Timed AI Protocol Research Articles

Pregnancy per artificial insemination after presynchronizing estrous cycles with the Presynch-10 protocol or prostaglandin F2α injection followed by gonadotropin-releasing hormone before Ovsynch-56 in 4 dairy herds of lactating dairy cows

The objective was to determine the effect of 2 presynchronization treatments on first-service pregnancy per artificial insemination (P/AI) in 4 dairy herds during warm and cool seasons of the year. Cows with ear tags ending with even digits at calving were enrolled in Presynch-10 (Presynch-10): two 25-mg injections of PGF2α (i.e., PG-1 and PG-2) 14 d apart. Cows with ear tags ending with odd digits were enrolled in PG-3-G: one 25-mg injection of PG (Pre-PG) 3 d before injection of 100μg of GnRH (Pre-GnRH), with the Pre-PG injection administered at the same time as PG-2 in the Presynch-10 treatment. Ten days after PG-2 or Pre-PG, all cows were enrolled in a timed AI protocol (Ovsynch-56; injection of GnRH 7 d before GnRH-1 and 56 h after GnRH-2 PG with AI 16 to 18 h after GnRH-2). Median days in milk (DIM) at scheduled timed AI were 75 d, which did not differ among herds. Cows detected in estrus before the scheduled timed AI were inseminated early (early bred, EB). Pregnancy was diagnosed at d 32 to 38 and at d 60 to 66 after timed AI by transrectal ultrasonography or transrectal palpation. Data were analyzed with herd as a random effect and with fixed effects of treatment (EB, Presynch-10, or PG-3-G), parity (primiparous vs. multiparous), season [hot (June through September) vs. cool-cold (October through May)], DIM, estrus at timed AI (0 vs. 1), and all 2-way interactions with treatment. The P/AI at d 32 to 38 for EB (n=472), Presynch-10 (n=1,247), and PG-3-G (n=1,286) were 31.4, 35.0, and 41.2%, respectively; P/AI at d 60 to 66 was 29.8, 32.2, and 37.3%, respectively. Season significantly influenced P/AI at d 32 to 38 and d 60 to 66, but a treatment by season interaction was not detected. The P/AI for PG-3-G and Presynch-10 treatments did not differ during cool-cold weather (d 32 to 38: 46.8 vs. 44.3%; d 60 to 66: 41.6 vs. 41.1%, respectively), but PG-3-G and Presynch-10 produced more P/AI than EB at d 32 to 38. During the summer, P/AI in PG-3-G was greater than in Presynch-10 (d 32 to 38: 35.9 vs. 26.7% and d 60 to 66: 33.2 vs. 24.4%, respectively), and P/AI in EB cows did not differ from that of Presynch-10 cows. Although pregnancy loss did not differ for EB, Presynch-10, and PG-3-G treatments (4.0, 6.7, and 9.3%, respectively), pregnancy loss from d 32 to 38 and d 60 to 66 was 2-fold greater in thinner cows (<2.5 vs. ≥2.5; 9.0 vs. 4.4%). We concluded that presynchronizing estrous cycles with PG-3-G produced more P/AI than inseminating cows at estrus during cooler weather and was superior to Presynch-10 during the summer.

Fertility in dairy cows following presynchronization and administering twice the luteolytic dose of prostaglandin F2α as one or two injections in the 5-day timed artificial insemination protocol

The objectives were to evaluate pregnancy per AI (P/AI) of dairy cows subjected to the 5-day timed AI protocol under various synchronization and luteolytic treatments. Cows were either presynchronized or received supplemental progesterone during the synchronization protocol, and received a double luteolytic dose of PGF2α, either as one or two injections. In Experiment 1, dairy cows (n = 737; Holstein = 250, Jersey = 80, and crossbred = 407) in two seasonal grazing dairy farms were randomly assigned to one of four treatments in a 2 × 2 factorial arrangement. The day of AI was considered study Day 0. Half of the cows were presynchronized (G6G: PGF2α on Day −16 and GnRH on Day −14) and received the 5-day timed AI protocol using 1 mg of cloprostenol, either as a single injection (G6G-S: GnRH on Day −8, PGF2α on Day −3, and GnRH + AI on Day 0) or divided into two injections of 0.5 mg each (G6G-T: GnRH on Day −8, PGF2α on Day −3 and −2, and GnRH + AI on Day 0). The remaining cows were not presynchronized and received a controlled internal drug-release (CIDR) insert containing progesterone from GnRH to the first PGF2α injection of the 5-day timed AI protocol, and 1 mg of cloprostenol either as a single injection on Day -3 (CIDR-S) or divided into two injections of 0.5 mg each on Days -3 and -2 (CIDR-T). Ovaries were examined by ultrasonography on Days −8 and −3 and plasma progesterone concentrations were determined on Days −3 and 0. In Experiment 2, 655 high-producing Holstein cows had their estrous cycle presynchronized with PGF2α at 46 ± 3 and 60 ± 3 days postpartum and were randomly assigned to receive 50 mg of dinoprost during the 5-day timed AI protocol, either as a single injection or divided into two injections of 25 mg each. Pregnancies per AI were determined on Days 35 and 64 after AI in both experiments. In Experiment 1, presynchronization with G6G increased the proportion of cows with a CL on Day −8 (80.6 vs. 58.8%), ovulation to the first GnRH of the protocol (64.2 vs. 50.2%), and the presence (95.6 vs. 88.4%) and number (1.79 vs. 1.30) of CL at PGF2α compared with CIDR cows. Luteolysis was greater for two injections compared to a single PGF2α injection (two PGF2α = 95.9 vs. single PGF2α = 72.2%), especially in presynchronized cows (G6G-T = 96.2 vs. G6G-S = 61.7%). For cows not presynchronized, two PGF2α injections had no effect on P/AI (CIDR-S = 30.2 vs. CIDR-T = 34.3%), whereas for presynchronized cows, it improved P/AI (G6G-S = 28.7 vs. G6G-T = 45.4%). In Experiment 2, the two-PGF2α injection increased P/AI on Days 35 (two PGF2α = 44.5 vs. single PGF2α = 36.4%) and 64 (two PGF2α = 40.3% vs. single PGF2α = 32.6%) after AI. Presynchronization and dividing the dose of PGF2α (either cloprostenol or dinoprost) into two injections increased P/AI in lactating dairy cows subjected to the 5-day timed AI protocol.

