Use of bovine somatotropin in lactating dairy cows receiving timed artificial insemination

Comparison of three reproductive management strategies for lactating dairy cows using combination of estrus detection or ovulation synchronization and Fixed-Timed Artificial Insemination

The objective of this study was to compare the reproductive performance of lactating dairy cows submitted to first AI after combination of estrus detection and fixed timed AI (FTAI) and FTAI only. Cows were randomly assigned to receive AI at detected estrus between 50 and 70 d in milk (DIM), if not detected in estrus, were enrolled in either Ovsynch (ED-Ov, n = 485) or PRIDsynch (ED-PR, n = 505) protocols; or received FTAI at 80 DIM after Double-Ovsynch protocol (DO, n = 501). Cows were body condition scored (BCS) at calving and at 43 DIM; and evaluated for postpartum disorders within 7 d postpartum; clinical mastitis, lameness and bovine respiratory disease were recorded until first AI. Ovarian cyclicity was monitored at 43 and 50 DIM, and at 70 and 77 DIM. Pregnancy diagnoses (PD) were performed at 32 and 63 d after AI. Overall prevalence of postpartum anovulation was 7.8%. Pregnancy per AI (P/AI) did not differ between reproductive strategies at 32 d PD (ED-Ov = 43.2%; ED-PR = 41.7%; DO= 45.3%). Primiparous cows had greater P/AI than multiparous cows (53.7% vs 36.8%). Cows on farm 1 had lower P/AI compared with their counterparts on farm 2 (42.1% vs 45.4%). Cows with BCS > 2.5 at 43 DIM had greater P/AI compared with cows with BCS ≤ 2.5 (44.5% vs 34.7%). Similar P/AI for cow's receiving AI at detected estrus and FTAI, low prevalence of disease anovulation may have contributed to the similar performance of ED-Ov, ED-PR and DO.

Use of new recombinant proteins for ovarian stimulation in ruminants

Currently, gonadotropin products (follicle stimulating hormone, FSH, and luteinizing hormone, LH) used in animal reproduction are produced by extraction and purification from abattoir-derived pituitary glands. This method, relying on animal-derived materials, carries the potential risk of hormone contamination and pathogen transmission. Additionally, chorionic gonadotropins are extracted from the blood of pregnant mares (equine chorionic gonadotropin; eCG) or the urine of pregnant women (human chorionic gonadotropin; hCG). However, recent advancements have introduced recombinant gonadotropins for assisted animal reproduction therapies. The traditional use of FSH for superovulation has limitations, including labor requirements and variability in superovulation response, affecting the success of in vivo (SOV) and in vitro (OPU/IVEP) embryo production. FSH treatment for superstimulation before OPU can promote the growth of a homogenous follicular population and the recovery of competent oocytes suitable for IVEP procedures. At present, a single injection of a preparation of long-acting bovine recombinant FSH (rFSH) produced similar superovulation responses resulting in the production of good-quality in vivo and in vitro embryos. Furthermore, the treatment with eCG at FTAI protocol has demonstrated its efficacy in promoting follicular growth, ovulation, and P/AI, mainly in heifers and anestrous cows. Currently, treatment with recombinant glycoproteins with eCG-like activity (r-eCG) have shown promising results in increasing follicular growth, ovulation, and P/AI in cows submitted to P4/E2 -based protocols. Bovine somatotropin (bST) is a naturally occurring hormone found in cows. Recombinant bovine somatotropin (rbST), produced through genetic engineering techniques, has shown potential in enhancing reproductive outcomes in ruminants. Treatment with rbST has been found to improve P/IA, increase donor embryo production, and enhance P/ET in recipients. The use of recombinant hormones allows to produce non-animal-derived products, offering several advantages in assisted reproductive technologies for ruminants. This advancement opens up new possibilities for improving reproductive efficiency and success rates in the field of animal reproduction.

Economics of Rebreeding Nonpregnant Dairy Cows Diagnosed by Transrectal Ultrasonography on Day 25 after Artificial Insemination

Pregnancy rates of Holstein cows showed a substantial decline in the past years, which caused intensive TAI programs for nonpregnant cows to shorten the period between unsuccessful insemination and the next attempt on the same cow. Although many studies examined the improvement in pregnancy rates following TAI, only a few examined the economic impact of such programs. In this study, we look at the feasibility of reproductive programs that included early pregnancy diagnosis performed by transrectal ultrasonography 25 days after artificial insemination (AI) and TAI of nonpregnant cows. This resulted in the following two TAI programs: a modified OvSynch program with a second PGF2α treatment at 24 h interval (GPPG, n = 100) and a modified OvSynch program with an intravaginal progesterone-release device inserted between days 0−7 (PRID + GPPG, n = 100). Cows included in the TAI programs recorded an improvement in the cumulative pregnancy rate (67% vs. 53%; 69% vs. 53%) compared to those in which this strategy was not applied (p < 0.05). An economic analysis was performed using a decision-support tool to estimate the net present value (NPV; USD/cow/year). The analysis revealed a difference in NPV of 89.6 USD/cow/year between the programs (rebreeding the nonpregnant cows following the TAI program vs. AI at detected estrus). In summary, rebreeding the nonpregnant cows after early negative pregnancy diagnosis (25 days after AI) using this strategy can improve the cumulative pregnancy rate and profitability of dairy farms.

Effects of Administering Exogenous Bovine Somatotropin During the First Trimester of Pregnancy Altered Uterine Hemodynamics in Suckled Beef Cows

The objective of this study was to examine the effects of recombinant bovine somatotropin (bST) administration on uterine hemodynamics and subsequent fetal programming in suckled cows during the first trimester of gestation. Crossbred beef cows (n = 152) were stratified by breed, days postpartum, parity, cyclicity status, and body condition score (BCS) before being assigned to either receive injections of bST every other week (BST; 500-mg/14 d) starting at fixed-time artificial insemination (TAI; d 0) until d 97 or to receive no bST (CTL). Blood samples were collected until d 97 for analysis of plasma concentrations of insulin-like growth factor 1 (IGF-1). Pregnancy was assessed via transrectal ultrasonography on d 41 and 173. A subset of pregnant cows (BST, n = 24; CTL, n = 28) were selected for assessment of uterine arterial blood flow (BF), pulsatility index, and resistance index (RI) of the uterine arteries ipsilateral and contralateral to the conceptus via color Doppler ultrasonography on d 97 and 233 of gestation. No differences (P = 0.99) were detected in body weight (BW) or BCS of dams; however, plasma concentrations of IGF-1 were greater (P &lt; 0.001) in BST-treated cows. Color Doppler ultrasonography parameters differed whereby a treatment × day interaction (P = 0.007) was detected for RI on d 97 (P = 0.048); however, on d 233, RI did not differ (P &gt; 0.10) but ipsilateral BF for BST-treated cows was greater (P = 0.0319) than controls. Mean heart girth diameter, crown-to-rump length, and neonate BW at 7 ± 5 d of calf age did not differ (P &gt; 0.10). Liver tissue samples from each calf were collected for analysis of mRNA expression of target insulin-like growth factor system ligands. There was no difference in gene expression of hepatic IGF-1 between treatments (P = 0.99). A treatment × sex interaction was determined, where BST heifers had increased mRNA expression of IGFR1 compared to BST bulls (P = 0.03). Bi-weekly administration of bST until d 97 of pregnancy increased plasma concentrations of IGF-1, altered uterine hemodynamics in dams, induced sex-specific changes in liver gene expression of the offspring but failed to alter calf morphometries or calf performance until weaning.

