Reduced period from follicular wave emergence to luteolysis generated greater steroidogenic follicles and estrus intensity in dairy cows.

The onset of productive life in dairy cattle, concomitant to parturition, is accompanied by a substantial decrease in fertility in comparison with non-lactating, nulliparous heifers. Follicular growth patterns differ between parous and nulliparous dairy cattle. Nulliparous heifers ovulate follicles with reduced antral age (RAA). This study aimed to exogenously reduce ovulatory follicle age in lactating dairy cows from 7 to 5 days old. Cows (n = 80) had their estrous cycles synchronized with the Double-Ovsynch program. At the final portion of this program, luteolysis was induced at either 5 (RAA) or 7 (Control) days following follicular wave emergence. RAA outcomes were estimated in comparison with Controls. RAA resulted in smaller follicles 2 days post-treatment. Despite lower serum concentrations of 17ß-estradiol before treatment compared with Controls, the rate of increase in this hormone was greater for the RAA treatment. There was no difference in luteolysis rates between treatments. Proestrus (luteolysis onset to estrus onset) was prolonged in RAA cows. Cows with RAA had more intense estruses. Collectively, these results indicate that decreasing the age of the ovulatory follicle may improve the steroidogenic capacity of the dominant follicle and estrus expression intensity in lactating dairy cows.

Review: Initial increase in pregnancy-specific protein B in maternal circulation after artificial insemination is a key indicator of embryonic survival in dairy cows.

Lactating dairy cows have reduced chances for pregnancy survival following 1st parturition. It appears that timing of conceptus attachment, defined as an initial daily rise in pregnancy-specific protein B (PSPB) postartificial insemination (AI), is key to the survival of the embryo. PSPB is a protein produced from binucleate cells of the trophectoderm of the conceptus. Once the conceptus has attached to the uterine epithelial cells, this large protein is detectable in maternal circulation. Daily sampling of serum allows for detection of the initial increase of PSPB. A percent increase threshold for PSPB was determined from results from each study using a conservative three-day minimum increase. Thus far, a 10 or 12.5% daily increase for three consecutive days had the greatest sensitivities and specificities for studies reported in this review. Nulliparous heifers receiving AI following estrus appear to have a reduced time to conceptus attachment compared to lactating cows that received either Ovsynch or AI following estrus. Increasing progesterone post-AI did not reduce time to conceptus attachment in lactating cows. Multiparous cows treated post-AI with human chorionic gonadotropin had a reduced percent with conceptus attachment in addition to greater time to conceptus attachment. Increased time to conceptus attachment increased the chances of multiparous cows having embryonic death before 35 d post-AI. Concentrations of PSPB are consistently reduced from conceptus attachment until d 28 post-AI in cows with pregnancy loss compared to cows that maintain pregnancy on d 34 post-AI. This novel model to determine timing of conceptus attachment provides a new perspective on percent of cows pregnant around d 20-23 post-AI and the potential for a greater understanding of subsequent pregnancy loss.

Time to increase in pregnancy-specific protein B following artificial insemination is a direct determinant of subsequent pregnancy loss in lactating dairy cows.

Increasing progesterone (P4) during early conceptus development may be crucial for establishment of pregnancy in dairy cattle. The objective of this study was to determine if human chorionic gonadotropin (hCG) at various times after ovulation will increase serum P4 during elongation and increase the chances for, and reduce variability to, initial increase in pregnancy-specific protein B (PSPB) following artificial insemination (AI). Time to PSPB increase was defined as the first day of increase in concentrations of PSPB between d 18 and 28 after ovulation in cows with ≥12.5% increases for 3 consecutive days compared with baseline. Lactating cows (n = 368) synchronized to Double-Ovsynch (first service) or Ovsynch (second or greater service) received one of 4 treatments: no hCG (control), or 3,000 IU of hCG on d 2 (D2), 2 and 5 (D2+5), or 5 (D5) after ovulation. All cows were examined via ultrasound on d 5 and 10 postovulation to determine percentage of cows with hCG-induced accessory CL (aCL) and to quantify and measure all luteal structures. Samples for serum P4 were collected on d 0, 5, 19, and 20 postovulation. The P4 was increased in D2, D2+5, and D5 groups compared with control. The D2+5 and D5 treatments increased aCL and P4 compared with D2 and control. The D2 treatment increased P4 on d 5 after ovulation compared with control. Serum PSPB samples were collected daily from all cows on d 18 through 28 after ovulation for determination of d of PSPB increase. Pregnancy diagnoses were performed via ultrasound examination on d 35, 63, and 100 after ovulation and AI. The D5 treatment reduced percentage of cows with, and increased the time to, PSPB increase. Primiparous cows with ipsilateral aCL had reduced pregnancy loss before d 100 postovulation compared with cows with contralateral aCL. Cows that had PSPB increase >21 d postovulation had 4× greater chances of pregnancy loss compared with cows that had PSPB increase on d 20 or 21. The highest quartile of P4 on d 5, but not on d 19 and 20, was associated with reduced time to PSPB increase. Time to PSPB increase appears to be an important measurement to understand reasons for pregnancy loss in lactating dairy cows. Increasing P4 utilizing hCG after ovulation did not enhance early pregnancy or reduce pregnancy losses in lactating dairy cows.

