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

Presynchronization with a progesterone device and prostaglandin F2α enhances ovulatory response to first GnRH, estrus expression and tended to increase fertility in beef heifers submitted to a 5-day CO-Synch protocol

The main objectives of the present study were to determine the effects of presynchronizing with a 1.0 g intravaginal progesterone device (IVPD) and prostaglandin F2α and to assess the effects of re-utilization of IVPD in a 2x2 factorial design, on the ovulatory response to first GnRH, ovarian status at different protocol stages, estrus expression and fertility in beef heifers submitted to a 5d-CO-Synch + Progesterone (P4) protocol. Beef heifers (n = 564) were assigned to 1 of 2 treatments at D-15: Pres5 (n = 283), where heifers received a (IVPD) for 5 days and administration of prostaglandin F2α (25 mg of dinoprost) at D-10; and Control (n = 281), where heifers received no treatment. At D-8, all heifers received 100 μg of GnRH (gonadorelin acetate) and were assigned to 1 of 2 IVPD-use treatments: new-IVPD (n = 279), where animals received a new IVPD for 5 days, and once-used IVPD (n = 285), where heifers received a once-used IVPD for 5 days (used previously for 5 days). On D-3, IVPD was removed and 50 mg of prostaglandin F2α was administered. All heifers were timed artificially inseminated (AI; D0) 62 h after IVPD removal concomitant with an administration of 100 μg of GnRH. Estrus detection patches were placed on heifers at D-3 and evaluated at the time of AI. In a subset of heifers (n = 278), transrectal ultrasonography of the ovaries was carried out at D-8 and D-3 to assess presence and diameter of CL and largest follicle diameter (LFD). A blood sample was collected on D-3 to determine serum P4 concentration. Heifers with a once-used IVPD had a greater (P = 0.01) pregnancy per AI (P/AI) than heifers treated with a new-IVPD [62.8 % (179/285) vs 51.2 % (143/279)]. There was a lower percentage of animals (P = 0.002) having a corpus luteum (CL) on D-8 in Pres5 group compared to Control [16.4 % (22/134) vs 69.4 % (100/144)]. Similarly, a greater percentage of Pres5 heifers had a dominant follicle on D-8 (P < 0.0001) than Control heifers [97.7 % (131/134) vs 75.7 % (109/144)]. At D-3, Pres5 heifers had a greater ovulatory response to D-8 GnRH (P < 0.0001) compared to Control animals [82.8 % (111/134) vs 49.3 % (71/144)]. In addition, Pres5 heifers had a greater estrus expression behavior [87.6 % (248/283) vs 72.9 % (205/281); P < 0.0001] and tended to have (P = 0.10) a greater P/AI [61.8 % (175/283) vs 52.3 % (147/281)] than Control heifers. In conclusion, the tendency for a greater fertility observed in Pres5 heifers (∼10 %) justifies the extra animal handling required for presynchronization. A once-used IVPD represents a viable strategy to enhance P/AI and reduce the cost in beef heifers submitted to timed AI.

Timed-artificial insemination protocols for Bos indicus beef heifers: Evaluation of protocol length and variations in prostaglandin F2α treatments

The aim was to compare reproductive outcomes of Nelore heifers submitted to timed AI (TAI) protocols, with 7 or 9 d of permanence of the intravaginal progesterone (P4) device and different times of prostaglandin F2α (PGF) administration, for first (n = 935) and second (n = 530) services. On Day -24, heifers without corpus luteum (CL) underwent a protocol for induction of ovulation. On Day 0, heifers received a P4 device (0.5 g) and 1.5 mg estradiol (E2) benzoate. In order for the TAI to be carried out on the same day, these treatments were performed 2 d later on the heifers treated with the 7-d protocol. Additionally, heifers received 0.5 mg PGF at different times, resulting in four experimental groups: 9dP4-PGFd9 (n = 365); 9dP4-PGFd7 (n = 369); 9dP4-PGFd0&9 (n = 364); 7dP4-PGFd0&7 (n = 367). These nomenclatures indicate for how many d the P4 device was kept and the specific day on which PGF was given. At P4 removal, all heifers received 0.5 mg E2 cypionate and 200 IU eCG, and TAI was performed 2 d later. Effects were considered significant when P ≤ 0.05 (superscript letters a,b) whereas a tendency was assumed when 0.05 < P ≤ 0.10. Groups 9dP4-PGFd0&9 and 7dP4-PGFd0&7 had lower percentage of heifers with CL at P4 removal. The diameter (mm) of the dominant follicle (DF) was affected by treatment at P4 removal (9dP4-PGFd9: 11.3 ± 0.3b; 9dP4-PGFd7: 11.8 ± 0.2ab; 9dP4-PGFd0&9: 12.6 ± 0.2a; 7dP4-PGFd0&7: 10.8 ± 0.2c) and at TAI (9dP4-PGFd9: 12.7 ± 0.3ab; 9dP4-PGFd7: 13.2 ± 0.2a; 9dP4-PGFd0&9: 13.4 ± 0.2a; 7dP4-PGFd0&7: 12.4 ± 0.3b). Expression of estrus (%) was affected by treatment (9dP4-PGFd9: 89.6a; 9dP4-PGFd7: 93.5a; 9dP4-PGFd0&9: 88.2ab; 7dP4-PGFd0&7: 85.6b). There were no differences among treatments for P/AI on Day 40 (30-35 d post AI), final P/AI (between Day 70 and parturition) and pregnancy loss (between Day 40 and final P/AI). When the permanence of the P4 device was compared, regardless of PGF treatments, 9-d protocols resulted in greater DF diameter at P4 removal and at TAI, and greater expression of estrus (90.4 vs. 85.6%) than the 7-d protocol. Despite that, the 7-d protocol resulted in greater P/AI on Day 40 (55.3 vs. 49.1%). In addition, there was an interaction between protocol duration and body weight, in which heavier heifers (≥ 307 kg) had greater P/AI when treated with the 7-d protocol, in comparison to 9-d. In conclusion, longer TAI protocols (9 d of P4 device duration) resulted in greater DF diameter and expression of estrus. However, the shorter TAI protocol (7 d of P4 device duration) produced greater P/AI on Day 40, particularly in heavier heifers. Within 9-d protocols, the additional dose of PGF on Day 0 or the anticipation of the PGF to Day 7 did not influence fertility.

The fertility of dairy heifers and cows is not influenced by the follicular wave of the ovulatory follicle

Two studies were conducted to evaluate the effects of the follicular wave on ovarian function and fertility in dairy heifers and lactating cows. In study 1, the estrous cycle of the selected Holstein heifers was initially synchronized using two intra-muscular prostaglandin F2α (PGF2α) administrations 11 days apart. Heifers in group FFW (n = 14) received an intra-muscular 500 μg PGF2α administration on day 7 after detecting standing estrus, while Heifers in group SFW (n = 14) were administered PGF2α 13 days after detecting standing estrus. The pregnancy rates of FFW (n = 98) and SFW (n = 100) heifers were also determined 35-37 days after artificial insemination (AI). In Study 2, healthy Holstein lactating cows (n = 28) were randomly assigned to either the FFW (n = 14) or SFW (n = 14) groups. The estrous cycles of the cows were presynchronized using two intra-muscular administrations of PGF2α given 14 days apart. Then, the emergences of the follicular waves were induced using an Ovsynch protocol. The pregnancy rate of FFW (n = 99) versus SFW (n = 98) cows was also determined 35-37 days after AI. The ovulatory follicle and corpus luteum (CL) resulting from the ovulatory follicle of FFW were larger than those of the dominant follicle and the CL of SFW in dairy heifers and lactating cows. However, the pregnancy rate did not differ between the FFW and SFW groups in heifers and lactating cows 35-37 days after AI. In conclusion, although the characteristics of the ovulatory follicles in FFW versus SFW animals differed, the follicular wave in dairy heifers or lactating cows did not affect fertility.