Development of a novel 21-day reinsemination program, ReBreed21, in Bos indicus heifers

The aim was to develop a program for resynchronization of ovulation (ReBreed21) that allowed reinsemination of non-pregnant Bos indicus heifers every 21 d using timed AI (TAI) without the need for detection of estrus. The Rebreed21 program begins 12 d after previous TAI (Day 0) by inserting an intravaginal P4 implant (Day 12) that is removed 7 d later (Day 19) combined with treatment with 300 IU of eCG. On Day 21, early pregnancy diagnosis (Doppler PD) is performed based on CL vascularity. Non-pregnant (NP) heifers immediately received AI combined with 100 μg of GnRH. The program is replicated 12 d after second TAI to produce a breeding season (BS) of 42 d with 3 potential TAIs. Two experiments were conducted as a proof of concept for this rapid rebreeding program. In Experiment 1, 76 heifers were enrolled in ReBreed21, as explained above. In Experiment 2, 300 Nellore heifers were synchronized for 1st TAI and randomly assigned to one of two groups: ReBreed21 (n = 147) or another early resynchronization procedure, Resynch14 (n = 153) with P4 implant inserted 14 d after previous TAI plus 50 mg of long-acting injectable P4; 8 d later P4 implant removed (Day 22) and early Doppler PD performed; NP heifers received 150 μg of cloprostenol, 0.5 mg of ECP, and 300 IU of eCG with TAI on Day 24. In both experiments, the largest follicle (LF) was measured at each Resynch TAI. Ultrasound was later used to confirm the early Doppler PD and to determine ovulation (OV) to Resynch at 12 d after TAI in ReBreed21 (Day 33 of pregnancy) and 14 d after TAI in Resynch14 (Day 38 of pregnancy). Final PD was performed 40 d after 3rd TAI. Results for Experiment 1 were: diameter of LF 11.8 ± 0.23 mm; 88.9% OV; 20.5% false positives; 38.1% P/AI at 1st TAI; 44.4% overall P/AI for ReBreed21 TAIs; 72.3% total pregnant at end of BS. In experiment 2, Rebreed21 vs. Resynch14 were different for: diameter of LF (10.9 ± 0.17 vs. 10.0 ± 0.17 mm, P = 0.0003), heifers with LF < 8.5 mm (10.2 vs. 26.4%, P = 0.04), or LF ≥ 11 mm (50.0 vs. 37.2%, P = 0.001), and P/AI at first TAI (29.3% [43/147] vs. 20.3% [31/153], P = 0.074) but similar for OV (overall 86.8% [239/275], P = 0.82), false positives (P = 0.52) overall P/AI for Resynch TAIs (33.6 vs. 28.8%, P = 0.4), and total pregnant at end of BS (58.5% [86/147] vs. 55.6% [85/153], P = 0.64). In addition, median time to pregnancy was 9 d earlier (P = 0.0007) for ReBreed21 than Resynch14. Thus, ReBreed21 is a novel protocol that allows earlier reinseminations than Resynch14 but with similar fertility.

Impact of recombinant bovine somatotropin, progesterone, and estradiol benzoate on ovarian follicular dynamics in Bos taurus taurus cows using a protocol for estrus and ovulation synchronization

This study aimed to evaluate the effect of recombinant bovine somatotropin (bST) in combination with progesterone (P4) and estradiol benzoate (EB) on ovarian follicular dynamics using a protocol for estrus and ovulation synchronization in crossbred Bos taurus taurus cows. Twenty-four non-lactating multiparous cows were randomly assigned to two groups: the recombinant bovine somatotropin group (GbST; n = 11) received an intravaginal P4 device (1.5 g), estradiol benzoate (EB = 1.0 mg IM), bST (500 mg SC), and an ovarian ultrasonography (US) on day zero (d0 = beginning of the study); d-cloprostenol (150 μg, IM), US, and P4 removal on d8; 1.0 mg of EB (IM) on d9; and US on d10 and d15. On the other hand, to the control group (GC; n = 13), the same protocol as the GbST was applied, except for the non-receipt of bST on d0. The follicles were measured and evaluated on d0, d8, and d10, as were the corpora lutea (CL) on d15 (using ultrasonography). The effect of the two treatments (GbST vs. GC) on the follicle size, CL (F-test), and ovulation rate (logistic regression) were evaluated. The GbST showed a greater follicle diameter on d10 (14.5 mm) than the GC (12.1 mm; P < 0.03), as well as a greater diameter of CL on d15 (19.7 vs. 16.9 mm, P < 0.01). In addition, in the former, the ovulation rate (90.9 vs. 69.2%, P = 0.09) was observed to be greater. It was concluded that the combination of bST, P4, and EB in synchronization for estrus and ovulation protocols significantly increased the diameter of the preovulatory follicle, produced a higher follicular growth rate, and a greater diameter of the corpus luteum. Additionally, there was a higher percentage of cows with ovulation compared to the group that did not receive bST.

A two-injection prostaglandin F2α presynchronization treatment decreases pregnancy rates of cycling replacement beef heifers

Improving artificial insemination (AI) pregnancy rates in replacement heifers improves the genetic advancement within a herd. Heifers that have completed at least three estrous cycles prior to breeding have greater pregnancy rates compared to acyclic females. Therefore, it was hypothesized that a presynchronization treatment program consisting of two injections of prostaglandin F_2α (PGF_2α) prior to the start of the CO-Synch + 5 d CIDR protocol would initiate earlier attainment of puberty and more estrous cycles prior to AI, thus increasing AI pregnancy rates. All heifers were managed the same at two locations over the course of 2 yr. Heifers were randomly assigned to receive either the two-injection PGF_2α presynchronization treatment (PreSynch; n = 105) or no presynchronization (Control; n = 106) prior to the start of estrous synchronization. On the first day of the trial, reproductive tract scores (RTSs), pelvic areas, body condition scores, and weights were collected on all heifers. All heifers were synchronized with the CO-Synch + 5 d CIDR protocol and fixed-time artificially inseminated with semen from a bull of known fertility. Blood samples were collected three consecutive times at 7 d intervals starting 45 d prior to estrous synchronization to determine the onset of puberty via analyzing progesterone concentrations. Pregnancy status to AI was assessed using ultrasonography diagnosis at approximately 30 and 60 d post insemination. Data were analyzed using PROC MIXED of SAS and reported as least square mean. The PreSynch treatment decreased AI pregnancy rates (52.2% vs. 38.1 ± 6.3% for Control vs. PreSynch, respectively; P = 0.06) and did not result in earlier attainment of puberty in beef heifers (P > 0.05). The PreSynch treatment did not impact pregnancy rates in heifers with an RTS of 3 or 4 (P > 0.05). However, PreSynch heifers with an RTS of 5 had decreased pregnancy rates (68.3% vs. 46.9 ± 10.1% for Control vs. PreSynch, respectively; P < 0.05). Finally, PreSynch heifers with increased body condition of 6 had decreased pregnancy rates when compared to Control heifers (37.5% vs. 62.5 ± 11.6%, respectively; P < 0.05). On the basis of these data, implementation of heifer breeding soundness examination at least 3 wk prior to the start of the breeding season may be beneficial for selecting replacement females; however, presynchronization with prostaglandins immediately prior to estrous synchronization will negatively affect AI pregnancy rates in cycling pubertal heifers.

Impact of recombinant bovine somatotropin, progesterone, and estradiol benzoate on ovarian follicular dynamics in Bos taurus taurus cows using a protocol for estrus and ovulation synchronization

This study aimed to evaluate the effect of recombinant bovine somatotropin (bST) in combination with progesterone (P4) and estradiol benzoate (EB) on ovarian follicular dynamics using a protocol for estrus and ovulation synchronization in crossbred Bos taurus taurus cows. Twenty-four non-lactating multiparous cows were randomly assigned to two groups: the recombinant bovine somatotropin group (GbST; n&#x202F;=&#x202F;11) received an intravaginal P4 device (1.5&#x202F;g), estradiol benzoate (EB&#x202F;=&#x202F;1.0&#x202F;mg IM), bST (500&#x202F;mg SC), and an ovarian ultrasonography (US) on day zero (d0&#x202F;=&#x202F;beginning of the study); d-cloprostenol (150&#x202F;μg, IM), US, and P4 removal on d8; 1.0&#x202F;mg of EB (IM) on d9; and US on d10 and d15. On the other hand, to the control group (GC; n&#x202F;=&#x202F;13), the same protocol as the GbST was applied, except for the non-receipt of bST on d0. The follicles were measured and evaluated on d0, d8, and d10, as were the corpora lutea (CL) on d15 (using ultrasonography). The effect of the two treatments (GbST vs. GC) on the follicle size, CL (F-test), and ovulation rate (logistic regression) were evaluated. The GbST showed a greater follicle diameter on d10 (14.5&#x202F;mm) than the GC (12.1&#x202F;mm; P&#x202F;<&#x202F;0.03), as well as a greater diameter of CL on d15 (19.7 vs. 16.9&#x202F;mm, P&#x202F;<&#x202F;0.01). In addition, in the former, the ovulation rate (90.9 vs. 69.2%, P&#x202F;=&#x202F;0.09) was observed to be greater. It was concluded that the combination of bST, P4, and EB in synchronization for estrus and ovulation protocols significantly increased the diameter of the preovulatory follicle, produced a higher follicular growth rate, and a greater diameter of the corpus luteum. Additionally, there was a higher percentage of cows with ovulation compared to the group that did not receive bST.