The high fertility cycle.

The development of fertility programs and their adoption by the dairy industry over the past decade is a major driving factor underlying the dramatic increase in reproductive performance in lactating dairy cows during the past 20 years. Another major driving factor underlying this increase in reproductive performance is what we describe in this minireview as the "high fertility cycle." We now know that reproductive performance and the incidence of certain periparturient health events are interrelated. The high fertility cycle describes the relationship between body condition score (BCS) change during the periparturient period and postpartum health events and subsequent reproductive performance in which lactating dairy cows that establish pregnancy by 130 d in milk have shorter calving intervals and thereby gain less BCS during the current lactation and dry off and calve at a lower BCS (2.75 to 3.0) than cows with a longer lactation. After calving, these cows undergo less BCS loss, experience fewer health issues, have greater fertility at first insemination, and have reduced early pregnancy losses after establishment of pregnancy and thereby become pregnant before 130 d in milk. This minireview overviews these relationships and highlights the key concepts underlying the high fertility cycle. Future randomized, controlled experiments are needed to causally link these relationships between BCS change and fertility in lactating dairy cows.

Dairy heifers have an earlier increase in serum pregnancy-specific protein B compared with lactating dairy cows. Is this an indicator of earlier conceptus attachment?

This study was designed to use within-individual daily increases in circulating pregnancy-specific protein B (PSPB) to determine time to increase in serum PSPB in nulliparous heifers and multiparous dairy cows following artificial insemination (AI). Weekly cohorts of lactating Holstein cows (n = 56) averaging 122 ± 7 d in milk at AI and nulliparous Holstein heifers (n = 23) averaging 16 ± 0.24 mo old at AI were used in this study. Lactating cows received AI to either Ovsynch (n = 38) or at ~12 h following observed standing estrus (n = 18). All heifers were inseminated ~12 h after observed standing estrus. Blood samples for measurement of PSPB were collected daily from d 15 through d 35 postovulation. Nulliparous heifers had increases in serum PSPB earlier compared with both primiparous and multiparous cows. Day of increase in serum PSPB was defined as the day serum PSPB optical density levels initially increased ≥10% from baseline and continued to increase from baseline of ≥10% the following 2 d. Average PSPB were greater in pregnant heifers compared pregnant cows from d 23 through 29. Early lactation nonpregnant cows maintained greater average optical density of serum PSPB from 15 to 35 d postovulation compared with nonpregnant heifers (n = 38). In summary, fertility differences in heifers versus lactating cows may be due to the differences in timing of increases in serum PSPB. This appears to be one of the first publications that used daily PSPB sampling to investigate possible differences in fertility in heifers versus lactating cows.

The effect of a double dose of cloprostenol sodium on luteal blood flow and pregnancy rates per artificial insemination in lactating dairy cows.

Inadequate luteolysis in fertility programs is a problem for lactating dairy cows treated with a single dose of PGF2α. The proportion of cows with complete luteolysis can be increased by administering 2 doses of PGF2α 24 h apart. This study hypothesized that a double dose of cloprostenol sodium (1.0 mg) could take the place of 2 doses 24 h apart due to its enhanced half-life. Cows were allocated to receive 1 of 3 treatments: negative controls: 0.5 mg of cloprostenol sodium (single; n = 337); positive controls: two 0.5-mg doses of cloprostenol sodium 24 h apart (two/24; n = 313); and treated: 1.0 mg of cloprostenol sodium (double; n = 298) at the final PGF2α of Double-Ovsynch. Cows received artificial insemination (AI) 16 h after final GnRH of Double-Ovsynch. Pregnancy diagnosis was determined at 24, 34, 62, and 184 d post-AI. Pregnancy loss was categorized in the following periods: between 24 to 34, 34 to 62, and 62 to 184 d post-AI. Ultrasonography (B-mode and color Doppler) was used to assess luteal function pre- and posttreatment with various doses of cloprostenol sodium. Luteal volume and luteal blood flow (LBF) from d 7 and 14 corpora lutea were determined before treatment (d -1), and 2 and 4 d after treatment. No evidence was observed of an effect of treatment on pregnancy rates per AI at 24, 34, or 62 d post-AI. No effect was observed of treatment on pregnancy losses occurring between d 24 and 34, 34, and 62, and between 62 and 184 d post-AI. However, third-plus parity cows treated with the single treatment had greater pregnancy loss compared with two/24 and double between d 24 and 34 post-AI. Third-plus parity cows that received the double treatment had lower LBF 2 and 4 d after treatment compared with cows treated with single. Amount of LBF present 4 d after treatment was not a predictor of pregnancy or pregnancy loss. A double dose (1.0 mg) of cloprostenol sodium may be a feasible alternative for fertility programs based on nondifferent outcomes to the two/24 treatment, lower pregnancy losses, and reduced LBF disappearance following treatment in third-plus parity cows in comparison with the single treatment.