Assessment of field fertility and several in vitro sperm characteristics following the use of different Angus sires in a timed-AI program with suckled Nelore cows

In order to provide information that may help researchers to understand the main cause(s) of differences in bull fertility frequently observed in field trials, this study aimed to investigate conception rates as well as several in vitro sperm characteristics of different sires of unknown fertility utilized in a Timed-AI (TAI) program. Suckled Nelore cows submitted to the same TAI protocol were allocated into eight breeding groups of approximately 120 animals each. Frozen semen doses from three Angus bulls and three different batches from each bull were utilized. Approximately 100 doses from each batch were used in TAI. Sires, batches and AI technicians were equally distributed across breeding groups. Cows were examined for pregnancy diagnosis 40d after TAI. For in vitro sperm analyses, the same thawing procedure was repeated in the laboratory to mimic field conditions. The following in vitro sperm characteristics were assessed: computerized motility, thermal resistance, plasma and acrosomal membrane integrity, lipid peroxidation, morphology, morphometry and chromatin structure. No effect of breeding group, body condition score, AI technician and sire was observed. However, some significant differences among bulls were detected in laboratory analyses. Semen from sire presenting numerically lower (P>0.05) pregnancy/AI also presented lower (P<0.05) values in all sperm characteristics analyzed in thermal resistance test at 4h (Total Motility, Progressive Motility, Average Path Velocity, Straight-Line Velocity, Curvilinear Velocity, Amplitude of Lateral Head Displacement, Beat Cross Frequency, Straightness, Linearity, and Percentage of Rapidly Moving Cells), higher (P<0.05) Major and Total Defects in sperm morphological test, lower (P<0.05) Length, Ellipticity and Fourier parameter (Fourier 0) in sperm morphometric analysis as well as higher (P<0.05) chromatin heterogeneity. It was concluded that, although no bull effect was observed in the field experiment, the sire that presented numerically lower pregnancy/AI also presented lower semen quality according to the laboratory analyses performed.

Improving fertility to timed artificial insemination by manipulation of circulating progesterone concentrations in lactating dairy cattle

This manuscript reviews the effect of progesterone (P4) during timed AI protocols in lactating dairy cows. Circulating P4 is determined by a balance between P4 production, primarily by the corpus luteum (CL), and P4 metabolism, primarily by the liver. In dairy cattle, the volume of luteal tissue is a primary determinant of P4 production; however, inadequate circulating P4 is generally due to high P4 metabolism resulting from extremely elevated liver blood flow. Three sections in this manuscript summarise the role of P4 concentrations before breeding, near the time of breeding and after breeding. During timed AI protocols, elevations in P4 are generally achieved by ovulation, resulting in an accessory CL, or by supplementation with exogenous P4. Elevating P4 before timed AI has been found to decrease double ovulation and increase fertility to the timed AI. Slight elevations in circulating P4 can dramatically reduce fertility, with inadequate luteolysis to the prostaglandin F2α treatment before timed AI being the underlying cause of this problem. After AI, circulating P4 is critical for embryo growth, and for establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI with marginal elevations in fertility. Thus, previous research has provided substantial insights into mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future research on P4 manipulation to improve timed AI protocols.