The influence of corpus luteum and first-wave dominant follicle location on conception rate after artificial insemination in Holstein cattle

The influence of post-ovulatory corpus luteum (CL) and first-wave dominant follicle (1DF) location on pregnancy establishment in cattle remains controversial. This study aimed to reveal the relationship between CL and 1DF positioning, pregnancy outcomes, and blood steroid hormone levels following artificial insemination (AI) in Holstein cattle. Data from heifers (n = 163) and cows (n = 69) with optimally timed AI, defined as ovulation within 24 h post-AI, were analyzed to determine associations between CL (left/right ovary) and 1DF (ipsilateral/contralateral to CL) locations and conception rates. Plasma progesterone (P4) and estradiol-17β (E2) concentrations were measured five days post-insemination. In heifers, neither CL (p = 0.24) nor 1DF location (p = 0.44) affected conception rates. Cows with left-sided CL tended to have higher conception rates than those with right-sided CL (p = 0.08). Relative 1DF location did not affect conception in cows. The location of CL and 1DF did not affect plasma P4 and E2 concentrations or the ratio of plasma E2 to P4 in heifers or cows. These findings suggest a trend towards improved conception rates in cows with CL located on the left ovary post-AI, regardless of 1DF location. The mechanism should not be associated with systemic ovarian hormones.

Importance of preovulatory estradiol on uterine receptivity and luteal function

Animals that exhibited estrus had greater pregnancy success compared to animals that did not exhibit estrus before fixed-time AI (FTAI). Estradiol is synthesized in bovine ovarian follicles under gonadotropin regulation and can directly and indirectly regulate the uterine receptivity and luteal function. Estradiol concentrations at FTAI impacted oviductal gene expression and has been reported to play an important role in establishing the timing of uterine receptivity. These changes have been reported to impact uterine pH and sperm transport to the site of fertilization. After fertilization, preovulatory estradiol has been reported to improve embryo survival likely by mediating changes in uterine blood flow, endometrial thickness and changes in histotroph. Cows with greater estradiol concentrations at the time of GnRH-induced ovulation also had a larger dominant follicle size and greater circulating progesterone concentrations on day 7. Therefore, it is impossible to accurately determine the individual benefit of greater estradiol concentrations prior to ovulation and greater progesterone concentrations following ovulation to pregnancy establishment, as these two measurements are confounded. Research has indicated an importance in the occurrence and timing of increasing preovulatory concentrations of estradiol, but increasing estradiol concentrations by supplementation may not be sufficient to increase fertility. Increased production of estradiol by the preovulatory follicle may be required to enhance fertility through the regulation of sperm transport, fertilization, oviductal secretions, the uterine environment, and embryo survival.

Influence of preovulatory estradiol treatment on the maintenance of pregnancy in beef cattle receiving in vivo produced embryos

This experiment was designed to determine the role of preovulatory estradiol in pregnancy retention after embryo transfer (ET). Cows were synchronized with the 7-d CO-Synch + CIDR® protocol. On d0 (d-2 =CIDR® removal), cows were grouped by estrual status (estrual [Positive Control] and nonestrual), and nonestrual cows were administered Gonadotropin Releasing Hormone (GnRH) and randomly assigned to either no treatment (Negative Control) or Estradiol (0.1 mg estradiol 17-β IM). All cows received an embryo on d7. Pregnancy status was retrospectively classified on d56, 30, 24, and 19 by either ultrasonography, plasma pregnancy-associated glycoproteins analysis (PAGs), expression of interferon-stimulated genes, plasma progesterone (P4) concentrations, or a combination of the factors. There was no difference in estradiol concentrations on day 0 h 0 (P > 0.16). At day 0 h 2, Estradiol cows (15.7 ± 0.25 pg/mL) had elevated (P < 0.001) estradiol compared with Positive Controls (3.4 ± 0.26 pg/mL) or Negative Controls (4.3 ± 0.25 pg/mL). On d19, pregnancy rates did not differ (P = 0.14) among treatments. On d24, Positive Controls (47%) had greater (P < 0.01) pregnancy rates than Negative Controls (32%); Estradiol cows were intermediate (40%). There was no difference (P = 0.38) in pregnancy rates between Positive Control (41%) and Estradiol (36%) cows on d30, but Negative Control (27%) cows had (P = 0.01) or tended (P = 0.08) to have decreased pregnancy rates, respectively. Thus, preovulatory estradiol may elicit an effect on early uterine attachment or alter histotroph components, consequently improving pregnancy maintenance through d30.

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

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

In Vivo Follicular and Uterine Arterial Indices as an Indicator of Successful Hormonal Stimulation for Inactive Ovaries in Repeat-Breeder Crossbred Dairy Cows Using a Short-Term Progesterone-Based Programme

Simple Summary

Blood supply of female reproductive organs plays an important role in reproductive performance in cattle. Ovarian and uterine arterial indices (vascularised area) from colour Doppler imaging provided important information about ovarian activity, supporting clinical diagnoses and reproductive management decisions in female cattle. However, the information regarding the relationship between reproductive vascular indices and resumption of follicular activity after hormonal stimulation for inactive ovaries in infertile dairy cows is scarce; thus, infertile crossbred dairy cows with inactive ovaries were induced using a 5-day progesterone-based programme. Our results highlighted that repeat-breeder crossbred dairy cows with greater follicular size and follicular and uterine arterial indices underwent a resumption of ovarian activity after hormonal stimulation. Therefore, additional information on follicular and uterine arterial indices that can be helpful in predicting the resumption of ovarian activity after hormonal stimulation in inactive ovary cows can be gained by reproductive vascularisation from colour Doppler ultrasonography.

Abstract

An investigation of vascularity of ovarian and uterine arteries after hormonal treatment for inactive ovaries using the short-term progesterone-based programme had not yet been explored in repeat-breeder crossbred dairy cows. To investigate the in vivo follicular and uterine arterial indices as an indicator of successful hormonal stimulation for inactive ovaries in repeat-breeder crossbred dairy cattle, 59 cows with inactive ovaries were induced with a 5-day progesterone-based protocol. At the completion of hormonal synchronisation, cows were divided into two groups according to the size of the largest follicle (LF) on their ovary: small (≤10.0 mm) and large (>10.0 mm) LFs. Vascularities of LF and uterine artery (UtA) were evaluated using a colour Doppler tool. Cows that presented with large LF had greater follicular and UtA vascular indices (p < 0.001) and pregnancy rate (p < 0.01) than cows bearing small LF on their ovary. There was a positive correlation (p < 0.001) between follicular size and LF and UtA vascular indices. Our findings highlighted that in vivo LF and UtA vascular indices at the completion of hormonal stimulation might be a promising indicator for predicting success in ovarian response to hormonal stimulation for inactive ovaries of infertile crossbred dairy cows.