Administration of recombinant bovine somatotropin prior to fixed-time artificial insemination and the effects on fertility, embryo, and fetal size in beef heifers

Our objectives were to determine the effects of the administration of recombinant bovine somatotropin (bST) at the initiation of a fixed-time AI (TAI) protocol on concentrations of plasma IGF-1, follicle diameter, embryo/fetal size, and pregnancy rates in replacement beef heifers. Four hundred and fourteen Angus-based beef heifers were enrolled in a completely randomized design at 4 locations from January to July of 2016. All heifers were exposed to the 7-d CO-Synch + controlled internal drug release (CIDR) protocol where they received a 100-µg injection of GnRH and a CIDR insert on day -9, 25 mg of PGF2α at CIDR removal on day -2, followed by a 100-µg injection of GnRH and TAI 54 ± 2 h later on day 0. Within location, all heifers were randomly assigned to 1 of 2 treatments: 1) heifers that received 650 mg of bST on day -9 (BST; n = 191); or 2) heifers that did not receive bST on day -9 (CONTROL; n = 223). Blood samples were collected on day -9, 0, 28, and 60 to determine the plasma concentrations of IGF-1. Follicle diameter was determined on day -2 and 0 by transrectal ultrasonography. Pregnancy was diagnosed via transrectal ultrasonography on day 28 or 35, and again at least 30 d after the end of the breeding season. Embryo morphometry was assessed by measuring crown-to-rump length (CRL) on day 28, and fetal size was assessed by measuring crown-to-nose-length (CNL) on day 60. Concentrations of plasma IGF-1 did not differ between treatments on day -9 (P = 0.924), 28 (P = 0.075), and 60 (P = 0.792); however, concentrations of plasma IGF-1 were greater (P < 0.001) in BST-treated heifers at TAI (372.4 ± 16.6 vs. 193.7 ± 16.6 ng/ml). No differences (P = 0.191) were detected for follicle diameter between CONTROL and BST treatments on day -2 or 0. Pregnancy rates to TAI (PR/AI) were greater (P = 0.028) for CONTROL compared to BST heifers (42.5 ± 4.0 vs. 29.9 ± 4.1%). No differences (P = 0.536) in CRL were observed on day 28 between CONTROL and BST heifers. In addition, no difference (P = 0.890) was observed for CNL between CONTROL and BST treatments. Final pregnancy rates did not differ (P = 0.699) between treatments. The administration of bST to beef heifers at the initiation of a TAI protocol increased plasma concentrations of IGF-1 at TAI; however, failed to enhance follicle diameter, embryo/fetal size, and reduced PR/AI.

Effect of presynchronization prior to Ovsynch on ovulatory response to first GnRH, ovulatory follicle diameter and pregnancy per AI in multiparous Holstein cows during summer in Iran

The aim was to evaluate the effect of presynchronization with GnRH and PGF2α prior to Ovsynch on ovulatory response to first GnRH, diameter of largest follicle at TAI and pregnancy per AI (P/AI) in multiparous dairy cows during summer. Cows (n=1069) were randomly assigned to one of three timed-AI (TAI) protocols. The TAI protocols were: 1) Ovsynch (O; n=425), GnRH- 7d-PGF2α-56h-GnRH-16h-TAI), 2) double-Ovsynch (DO; n=302), GnRH-7d-PGF2α-3d-GnRH and Ovsynch was initiated 7 days later, and 3) G7G-Ovsynch (G7G; n=342), PGF2α-2d-GnRH and Ovsynch was initiated 7 days later. Ovarian examinations were performed by transrectal ultrasonography during Ovsynch to determine ovulatory response to first GnRH and diameter of largest follicle at TAI. Presynchronization increased ovulatory response after first GnRH of Ovsynch (P=0.001), which was greater in DO (74.0%) and G7G (76.0%) groups compared to O group (50.0%). Means (±SEM) diameter (mm) of largest follicle at TAI was smaller in cows presynchronized before Ovsynch (DO and G7G, overall 15.7±0.3) compared to that in cows subjected to a standard Ovsynch without presynchronization (18.5±0.42). P/AI at 32 d after Al was greater (P=0.001) in G7G (32.7%) and DO (31.1%) groups compared to Ovsynch (19.7%) group. Presynchronization prior to Ovsynch also affected P/AI at 60 and 150 d after AI (P<0.05). In conclusion, DO and G7G protocols resulted in greater ovulatory response to first GnRH, smaller ovulatory follicles and greater P/AI compared to a standard Ovsynch protocol. Therefore, TAI protocols that include a presynchronization with GnRH and PGF2α prior to Ovsynch should be used in multiparous cows during summer to achieve acceptable reproductive performance.

Effects of recombinant bovine somatotropin administration at breeding on cow, conceptus, and subsequent offspring performance of beef cattle

The effects of administration of recombinant bovine ST (bST) on plasma hormone concentrations of cows, conceptus development, and postnatal calf performance were examined. Lactating beef cows ( = 190) were exposed to a fixed-time AI (TAI) protocol from d -10 to 0 (TAI on d 0). Cows were blocked by breed and stratified by days postpartum and then randomly assigned to receive, subcutaneously 1) 2 injections of saline (1 mL of 0.9% saline), 1 on d 0 at TAI and a second injection on d 14 (CTRL; = 53); 2) an injection of 325 mg of bST on d 0 and a saline injection on d 14 (bST0; = 48); 3) a saline injection on d 0 and an injection of 325 mg of bST on d 14 (bST14; = 49); or 4) 2 injections of 325 mg of bST, 1 on d 0 and a second injection on d 14 (bST0+14; = 40). Pregnancy status, crown-to-rump length (CRL) on Day 35, and crown-to-nose length (CNL) on Day 65 were determined via transrectal ultrasonography. Blood samples were collected on d 0, 7, 14, 21, 35, and 65, relative to TAI, to determine plasma concentrations of progesterone (P4), IGF-1, and pregnancy-specific protein B (PSPB) and also on d 18 and 21 for isolation of peripheral blood leukocytes for RNA extraction and measurement of interferon-stimulated genes transcript abundance. Individual calf BW was determined at birth and every 30 d until weaning. A subset of 24 calves was randomly selected for liver biopsies at birth to determine mRNA expression of target genes. Administration of bST to cows increased ( < 0.0001) concentrations of plasma IGF-1 for 14 d after injection compared with CTRL but did not affect fetal CRL and CNL ( = 0.23). Cows receiving bST only on d 0 had a greater ( = 0.05) transcript abundance in myxovirus resistance 2 on d 21 compared with 2bST cows (2.0- and 0.8-fold for bST0 and 2bST, respectively), whereas cows receiving bST14 and CTRL were intermediate (1.2- and 0.9-fold, respectively). Calf BW did not differ ( ≥ 0.100) among treatments on d 0, 30, 60, 90, 120, and 150 relative to birth. Injection of bST only on d 0 tended ( = 0.062) to increase calf liver mRNA expression of at birth compared with the calves born to cows in other treatments. Therefore, during a TAI protocol, the administration of 1 or 2 injections of 325 mg of bST to lactating beef cows enhanced their plasma concentrations of IGF-1 but failed to improve fetal size and plasma concentrations of maternal PSPB and P4 and had no effect on postnatal calf growth performance.