The use of endocrine treatments to improve pregnancy rates in cattle

Reproduction is critical for the success of both dairy and beef cattle production. Inadequate reproduction impairs profitability by compromising production, delaying genetic progress and increasing expenses. A major impediment to the use of artificial insemination (AI) is the ability to detect oestrus for optimum timing of breeding. However, increased understanding of the bovine oestrous cycle has led to the development of reproductive programmes that allow precise synchrony of follicle development, luteal regression and ovulation. The advent of timed-AI protocols revolutionised reproductive management in dairy and beef herds. It allows for AI at a more desired time post partum despite oestrous cyclicity. It also allows for pre-determined re-insemination of cows diagnosed as not pregnant. In subfertile cows, such as the post partum, anoestrous beef cow and the high-producing dairy cow, strategic hormone supplementation has been used to overcome hormone deficiencies and improve pregnancy rates. Several physiological windows have been identified to optimise fertility in synchronisation programmes and they include, but are not limited to, follicle turnover, synchrony of follicular development, length of dominance, progesterone concentrations during development of the ovulatory follicle, luteal regression, peri-ovulatory steroid concentrations, length of pro-oestrus, synchrony of ovulation and AI, and progesterone rise after ovulation.

Effect of duration of progesterone-releasing device (controlled internal drug-release insert) treatment on reproductive performance in beef cows

The objective of this experiment was to determine the effect of reducing the duration of progesterone-releasing device (CIDR) treatment, in a CIDR-based timed AI synchronization protocol [CIDR-prostaglandin F2α (PGF2α)– gonadotropin-releasing hormone (GnRH) and AI], on AI pregnancy rate (P/AI) and overall pregnancy rates in primiparous and multiparous, suckled beef cows. British crossbred cows (n = 138) were paired by parity, days postpartum (DPP), age, and BW and were assigned to one of 2 treatments: 1) cows (n = 68) received a CIDR (d -7) for 7 d, PGF2α (25 mg) at CIDR removal (d 0), GnRH (75 μg) 56 h after CIDR removal, and immediate AI on d 3 (CIDR7) or 2) cows (n = 70) received a CIDR (d -5) for 5 d, PGF2α at CIDR removal (d 0), GnRH 56 h after CIDR removal, and immediate AI on d 3 (CIDR5). All cows received AI by a single inseminator. Cows were exposed to bulls 15 d after timed AI. Pregnancy status was determined by ultrasonography 32 and 70 d after AI. Treatment had no effect on P/AI (54.4 and 57.1% for CIDR7 and CIDR5, respectively). Overall pregnancy rate was also unaffected by treatment protocol (79.4 and 77.1% for CIDR7 and CIDR5, respectively). Age, BW, and BCS did not have an effect on P/AI and overall pregnancy rate. Days postpartum had a significant effect (P 60 DPP) and overall pregnancy rate (50% for 60 DPP). Results indicate that reducing the duration of CIDR treatment from 7 to 5 d in a CIDR-based timed AI protocol did not influence P/AI and overall pregnancy rate in suckled beef cows.

Comparison of Plasma Concentrations of Estradiol-17.BETA. and Progesterone, and Conception in Dairy Cows with Cystic Ovarian Diseases between Ovsynch and Ovsynch plus CIDR Timed AI Protocols

The objectives of this study were 1) to determine the effects of adding a CIDR to the Ovsynch protocol on plasma concentrations of estradiol-17β and progesterone and conception in dairy cows with cystic ovarian diseases and 2) to examine associations among the estradiol-17β and progesterone concentrations and conception. Cows were diagnosed as having cystic ovarian diseases if they were found to have a cystic follicle (diameter ≥25 mm) without a corpus luteum by two palpations per rectum with an interval for 7 to 14 days. They were treated with either the Ovsynch (GnRH on Day 0, PGF(2α) on Day 7 and GnRH on Day 9, with AI on Day 10; n=15) or Ovsynch+CIDR protocol (Ovsynch protocol plus a CIDR from Day 0 to Day 7; n=23). Plasma estradiol-17β concentrations were determined on Days 0, 7 and 9, and plasma progesterone concentrations were determined on Days 0, 7, 9 and 17. The plasma estradiol-17β and progesterone concentrations at all of the days examined and conception rates did not differ significantly between the two timed AI protocols. The progesterone concentrations on Day 17 and conception rates were lower (P<0.05) for cows with low concentrations of estradiol-17β (<2 pg/ml) on Day 9 than for cows with high concentrations of estradiol-17β (≥2 pg/ml). The present study suggests that, in dairy cows with cystic ovarian diseases, addition of a CIDR to the Ovsynch protocol had no remarkable effects on plasma estradiol-17β and progesterone concentrations during and after the treatments or on conception after timed AI. This study indicates that the low plasma estradiol-17β concentration at the second administration of GnRH in the protocols can be a predictor for impaired luteal formation and lower likelihood of pregnancy in dairy cows with cystic ovarian diseases.