Effect of advancing the breeding season on reproductive performance of dromedary camels

This study examines the effect of advancing the breeding season on the reproductive performance of dromedary camels under an intensive management system. Using a synchronization protocol, timed natural mating in female camels was carried out either in September (2 months ahead of the natural breeding season, n = 182) or December (peak breeding season, n = 115). The ovarian responses (size of the dominant follicle at the time of mating and ovulation), pregnancy rate, and pregnancy losses were evaluated using ultrasonography. Blood samples were collected after mating to assess progesterone concentrations by RIA. The libido of male camels (n = 13) was evaluated objectively. Results showed that the percentage of female camels with an optimal sized follicle (11-17 mm) for breeding at the time of mating was lower in September compared to December (81.9 vs 91.3%, P = 0.03). The libido of male camels was lower in September than in December (P <0.001). The ovulation rate (86.3 vs 93.9%, P = 0.04), size of the ovulated follicle (12.7 ± 0.1 vs 13.7 ± 0.2 mm, P <0.001), pregnancy rates on Day 14 (47.8 vs 72.2%, P <0.001) and Day 90 (38.5 vs 60.9%, P <0.001) after mating was lower in September compared to December. However, pregnancy loss was not affected between months (15.7 vs 19.5%, P = 0.3). Among pregnant camels, the progesterone concentrations on Days 6, 8, 10, 12 and 14 after mating were lower in September as compared to December (P <0.001). In non-pregnant camels, the progesterone concentrations on Days 6, 8 and 10 after mating were also lower in September as compared to December (P <0.001). In conclusion, advancing the breeding season by two months, significantly affects the reproductive performance of dromedary camels, yet, acceptable pregnancy rates can be achieved.

Seasonal variation of the estrous cycle length, corpus luteum area, and size of the pre-ovulatory follicle in Criollo Limonero heifers

In order to determine whether seasonal variations may influence the estrous cycle length (ECL), corpus luteum size (CLS), maximum area of CL (MACL), day of cycle with maximum area of CL (DCMACL), and pre-ovulatory follicles size (PFS), ten Criollo Limonero heifers were subjected to daily ultrasound ovary scanning throughout their estrous cycles during three seasons: hot-dry (HD), hot-humid (HH), and wind-rain (WR). The effect of season on ECL, MACL, DCMACL, and PFS was analyzed with an ANOVA (PROC GLM, SAS), whereas, for the effect of season on CLS, an ANOVA with repeated measures (PROC MIXED, SAS) was used. Results showed no effect (P > 0.05) of season on ECL, MACL, and DCMACL. However, size of PFS was larger (P < 0.02) during the WR season and the CLS tended (P < 0.09) to be lower during the HH. In conclusion, the relative stability of ECL, MACL, DCMACL, PFS, and CLS measures suggests no major seasonal variations which could imply adaptation capability of Criollo Limonero cattle to the tropical environment.

Replacing the first gonadotropin-releasing hormone treatment in an Ovsynch protocol with human chorionic gonadotropin decreased pregnancies per artificial insemination in lactating dairy cows

Our objective was to compare the effect of treatment with GnRH at the first treatment (G1) of the Breeding-Ovsynch portion of a Double-Ovsynch (DO) protocol with human chorionic gonadotropin (hCG) on pregnancies per artificial insemination (P/AI) in lactating dairy cows. In experiment 1, lactating dairy cows (n = 1,932) submitted to a DO protocol for first timed artificial insemination (TAI) on 2 commercial dairy farms were blocked by parity (primiparous vs. multiparous) and were randomly assigned to receive 100 µg of GnRH versus 2,500 IU of hCG at G1. Overall, P/AI 39 d after TAI for cows inseminated with sexed dairy semen was greater for cows treated with GnRH than for cows treated with hCG within each parity (primiparous: 42.6% vs. 38.2%; multiparous: 39.4% vs. 30.3%). Similarly, P/AI 39 d after TAI for multiparous cows inseminated with conventional beef semen tended to be greater for cows treated with GnRH than for cows treated with hCG (41.1% vs. 34.3%). In experiment 2, lactating Holstein cows (n = 43) were blocked by parity and were randomly assigned to the treatment protocols described for experiment 1. Ovaries were evaluated with transrectal ultrasonography immediately before treatment and 24, 28, 32, 36, and 40 h after treatment to assess time from treatment to ovulation, and blood samples were collected immediately before G1, at the first PGF_2α treatment, 8 and 16 h later, at the second PGF_2α treatment, 8 and 16 h later, at the second GnRH (G2) treatment, and at TAI to compare luteolysis based on serum progesterone (P4) concentrations. Although mean (± standard error of the mean) time from treatment to ovulation was approximately 2 h greater for cows treated with hCG than for cows treated with GnRH (33.7 ± 0.6 vs. 31.5 ± 0.6 h), P4 concentrations during luteolysis and the proportion of cows with complete luteolysis (P4 <0.4 ng/mL at G2) did not differ between treatments. We conclude that replacing 100 µg of GnRH with 2,500 IU of hCG at G1 of a DO protocol decreased fertility to TAI in lactating dairy cows but did not affect the rate or completeness of luteolysis despite the increased interval from treatment to ovulation.

Likelihood of pregnancy in cows identified with different amounts of anechoic intrauterine fluid at the time of insemination

Effects of amount of anechoic intrauterine fluid (IUF) and size of largest follicle at insemination on proportion of cows pregnant as a result of AI (P/AI percentage), as well as factors associated with amount of IUF and size of the follicle were investigated. Follicle size was determined, and amount of IUF in the largest uterine segment was categorized as containing no fluid, ≤10, >10-20, and >20 mm using the ultrasonic monitor grid in 735 cows at time of insemination. Multivariable regression models were constructed to evaluate effects of different variables on P/AI percentage, and variables associated with the IUF score and follicle size. On day 30 post-insemination, the P/AI percentage was greater in cows that had >10 to 20 mm IUF than cows with no IUF (OR = 1.9, P = 0.01), but on day 70 post-insemination, the P/AI percentage was similar in cows with different amounts of IUF. Follicle size was not associated with P/AI percentage on days 30 and 70 post-insemination. Cows in spontaneous estrus, multiparous cows, cows with a cystic structure and a typically functional follicle, and Holstein cows had a greater likelihood for a larger IUF value. Primiparous cows, cows on which there was imposing of a hormonal-ovulation-synchronization regimen, and crossbred cows were more likely to have smaller follicles. In conclusion, amount of IUF at the time of insemination and size of the follicle were not associated with P/AI percentage, and several variables were associated with amount of IUF or follicle size.