Lambing rate and prolificacy in inseminated hair sheep treated with bovine somatotropin

This study evaluated whether the administration of 50 and 100 mg bovine somatotropin (bST) at the start of estrous synchronization and at the time of artificial insemination improves lambing rate and prolificacy in hair sheep. Four hundred eighty adult hair ewes (Pelibuey, Blackbelly, Dorper, Katahdin, and their crosses) were synchronized with intravaginal sponge containing 40 mg of fluorogestone acetate. On the day of sponge insertion, ewes were assigned to three treatments: the bST-100 treatment (n = 156) received 100 mg bST at the start of synchronization (d 0) and at the time of insemination (d 14), the bST-50 treatment (n = 159) received 50 mg bST in the same schedule as the previous group, and the control (n = 165) did not receive any bST. Lambing rate and percentage of multiple births were analyzed using the GENMOD procedure of SAS. Prolificacy data were analyzed using the MIXED procedure of SAS. The IGF-1 and insulin concentrations were analyzed with ANOVA for repeated measures. The bST application did not affect the lambing rate (P = 0.06). The proportion of ewes with multiple births (P = 0.01) and prolificacy (P = 0.04) were higher in the bST-50 (54.3% and 1.57 ± 0.1) than the bST-100 (18.2% and 1.25 ± 0.1) and control (33.3% and 1.28 ± 0.1) groups. The IGF-1 and insulin concentrations were higher (P < 0.05) in the bST-treated groups, but the insulin concentration was higher (P = 0.001) in the bST-100 group than in the bST-50 group. The administration of 50 or 100 mg bST at the start of synchronization and at the time of artificial insemination does not increase lambing rate. However, the dose of 50 mg increased the proportion of multiple births and prolificacy.

Meta-analysis of the effects of sometribove zinc suspension on the production and health of lactating dairy cows

OBJECTIVE

To provide an updated evaluation of the efficacy and safety of sometribove zinc suspension (rbST-Zn), a form of recombinant bovine somatotropin, in lactating dairy cows.

DESIGN

Meta-analysis.

SAMPLE

26 studies published in peer-reviewed journals or reviewed by a regulatory agency.

PROCEDURES

To be included, a study had to involve the use of the rbST-Zn formulation available to US producers in accordance with the label instructions for treatment initiation (57 to 70 days postpartum), dose (500 mg, q 14 d), and route (SC).

RESULTS

For cows treated with rbST-Zn, mean milk, 3.5% fat-corrected milk, fat, and protein yields were increased by 4.00, 4.04, 0.144, and 0.137 kg/d (8.8, 8.89, 0.32, and 0.30 lb/d), respectively; however, the concentration of milk components did not change. Pregnancy proportion for the first 2 breeding cycles was increased by 5.4%, and pregnancy proportion for the duration of the trial was reduced by 5.5% for rbST-Zn-treated cows, compared with proportions for untreated cows. Mean body condition score (1 to 5 scale) was reduced by 0.06 points during the period of rbST-Zn use for treated cows. Administration of rbST-Zn had no effect on milk somatic cell count, the number of days to pregnancy, or inseminations per pregnancy; rates of fetal loss, twins, cystic ovaries, clinical lameness, lameness lesions, or traumatic lesions of the integumentary system; and odds of clinical mastitis or culling.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that rbST-Zn administration to dairy cows effectively increases milk production with no adverse effects on cow health and well-being.

Reproductive performance of dairy cows resynchronized after pregnancy diagnosis at 31 (±3 days) after artificial insemination (AI) compared with resynchronization at 31 (±3 days) after AI with pregnancy diagnosis at 38 (±3 days) after AI

An important part of reproductive management programs on dairy farms is identification of nonpregnant cows and early re-insemination to achieve higher pregnancy rates. The objective of this study was to compare the effect on reproductive performance and pregnancy loss of 2 pregnancy diagnosis protocols: (1) pregnancy diagnosis performed 31±3 d after artificial insemination (AI) by ultrasonography (ULTRA), and (2) resynchronization started 31±3 d after AI but with pregnancy diagnosis performed 38±3 d after AI by palpation per rectum (PALP). Cows were randomly allocated into 1 of the 2 management programs. For cows enrolled in ULTRA, the initial pregnancy diagnosis (P1) was performed by transrectal ultrasonography at 31±3 d after AI, and nonpregnant cows were enrolled in the Ovsynch protocol for resynchronization of ovulation to receive timed AI (TAI). For cows enrolled in PALP, the Ovsynch protocol for resynchronization of ovulation to receive TAI was initiated at 31±3 d after AI regardless of pregnancy status, with the initial pregnancy diagnosis (P1) performed by palpation per rectum at 38±3 d after AI. For both groups, reconfirmation of pregnancy was performed by palpation per rectum at 63±3 d after AI (P2). Cows were inseminated after detection of estrus by use of activity monitors at any time during the study. Two levels of activity were used as a reference for cows AI after detection of estrus based on activity: an activity level of ≥2 when a cow was coded in DairyComp 305 (Valley Agricultural Software, Tulare, CA) as open (nonpregnant) and an activity level of ≥3 when the pregnancy status of the cow was unknown. Our findings showed that the odds of pregnancy loss cows in ULTRA was 2 times higher between P1 and P2 compared with that of cows in PALP. Furthermore, pregnancy diagnosis method (ULTRA vs. PALP) did not have a significant effect on the Cox proportional hazard of pregnancy at P2. The occurrence of assisted parturition, metritis, or retained placenta was associated with a reduced hazard of pregnancy at P2. An economic analysis was performed by simulating a 1,000-cow commercial dairy herd using a decision support tool to estimate the net present value (NPV; $/cow per yr) from using the 2 different pregnancy diagnosis methods. The analysis revealed minor differences in NPV between the programs, depending on the cost to perform ULTRA or PALP. In summary, we observed no difference in the reproductive performance and only a minor and fluctuating economic difference when using either PALP or ULTRA for pregnancy diagnosis of dairy cows.

Effects of cloprostenol sodium at final prostaglandin F2α of Ovsynch on complete luteolysis and pregnancy per artificial insemination in lactating dairy cows

Luteolysis is a key event in Ovsynch programs of lactating dairy cows. Studies indicate that as many as 20% of cows treated with a Presynch/Ovsynch program have delayed or incomplete luteolysis using dinoprost tromethamine. Cows must have complete luteolysis to have a chance to become pregnant. Dinoprost tromethamine has a short half-life of approximately 7 to 8min. Cloprostenol sodium is more resistant to endogenous metabolism and is maintained in circulation for a longer time (half-life=3h). The objective was to determine if cloprostenol sodium could increase the percentage of cows with complete luteolysis and subsequent pregnancy per artificial insemination (P/AI) in lactating dairy cows compared with dinoprost tromethamine when administered within a presynchronization plus Ovsynch program for first artificial insemination (n=652) and an Ovsynch resynchronization program for second or later AI (second+; n=394). Blood samples were collected daily for 5 d beginning at the PGF(2α) of Ovsynch in a subset of cows (n=680) for first and second+ AI to measure circulating concentrations of progesterone (P(4)) and estradiol (E(2)). Complete luteolysis was defined as cows with functional corpus luteum (CL) at time of treatment and serum concentrations of P(4) <0.5 ng/mL at 56, 72, and 96 h after treatment. Percentage of cows with functional CL that had complete luteolysis after treatment was not greater for cloprostenol sodium compared with dinoprost tromethamine in first (79 vs. 80%, respectively) or second+ AI (70 vs. 72%, respectively). In addition, mean serum concentrations of P(4) were not less for cows treated with cloprostenol sodium following treatment. Pregnancy per AI of cows treated with cloprostenol sodium tended to be greater than dinoprost tromethamine for first (40 vs. 35%; respectively) but not second+ AI (23 vs. 21%, respectively). Cows with greater serum P(4) concentrations at time of PGF(2α) of Ovsynch had a greater probability of undergoing complete luteolysis after PGF(2α) of Ovsynch and pregnancy at 39 d after timed AI (i.e., 50% pregnant at 8 vs. 28% pregnant at 4 ng/mL P(4)). Serum concentrations of E(2) at 56 h after PGF(2α) of Ovsynch were a positive predictor of pregnancy at 39 d after timed AI. In summary, cloprostenol sodium tended to improve P/AI. Cows with greater serum concentrations of P(4) at time of PGF(2α) of Ovsynch had a greater chance of luteolysis and pregnancy.

