicles present at AI was not affected by estrous expression. The mean (± SD) ovulatory response was 67.5 ± 26.3%. We found an effect of estrous expression as detected by the breeding indicator on the ovulatory response (42.1 ± 8.0, vs. 78.2 ± 9.0, vs. 74.0 ± 4.9%, for scores 1, 2, and 3, respectively) but not from the AAM. Heifers that had a score of 3 (versus those with scores of 1 and 2) on the breeding indicator had a greater number of embryos (4.1 ± 0.5, vs. 1.2 ± 1.0, vs. 1.8 ± 1.0 embryos), and a greater percentage of these embryos were viable (43.1 ± 0.05, vs. 35.5 ± 0.1, vs. 34.3 ± 0.1%). Similarly, heifers that showed a greater intensity of activity (as measured by the AAM) had a greater number of embryos collected (10.2 ± 1.2 vs. 6.0 ± 1.3 embryos), and a greater percentage of those embryos were viable (53.1 ± 5.0 vs. 23.4 ± 5.1%). Longer-duration estrus episodes were associated with a higher percentage of viable embryos (51.2 ± 5.2 vs. 25.3 ± 5.3%). In conclusion, stronger estrous intensity was associated with a greater number of total embryos collected and a greater percentage of viable embryos. These results suggest that monitoring the intensity of estrus could be used to predict superovulatory response as well as embryo quality in Holstein heifers.