Effects of Equine Chorionic Gonadotropin on Ovulatory and Luteal Characteristics of Mares Submitted to an P4-Based Protocol of Ovulation Induction With hCG

The aim of this study was to evaluate the effect of equine chorionic gonadotropin (eCG) at the end of progesterone (P4) treatment on follicular and luteal characteristics during transition period (TP) and reproductive breeding season (RP). A total of 13 crossbred mares were distributed in two experimental groups in the spring and summer (n = 26). The animals received intravaginal P4 (1.9 g) releasing device from D0 to D10. On removal of P4 device, the mares received 400 IU of eCG (eCG group) or saline solution (control group). Human chorionic gonadotropin (hCG; 1.750 IU) was administered (DhCG) as soon as ovulatory follicle (OF) ≥35 mm was detected. Ovarian ultrasonography was performed from D0 until 15 days after ovulation. Blood samples were collected on D0, D5, D10, DhCG, 9 days after ovulation (CL9D), and 13 days after ovulation (CL13D). P4 and estradiol concentrations were assessed by chemiluminescence. Data were compared by Tukey test at P < .05. Ovulation rate was similar (P = .096) between seasons (RP = 100%; TP = 70%) but occurred earlier (P = .015) in RP (34.8 ± 10.1 hours) compared with TP (42.0 ± 10.4 hours). Interactions between season and treatment were observed for OF diameter (mm) (RP/control = 36.2 ± 1.8ab; RP/eCG = 32.9 ± 2.8 b; TP/control = 32.2 ± 1.2 b; TP/eCG = 37.2 ± 1.9a; P = .004) and for corpus luteum (CL) diameter (mm) on CL13D (RP/control = 25.4 ± 3.5a; RP/eCG = 22.5 ± 1.8ab; TP/control = 21.6 ± 4.9 b; TP/eCG = 27.4 ± 4.3a; P = .023), although no differences were observed for serum P4 on CL13D (RP/control = 6.0 ± 3.1 ng/mL; RP/eCG = 5.8 ± 0.9 ng/mL; TP/control = 3.6 ± 2.7 ng/mL; TP/eCG = 5.1 ± 2.3 ng/mL; P = .429) or for day of structural CL regression (RP/control = 12.8 ± 1.9; RP/eCG = 12.1 ± 1.1; TP/control = 11.0 ± 1.7; TP/eCG = 13.2 ± 2.0; P = .102). The application of eCG at the moment of P4 implant removal seemed to increase the capacity of luteal maintenance during spring TP. However, eCG treatment was worthless during the breeding season.

Influence of ipsilateral coexistence of the first wave dominant follicle and corpus luteum on ovarian dynamics and plasma sex steroid hormone concentrations in lactating dairy cows treated with human chorionic gonadotropin

We examined the effect of human chorionic gonadotropin (hCG) treatment 5 days after estrus on ovarian dynamics and plasma progesterone (P₄) and estradiol (E₂) concentrations when the first-wave dominant follicle (DF) was ipsilateral or contralateral to the corpus luteum (CL) in lactating dairy cows. Seventy cows were divided into two groups: (1) ipsilateral group (IG; n = 37), in which the first-wave DF was ipsilateral to the CL, and (2) contralateral group (CG; n = 33), in which the first-wave DF was contralateral to the CL. IG and CG were further subdivided into two groups: non-treatment group (IG, n = 18; CG, n = 19), and hCG treatment group: administrated 1500 IU of hCG 5 days after estrus (IG, n = 19; CG, n = 14). Blood sampling and ovarian examination were performed at 3, 5, 7, 9, 11, and 13 days after estrus. Mean diameter of the first-wave DF on Day 9 tended (P = 0.067) to be larger in IG than in CG in the non-treatment group. Mean diameter of CL and plasma P₄ and E₂ concentrations did not differ between IG and CG in the non-treatment and hCG treatment groups. Accessory CL development did not differ between IG and CG in the hCG treatment group. Our findings indicate that CL development and plasma P₄ and E₂ concentrations were not affected by the existence of the first-wave DF; however, first-wave DF development was affected by the existence of a CL in the same ovary.

Cyclicity, estrus expression and pregnancy rates in beef heifers with different reproductive tract scores following progesterone supplementation

Two experiments were conducted to determine effects of progesterone (P4) on cyclicity, estrus expression rate (EER) and artificial insemination pregnancy rate (AIPR) in beef heifers with various reproductive tract scores (RTS; 1 to 5; 1, immature, acyclic; 5, mature, cyclic). In Experiment 1, Angus-cross heifers (n = 100, 20 per RTS category; mean (±SEM) age, 15 ± 0.8 mo) were randomly assigned to receive a CIDR (Days -17 to -10) or no CIDR (untreated control), with weekly blood samples and ultrasonography (Days 0-85). Among heifers with RTS 2 to 4, median interval to cyclicity were shorter (P < 0.05) for heifers in CIDR versus control. In Experiment 2, Angus-cross heifers (n = 11,098) were assigned RTS, body condition score (BCS; 1 to 9; 1, emaciated; 9, obese) and temperament score (calm versus excitable). Heifers with RTS 2-5 (n = 10,569) were allocated to CO-Synch (n = 5099) or CO-Synch + CIDR (n = 5470). Estrus was detected until AI (72 h after PGF2α), with pregnancy diagnosis ∼70 d later. Controlling for RTS (P < 0.0001), BCS (P < 0.0001), temperament (P < 0.0001), age (P < 0.0001), treatment by RTS (P < 0.01), treatment by BCS (P < 0.01), and treatment by age, EER differed between CO-Synch and CO-Synch + CIDR (71.0 vs 75.9%, respectively, P < 0.0001). Accounting for RTS (P < 0.0001), BCS (P < 0.0001), temperament (P < 0.0001), age (P < 0.0001), heifers detected in estrus (P < 0.0001), RTS by treatment (P < 0.01), BCS by treatment (P < 0.01), and age by treatment, AIPR differed between CO-Synch versus CO-Synch + CIDR (55.3 vs 61.0%, P < 0.0001). In conclusion, exogenous P4 hastened cyclicity in pre- and peri-pubertal beef heifers. Further, it increased EER and AIPR. However, RTS, BCS and age influenced EER and AIPR. Among RTS 4 and 5, EER was greater for CO-Synch + CIDR vs CO-Synch. Among RTS 3 to 5, AIPR was greater for CO-Synch + CIDR versus CO-Synch. Progesterone status or supplementation at onset of synchronization protocols was critical to pregnancy outcomes, emphasizing heifer development for early puberty or progesterone supplementation.

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.

Resveratrol addition to in vitro maturation and in vitro culture media enhances developmental competence of sheep embryos