The applications of timed artificial insemination and timed embryo transfer in reproductive management of dairy cattle

Fertility of dairy cattle is generally decreasing. Overall estrus detection efficiency in lactating dairy cattle is low, as expression of estrus is often compromised. Consequently, undetected estrus, low AI-submission rates, and long inter-breeding intervals are the main contributors to poor reproductive efficiency. Although failure to become pregnant is the most common reason for culling dairy cattle, pregnancy rates could be improved by increasing the AI-submission rate through increased estrus detection efficiency, timed insemination (Timed-AI), or timed embryo transfer (Timed-ET). In these protocols, ovarian follicular development and luteolysis are controlled, culminating in synchronous ovulation in most cows. There are several modifications to improve pregnancy rates in Timed-AI protocols, e.g. presynchronization with 2 doses of PGF2a 14 d apart, and starting the Ovsynch protocol 12 d after the 2nd PGF2a. Timed-AI programs ensure a timely first breeding; this should be followed with early pregnancy diagnosis to identify nonpregnant cows, and prompt re-insemination. However, in a recent field study involving 23 dairy herds, the mean interval between 1st and 2nd breeding was 42 d; only 28% of the cows were rebred within 24 d after 1st breeding. Fortunately, there are several resynchronization protocols to reduce inter-breeding intervals. Anestrus cows, or those with cystic ovarian follicles, have a good chance of conceiving when subjected to synchronization of ovulation and Timed-AI. Furthermore, Timed-ET is a practical and viable option for synchronizing and selecting recipient cattle for embryo transfers. In summary, systematic and judicious use of Timed-AI and Timed-ET protocols can greatly enhance reproductive performance, and improve herd productivity.

Comparison in Effect of Heatsynch with Heat Detection Aids and CIDR‐Heatsynch in Dairy Heifers

The objective of the present study was to determine whether oestrous detection with the help of oestrous detection aids during the Heatsynch without timed AI protocol is equally effective with the progesterone-combined protocol in dairy heifers. A total of 148 heifers were randomly assigned to one of the two groups. A group of heifers treated with Heatsynch with heat detection aids (n = 72) received GnRH on day 0, prostaglandin F(2alpha) (PGF(2alpha)) on day 7 and oestradiol benzoate (EB) on day 8, while in controlled internal drug release (CIDR)-Heatsynch group (n = 76), CIDR was included during a period from GnRH to PGF(2alpha). Heifers were checked for oestrus twice daily, i.e. from 09:00 to 10:00 hours and from 15:00 to 16:00 hours starting on day 2 for Heatsynch group and on day 8 in CIDR-Heatsynch group, and continued up to day 12. KAMAR heat mount detector (KAMAR Inc., Steamboat Springs, CO, USA) and ALL-WEATHER PAINTSTIK (LA-CO Industries Inc., Elk Grove Village, IL, USA) were used as heat detection aids. AI was conducted within 1 h after confirming oestrus in 72 heifers, while 19 animals were transferred with embryo 7 days after oestrus according to the request of the owners. Premature oestrus before PGF(2alpha) injection occurred in 18% of Heatsynch group. Of 13 heifers which showed premature oestrus, six were inseminated and two of them conceived. Oestrus detection rate within 12 days after initiation of the protocols did not differ between the two groups (94% vs 95%). There was no difference in the conception rate after first AI (including heifers that were inseminated before PGF(2alpha) injection) and embryo transfer between Heatsynch with heat detection aids and CIDR-Heatsynch groups (36% vs 44% and 70% vs 56%). It is concluded that the use of heat detection aids to monitor the occurrence of premature oestrus prior to PGF(2alpha) injection in Heatsynch protocol in dairy heifers was equally effective to the inclusion of CIDR.

Factors affecting preovulatory follicle diameter and ovulation rate after gonadotropin-releasing hormone in postpartum beef cows. Part I: Cycling cows1

Cows induced to ovulate small dominant follicles were reported to have reduced pregnancy rates compared with cows that ovulated large follicles. The reason for the presence of small dominant follicles at the time of GnRH-induced ovulation in timed AI protocols is unknown. The objectives of this experiment were to examine the role of day of the estrous cycle at initiation of treatment on ovulation after the first GnRH injection (GnRH1) and associated effects on growth rate and final size of the ovulatory follicle at the second GnRH injection (GnRH2), serum concentrations of estradiol at GnRH2, and subsequent luteal concentrations of progesterone in suckled beef cows. Estrous cycles of cows were manipulated to be at 1 of 5 specific days of the cycle (d 2, 5, 9, 13, and 18, d 0 = estrus; n = 12 per treatment group) at the beginning of the CO-Synch protocol (GnRH1 on d -9, PGF(2alpha) on d -2, and GnRH2 on d 0). Day of the estrous cycle at GnRH1 did not affect the size of the preovulatory follicle or the proportion of cows ovulating at GnRH2 (P = 0.65 and 0.21, respectively). When all cows were included in the analysis, cows that ovulated after GnRH1 had similar follicle size at GnRH2 compared with cows that did not ovulate after GnRH1 (11.4 and 10.4 mm, respectively; P = 0.23). When only cows that could ovulate after GnRH1 (excluding cows treated on d 2) were included in the analysis, cows that ovulated to GnRH1 had a larger follicle at GnRH2 than cows that did not ovulate after GnRH1 (11.4 and 9.5 mm, respectively; P = 0.04). Follicle growth from d -5 to 0 was similar between cows that ovulated after GnRH1 and cows that did not (1.01 vs. 0.89 mm/d, respectively; P = 0.75). There was a tendency for faster follicle growth rate in cows that ovulated a large follicle (>11 mm) compared with cows that ovulated a small follicle (< or = 11 mm; 1.01 vs. 0.86 mm/d, respectively; P = 0.07). Serum concentrations of estradiol at GnRH2 and progesterone after ovulation were reduced in cows that ovulated small follicles compared with cows that ovulated large follicles (P = 0.006 and 0.005, respectively). In summary, day of the estrous cycle at initiation of synchronization did not affect ovulatory follicle size, but follicle growth rates affected the size of the follicle at GnRH2. Cows that ovulated a small follicle had reduced serum concentrations of estradiol at GnRH2 and progesterone after ovulation.