Effect of cloprostenol sodium dose on luteal blood flow and volume measurements in Holstein heifers with both day-4 and day-10 corpora lutea.

Establishment of a vascular system within the corpus luteum (CL) is critical for progesterone (P4) secretion. Measurement of luteal blood flow (LBF) may be a feasible way to determine luteolysis induced with cloprostenol sodium (CLO). Our overall objective was to establish timelines to assess luteolysis via Doppler ultrasonography. Estrous cycles were synchronized in 11- to 12-mo-old Holstein heifers (n = 37). Heifers were injected CLO at a random stage of the estrous cycle 12 d from treatment. Gonadotropin-releasing hormone (GnRH) was administered 2 (d -10) and 8 d (d -4) after the initial CLO. This satisfied the study objective of inducing simultaneous presence of CL at d 4 of development (D4 CL) and CL at d 10 of development (D10 CL) on the day of treatment with different CLO doses (hereafter referred to as d 0). Heifers were randomly assigned to 1 of 5 treatments on d 0: negative control (NC) consisting of no treatment with CLO (n = 8); a quarter dose of CLO (0.125 mg; n = 8); half dose of CLO (0.25 mg; n = 8); full dose of CLO (0.5 mg; n = 8); or positive control (PC) consisting of 4 doses of 0.5 mg of CLO at 24-h intervals starting at d 0 (n = 5). Data collection was performed at d 0 (before and 1 h after treatment) and 2, 4, 6, and 8 d following treatment, to determine luteal volume (LV), LBF, and circulating concentrations of P4. Both NC and PC were efficient in mimicking physiological scenarios that occur during normal luteal development and luteolysis. Heifers that received PC had complete LBF disappearance of both D4 and D10 CL between d 2 and 4 after the first of 4 CLO treatments given 24 h apart (average 4.0 ± 0.0 and 3.2 ± 0.7 d, respectively). Complete LBF disappearance was used as a luteolysis marker. Treatment with different doses of CLO did not impair luteal development of the D4 CL. However, concurrent complete LBF disappearance for D10 CL in heifers treated with half (5/8 heifers) and full doses of CLO (8/8 heifers) resulted in less LBF in the half dose, and less LV and LBF in the full-dose treatment, in D4 CL at d 8 post-treatment, compared with NC. Treatment with various doses of CLO induced an acute increase in LBF 1 h after treatment, regardless of dose in D10 but not in D4 CL. We found a lack of dose response in LV reduction of D4 and D10 CL. Interestingly, LV of the D10 CL decreased in untreated NC between d 0 and 8 after treatment (d 10-18 of luteal development). Assessment with color Doppler ultrasound was sensitive enough to identify dose-response patterns in Holstein heifers (absence, partial, or complete luteolysis) following various doses of CLO. Variability in time to complete LBF disappearance of mature D10 CL following a full dose of CLO limits the use of Doppler ultrasonography to detect luteolysis at a single time point following treatment.

Short communication: Blood samples before and after embryonic attachment accurately determine non-pregnant lactating dairy cows at 24 d post-artificial insemination using a commercially available assay for pregnancy-specific protein B.

Early pregnancy diagnosis is critical to reproductive success on dairy farms. Reproductive success depends on cows becoming pregnant before 130 d in milk and then maintaining that pregnancy. The earlier non-pregnant cows are identified, the sooner they can be reinseminated, thus reducing days to pregnancy. Assays for pregnancy-specific protein B (PSPB) and pregnancy-associated glycoproteins can be used to diagnose pregnancy >28 d post-artificial insemination (AI) in lactating cows. The objective of this study was to determine whether percentage change in serum levels of PSPB within cow from d 17 to 24 can be used to identify non-pregnant cows using a commercially available assay. This study was performed on a large commercial dairy. Blood samples were taken at d 17 and 24 post-AI. The d 17 sample served as a baseline based on previous data. Cows with a 10% increase in serum PSPB levels from d 17 to 24 were considered pregnant. Lactating dairy cows (n = 206; 39% primiparous and 61% multiparous) were synchronized using G6G-Ovsynch. The PSPB diagnosis was compared with the herd veterinarian's diagnosis via ultrasound on d 34. The sensitivity for a 10% cutoff as a non-pregnant diagnosis was 100%, and the specificity was 93.58%. The positive predictive value was 93.27%, and the negative predictive value was 100%. Low PSPB levels at d 24 were predictive of early pregnancy loss by 60 d post-AI. To our knowledge no other method can diagnose non-pregnancy with 100% accuracy and predict pregnancy loss earlier than 24 d post-AI. Using comparative PSPB samples at d 17 and 24 post-AI provides an accurate non-pregnancy diagnosis earlier than any other pregnancy diagnosing method.