The present study aimed to examine the effects of adding different concentrations of resveratrol during in vitro culture (IVC) alone and during both in vitro maturation (IVM) and IVC on ovine blastocyst yield and quality. Therefore, this study was conducted in two separate experiments. The first experiment was carried out to test the effect of different concentrations of resveratrol (0, 0.1, 0.25, 0.5, 2.0, and 5.0 μM) in the IVC medium on cleavage, morula, developmental potential of blastocyst, and total cell number (TCN) of the embryos. Addition of 0.25 and 0.5 μM of resveratrol during IVC significantly enhanced morula and blastocyst rates as compared with other groups (P < 0.05). Also, supplementation of the IVC medium with 0.5 μM of resveratrol had beneficial effects on trophectoderm cells (TE), inner cell mass (ICM), and TCN of blastocysts. In the second experiment, the same concentrations of resveratrol (0, 0.1, 0.25, 0.5, 2.0, and 5.0 μM) were applied during IVM and IVC. Therefore, oocytes were matured in vitro in the presence of different concentrations of resveratrol for 22-24 h. After in vitro fertilization, presumptive zygotes were cultured in media containing 0, 0.1, 0.25, 0.5, 2.0, and 5.0 μM of resveratrol for 8 d. No significant difference was found in the percentage of oocytes developed to MII (0, 0.1, 0.25, 0.5, and 2.0 μM of resveratrol), but the percentage of oocytes developed to MII were significantly lower in 5.0 μM of resveratrol in comparison with other groups. Addition of 0.5 μM of resveratrol to the maturation and culture media significantly increased morula and blastocyst rates compared with other groups (P < 0.05). However, a too high concentration of resveratrol (5.0 μM) during IVM and IVC decreased cleavage, morula, and blastocyst rates compared with low concentrations (P < 0.05). Treatment with 0.5/0.5 μM of resveratrol during IVM/IVC significantly improved the TE, ICM, and TCN of blastocysts. In conclusion, sequential treatment with 0.5 μM of resveratrol during IVM and IVC and during IVC alone improved the developmental competence of oocytes, which was reflected in higher blastocyst rates and TCN of blastocysts.

Physiological characteristics and effects on fertility of the first follicular wave dominant follicle in cattle

The first follicular wave emerges soon after ovulation, and its dominant follicle (DF) develops during the first 8–10 days of the estrous cycle in cattle. And, the first-wave DF is a non-ovulatory follicle, because it develops during the first half of the estrous cycle simultaneously with the corpus luteum (CL), which produces and secretes progesterone. Regarding the characteristics of development and the mechanisms of deviation in the DF during the follicular wave, the first-wave DF has been well studied. However, the characteristics of the first-wave DF, such as growth, blood flow in the follicular wall, concentration of sex steroid hormones in the peripheral blood and follicular fluid, amounts of mRNA in granulosa cells, as well as the characteristics of the CL formed after the first-wave DF and the influence of the first-wave DF on fertility (conception rate), have not been well studied. Additionally, the first-wave DF synthesizes and secretes 17β-estradiol (E₂), and plasma E₂ concentration increases during the early stage of the estrous cycle. Consequently, there is a possibility that the first-wave DF might affect the fertility in cattle. In this review, to provide the new perspective on reproductive physiology in cattle, characteristics of the first-wave DF were examined in detail and its characteristics were compared with that of the second-wave DF. In addition, the locational effects of the first-wave DF and CL on conception rate are discussed.

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.

Effects of human chorionic gonadotropin treatment after artificial inseminations on conception rate with the first follicular wave dominant follicle in the ovary ipsilateral to the corpus luteum in lactating dairy cows

We examined the effect of human chorionic gonadotropin (hCG) treatment 5 days after artificial insemination (AI) on conception rate when the first-wave dominant follicle (DF) in the ovaries was either ipsilateral or contralateral to the corpus luteum (CL) in lactating dairy cows. 577 cows from 4 dairy farms were divided into the following two groups 5 days after AI using transrectal ultrasonography: (1) the ipsilateral group (IG; n = 348), in which the DF was ipsilateral to the CL, and (2) the contralateral group (CG; n = 229), in which the DF was contralateral to the CL. IG and CG were further subdivided into two groups: non-treatment groups, which received no treatment (IG, n = 220; CG, n = 128), and hCG treatment group, that was administrated 1500 IU hCG 5 days after AI (IG, n = 143; CG, n = 86). Pregnancy was diagnosed by rectal palpation or transrectal ultrasonography from 53 to 67 days after AI. Conception rate was significantly (P < 0.01) higher in the hCG treatment group of IG (40.6%) than in the non-treatment group of IG (21.4%); however, there was no difference in the non-treatment (51.7%) and hCG treatment (43.0%) groups of CG. Parity, farm, days in milk at AI, interaction between the farm and hCG treatment and interaction between the farm and location of the first-wave DF and CL did not affect conception rate. Our results suggest that conception rate can be improved by administrating hCG only to cows with the first wave DF ipsilateral to the CL.

Effects of live yeast dietary supplementation on hormonal profile, ovarian follicular dynamics, and reproductive performance in dairy cows exposed to high ambient temperature

Two experiments were conducted to investigate the effects of dietary supplementation with live yeast culture on hormonal profile, ovarian follicular dynamics and reproductive performance of lactating dairy cows exposed to high ambient temperature. In Expt. 1, Holstein cows were fed a diet with (n = 6) or without (n = 6) 4 g yeast/h/d from 21 d before expected calving date until 8 weeks postpartum. Concentrations of glucose, insulin, insulin like growth factor-I (IGF-I), estradiol-17β (E-17β) and progesterone (P4) were determined in plasma, and transrectal ultrasonography was used to monitor ovarian follicular dynamics. In Expt. 2, 150 Holstein cows (75/dietary group) received same diets as Expt. 1 with the exception that diets were fed from d 1 to d 70 postpartum. The effect of dietary treatments on reproductive performance was examined. In Expt. 1, plasma IGF concentrations during dietary treatment were higher (P = 0.05) in cows fed diets supplemented with yeast. On d 60 postpartum, average plasma concentrations of glucose (48.3 vs. 41.0 mg/dL) and insulin (0.90 vs. 0.23 μU/mL), were also greater in cows fed diets supplemented with yeast compared to that in cow fed diets without supplementation. Similarly, plasma concentrations of E-17β at estrus (P = 0.016) and P4 on d 10 of the estrous cycle (P = 0.021) were greater in yeast-supplemented cows. Moreover, yeast supplementation resulted on average in an estrous cycle 2.6 d shorter (P = 0.05) and in the development of larger ovulatory follicles (18.4 vs. 17.2 mm in diameter; P < 0.01). In Expt. 2, days open were fewer and the proportion of pregnant cows at 120 and 150 d postpartum were greater (P < 0.01) in cows fed diets supplemented with yeast compared to those receiving diets without yeast. In summary, cows fed diets supplemented with yeast had greater plasma IGF-I, E-17β and P4 concentrations, larger ovulatory follicles, shorter estrous cycles, and improved reproductive performance. Therefore, live yeast dietary supplementation could enhance lactating dairy cow's fertility during heat stress through improvement in hormonal profile and development of larger ovulatory follicles.

Steroid hormone concentrations and body mass are differently affected by polyunsaturated fatty acids during the oestrous cycle in guinea pigs

Reproductive functions in female mammals can be significantly affected by the actions of dietary polyunsaturated fatty acids (PUFAs) on steroid hormone secretion rates. Nevertheless, the effects of plasma free PUFAs on the oestrous cycle have seldom been considered. Therefore, in the present study, the diet of domestic guinea pigs was supplemented with high concentrations of different PUFAs and the effects of altered plasma PUFA patterns on steroid hormone concentrations, measured non-invasively, and body mass during oestrus and dioestrus were analysed. The oestrous cycle was characterised by increased oestrogen and cortisol concentrations in oestrus, corroborated by lowest bodyweight, whereas progesterone concentrations were highest in dioestrus. Plasma concentrations of the long-chain PUFAs docosahexaenoic acid (DHA; 22:6 ω3) and arachidonic acid (AA; 20:5 ω6) affected steroid hormone concentrations differently in oestrus and dioestrus. DHA positively affected oestrogen and progesterone concentrations and diminished cortisol concentrations only in oestrus. In contrast, AA negatively affected oestrogen and stimulated cortisol concentrations in oestrus and reduced progesterone concentrations in general. These findings imply selective and opposite contributions of DHA and AA to ovarian functions during different stages of the oestrous cycle, indicating a high biological relevance of plasma free PUFAs in female reproductive function.