Use of a five-day progesterone-based timed AI protocol to determine if flunixin meglumine improves pregnancy per timed AI in dairy heifers

Two experiments were conducted to test the hypothesis that the 5 d Co-Synch + CIDR (Controlled Internal Drug Release insert containing progesterone) protocol could be applied as an efficient timed AI (TAI) protocol in dairy heifers, and that treatment with flunixin meglumine (FM) during the period of CL maintenance would increase pregnancy per TAI (P/TAI) and late survival of embryos. Objectives were: 1) in Experiment 1, to compare P/TAI with the 5 d Co-Synch+CIDR protocol to a PGF2α/GnRH protocol; and 2) in Experiment 2, to determine if FM administered 15.5 and 16 d after first TAI would increase P/TAI, using the 5 d Co-Synch+CIDR protocol with a new or previously used (5 d) CIDR insert.In Experiment 1, 248 heifers were assigned randomly to either the PGF2α/GnRH protocol (n=120) or the 5 d Co-Synch+CIDR protocol (n=128). Pregnancy per TAI did not differ between the 5 d Co-Synch+CIDR protocol (53.1%) and the PGF2α/GnRH protocol (45.8%; P=0.22). In Experiment 2, 325 heifers synchronized with the 5 d Co-Synch+CIDR protocol were assigned randomly to receive two injections of FM (FM group; n=158) at 15.5 and 16 d after TAI, or to remain as untreated controls (n=165). Pregnancy per TAI in Experiment 2 was 59.4 and 59.5% at 45 d for control and FM groups, respectively, with no differences between groups (P=0.83). The 5 d Co-Synch+CIDR protocol resulted in an acceptable P/TAI in dairy heifers. However, FM did not improve P/TAI in dairy heifers.

Rates of luteolysis and pregnancy in dairy cows after treatment with cloprostenol or dinoprost

Our objective was to determine whether rates of luteolysis or pregnancy differed in lactating dairy cows of known progesterone status and either known or unknown luteal status after either cloprostenol or dinoprost was injected as part of a timed-insemination program. In Experiment 1, 2358 lactating dairy cows in six herds were given two injections of PGF 2α 14 d apart (Presynch), with the second injection given 12 to 14 d before the onset of a timed AI protocol (Ovsynch). Cows (n = 1094) were inseminated when detected in estrus after the Presynch PGF 2α injections. Cows not inseminated (n = 1264) were enrolled in the Ovsynch protocol and assigned randomly to be treated with either cloprostenol or dinoprost as part of the timed-AI protocol. In cows having pretreatment concentrations of progesterone ≥ 1 ng/mL and potentially having a functional corpus luteum (CL) responsive to cloprostenol (n = 558) or dinoprost (n = 519), dinoprost increased (P < 0.05) luteal regression from 86.6 to 91.3%. Despite a significant increase in luteolysis, pregnancies per AI did not differ between luteolytic agents (dinoprost = 37.8% and cloprostenol = 36.7%). Fertility was improved in cows of both treatments having reduced concentrations of progesterone at 72 h and in cows showing signs of estrus. In Experiment 2, an ovulation-resynchronization program was initiated with GnRH or saline in 427 previously inseminated lactating dairy cows of unknown pregnancy status in one herd. Seven days later, pregnancy was diagnosed and nonpregnant cows were blocked by number of CL and assigned randomly to be treated with cloprostenol or dinoprost. Compared with cloprostenol, dinoprost increased (P < 0.05) luteal regression from 69.1 to 78.5%, regardless of the number of CL present or the total luteal volume per cow. Pregnancies per AI did not differ between dinoprost (32.8%) and cloprostenol (31.3%). Although dinoprost was more effective than cloprostenol at inducing luteolysis in lactating dairy cows exposed to an Ovsynch or ovulation-resynchronization protocol, resulting fertility did not differ between products.