Effects of flunixin meglumine, recombinant bovine somatotropin and/or human chorionic gonadotropin on pregnancy rates in Nelore cows

The objective was to compare pharmacological strategies aiming to inhibit prostaglandin F2 alpha (PGF(2α)) synthesis (flunixin meglumine; FM), stimulate growth of the conceptus (recombinant bovine somatotropin; bST) and progesterone (P(4)) synthesis (human chorionic gonadotropin; hCG), as well as their combinations, regarding their ability to improve pregnancy rates in beef cattle. Lactating Nelore cows (N = 975), 35 to 70 days postpartum, were synchronized and inseminated by timed artificial insemination (TAI) on Day 0. On Day 7, cattle were allocated into eight groups and received one of the following treatments: saline (S) on Days 7 and 16 (Group Control); S on Day 7 and FM on Day 16 (Group FM); bST on Day 7 and S on Day 16 (Group bST); bST on Day 7 and FM on Day 16 (Group bST + FM); hCG on Day 7 and S on Day 16 (Group hCG); hCG on Day 7 and FM on Day 16 (Group hCG + FM); bST and hCG on Day 7 and S on Day 16 (Group bST + hCG), or bST and hCG on Day 7 and FM on Day 16 (Group bST + hCG + FM). The aforementioned treatments were administered at the following doses: 2.2 mg/kg FM (Banamine®; Intervet Schering-Plough, Cotia, SP, Brazil), 500 mg bST (Boostin®; Intervet Schering-Plough), and 2500 IU hCG (Chorulon®; Intervet Schering-Plough). Pregnancy diagnosis was performed 40 days after TAI by transrectal ultrasonography. Pregnancy rates were not significantly different among treatments. However, there was a main effect of hCG treatment to increase pregnancy rates (63.0 vs. 55.4%; P = 0.001). Concentrations of P(4) did not differ significantly among groups on Day 7 or on Day 16. However, consistent with the higher pregnancy rates, hCG increased P(4) concentrations on Day 16 (10.6 vs. 9.6 ng/mL, respectively; P = 0.05). We concluded that hCG treatment 7 days after TAI improved pregnancy rates of lactating Nelore cows, possibly via a mechanism leading to induction of higher P(4) concentrations, or by reducing the luteolytic stimulus during maternal recognition of pregnancy.

Increased cleavage and blastocyst rate in ewes treated with bovine somatotropin 5 days before the end of progestin-based estrous synchronization

Treatment with bovine somatotropin (bST) during estrous synchronization increased fertility and prolificacy in sheep. In the present study, a single dose of bST 5 days before the end of progestin treatment improved cleavage and embryo development. Stage of estrous cycle was synchronized in ewes (n=32) with progestin and superovulation was induced by use of FSH. Five days before the end of progestin treatment, ewes were randomly assigned to two groups: bST group (n=16) received a depot injection of 125 mg of bST sc (Lactotropina, Elanco, México) and the control group (n=16) received saline solution. Estrous was detected with rams fitted with an apron every 2 h and estrous sheep were mated every 8 h whilst in estrous. Embryos were recovered on Day 7 post mating, assessed microscopically and fixed in 4% paraformaldehyde. Cell number in blastocysts was counted after Hoechst 33342 staining. Plasma concentrations of IGF-I, insulin and progesterone were determined in eight sheep per group from the day of bST treatment to the day of embryo recovery. Cleavage rate, percentage of transferable embryos (transferable embryos/cleaved) and percentage of embryos reaching the blastocyst stage (blastocyst/cleaved) were compared between groups by logistic regression. IGF-I, insulin and progesterone plasma concentrations were analyzed by ANOVA for repeated measurements and cell number by ANOVA. Cleavage rate was greater (P<0.01) in bST treatment group (86%) than in the control group (62%). Similarly, the proportion of embryos reaching the blastocyst stage (bST=68.7 vs control=42.5) and the number of cells per blastocyst (bST group 91.8±5.5 compared to control group 75±6) were greater (P<0.01) in the bST-treated sheep. Plasma concentrations of IGF-I and insulin were greater (P<0.01) in the bST-treated group. No changes were observed in progesterone concentrations (P=0.5). It is concluded that bST injection 5 days before progestin removal increases cleavage rate and the proportion of embryos that reach the blastocyst stage. These effects are associated with an increase in IGF-I and insulin concentrations.

Effect of bovine somatotropin (500 mg) administered at ten-day intervals on ovulatory responses, expression of estrus, and fertility in dairy cows

The objectives of this study were to evaluate the effect of administering 500 mg of recombinant bovine somatotropin (bST) every 10 d on ovulatory responses, estrous behavior, and fertility of lactating Holstein cows. Lactating dairy cows were assigned to 1 of 2 treatments: a control with no administration of bST (73 primiparous and 120 multiparous cows) or 6 consecutive administrations of 500 mg of bST (83 primiparous and 123 multiparous cows) given subcutaneously at 10-d intervals starting 61+/-3 d postpartum (study d 0), concurrent with the initiation of the timed artificial insemination (AI). Blood samples were collected thrice weekly from 61+/-3 to 124+/-3 d in milk (DIM), and plasma samples were analyzed for concentrations of estradiol, glucose, insulin, insulin-like growth factor 1, and progesterone. The estrous cycle of cows was presynchronized with 2 injections of PGF(2alpha) at 37+/-3 and 51+/-3 DIM, and the Ovsynch timed AI protocol was initiated at 61+/-3 DIM. Ovaries were scanned to determine ovulatory responses during the Ovsynch protocol. Pregnancy was diagnosed at 33 and 66 d after AI. Body condition was scored on study d 0, 10, 42, and 76. Sixty-four cows were fitted with a pressure mounting sensor with radiotelemetric transmitters to monitor estrous behavior. Treatment of lactating dairy cows with 500 mg of bST at 10-d intervals increased yields of milk and milk components in the first 2 mo after treatment. Body condition of bST-treated cows remained unaltered, whereas control cows gained BCS. Treatment with bST increased concentrations of insulin-like growth factor 1 chronically, but concentrations of insulin and glucose increased only transiently in the first 7 d after the first injection of bST. Concentrations of progesterone during and after the Ovsynch protocol remained unaltered after treatment with bST; likewise, ovulatory responses during the Ovsynch protocol were mostly unaltered by treatment. Concentration of estradiol tended to be greater for bST cows than for control cows immediately before induction of ovulation in the Ovsynch protocol. Similarly, the mean and the peak concentrations of estradiol were greater for bST cows than for control cows when monitored during spontaneous estrus. Nevertheless, duration of estrus and the median number of standing events were less for bST cows than for control cows. Pregnancies per AI after the first and second postpartum inseminations were not affected by bST treatment. Treatment of lactating dairy cows with 500 mg of bST every 10 d improved lactation performance, but it did not affect pregnancies per AI and it reduced expression of estrus.

Synchronization and resynchronization of inseminations in lactating dairy cows with the CIDR insert and the Ovsynch protocol

Pregnancy per artificial insemination (AI) was evaluated in dairy cows (Bos taurus) subjected to synchronization and resynchronization for timed AI (TAI). Cows (n=718) received prostaglandin F(2alpha) (PGF) on Days -38 and -24 (Days 39 and 53 postpartum), gonadotropin-releasing hormone (GnRH) on Day -10, PGF on Day -3, and GnRH and TAI on Day 0. Between Days -10 and -3, cows received a progesterone intravaginal insert (CIDR group) or no CIDR (Control group). Between Days 14 and 23, cows received a CIDR (Resynch CIDR group) or no CIDR (Resynch control group), GnRH on Day 23, with pregnancy diagnosis on Day 30. Cows in estrus (between Days 0 and 30) were re-inseminated at detected estrus (RIDE). Nonpregnant cows received PGF on Day 30 and GnRH and TAI on Day 33. Plasma progesterone was determined to be low or high on Days -24 and -10. Pregnancy rates were evaluated 30 and 55 d after AI. The CIDR insert included in the Presynch-Ovsynch protocol did not increase overall pregnancy per AI for first service (36.1% and 33.6% for CIDR; 34.1% and 28.8% for Control) but did decrease pregnancy loss (7.0% for CIDR and 15.6% for Control). The CIDR insert increased pregnancy per AI in cows with high progesterone at the time the CIDR insert was applied. Administration of a CIDR insert between Days 14 and 23 of the estrous cycle after first service did not increase overall pregnancy per AI to second service (24.7% and 22.7% for Resynch CIDR; 28.6% and 25.3% for Resynch control). For second service, RIDE cows had lower pregnancy rates in the Resynch CIDR group than in the Resynch control group. Cows with a CL (corpus luteum) at Day 30 had higher pregnancy rates in the Resynch CIDR group than those in the Resynch control group.