Effects of preovulatory follicle size on estradiol concentrations, corpus luteum diameter, progesterone concentrations and subsequent pregnancy rate in buffalo cows (Bubalus bubalis)

The present study was undertaken to investigate the effects of preovulatory follicle (POF) size on estradiol concentrations, luteal profile (CL diameter and progesterone concentration) and subsequent pregnancy rate in Murrah buffalo cows. The buffalo cows (n = 49) were synchronized for estrus by two doses of PGF₂α given 11 days apart. The buffalo cows were inseminated during standing estrus and again after 24 h. Ovaries were scanned at estrus and 24 h intervals until ovulation, thereafter on days 5, 12 and 16 post-ovulation to examine the POF and CL diameter. Size of POF at estrus was divided into three categories; I: 10 to ≤12; II: >12.0 to ≤14.0; III: >14.0-16.0 mm. Blood samples were collected for estradiol (on day of estrus) and progesterone concentration (on days 5, 12 and 16). The estradiol concentrations were greater (P < 0.05) in category II than category I with the greatest (P < 0.05) concentrations estimated in category III. A positive correlation (P < 0.05) between POF and progesterone concentration, CL diameter and progesterone concentration was observed on all sampling day. Pregnant buffalo cows exhibited greater (P < 0.05) plasma progesterone as compared with their non-pregnant counterpart. Greater pregnancy rates were observed with an increased size of POF (χ² = 2.9, P > 0.05). It was concluded that the POFs having diameters between 12 and 16 mm are mature enough to be transformed into CL of such optimum diameter and can secrete optimum progesterone concentrations that can sustain the pregnancy in Murrah buffalo cows.

Hormonal profile and follicular dynamics concurrent with CIDR and insulin modified Ovsync TAI programs and their impacts on the fertility response in buffaloes

Fifty one cyclic Egyptian buffaloes were used to study the hormonal profile and follicular dynamics concurrent with CIDR and insulin modified Ovsync TAI programs and their impacts on the consequent fertility responses. The buffaloes were randomly assigned into 3 ovulation synchronization protocols: Ovsync-alone (n = 13, control) CIDR-sync (n = 20) and Insulin-sync (n = 18). Ovsync-alone protocol consisted of two im injections of 20 μg bueserlin (GnRHa) on Day 0 (GnRH 1) and on Day 9 (GnRH 2) with an im injection of 500 μg of cloprostenol sodium (PGF₂ α) on Day 7. The CIDR-sync protocol consisted of the same treatment protocol as in Ovsync in addition to intra-vaginal insertion of CIDR (contains 1.38 gm of progesterone) on Day 0 followed by removal on Day 7. The Insulin-sync protocol consisted of the same treatment protocol as in Ovsync plus 3 sc injections of insulin at a dose of 0.25 i.u/1 kg, on Days 7, 8, and 9. Buffaloes in all groups were inseminated 16 h after GnRH2 by the same inseminator using frozen semen in straws. Blood samples were collected on Days 0, 3, 5 for serum progesterone assay and on Day 9 to measure serum concentrations of estradiol, insulin and IGF-1. Transrectal ultrasonographic scanning of the ovaries was conducted on Days 7, 8 and 9 to record the diameter of the largest follicle. Pregnancy diagnosis was conducted on Day 30 post-TAI by trans-rectal ultrasonographic scanning of the uterus to calculate conception rate. The serum progesterone concentration showed an increase (p < 0.01) in pregnant compared with non-pregnant buffaloes in both Ovsync-alone and Insulin-sync groups, but not in CIDR-sync group (p > 0.05) on Days 3 and 5. The serum estradiol concentration on Day 9 showed an increase (p < 0.01) in pregnant compared with the non-pregnant buffaloes in all of the treated groups. In Insulin-sync and Ovsync-alone groups, the diameter of the largest follicle (LF) was larger (p < 0.01) in pregnant compared with non-pregnant buffaloes, but in CIDR-sync, the diameter of the (LF) was larger (p < 0.01) in non-pregnant compared with pregnant buffaloes. Also, the results showed that the greatest diameter of LF was observed in pregnant buffaloes in Insulin-sync compared with either pregnant or non-pregnant buffaloes in all groups. It is concluded that modified CIDR-sync and Insulin-sync could improve fertility response through modulating hormonal profile and follicular dynamics in buffaloes during low breeding season.

Evidence of endometrial amino acid metabolism and transport modulation by peri-ovulatory endocrine profiles driving uterine receptivity

Background

In beef cattle, changes in the periovulatory endocrine milieu are associated with fertility and conceptus growth. A large preovulatory follicle (POF) and the resulting elevated concentrations of progesterone (P4) during diestrus positively affect pregnancy rates. Amino acids (AA) are important components of maternally derived secretions that are crucial for embryonic survival before implantation. The hypothesis is that the size of the POF and the concentration of P4 in early diestrus modulate the endometrial abundance of SLC transcripts related to AA transport and metabolism and subsequently impact luminal concentrations of AA. The follicle growth of Nelore cows was manipulated to produce two experimental groups: large POF and CL (LF-LCL group) and small POF and CL (SF-SCL group). On Day 4 (D4; Experiment 1) and Day 7 (D7; Experiment 2) after GnRH-induced ovulation (GnRH treatment = D0), the animals were slaughtered and uterine tissues and uterine washings were collected. qRT-PCR was used to evaluate the expression levels of AA transporters in D4 and D7 endometrial tissues. The concentrations of AA were quantified in D4 and D7 uterine washings by HPLC.

Results

Transcript results show that, on D4, SLC6A6, SLC7A4, SLC17A5, SLC38A1, SLC38A7 and SCLY and on D7 SLC1A4, SLC6A1, SLC6A14, SLC7A4, SLC7A7, SLC7A8, SLC17A5, SLC38A1, SLC38A7, SLC43A2 and DDO were more abundant in the endometria of cows from the LF-LCL group (P < 0.05). In addition, concentrations of AA in the uterine lumen were influenced by the endocrine profiles of the mother. In this context, D4 uterine washings revealed that greater concentrations of taurine, alanine and α-aminobutyric acid were present in SF-SCL (P < 0.05). In contrast, lower concentrations of valine and cystathionine were quantified on D7 uterine washings from SF-SCL cows (P < 0.05).

Conclusion

The present study revealed an association between the abundance of transcripts related to AA transport and metabolism in the endometrium and specific periovulatory endocrine profiles related to the receptive status of the mother. Such insights suggest that AAs are involved in uterine function to support embryo development.