203 EFFECT OF SUPPLEMENTAL FOLLICLE-STIMULATING HORMONE OR EQUINE CHORIONIC GONADOTROPIN DURING THE PROTOCOL FOR TIMED AI IN HIGH-PRODUCING HOLSTEIN COWS

Programs that allow timed AI (TAI) have been used to improve reproductive efficiency in dairy herds; however, in many cases pregnancies per AI (P/AI) during these programs remain suboptimal. In the present experiment, it was hypothesized that treatment with FSH or eCG at the time of the PGF2 treatment of the TAI protocol would increase fertility in dairy cattle. This experiment was performed in June 2008 (winter) and January 2009 (summer) on 2 commercial dairy farms located in southeast Brazil. On a random day of the estrous cycle (Day 0), 694 cows at 196 ± 138 days in milk (DIM) received 2 mg of estradiol benzoate (RICB®, Tecnopec, São Paulo, Brazil) i.m. and a releasing intravaginal device (P4; Primer®, Tecnopec), which was removed on Day 8 when 150 μg of PGF (Prolise®, ARSA, Buenos Aires, Argentina) i.m. were administered. At this time, the cows were stratified by days in milk (DIM), parity, number of insemination, milk production, presence of a CL on Day 0, and body condition score (BCS) and were randomly assigned to 1 of 3 treatments: control (n = 232), consisting of no additional treatment; eCG (n = 232), consisting of 400 IU of eCG (Folligon®, Intervet, São Paulo, Brazil); and FSH (n = 230), consisting of 20 mg of FSH (Folltropin®, Bioniche, Belleville, Ontario, Canada). All cows received GnRH (100 μg of gonadorelin; Fertagyl®, Intervet) and were TAI 56 h after the removal of the device. Pregnancy diagnosis was performed 30 and 60 days after TAI. Also, a subset of animals (n = 89) was submitted to ultrasonographic exams to evaluate the diameter of the ovulatory follicles (ØOF), time to ovulation after P4 removal (TOV), and ovulation rate (OR). Statistical analyses were performed with logistic regression by PROC GLIMMIX of SAS (SAS Institute, Cary, NC, USA). There were no interactions of treatment with DIM, parity, number of insemination, BCS, locomotion score, sire, batch, inseminator, farm, or month; therefore, these variables were removed from the statistical model. The overall P/AI was different between treatments at 30 days after TAI [control = 28.0% (65/232), eCG = 29.7% (69/232), and FSH = 18.7% (43/230); P = 0.01], but not at 60 days [control = 21.6% (50/232), eCG = 24.1% (56/232), and FSH = 16.1% (37/230); P = 0.08]. Pregnancy loss was also similar among treatments [control = 23.1% (15/65), eCG = 18.8% (13/69), and FSH = 14.0% (6/43); P = 0.08]. In addition, the treatments (control, eCG, and FSH, respectively) were not different among ØOF (13.78 ± 0.52; 14.50 ± 0.59; and 15.35 ± 0.69 mm; P = 0.15); TOV (82.50 ± 2.14; 78.48 ± 2.35; and 78.96 ± 2.39 h after P4 withdrawal; P = 0.30); or OR [82.76% (24/29); 83.33% (25/30); and 83.33% (25/30); P = 0.44]. Thus, these data do not indicate a major fertility-enhancing effect of a single eCG or FSH treatment during protocol for TAI in high-producing dairy cows, contrary to the hypothesis of the present study. Tecnopec, Fazenda Campestre, Agrindus S/A, Echoa e Nutricell Nutrientes Celulares.

The Use of Gonadotropin-Releasing Hormone in a Progesterone-Based Timed Artificial Insemination Protocol in Replacement Beef Heifers

The objective of this experiment was to determine the effect of supplemental gonadotropin-releasing hormone (GnRH) at the time of progesterone controlled internal drug-release (CIDR) insertion, when incorporated into a CIDR-prostaglandin F2α (PGF2α)-GnRH timed AI (TAI) protocol on pregnancy per AI of beef heifers. One hundred ninety-two beef replacement heifers in 2 locations were paired by BCS and BW and received a CIDR on d 0. At the time of CIDR insertion, heifers were assigned randomly to receive either GnRH (100 μg, i.m.) or physiological saline. On d 7, the CIDR was removed and all heifers received 25 mg PGF2α On d 9, all heifers were administered GnRH (100 μg, i.m.), followed immediately by TAI by a single inseminator. Pregnancy status was determined by ultrasound on d 35 after AI. Blood samples were collected on d −8, 0, and 9 to measure progesterone concentrations. There was no effect of location or a location × treatment interaction on pregnancy incidence (P = 0.47), and 97.8% of heifers were cyclic. Pregnancy per AI did not differ between treatments (P > 0.5). Body weight and BCS had no effect on the odds ratio of pregnancy (P > 0.5). Administration of GnRH at CIDR insertion did not improve pregnancies per AI when a 7-d CIDR-PGF2α-GnRH TAI protocol was used in cyclic beef heifers.