The high-fertility cycle: How timely pregnancies in one lactation may lead to less body condition loss, fewer health issues, greater fertility, and reduced early pregnancy losses in the next lactation.

Body condition loss during early lactation varies among cows in the herd and is associated with future health and reproductive outcomes. The objective of this study was to gain a greater understanding of the relationship between previous calving interval and body condition change during the first 30 d in milk (DIM) and their relationship to subsequent fertility and health variables and sex ratio at birth. Dry cows and heifers (n = 851) from a single farm entered the study approximately 25 d before the due date. They were evaluated and given a body condition score on a 1-to-5 scale with 0.1-point increments weekly until parturition. Body condition score was assessed within 1 wk of parturition and then again 27 to 33 DIM. Previous calving interval, gestation length, periparturient health events (giving birth to twins, dystocia, retained placentas, ketosis, metritis, and displaced abomasum), sire net merit ($), and milk data were used for each cow as recorded in PCDART (Dairy Records Management Systems, Raleigh, NC) by the herd managers. Longer previous calving intervals were related to greater body condition at parturition and body condition loss during the first 30 DIM. A 75% greater proportion of cows with a calving-to-pregnancy interval shorter than 130 d maintained or gained body condition during the first 30 DIM compared with cows with calving-to-pregnancy intervals longer than 130 d. Multiparous cows that maintained or gained body condition (n = 144) had greater pregnancies per AI following first service compared with cows that lost body condition (n = 577) during the first 30 DIM when health events were considered or removed. When cows with health events were considered, multiparous cows that maintained or gained body condition had a greater percentage pregnant by 130 DIM compared with cows that lost body condition (67 vs. 55%; n = 522). Cows that lost body condition during the first 30 DIM regardless of health events experienced greater pregnancy loss (n = 224) between 35 and 60 d after first AI (0.0 vs. 6.7%) compared with cows that maintained or gained body condition (n = 69) during that period. Based on data in this study from a single herd, maintaining a cycle of pregnancy before 130 DIM may reduce the amount of body condition lost after the next parturition, enhance subsequent pregnancies per AI, and reduce the possibility of early pregnancy loss. We refer to this phenomenon as the high-fertility cycle.

Level of circulating concentrations of progesterone during ovulatory follicle development affects timing of pregnancy loss in lactating dairy cows.

The objective of this experiment was to determine the effect of high versus low progesterone (P4) during the pre-dominance or dominance phase (or both) of ovulatory follicle development on follicular dynamics and fertility of lactating dairy cows. Progesterone (P4) was manipulated to reach high (H) or low (L) serum concentrations during the pre-dominance phase (d 0 to 4 of the wave) and dominance phase (d 5 to 7 of the wave) of a second follicular wave ovulatory follicle, creating 4 treatments: H/H, H/L, L/H, and L/L. Luteolysis was induced with PGF2α on d 7 of the wave and ovulation was induced with GnRH 56 h after PGF2α. Cows (n = 558) received artificial insemination (AI) 16 h following GnRH. Pregnancy was determined at 6 intervals during gestation and at calving to quantify pregnancy loss beginning at d 23 post-AI utilizing pregnancy-specific protein B (PSPB) in novel within-cow comparisons. Cows with single ovulations assigned to the L/L treatment had greater pre-ovulatory follicle diameter compared with cows assigned to the L/H or H/L treatments. Cows with single ovulations had greater pre-ovulatory follicle diameter compared with cows with double ovulations. Low P4 in H/L, L/H, and L/L increased double ovulation rate compared with H/H. Cows with double ovulations had greater pregnancies per AI (P/AI) on d 23 post-AI compared with cows with single ovulations but had greater losses if ovulations were unilateral. Cows with low P4 during the entire period of the ovulatory follicle development also had greater P/AI on d 23 post-AI compared with cows with high P4 during both phases. However, full-term P/AI was not different between treatments. This was a result of the greater incidence of pregnancy losses between d 35 and 56 of gestation for cows with unilateral double ovulations compared with bilateral double ovulations and single ovulatory cows. Cows with single ovulation and low circulating P4 during the dominance period of follicle development had increased pregnancy losses between d 35 and 56 of gestation compared with cows with single ovulations and high P4. The PSPB measurements on d 16 and 23 post-AI were highly accurate in the prediction of pregnancy at d 28. The PSPB differed on d 23 and 28 between cows that had versus cows that did not have pregnancy losses between d 28 and 35 of gestation. In summary, circulating concentrations of P4 during ovulatory follicle development affected numbers of follicles ovulated and timing of subsequent pregnancy losses.