Effects of additional prostaglandin F2alpha and estradiol-17beta during Ovsynch in lactating dairy cows

This study was designed to evaluate whether decreasing circulating progesterone (P4) or increasing circulating estradiol-17beta (E2) near the time of artificial insemination (AI) in an Ovsynch protocol would increase pregnancies per AI (P/AI) in lactating dairy cows. Six hundred nineteen lactating Holstein cows (n = 772 inseminations) received Ovsynch (GnRH-7 d-PGF(2alpha)-56 h-GnRH-16 h-timed AI). Cows were randomized in a 2 x 2 factorial experiment of 4 treatments to receive or not receive 25 mg of PGF(2alpha) 24 h after the standard PGF(2alpha) of Ovsynch, or 0.5 mg of E2 at the time of the final GnRH of Ovsynch, or both. Blood samples were collected 24 h after normal PGF(2alpha) and at final GnRH to evaluate circulating P4. Ovarian ultrasound was done at final GnRH to determine preovulatory follicle size. Ovulation was confirmed by ultrasound 5 d after AI. Treatment with additional PGF(2alpha) increased the percentage of cows that had complete luteal regression (95.6%) compared with control cows (84.6%). In contrast, additional PGF(2alpha) had no detectable effect on P/AI (control = 41.5% vs. + PGF(2alpha) = 44.7%). Supplementation with E2 increased expression of estrus (84.4 vs. 37.2%), but had no effect on overall fertility and even tended to have a negative effect on fertility in cows that ovulated to the second GnRH (control = 51.5% vs. +E2 = 44.0%). Thus, additional treatments with PGF(2alpha) or E2 during Ovsynch can be used to increase synchronization and expression of estrus during Ovsynch, although the lack of improvement in fertility makes these treatments unwarranted.

Eficácia da dose reduzida de gonadorelina e diferentes prostaglandinas no protocolo ovsynch em vacas holandesas

Avaliou-se a eficácia da dose de 0,10 ou de 0,25mg de gonadorelina nas taxas de ovulação e de sincronização no protocolo Ovsynch e de 150mcg de D-cloprostenol ou 0,530mg de cloprostenol sódico na regressão do corpo lúteo (CL) de sete dias e de todos os CL. Foram utilizadas 136 vacas lactantes da raça Holandesa, com média de produção de leite de 23,75,8kg/dia, com 138,4±72,0 dias em lactação. As vacas foram distribuídas aleatoriamente em quatro grupos, de acordo com a dose de gonadorelina e o tipo da prostaglandina. As taxas de ovulação e de sincronização foram de 52,9% e 80,9% para 0,10mg de gonadorelina e de 57,4% e 80,9% para 0,25mg de gonadorelina, respectivamente. A taxa de regressão do CL de sete dias foi de 97,1% para o D-cloprostenol e de 97,5% para o cloprostenol sódico. A taxa de prenhez não foi influenciada pelos tratamentos, mas foi influenciada pela taxa de ovulação à primeira aplicação de gonadorelina, 16,0% vs. 6,6% para as vacas que ovularam e não ovularam, respectivamente. Conclui-se que 0,10mg de gonadorelina foi eficiente e ambas prostaglandinas podem ser usadas em protocolos de sincronização da ovulação.

Effects of plasmid growth hormone-releasing hormone treatment during heat stress

A gene therapy treatment with plasmid-based growth hormone-releasing hormone (GHRH) delivered by electroporation (EP) was investigated during heat stress; 32 primiparous cows received 2.5 mg of a GHRH-expressing myogenic plasmid (pSP-HV-GHRH), while 20 were designated as controls. Offspring of treated animals showed a reduction in mortality (47%; p < 0.02), and survival from birth to 260 days was dramatically improved (0% mortality vs. 21% in controls) along with an increase in weight gain (p < 0.05). Milk production was increased compared to controls with an average yield gain of 421 kg/cow (p = 0.028). Prolactin (PRL) levels were also significantly increased compared to controls (p < 0.05). The second pregnancy rate was improved by GHRH treatment (53.3% vs. 30.8%). This study shows that the use of plasmid-mediated therapy delivered by EP can maintain health status during periods of heat stress, important for both animals and potentially humans in hot, challenging climates.

Progesterone regulates FGF10, MET, IGFBP1, and IGFBP3 in the endometrium of the ovine uterus

Progesterone (P4) is unequivocally required to maintain a uterine environment conducive to pregnancy. This study investigated the effects of P4 treatment on expression of selected growth factors (fibroblast growth factor 7 [FGF7], FGF10, hepatocyte growth factor [HGF], and insulin-like growth factors [IGF1 and IGF2]), their receptors (MET, FGFR2(IIIB), and IGF1R), and IGF binding proteins (IGFBPs) in the ovine uterus. Ewes received daily injections of corn oil vehicle (CO) or 25 mg of P4 in vehicle from 36 h after mating (Day 0) to hysterectomy on Day 9 or Day 12. Another group received P4 to Day 8 and 75 mg of mifepristone (RU486, a P4 receptor antagonist) from Day 8 through Day 12. Endometrial FGF10 mRNA levels increased between Day 9 and Day 12 and in response to P4 on Day 9 in CO-treated ewes, which had larger blastocysts, and were substantially reduced in P4+RU486-treated ewes, which had no blastocysts on Day 12. Endometrial FGF7 or HGF mRNA levels were not affected by day or reduced by RU486 treatment, but MET mRNA levels were higher in P4-treated ewes on Day 9 and Day 12. Levels of IGF1, IGF2, and IGF1R mRNA in the endometria were not affected by early P4 treatment. Although stromal IGFBPs were unaffected by P4, levels of IGFBP1 and IGFBP3 mRNA in uterine luminal epithelia were increased substantially between Day 9 and Day 12 of pregnancy in CO-treated ewes and on Day 9 in early P4-treated ewes. Therefore, FGF10, MET, IGFBP1, and IGFBP3 are P4-regulated factors within the endometrium of the ovine uterus that have potential effects on endometrial function and peri-implantation blastocyst growth and development.

Pregnancy success of lactating Holstein cows after a single administration of a sustained-release formulation of recombinant bovine somatotropin

Background

Results regarding the use of bovine somatotropin for enhancing fertility in dairy cattle are variable. Here, the hypothesis was tested that a single injection of a sustained-release preparation of bovine somatotropin (bST) during the preovulatory period would improve pregnancy success of lactating dairy cows at first service.

Results

The first experiment was conducted in a temperate region of Mexico. Cows inseminated following natural estrus or timed artificial insemination were given a single injection of bST or a placebo injection at insemination (n = 100 cows per group). There was no significant difference between bST and control groups in the proportion of inseminated cows diagnosed pregnant (29 vs 31% pregnant). The second experiment was performed during heat stress in Florida. Cows were subjected to an ovulation synchronization regimen for first insemination. Cows treated with bST received a single injection at 3 days before insemination. Controls received no additional treatment. As expected, bST did not increase vaginal temperature. Treatment with bST did not significantly increase the proportion of inseminated cows diagnosed pregnant although it was numerically greater for the bST group (24.2% vs 17.8%, 124–132 cows per group). There was a tendency (p = 0.10) for a smaller percent of control cows to have high plasma progesterone concentrations (≥ 1 ng/ml) at Day 7 after insemination than for bST-treated cows (72.6 vs 81.1%). When only cows that were successfully synchronized were considered, the magnitude of the absolute difference in the percentage of inseminated cows that were diagnosed pregnant between bST and control cows was reduced (24.8 vs 22.4% pregnant for bST and control).

Conclusion

Results failed to indicate a beneficial effect of bST treatment on fertility of lactating dairy cows.