Profitability of bovine somatotropin administration to increase first insemination conception rate in seasonal dairy herds with heat stress

A dairy farm simulation program was used to estimate the economic value of increased conception rate at first insemination (FCR) as a result of one administration of bovine somatotropin (BST) per lactation. Further, the economically optimal BST administration period in a year was investigated. Typical conditions in Florida were assumed, including reduced milk production and conception rates in the summer and early fall due to heat stress. Administration of a single dose of BST ($6 per dose) per lactation was incorporated into a timed AI protocol for first insemination at 61 days after calving. Increases in FCR of 0, 4, 8, and 12 percentage points (PP) were compared including changes in prices, fertility, and seasonality of cow performance. No direct effect of BST on milk production was assumed. With default inputs and an increase in FCR of 4 PP, the optimal administration period was February through June which resulted in a small gain in profitability of $0.80/slot/year. Typically, one administration of BST per lactation to increase FCR was profitable in the cooler winter and spring, but not the hotter season. The use of BST in the cooler winter and spring resulted in increased seasonality of herd performance and demographics. When no seasonality in milk production was assumed, administration of BST was profitable throughout the year when FCR increased at least 8 PP. In conclusion, increases in FCR were most profitable during the cooler season of the year when basic conception rates were already greater than in the hotter season.

Effects of equine chorionic gonadotropin and type of ovulatory stimulus in a timed-AI protocol on reproductive responses in dairy cows

The objectives were to evaluate the effects of equine chorionic gonadotropin (eCG) supplementation (with or without eCG) and type of ovulatory stimulus (GnRH or ECP) on ovarian follicular dynamics, luteal function, and pregnancies per AI (P/AI) in Holstein cows receiving timed artificial insemination (TAI). On Day 0, 742 cows in a total of 782 breedings, received 2 mg of estradiol benzoate (EB) and one intravaginal progesterone (P4) insert (CIDR). On Day 8, the CIDR was removed, and all cows were given PGF2α and assigned to one of four treatments in a 2 × 2 factorial arrangement: (1) CG: GnRH 48 h later; (2) CE: ECP; (3) EG: eCG + GnRH 48 h later; (4) EE: eCG + ECP. There were significant interactions for eCG × ovulatory stimulus and eCG × BCS. Cows in the CG group were less likely (28.9% vs. 33.8%; P < 0.05) to become pregnant compared with those in the EG group (odds ratio [OR] = 0.28). There were no differences in P/AI between CE and EE cows (30.9% vs. 29.1%; OR = 0.85; P = 0.56), respectively. Thinner cows not receiving eCG had lower P/AI than thinner cows receiving eCG (15.2% vs. 38.0%; OR = 0.20; P < 0.01). Treatment with eCG tended to increase serum progestesterone concentrations during the diestrus following synchronized ovulation ( P < 0.10). However, the treatment used to induce ovulation did not affect CL volume or serum progesterone concentrations. In conclusion, both ECP and GnRH yielded comparable P/AI. However, eCG treatment at CIDR removal increased pregnancy rate in cows induced to ovulate with GnRH and in cows with lower BCS.

Modification of a CIDR/OvSynch Timed Artificial Insemination Protocol for Reproductive Management of Dairy Heifers

Acceptable pregnancy rates (PR) after timed AI (TAI) could improve reproductive management of dairy heifers. In beef cattle (Helser, 2006) the CIDR/OvSynch TAI protocol was improved by reducing the interval between GnRH and PGF to five days, giving two injections (AM/PM) of PG F and administering GnRH and TAI at 72 h after withdrawal of the CIDR to increase the proestrus period. The overall PR was 65.3%. Using this procedure in dairy heifers, PR was 58.3% at day 32 post TAI (Thatcher, 2007). Objectives of Exp. 1 were to compare PR of dairy heifers relative to whether one vs. two injections of PGF is required for effective use of the CIDR/OvSynch TAI protocol, and to compare PRs to CIDR/OvSynch TAI resynchronization programs of non-pregnant heifers involving estrus and no estrus detection. A second objective was to evaluate PR in two additional groups of heifers using the CIDR/OvSynchTAI protocol with one injection of PGF for first and second service without estrus detection (Exp. 2).

Effect of feeding yeast culture on reproduction and lameness in dairy cows under heat stress