A single ultrasound determination of ≥25 follicles ≥3 mm in diameter in dairy heifers is predictive of a reduced productive herd life.

Fertility and productive herd life (time in herd after birth of first calf) are inferior in dairy cows with relatively low compared with intermediate but not high numbers of follicles growing during ovarian follicular waves. The present study, therefore, tested the hypothesis that fertility and productive herd life are lower in dairy heifers with high follicle numbers compared with age-matched herdmates with fewer follicles. To test this hypothesis, 11 to 15 mo old Holstein heifers were subjected to a single ultrasound measurement of the number of follicles ≥3 mm in diameter. Heifers were classified into a high- (≥25 follicles), mid- (16-24), or low-range (≤15) follicle number group (FNG). All heifers not removed from the herd before first calving (n = 408) had the opportunity to start their fifth or sixth lactation after birth of their first calf. During this time, performance and health parameters for each individual were recorded daily by herd managers. Results showed that heifers in the high-range FNG had a 180-d shorter productive herd life, reduced survival rate, and greater probability of being culled after birth of the first calf, as well as fewer lactations compared with heifers in the low-range FNG. Cows in the high-compared with the mid- or low-range FNG also had greater involuntary culling rates, days open, and services per conception, and lower pregnancy rates during the first, second, or third lactations. We concluded that dairy heifers with ≥25 follicles ≥3 mm in diameter have suboptimal fertility and a shorter productive herd life compared with herdmates with fewer follicles.

The effect of presynchronization with prostaglandin F2α and gonadotropin-releasing hormone simultaneously, 7 d before Ovsynch, compared with Presynch-10/Ovsynch on luteal function and first-service pregnancies per artificial insemination.

Pregnancy per artificial insemination (P/AI) following Ovsynch is optimized when cows ovulate to the first GnRH of Ovsynch. Fertility programs are designed to presynchronize cows to d 6 or 7 of the estrous cycle to increase the chances of ovulation of a first-wave dominant follicle to the first GnRH of Ovsynch. The hypothesis of this experiment was that simplification of a presynchronization program through the combination of PGF2α and GnRH on the same day, 7 d before Ovsynch, would allow for similar P/AI compared with Presynch-10. Lactating dairy cows (n = 432) 41 to 47 d in milk (DIM) were randomly assigned to 2 treatments within parities for first service. Control cows received Presynch-10/Ovsynch consisting of the following: PGF2α-14 d-PGF2α-10 d-GnRH-7 d-PGF2α-56 h-GnRH-16 h-AI. Treated cows received PGF2α and GnRH-7 d-GnRH-7 d-PGF2α-56 h-GnRH-16 h-AI. All cows received a supplemental injection of PGF2α 24 h after the PGF2α of Ovsynch to enhance complete luteolysis. All cows received timed AI between 75 and 81 DIM. Blood was collected to assess circulating concentrations of progesterone (P4), and the number and size of corpora lutea (CL) were recorded using ultrasonography on day of PGF2α of Ovsynch. The administration of PGF2α simultaneously with GnRH and 7 d before Ovsynch (PG+G) had similar P/AI at 28 (46 vs. 48%), 35 (43 vs. 43%), 49 (39 vs. 39%), and 77 d post-AI (38 vs. 39%) compared with Presynch-10. No differences were observed in P/AI in primiparous versus multiparous cows at 28 (52 vs. 45%), 35 (48 vs. 41%), 49 (45 vs. 37%), and 77 d post-AI (43 vs. 36%). No difference existed between treatments in percentage of cows with functional CL at PGF2α of Ovsynch, total luteal area (mm2), or serum concentrations of P4 at time of PGF2α of Ovsynch, regardless of parity. Number of CL had a tendency to be greater for multiparous PG+G vs. Presynch-10 cows (2.34 ± 0.09 vs. 2.15 ± 0.08) but not in primiparous cows (1.95 ± 0.10 vs. 1.98 ± 0.11). In summary, administering both PGF2α and GnRH on the same day, 7 d before the start of Ovsynch, appears to be a simple and effective alternative to Presynch-10 Ovsynch.

Effect of timing of insemination after CIDR removal with or without GnRH on pregnancy rates in Nili-Ravi buffalo.