Reduced fertility in high-yielding dairy cows: are the oocyte and embryo in danger? Part I. The importance of negative energy balance and altered corpus luteum function to the reduction of oocyte and embryo quality in high-yielding dairy cows

Fertility in high yielding dairy cows is declining, and there is increasing evidence to presume that oocyte and embryo quality are major factors in the complex pathogenesis of reproductive failure. In this report we present an overview of possible mechanisms linking negative energy balance (NEB) and deficiencies in oocyte and embryo developmental competence; specifically, in the high producing dairy cow. Changes in follicular growth patterns during a period of NEB can indirectly affect oocyte quality. The endocrine and biochemical changes, which are associated with NEB, are reflected in the microenvironment of the growing and maturing female gamete, and likely result in the ovulation of a developmentally incompetent oocyte. Even after an oocyte is successfully ovulated and fertilized, a full-term pregnancy is still not guaranteed. Inadequate corpus luteum function, associated with reduced progesterone, and probably also low insulin-like growth factor concentrations, can cause a suboptimal microenvironment in the uterus that is incapable of sustaining early embryonic life. This may partly account for the low conception rates and the high incidence of early embryonic mortality in high yielding dairy cows.

Uterine and hepatic gene expression in relation to days postpartum, estrus, and pregnancy in postpartum dairy cows

The somatotropic axis consisting of growth hormone, the growth hormone receptor (GHR) insulin-like growth factor (IGF)-I, and IGF binding proteins changes with the stage of lactation and nutrition of the cow and may be 1 mechanism through which lactation and nutrition affect the establishment of pregnancy. The objective of this study was to quantify GHR, IGF-I, and IGF binding protein-2 (IGFBP-2) mRNA in liver and uterine endometrial tissue at 4 stages of lactation (40, 80, 120, and 160 days in milk) and around the time of artificial insemination. Estrus was synchronized with GnRH and PGF2alpha, and cows were inseminated 12 h after estrus. Uterine biopsies were collected immediately before the second injection of PGF2alpha (before estrus), at the initiation of standing estrus, and 4 d after estrus. Liver biopsies were collected once on 4 d after estrus. The abundance of GHR, IGF-I, and IGFBP-2 mRNA in liver and uterus was determined by real-time quantitative PCR. The amount of liver IGF-I mRNA was positively correlated with plasma IGF-I concentrations. Cows that became pregnant after AI had more GHR and IGFBP-2 mRNA in their liver than cows that did not become pregnant. There was no effect of DIM or pregnancy status on abundance of uterine mRNA; however, uterine GHR and IGF-I mRNA was most abundant at estrus. In summary, cows at different stages of lactation or with different pregnancy statuses had similar quantities of uterine mRNA. In contrast, liver quantities of mRNA differed relative to pregnancy status. These data provide evidence that liver indices of metabolic state may be indicative of pregnancy success.

Accuracy of a Pregnancy-Associated Glycoprotein ELISA to Determine Pregnancy Status of Lactating Dairy Cows Twenty-Seven Days After Timed Artificial Insemination

To determine the accuracy of a pregnancy-associated glycoprotein (PAG) ELISA in identifying pregnancy status 27 d after timed artificial insemination (TAI), blood samples were collected from lactating Holstein cows (n = 1,079) 27 d after their first, second, and third postpartum TAI services. Pregnancy diagnosis by transrectal ultrasonography (TU) was performed immediately after blood sample collection, and pregnancy outcomes by TU served as a standard to test the accuracy of the PAG ELISA. Pregnancy outcomes based on the PAG ELISA and TU that agreed were considered correct, whereas the pregnancy status of cows in which pregnancy outcomes between PAG and TU disagreed were reassessed by TU 5 d later. The accuracy of pregnancy diagnosis was less than expected when using TU 27 d after TAI (93.7 to 97.8%), especially when pregnancy outcomes were based on visualization of chorioallantoic fluid and a corpus luteum but when an embryo was not visualized. The accuracy of PAG ELISA outcomes 27 d after TAI was 93.7, 95.4, and 96.2% for first, second, and third postpartum TAI services, respectively. Statistical agreement (kappa) between TU and the PAG ELISA 27 d after TAI was 0.87 to 0.90. Pregnancy outcomes based on the PAG ELISA had a high negative predictive value, indicating that the probability of incorrectly administering PGF(2alpha) to pregnant cows would be low if this test were implemented on a commercial dairy.

Use of insulin-like growth factor-1 to improve post-transfer survival of bovine embryos produced in vitro

Use of in vitro produced embryos in commercial settings is limited by alterations in embryo function that result in reduced embryo and fetal survival and increased fetal, placental and neonatal abnormalities. One potential strategy to improve the efficiency of in vitro embryo production systems is to modify embryo culture conditions to more closely mimic embryo physiology in vivo. The milieu of the reproductive tract contains various growth factors and regulatory molecules which can regulate embryonic development. One of these molecules, insulin-like growth factor-1 (IGF-1), has been reported to have beneficial effects on bovine embryo development in vitro. Addition of IGF-1 to embryo culture can increase pregnancy and calving rates in lactating dairy cows. However, recent research indicates that such an effect is only observed when recipients are heat-stressed. In non-heat stressed animals, IGF-1 treatment does not affect conceptus length or interferon-tau secretion; thus, it is not likely that IGF-1 promotes embryo survival by blocking the luteolytic cascade. On the other hand, IGF-1 treatment can alter the relative abundance of certain developmentally important transcripts. Such differences may be important to improve embryo survival during heat stress. Further research into the effect of IGF-1 on gene expression and DNA methylation are warranted. Results indicate that modification of embryo culture with a growth factor can affect embryo survival after transfer. It is important that future research evaluating modifications to embryo culture also includes experiments involving transfer of embryos to recipients. Such experiments are important to demonstrate that proposed modifications actually improve post-transfer embryonic survival.

Relationship of pre-ovulatory follicle size, estradiol concentrations and season to pregnancy outcome in dairy cows

This study was carried out to evaluate effects of pre-ovulatory follicle size, plasma concentrations of estradiol and progesterone, and season on pregnancy outcomes in dairy cows. Holstein cows (n = 144) were synchronized and inseminated (Ovsynch/TAI protocol) in two distinct periods (cold versus warm season). Blood samples were collected daily from AI (day 0) to day 8 and on days 15, 22, 29, 36 and 64 to measure progesterone and estradiol. Pregnancy diagnosis was performed at days 29, 43 and 64. The pre-ovulatory follicle size was larger and the plasma estradiol concentrations on the day of AI were greater in animals that became pregnant. Plasma progesterone concentrations diverged and became greater after day 5 post-AI, in cows diagnosed pregnant, as compared to non-pregnant cows. The overall pregnancy rate (33%) or late embryonic/early fetal losses (23%) did not differ between seasons, but plasma estradiol concentrations on the day of AI and plasma concentrations of progesterone in pregnant cows were lower in the warm season. Reduced CL function, measured as plasma progesterone concentrations, from days 22 or 29 post-AI onward for cold and warm season, respectively, was associated with subsequent late embryonic/early fetal mortality. Overall, pregnancy was related to diameter of the pre-ovulatory follicle and plasma E2 on the day of AI, but embryonic/fetal losses were not. Season did not affect these outcomes, even though it influenced luteal function after AI.

Influence of body condition and bovine somatotropin on estrous behavior, reproductive performance, and concentrations of serum somatotropin and plasma fatty acids in postpartum Brahman-influenced cows1,2

Ninety-nine multiparous Brahman-influenced (1/4 to 3/8 Brahman) cows were managed to achieve low (BCS = 4.3 +/- 0.1; n = 50) or moderate (BCS = 6.1 +/- 0.1; n = 49) body condition (BC) to determine the influence of bovine somatotropin (bST) on estrous characteristics, reproductive performance, and concentrations of serum GH and plasma NEFA. Beginning 32 d postpartum, cows within each BC were assigned randomly to treatment with or without bST. Non-bST-treated cows received no treatment, and treated cows were administered bST (Posilac, 500 mg s.c.) on d -35, -21, and -7 before initiation of the breeding season. On d -7, all cows received an intravaginal, controlled internal drug-releasing (CIDR) device. On d 0 (initiation of the 70-d breeding season), the CIDR were removed and cows received prostaglandin F2alpha (PGF2alpha). Blood samples were collected from the median caudal vein of the cows at each bST treatment and at d -28 and 0. Estrous behavior was monitored by radiotelemetry during the first 30 d of the breeding season. Growth hormone was increased (P < 0.05) in low and moderate BC cows treated with bST. The percentage of cows detected in estrus during the first 30 d of the breeding season was decreased (P = 0.05) for low BC (64%) compared with moderate BC (82%) cows. The interval to first estrus tended (P = 0.07) to be shorter in low BC-bST-treated cows (3.7 +/- 1.9 d) than in moderate BC-bST-treated cows (9.6 +/- 1.8 d). During the first 30 d of the breeding season, cows in low BC had a decreased (P = 0.02) number of mounts received and increased (P = 0.001) quiescence between mounts compared with cows in moderate BC. The number of mounts received was reduced (P = 0.04) in bST-treated cows. More (P = 0.02) cows treated with bST became pregnant during the first 3 d of the breeding season compared with non-bST-treated cows. The cumulative first-service conception rate tended (P = 0.07) to be greater for bST-low BC cows than non-bST-treated cows in low or moderate BC. On d 0, NEFA were greater (P < 0.05) in bST-treated vs. non-bST-treated cows. Low BC and bST reduced the intensity of behavioral estrus in postpartum Brahman-influenced cows. However, bST increased the first-service conception rate during the first 30 d of breeding and pregnancy rates during the first 3 d of breeding in postpartum Brahman-influenced cows.