Multiparous Holstein cows ( n = 717) from two dairy farms were blocked at calving by parity and previous lactation milk yield and, within each block, randomly assigned to one of two treatments: a diet containing no yeast culture (Control; n = 359) or 30 g/d of a culture of Saccharomyces cerevisiae (YC; n = 358) from 20 to 140 d postpartum. Only cows calving during months of heat stress, May–August were enrolled. Lameness score (1–5 scale) was evaluated at study enrollment and again at 100 d postpartum. The body condition score (BCS, 1–5 scale) was evaluated at calving, 28, 58 and 140 d postpartum. Cows received two injections of PGF 2α at 37 and 51 d postpartum, and those observed in estrus were inseminated. Cows not in estrus were enrolled in a timed AI protocol at 65 d postpartum and inseminated at 75 d postpartum. Ovaries were examined by ultrasonography at 37 and 51 d postpartum to determine whether estrous cycling had been initiated by the presence of a corpus lutem (CL) in at least one of the two examinations. Pregnancy was diagnosed at 31, 38 and 66 d after the first AI and at 38 and 66 d after the second and third AI. Diet did not affect time of onset of estrous cycles postpartum, and 8.2% of the cows were anovular. Detection of estrus in the 7 d after the second injection of PGF 2α was similar for control and YC. For control and YC, conception rates 38 d after AI at first (30.8% and 31.4%), second (39.3% and 35.1%) and third (25.8% and 30.6%) inseminations, and pregnancy losses did not differ, which resulted in similar median days to pregnancy and proportion of pregnant cows at 140 d postpartum. Yeast culture did not affect incidence of lameness, but tended to reduce lameness score. Lame cows and anovular cows had lesser conception rates at first AI, and extended interval from calving to conception. A THI of 71 was identified as the critical point in which fertility was reduced in lactating dairy cows, although the sensitivity and specificity were minimal. Cows exposed to a THI > 71 on the day of first AI had a 33% reduction in the rate of pregnancy resulting in extended interval to pregnancy. Feeding a yeast culture of S. cerevisiae had minor effects on lameness score, but no impact on reproduction of multiparous cows under heat stress.

Efficacy of Intravaginal Progesterone Administration as an Additional Treatment on Two Types of Timed AI Protocols in a Commercial Herd of Holstein Heifers

Reproductive performance of two types of timed artificial insemination (TAI) protocols with or without intravaginal progesterone insert (CIDR) was investigated in a commercial herd of Holstein heifers. A total of seventy-four heifers with 14.4 months of age were allocated to two groups; Ovsynch (n=44) and estradiol benzoate (EB) used Heatsynch (EB-Heatsynch, n=30), and each group was additionally divided into two subgroups with CIDR insertion from day 0 to 7 (n=36) and without CIDR group (n=38). Blood was collected for progesterone (P4) analysis and ovarian finding was monitored with ultrasonography. Heifers in CIDR-treated group resulted in higher pregnancy rate as compared to No-CIDR-treated group (63.9% vs 21.1%, P<0.01). Heifers with functional corpus luteum (CL) on day 0 resulted in significantly higher pregnancy rate in CIDR-treated group than No-CIDR-treated group (day 0: 67.9% vs 13.0%, P<0.01). CIDR insertion suppressed the intermediate ovulation during the first 7 days and the period from the second GnRH or EB administration to TAI as compared to No-CIDR-treated group (first 7 days: 33.3% vs. 52.6%; P<0.05, before TAI: 11.1% vs. 37.0%; P<0.05). In conclusion, the selected TAI protocols with CIDR provided acceptable pregnancy rate and contributed to the economical improvement by shortening the average age of first calving approximately for 2.5 months as compared to the previous management without TAI protocols.

Effect of early luteolysis in progesterone-based timed AI protocols in Bos indicus, Bos indicus×Bos taurus, and Bos taurus heifers

The objective of this study was to evaluate the effects of treatment with an intravaginal progesterone-releasing device (CIDR) and estradiol benzoate (EB) on follicular dynamics in Bos indicus (n=23), Bos taurus (n=25), and cross-bred (n=23) heifers. To assess the influence of reduced serum progesterone concentrations during 8 days of treatment with a progesterone-releasing device on follicular dynamics, half of the heifers received PGF at CIDR insertion (Day 0; 3 x 2 factorial design). Mean (+/-S.E.M.) serum progesterone concentrations during CIDR treatment varied (P<0.05) among genetic groups: B. indicus (5.4+/-0.1 ng/mL), B. taurus (3.3+/-0.0 ng/mL), and cross-bred (4.3+/-0.1 ng/mL). Maximum diameter of the dominant follicle (DF) was smaller (P<0.01) in B. indicus heifers (9.5+/-0.5 mm) than in cross-bred (12.3+/-0.4 mm) or B. taurus heifers (11.6+/-0.5 mm). B. indicus experienced lower (P<0.01) ovulation rate (39.1%) than did B. taurus (72.7%) and cross-bred (84.0%). Heifers treated with PGF on Day 0 had lower (P<0.05) serum progesterone concentrations during progesterone treatment. The PGF treatment on Day 0 increased (P<0.01) the diameter of the DF (11.9+/-0.4 mm vs. 10.5+/-0.4 mm). Moreover, greater (P=0.02) ovulation rates (78.8 vs. 54.0%) occurred in heifers treated with PGF on Day 0. In summary, B. indicus heifers had greater serum progesterone concentrations, smaller DF diameter, and a lower ovulation rate compared to B. taurus heifers. Prostaglandin treatment on the day of CIDR insertion reduced serum progesterone during treatment, and resulted in increased maximum DF diameter and ovulation rate.