Mastitis outcomes on pre-ovulatory follicle diameter, estradiol concentrations, subsequent luteal profiles and conception rate in Buffaloes

The objectives of this study was to investigate the outcome of mastitis, in its clinical or subclinical forms, on the mean diameter of pre-ovulatory follicle (POF), plasma estradiol concentration on the day of estrus, subsequent luteal profile and subsequent conception rate in buffaloes. Sixty dairy buffalo (Bubalus bubalus) conducted in this study were divided into three groups {healthy (H), n=20; subclinical mastitis (SCM), n=18; and clinical mastitis (CM), n=22}. Ultrasonography of ovaries revealed that mean diameter of POF was larger (P<0.05) in H buffalo (14.35mm) compared to SCM (12.40mm) and CM (10.25mm). Also, plasma estradiol concentration on the day of estrus was higher (P<0.05) in H buffalo compared to SCM and CM counterparts; 34.95 vs. 32.87 and 27.50pg/ml, respectively. Besides, positive correlation was observed between the POF diameter with plasma estradiol concentration in H, SCM and CM buffaloes (r=0.64, 0.74, 0.72 respectively, P<0.05). Moreover, positive correlations (P<0.01) were found on days 9, 12, 16, and 21 post-ovulation between POF diameter and luteal profile. Thus, the conception rate in H buffalo was higher (P<0.05) compared with SCM and CM counterparts; 55% vs. 38.89 and 18.18%, respectively. In conclusion, mastitis in its clinical or subclinical forms disrupts the functioning of the pre-ovulatory follicle on the day of estrus, associated with low follicular estradiol production, resulting in suppression to subsequent luteal profile leading to substantial decrease in pregnancy consequence of buffaloes.

The effect of follicular wave on fertility characteristics in beef cattle

The objectives of this experiment were to determine the effects of follicular wave (first or second) on diameter of the dominant follicle, concentrations of progesterone and estradiol and the hepatic enzymes that inactivate them, thickness of the endometrium, and pregnancy rates to AI. Beef heifers ( = 101) and cows ( = 106) were randomly assigned to 1 of 2 treatments: insemination to the first follicular wave (FFW) or insemination to the second follicular wave (SFW). Estrous cycles of females were synchronized to ensure appropriate timing for the treatments. The MIXED procedure of SAS was used for analysis. A similar proportion of females in each treatment responded to presynchronization; however, females in the FFW group ovulated in response to the first injection of GnRH of the CO-Synch protocol more frequently. Only females ( = 94) that properly responded to ovulation synchronization were included in further analyses. Cows in the FFW group tended ( 0.06) to have larger ovulatory follicles 36 h post-PGF of the CO-Synch protocol compared to cows in the SFW group (14.22 ± 0.42 and 11.83 ± 0.49, respectively), whereas heifers were similar between treatment groups. Three d prior to AI, circulating concentrations of progesterone were lesser ( 0.01) in females in the FFW (3.63 ± 0.80 ng/mL) than in the SFW (7.12 ± 0.83 ng/mL), whereas concentrations of estradiol tended ( 0.08) to be greater in those in the FFW (82.72 ± 6.48 pg/mL) than in the SFW (65.55 ± 6.74 pg/mL). Concentrations of cytochrome P450 1A in the liver were lesser ( 0.01) in females in the FFW than those in the SFW (0.68 ± 0.08 vs. 0.96 ± 0.06, respectively). Endometrial thicknesses were similar between treatments but were thicker ( < 0.0001) in cows (9.73 ± 0.24 mm) than heifers (7.22 ± 0.26 mm). When considering all females or only those that were properly presynchronized, pregnancy rates were similar between treatments. However, when evaluating females that ovulated to the assigned follicular wave, there was a treatment by parity interaction ( = 0.04) with heifers in the FFW having a lesser pregnancy rate (25.9%) than heifers in the SFW (72.0%) while cows in both treatment groups were intermediate (45.4% in FFW and 50.0% in SFW). The differences in concentrations of steroids between treatment groups may affect fertility of heifers; however, additional research is necessary.

Association analysis of polymorphism in KiSS1 gene with reproductive traits in goats

Understanding the genetic information of related genes is helpful for the selection and breeding course through marker assisted selection. The aim of the current study was to detect polymorphisms of the KiSS1 gene in 137 animals, including Baladi, Zaraibi and Damascus goat breeds by PCR-RFLP, and DNA sequencing and to investigate the association between these variants and reproductive traits. Comparison of the nucleotide sequence indicated the substitution of T with A at position 121 (T121A) in the intron 1 of the KiSS1 gene in all goat breeds. This substitution distorts the restriction site of the XmnI restriction enzyme and consequently two genotypes were detected (TA and TT). The T121A SNP is associated significantly with litter size in Damascus and Zaribi breeds (p=0.025 and 0.001, respectively). The animals with the TT genotype in Damascus and Zaribi breeds had a significantly higher estradiol_17β level than that recorded in TA genotype at estrus phase (p=0.013 and 0.028, respectively) and late-luteal phase (p=0.067 and 0.041, respectively) of the estrus cycle. Furthermore, animals with the TT genotype in Damascus and Zaribi breeds had significant higher progesterone level at mid-luteal (p=0.037 and 0.045, respectively) phase. Meanwhile, there were no significant differences in progesterone level in late-luteal phase between both genotypes in Zaribi breed (p=0.267). The current trial indicated that the prolific TT genotype in both Damascus and Zaribi breeds had superior estradiol_17β level at estrus phase and an eminent progesterone level at both early and mid-luteal phases of the estrous cycle.

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

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

Expression of estrus modifies the gene expression profile in reproductive tissues on Day 19 of gestation in beef cows

The aim of this study was to test the effect of expression of estrus at artificial insemination (AI) on endometrium, conceptus, and CL gene expression of beef cows. Thirty-six multiparous nonlactating Nelore cows were enrolled on an estradiol- and progesterone (P4)-based timed AI protocol (AI = Day 0) and then slaughtered for the endometrium, CL, and conceptus collection on Day 19. The animals were retrospectively grouped on the basis of cows that (1) showed signs of estrus near AI (n = 19; estrus) and (2) did not show any signs of estrus (n = 17; nonestrus). Body condition score, blood sampling, and ultrasound examination were performed on Days 0, 7, and 18 of the experiment followed by messenger RNA extraction and quantitative reverse transcription polymerase chain reaction analysis of 58 target genes. Data were checked for normality and analyzed by ANOVA for repeated measures using proc GLM, MIXED, and UNIVARIATE of SAS. Only pregnant cows were included in the analyses (n = 12; nonestrus, n = 11). Estrous expression had no correlation with parameters such as body condition score, preovulatory follicle and CL diameter, P4 concentration in plasma on Days 7 and 18 after AI, and interferon-tau concentration in the uterine flushing (P > 0.15); however, a significant increase was observed in conceptus size from cows that expressed estrus (P = 0.02; 38.3 ± 2.8 vs. 28.2 ± 2.9 mm). The majority of transcripts affected by estrous expression in the endometrium belong to the immune system and adhesion molecule family (MX1, MX2, MYL12A, MMP19, CXCL10, IGLL1, and SLPI; P ≤ 0.05), as well as those related with prostaglandin synthesis (OTR and COX-2; P ≤ 0.05). Genes related to apoptosis, P4 synthesis, and prostaglandin receptor were downregulated (CYP11A, BAX, and FPr; P < 0.05) in the CL tissue of cows that expressed estrus. In addition, four genes were identified as differentially expressed in the 19-day-old conceptus from cows that expressed estrus (ISG15, PLAU, BMP15, and EEF1A1; P < 0.05). There was also a significant effect of Day 7 concentration of P4 mainly affecting the immune system, adhesion molecules, and wnt signaling pathway of the endometrium (IGLL1, MX2, SLPI, TRD, APC, WNT2, GLYCAM1, and MYL12A; P < 0.05). A significant interaction between estrous expression and P4 concentration on Day 7 was more pronounced in immune system genes (MX1, MX2, TRD, SLPI, and IGLL1; P < 0.05). This study reported that estrous expression at the time of AI favorably altered the gene expression profile in reproductive tissues during the preimplantation phase toward a more receptive state to the elongating conceptus. These effects seem to be more evident in the endometrium during the time of dynamic remodeling for embryo implantation.