Interaction between season and culture with insulin-like growth factor-1 on survival of in vitro produced embryos following transfer to lactating dairy cows

Culture of bovine embryos in the presence of insulin-like growth factor-1 (IGF-1) can increase pregnancy rates following transfer to heat-stressed, lactating dairy cows. The objective of the present experiment was to determine whether the effect of IGF-1 on post-transfer embryo survival was a general effect or one specific to heat stress. Lactating recipients (n=311) were synchronized for timed-embryo transfer at four locations. Embryos were produced in vitro and cultured with or without 100 ng/mL IGF-1. At Day 7 after anticipated ovulation (Day 0), a single embryo was randomly transferred to each recipient. Pregnancy was diagnosed at Day 21 by elevated plasma progesterone concentrations, at Days 27-32 by ultrasonography, and at Days 41-49 by transrectal palpation. Transfers were categorized into two seasons, hot or cool (based on the month of transfer). There was a tendency (P<0.09) for an interaction between embryo treatment and season for pregnancy rate at Day 21; this interaction was significant at Days 30 and 45 (P<0.02). Recipients receiving IGF-1 treated embryos had higher pregnancy rates in the hot season but not in the cool season. There was a similar interaction between embryo treatment and season for overall calving rate (P<0.05). There was also an interaction between season and treatment affecting pregnancy loss between Days 21 and 30; recipients that received IGF-1 treated embryos had less pregnancy loss during this time period in the hot season but not in the cool season. The overall proportion of male calves born was 77.5%. In conclusion, treatment of embryos with IGF-1 improved pregnancy and calving rates following the transfer of in vitro produced embryos into lactating recipients, but only under heat-stress conditions.

Comparison of two types of CIDR-based timed artificial insemination protocols for repeat breeder dairy cows

This study compared two types of controlled internal drug release (CIDR)-based timed artificial insemination (TAI) protocol for treatment of repeat breeder dairy cows. In the first trial of the experiment, 55 repeat breeder cows were randomly assigned to the following two treatments. (1) In the EB group, a CIDR device was inserted into the cows, and then the cows were administered an injection of 1 mg estradiol benzoate (EB) plus 50 mg progesterone (P4; Day 0). On Day 7, they were given an injection of PGF(2alpha) and the CIDR device was removed. The cows were given an injection of 1 mg EB on Day 8 and were subjected to TAI 30 h later (n=27). (2) In the gonadotrophin releasing hormone (GnRH) group, a CIDR device was inserted into the cows, and then the cows were administered an injection of 250 microg gonadorelin (GnRH; Day 0). On Day 7, they were given an injection of PGF(2alpha) and the CIDR device was removed. The cows were given an injection of 250 microg GnRH on Day 9 and were subjected to TAI 17 h later (n=28). In the second trial, 41 repeat breeder cows that were confirmed as not pregnant in the first trial were randomly assigned to the same two treatments used in the first trial (an EB group of 20 cows and a GnRH group of 21 cows). The ovaries of 15 cows from each group were examined by transrectal ultrasonography in order to observe the changes in ovarian structures, and blood samples were collected for analysis of serum P4 concentrations. The pregnancy rates following TAI in the first (18.5 vs. 32.1%) and second (40.0 vs. 38.1%) trials and the combined rates (27.7 vs. 34.7%) did not differ between the EB and GnRH groups. The proportions of cows with follicular wave emergence within 7 days did not differ between the EB (12/15) and GnRH groups (13/15). The interval to wave emergence was shorter (P<0.01) in the GnRH group than in the EB group, but there was no difference in the mean diameters of dominant follicles on Day 7 between the groups. Moreover, the proportions of cows with synchronized ovulation following a second EB or GnRH treatment did not differ between the groups. In conclusion, treatment with either EB or GnRH in a CIDR-based TAI protocol results in synchronous follicular wave emergence, follicular development, synchronous ovulation, and similar pregnancy rates for TAI in repeat breeder cows.

Fertility of Lactating Dairy Cows Administered Recombinant Bovine Somatotropin During Heat Stress

Administration of recombinant bovine somatotropin (bST) to lactating dairy cows during heat stress increases milk yield, but it also can increase body temperature and may therefore compromise fertility. However, it is possible that bST treatment could increase fertility during heat stress because it has been reported to increase fertility in lactating cows. In addition, bST increases secretion of insulin-like growth factor-I (IGF-I) that promotes embryo survival. The purpose of this study was to determine effects of bST on reproductive function in lactating dairy cows during heat stress. The experiment was conducted in southern Georgia from July to November 2005 using lactating Holstein cows (n = 276 for reproductive traits). For first service timed artificial insemination (TAI), cows were presynchronized with 2 injections of PGF(2alpha) given 14 d apart followed by a modified Ovsynch protocol (GnRH and insemination at 72 h following PGF(2alpha) ). Pregnancy was diagnosed by using ultrasonography on d 29 and reconfirmed by palpation between d 45 and 80 post-TAI. Nonpregnant cows were resynchronized with the modified Ovsynch protocol and received a second TAI. Treatment with bST started 1 wk before the start of Ovsynch and continued at 2-wk intervals. Blood samples were collected from a subset of cows to determine IGF-I profiles immediately before the first bST injection, 1 wk later, and at d 35 of bST treatment. Rectal temperatures were assessed on d 29 of bST treatment. Pregnancy rates (d 45 to 80 post-TAI) did not differ between bST and control cows for first- (16.7 vs. 15.2%) or second-service TAI (14.8 vs. 17.2%). Plasma concentrations of IGF-I and milk yield were greater for bST-treated cows following the initiation of bST treatment and bST increased rectal and vaginal temperatures. Body condition score was less for bST-treated cows. In conclusion, treatment with bST during heat stress increased IGF-I concentrations, milk yield over time, and rectal and vaginal temperatures without affecting first- or second-service pregnancy rates. Thus, at least under certain housing conditions, bST can be used to improve milk yield during heat stress without compromising fertility.

Pre-partum monensin supplementation improves body reserves at calving and milk yield in Holstein cows dried-off with low body condition score

The objective of this study was to determine the effect of a monensin controlled-release capsule administered intraruminally at drying-off on body condition score (BCS) at calving, milk yield, fertility and concentration of energy-related blood metabolites in Holstein cows dried-off with low BCS (< or = 3.0, scale 1 to 5 with a 0.25 point of increment). Between July and August, 2001, 220 cows from parity 2 or more and dried-off 50-70 days before expected parturition, with a BCS < or = 3.0 were randomly assigned to either a treatment group (n=110; oral capsule of monensin releasing 335 mg/day for 95 days) or a control group (no capsule, n=110). At assignment, on day 21 before expected parturition, at calving, and at 7, 14, and 21 days in milk a blood sample was obtained from a random sub sample of 10 cows per group. Effects of monensin on serum NEFA, BHBA and glucose were measured. Milk yield, milk fat and protein content (%) at DHIA test days during the entire lactation, 305 ME milk production and reproductive responses were compared. Monensin significantly improved BCS at calving, increased milk yield at test days 4 and 8, decreased the percentage of milk protein, did not change the percentage of milk fat, and decreased NEFA and BHBA during the post-partum period.