There are limited studies available on when to inseminate, if using CIDR or CIDR-GnRH protocols for optimal fertility in buffalo. Therefore, the objective of the present study was to determine the optimum time of AI in relation to CIDR removal with or without GnRH in buffalo. All buffalo (n=201) received CIDR on Day 0, PGF2α on Day 6 and CIDR were removed on Day 7. In 50 of these buffalo GnRH was administered 36 h after CIDR removal. Furthermore, CIDR (n=151) and CIDR-GnRH (n=50) were randomly divided to receive timed artificial insemination (TAI), either at 48, 60 or 72 h after CIDR removal. Ultrasonography was performed for follicular development and for pregnancy diagnosis. The results revealed that, mean interval to ovulation was shorter (P<0.05) in buffalo receiving CIDR-GnRH than CIDR (68.40 ± 1.73 compared with 76.13 ± 1.66 h, respectively). The pregnancy rates were higher (P<0.05) in buffalo inseminated either at 48 (50%) or 60 (59%) than at 72 h (18%) in CIDR-GnRH protocol; whereas, in CIDR buffalo pregnancy rates were higher (P<0.05), at 60 (37%) or 72 (40%) than at 48 h (10%). In conclusion, the optimal time of AI is between 48-60 h in CIDR-GnRH and between 60-72 h in CIDR protocol for enhancing fertility in buffalo.

Concentration of anti-Müllerian hormone in dairy heifers is positively associated with productive herd life.

Reliable biomarkers predictive of productive herd life (time in herd after birth of first calf) have heretofore not been discovered in dairy cattle. However, circulating concentrations of anti-Müllerian hormone (AMH) are positively associated with number of follicles or antral follicle count (AFC), ovarian function, and fertility, and approximately 25% of cows have a relatively low AFC and low AMH concentrations. The present study tested the hypothesis that heifers with the lowest AMH concentrations have suboptimal fertility and are removed from a herd for poor reproductive performance at a greater rate, and therefore have a shorter productive herd life compared with age-matched herdmates with higher AMH. To test this hypothesis, 11- to 15-mo-old Holstein heifers (n=281) were subjected to a single measurement of AMH. All heifers not removed from the herd had the opportunity to complete 2 lactations and start their third lactation after calving. During this time, performance and health parameters for each individual were recorded daily by herd managers. Results showed that the quartile of heifers with the lowest AMH concentration also had, on average, a shorter productive herd life (by 196 d), a reduced survival rate after birth of the first calf, the lowest level of milk production (first lactation), the lowest total percentage of cows pregnant (across all lactations), the highest culling rates (first and second lactations and overall), and the highest culling rate for poor reproduction (first lactation) compared with age-matched herdmates with higher AMH. We concluded that a single determination of AMH concentration in young adult dairy heifers may be a simple diagnostic method to predict herd longevity, and AMH may be a useful phenotypic marker to improve longevity of dairy cows.

Compared to dinoprost tromethamine, cloprostenol sodium increased rates of estrus detection, conception and pregnancy in lactating dairy cows on a large commercial dairy.

Using two PGF(2α) treatments 14 days apart as a way to enhance estrus detection rate following the 2nd treatment is a reproductive management tool that continues to be used on large dairy farms. In one study, in cows with a functional CL and a dominant follicle, treatment with cloprostenol vs. dinoprost resulted in greater peripheral estradiol concentrations. The objective of the present study was to determine if cloprostenol could enhance pregnancy rates of cows in a large dairy herd using a PGF(2α) program for 1st artificial insemination (AI). Lactating dairy cows (n = 4549) were randomly assigned to receive two treatments of either 500 µg cloprostenol or 25 mg dinoprost 14 days apart, with the 2nd treatment on the 1st day of the voluntary waiting period (57 DIM). Cows detected in estrus within 5 days after the 2nd treatment were inseminated. There was no effect of treatment on day of estrus detection, with 78% of cows inseminated on Days 3 or 4 following treatment. Cloprostenol increased (P < 0.01) estrus detection rates in 1st parity cows compared to dinoprost, 42.4 vs. 34.0%. In cows inseminated on Days 3 or 4 after treatment, cloprostenol increased (P = 0.05) conception rates compared to dinoprost, 38.3 vs. 34.4%. When treatments and parities were combined, conception rates increased (P < 0.02) with interval after treatment (27.0, 36.4, and 44.5% for Days 1 or 2, Days 3 or 4, and Day 5, respectively). Cloprostenol increased (P = 0.02) overall pregnancy rate compared to dinoprost, 14.4 vs. 12.2%. In summary, cloprostenol increased fertility in 1st parity cows inseminated on Days 3 or 4 following treatment and subsequently enhanced pregnancy rates of 1st parity lactating dairy cows compared to dinoprost. Fertility appeared greater in cows expected to have had a young antral ovarian follicle at treatment.