Ovulation of the preovulatory follicle originating from the first-wave dominant follicle leads to formation of an active corpus luteum

The objective of our study was to compare the characteristics of the corpus luteum (CL) formed after ovulation of the dominant follicle (DF) of the first follicular wave (W1) and those of the CL formed after ovulation of the DF of the second (induced) follicular wave (W2). Non-lactating Holstein cows were used for this study. In Experiment 1, cows were treated with PGF2α and GnRH on days 6 and 8 (day 0 = day of follicular wave emergence) for W1 (n = 6) and W2 (n = 6), respectively. Dominant follicles were aspirated on day 9 to quantify the amounts of mRNA (VEGF120, VEGF164, FGF-2, StAR, P450-scc and 3β-HSD) in granulosa cells (GC). In Experiment 2, the size and blood flow area of the CL formed after ovulation of the DF in W1 (W1CL; n = 6) and W2 (W2CL; n = 6) (the day of DF ovulation in W1 and W2 was day 10) were evaluated on days 12, 15, 18 and 21. The plasma P4 concentration was measured on days 10 to 21. The amounts of VEGF164, P450-scc and 3β-HSD mRNA were higher (P < 0.05) in the DF in W1, and those of VEGF120,FGF-2 and StAR mRNA tended to be higher (P < 0.1) in the DF in W1. The size of the CL was greater in the W1CL on days 15, 18 and 21. The blood flow area of the CL was greater in the W1CL on days 12 and 15. The plasma P4 concentrations were higher in the W1CL. These results indicate that the CL formed after ovulation of the DF in W1 was greater in terms of size, blood flow and plasma P4 concentration.

Spatio-specific regulation of endocrine-responsive gene transcription by periovulatory endocrine profiles in the bovine reproductive tract

In cattle, pro-oestrous oestradiol and dioestrous progesterone concentrations modulate endometrial gene expression and fertility. The aim was to compare the effects of different periovulatory endocrine profiles on the expression of progesterone receptor (PGR), oestrogen receptor 2 (ESR2), oxytocin receptor (OXTR), member C4 of aldo-keto reductase family 1 (AKR1C4), lipoprotein lipase (LPL), solute carrier family 2, member 1 (SLC2A1) and serpin peptidase inhibitor, clade A member 14 (SERPINA14): (1) between uterine horns ipsi- and contralateral to the corpus luteum (CL), (2) between regions of the ipsilateral horn and (3) in the vagina. Endometrium and vagina tissue samples were collected from cows that ovulated a larger (large follicle-large CL, LF-LCL; n=6) or smaller follicle (small follicle-small CL, SF-SCL; n=6) 7 days after oestrus. Cows in the LF-LCL group had a greater abundance of transcripts encoding ESR2, AKR1C4, LPL, SLC2A1 and SERPINA14, but a reduced expression of PGR and OXTR in the endometrium versus the SF-SCL group (PPGR and OXTR was greater in the contralateral compared with the ipsilateral horn (PPGR, ESR2, LPL, SLC2A1 and SERPINA14 (P<0.05). Different periovulatory endocrine profiles, i.e. LF-LCL or SF-SCL, did not influence gene expression in the vagina and had no interaction with inter- or intra-uterine horn gene expression. In conclusion, inter- and intra-uterine horn variations in gene expression indicate that the expression of specific genes in the bovine reproductive tract is location dependent. However, spatial distribution of transcripts was not influenced by distinct periovulatory sex-steroid environments.

Estrus behavior, ovarian dynamics, and progesterone secretion in Criollo cattle during estrous cycles with two and three follicular waves

In beef and dairy cattle, the number of follicular waves affects endocrine, ovarian, and behavioral events during a normal estrous cycle. However, in Mexican-native Criollo cattle, a shortly and recently domesticated breed, the association between wave patterns and follicular development has not been studied. The objective of this study was to evaluate the effect of number of follicular waves in an estrous cycle on development of anovulatory and ovulatory follicles, corpus luteum (CL) development and functionality, as well as estrual behavior in Criollo cows. Ovarian follicular activities of 22 cycling multiparous Criollo cows were recorded daily by transrectal ultrasound examinations during a complete estrous cycle. Additionally, blood samples were collected daily to determine serum progesterone concentrations. Only two- (n = 17, 77.3%) and three-wave follicular (n = 5, 22.7%) patterns were observed. Duration of estrus, length of estrous cycle, and length of follicular and luteal phases were similar (P > 0.05) between cycles of two and three waves. Two-wave cows ovulated earlier (P < 0.05) after detection of estrus than three-wave cows. Detected day and maximum diameter of first anovulatory follicle were not affected (P > 0.05) by number of waves. Growth rate of first dominant follicle was higher (P < 0.05) in three-wave cycles. Onset of regression of the first dominant follicle was earlier (P < 0.01) in cycles with three waves than in those with two waves. In two-wave cycles, ovulatory follicles were detected earlier (P < 0.01) and had lower (P < 0.01) growth rate than in three-wave cycles. Development (i.e., maximum diameter and volume) and functionality (minimum and maximum progesterone concentration) of CL were similar (P > 0.05) between two- and three-wave patterns. In conclusion, Criollo cows have two or three follicular waves per estrous cycle, which alters partially ovulatory follicle development and ovulation time after detection of estrus. Length of estrous cycle, as well as CL development and functionality, was not affected by number of follicular waves.

Triennial Reproduction Symposium: deficiencies in the uterine environment and failure to support embryonic development

Pregnancy failure in livestock can result from failure to fertilize the oocyte or embryonic loss during gestation. The focus of this review is on cattle and factors affecting and mechanisms related to uterine insufficiency for pregnancy. A variety of factors contribute to embryonic loss and it may be exacerbated in certain animals, such as high-producing lactating dairy cows, and in some cattle in which estrous synchronization and timed AI was performed, due to reduced concentrations of reproductive steroids. Recent research in beef cattle induced to ovulate immature follicles and in lactating dairy cows indicates that deficient uterine function is a major factor responsible for infertility in these animals. Failure to provide adequate concentrations of estradiol before ovulation results in prolonged effects on expression and localization of uterine genes and proteins that participate in regulating uterine functions during early gestation. Furthermore, progesterone concentrations during early gestation affect embryonic growth, interferon-tau production, and uterine function. Therefore, an inadequate uterine environment induced by insufficient steroid concentrations before and after ovulation could cause early embryonic death either by failing to provide an adequate uterine environment for recognition of embryo signaling, adhesion, and implantation or by failing to support appropriate embryonic growth, which could lead to decreased conceptus size and failed maternal recognition of pregnancy.