Luteolytic effects of cloprostenol sodium in lactating dairy cows treated with G6G/Ovsynch.

The probability of a pregnancy decreases substantially in lactating dairy cows treated with Ovsynch if luteolysis is delayed or incomplete. Two PGF(2α) products are currently approved in the United States for luteolysis in lactating dairy cattle, dinoprost tromethamine and cloprostenol sodium. Cloprostenol has a longer half-life compared with dinoprost, is more resistant to endogenous metabolism, and is maintained in circulation longer. We hypothesized that cloprostenol could reduce the time to complete luteolysis compared with dinoprost because of differences in half-life. Lactating dairy cows received the same presynchronization strategy (G6G; 25mg of PGF(2α) - 2 d - 100 µg of GnRH - 6 d - 100 µg of GnRH - 7 d - final PGF(2α) treatment). At the time of the final PGF(2α), cows (n=35) were randomly assigned to receive either 500µg of cloprostenol or 25mg of dinoprost. Blood samples were collected daily before and serially after PGF(2α) treatment to analyze circulating concentrations of progesterone (P(4)) and estradiol (E(2)). Ultrasound examinations of ovaries were performed to measure sizes of follicles and corpora lutea (CL) and determine time of ovulation. Considering only cows with complete luteolysis, mean circulating P(4) was lower for cows given cloprostenol than for those given dinoprost between 0 and 12h postinjection, but not at 24, 36, or 48 h. A rapid decrease in P(4) was observed 1h after PGF(2α) (6.54 ± 0.27 to 3.77 ± 0.22 ng/mL) followed by a complete rebound 1h later (3.77 ± 0.22 to 5.07 ± 0.31 ng/mL) followed by a steady decline in both treatment groups. Serum concentrations of E(2) were greater at 48 h posttreatment in cloprostenol-treated cows (2.74 ± 0.15 pg/mL) than in dinoprost-treated cows (2.37 ± 0.19 pg/mL). Cows that did not have complete luteolysis did not ovulate (0/7) during the 6-d period following treatment. Time to complete luteolysis and ovulation was 29.1 ± 1.1 versus 29.4 ± 1.7 and 101 versus 103 h posttreatment in cloprostenol compared with dinoprost. A negative relationship was observed between P(4) at 12h posttreatment and concentrations of E(2) 48 h posttreatment (b=-0.6905; R(2)=0.23). In summary, cows treated with cloprostenol had lower concentrations of P(4) for the first 12h following treatment and subsequently greater concentrations of E(2) compared with dinoprost, although no differences were observed in these 2 PGF(2α) analogs for time to complete luteolysis or time to ovulation.

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.

Managing the dominant follicle in high-producing dairy cows.

Reduced reproductive efficiency has been reported in high-producing dairy cows. Sources of reproductive inefficiency include decreased expression of estrus, increased diameter of the ovulatory follicle and reduced fertility when cows are inseminated after estrus, increased incidence of double ovulation and twinning, and increased pregnancy loss. To overcome some of these inefficiencies, reproductive management programs have been developed that synchronize ovulation and enable effective timed artificial insemination (AI) of lactating dairy cows. Effective regulation of the corpus luteum (CL), follicles, and hormonal environment are critical for optimizing these programs. Recent programs, such as the 5-day CIDR program, Double-Ovsynch, G-6-G, and estradiol benzoate-CIDR programs were designed to more effectively control one or more physiological events. These events include synchronization of a new follicular wave at the beginning of the program, optimization of the circulating progesterone (P4) concentrations and duration of follicular dominance, optimized reductions in P4 and increases in circulating estradiol (E2) concentrations during the preovulatory period, and tightly synchronized ovulation of a follicle of optimal size and fertility for implementation of timed AI. The success of these programs has been remarkable, although there is substantial variability in effectiveness due to environmental, management, nutritional, genetic, and disease factors as well as potential variability in some aspects of reproductive physiology among commercial dairy farms. Future programs will optimize the reproductive physiology while simplifying the protocol implementation and also match specific reproductive management protocols to specific farms and even specific cows (for example primiparous vs. multiparous).

Detection of anovulation by heatmount detectors and transrectal ultrasonography before treatment with progesterone in a timed insemination protocol.

Our objective was to determine the accuracy of identifying noncycling lactating dairy cows before the application of a timed artificial insemination (AI) protocol [with or without progesterone supplementation via a controlled internal drug-release (CIDR) insert and 2 different timings of AI] by using heatmount detectors and a single ovarian ultrasound examination. At 6 locations in the Midwest, 1,072 cows were enrolled in a Presynch protocol (2 injections of PGF(2alpha) 14 d apart), with the second injection administered 14 d before initiating the Ovsynch protocol (injection of GnRH 7 d before and 48 h after PGF(2alpha) injection, with timed AI at 0 or 24 h after the second GnRH injection). Heatmount detectors were applied to cows just before the first Presynch injection, assessed 14 d later at the second Presynch injection (replaced when activated or missing), and reassessed at initiation of the Ovsynch protocol. Ovaries were examined for the presence of a corpus luteum (CL) by ultrasound before the initiation of treatment. Treatments were assigned to cows based on the presence or absence of a CL detected by ultrasound: 1) no CL + no CIDR; 2) no CL + CIDR insert for 7 d; and 3) CL present. Further, alternate cows within the 3 treatments were assigned to be inseminated concurrent with the second GnRH injection of Ovsynch (0 h) or 24 h later. Pregnancy was diagnosed at 33 and 61 d after the second GnRH injection. By using low (<1 ng/mL) concentrations of progesterone in serum as the standard for noncycling status, heatmount detectors were activated on a large percentage of noncycling cows (>60%), whereas the single ultrasound examination incorrectly classified noncycling cows only 21% of the time. Conversely, cycling cows (progesterone > or =1 ng/mL) were correctly identified 70 to 78% of the time by heatmount detectors, but 85 to 92% were correctly identified by ultrasound. Overall accuracy of heatmount detectors and ultrasound was 71 and 84%, respectively. Application of progesterone to cows without a CL at the time of the first injection of GnRH reduced the incidence of ovulation but increased the proportions of pregnancies per AI at d 33 or 61 compared with nontreated cows without a CL at the onset of the Ovsynch protocol. Percentages of cows pregnant and pregnancy survival did not differ for cows having a CL before treatment compared with those not having a CL and treated with progesterone. Compared with no response, when a follicle ovulated in response to the first GnRH injection, percentage of cows becoming pregnant after the timed AI increased from 33.3 to 41.6%. Timing of AI at 0 or 24 h after the second GnRH injection did not alter pregnancies per AI, but cows having luteal activity before treatment had improved pregnancies per AI compared with noncycling cows. We conclude that identifying noncycling cows by ultrasound was more accurate than by heatmount detectors. Subsequent progesterone treatment of previously cycling cows not having a CL at the onset of Ovsynch increased the proportion of pregnant cows, equal to that of cows having a CL but not treated with progesterone.

Optimizing ovulation to first GnRH improved outcomes to each hormonal injection of ovsynch in lactating dairy cows.

Ovulatory response to the first GnRH of Ovsynch is the critical determinant for successful synchronization of ovulation in dairy cows. Our objective in this study was to develop a pre-Ovsynch treatment that increased the percentage of cows that ovulated in response to the first GnRH injection of Ovsynch. To accomplish our goal, we evaluated a hormonal strategy that consisted of PGF2alpha and GnRH before the first GnRH of Ovsynch. Lactating dairy cows (n = 137) were assigned to receive either no treatment before Ovsynch (control) or 25 mg of PGF2alpha (PreP) followed 2 d later by 100 microg of GnRH (PreG), administered 4 (G4G), 5 (G5G), or 6 (G6G) d before initiating the Ovsynch protocol. Transrectal ultrasonography was performed to assess follicular size and resulting ovulation, and blood samples were collected to measure circulating concentrations of progesterone and estradiol immediately before each hormonal injection. Cows were inseminated at a fixed time 16 h after final GnRH of Ovsynch. Pregnancy diagnosis was performed 35 d later by palpation per rectum of uterine contents. Proportion of cows that ovulated to first GnRH of Ovsynch was 56.0, 66.7, 84.6, and 53.8% for G4G, G5G, G6G, and controls, respectively, and was greater for G6G than for control cows. Luteolytic response to PGF2alpha of Ovsynch was greater in all treated than control cows (92.0, 91.7, 96.2, and 69.2% for G4G, G5G, G6G, and control, respectively). Synchronization rate to Ovsynch was greater (92 vs. 69%, respectively) in G6G than in control cows. In addition, cows that ovulated in response to first GnRH of Ovsynch had greater response to PGF2alpha of Ovsynch (92.7 vs. 77.1%, respectively) and greater synchronization rate to the overall protocol (87.9 vs. 62.9%, respectively) than those that did not ovulate. Concentrations of progesterone at PGF2alpha of Ovsynch, and estradiol and follicle size at final GnRH of Ovsynch, were identified as significant predictors of probability of pregnancy 35 d after artificial insemination. In summary, a PGF2alpha-and-GnRH based pre-Ovsynch strategy consisting of a 6-d interval between PreG and first GnRH of Ovsynch resulted in a greater ovulatory and luteolytic response to first GnRH and PGF2alpha of Ovsynch, respectively, compared with control cows. This, in turn, optimized synchronization rate to Ovsynch.