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Purpose Reproductive efficiency is an important contributor to a dairy farm’s profitability; however, there are many factors that influence reproductive success, including, but not limited to, embryonic loss. This review summarizes research findings related to the use of prostaglandin F2α (PGF2α) inhibitors to improve fertility in cattle. Sources Peered-reviewed literature and conference proceedings were reviewed in this article. Synthesis Approximately one-third of total embryonic loss occurs between d 8 and 27 after fertilization. Because of a large incidence of early embryonic loss in cattle, researchers have been searching for strategies to reduce the risk of embryonic loss. Provided that the embryonic loss, in part, is related to untimely secretion of PGF2α and premature luteolysis, any management strategy to delay the synthesis and secretion of PGF2α during the time of maternal recognition of pregnancy may reduce the occurrence of early embryonic loss. Consequently, researchers have investigated the potential use of PGF2α inhibitors to address the risk of embryonic loss. Conclusions and Applications Non-steroidal anti-inflammatory drugs (NSAID) are known inhibitors of PGF2α. In cattle, application of NSAID, as a reproductive tool, to improve fertility has been investigated extensively using a variety of NSAID, timing of administration, and breeding techniques. It seems that many NSAID do not consistently improve reproductive efficiency in cattle, and perhaps, treating all cows with an NSAID after calving is unlikely to be economically advantageous. Nevertheless, the research supports the fact that NSAID, in the form of flunixin meglumine or ibuprofen, consistently improved fertility in cattle, when administered at the time of embryo transfer.

Epidermal growth factor (EGF) concentrations in the uterus show two peaks on days 2-4 and 13-14 during the estrous cycle in fertile cows. Loss of the two peaks has been linked to reduced fertility in repeat breeder cows. This study aimed to examine the effect of seminal plasma (SP) on normalizing endometrial EGF concentrations and restoring fertility in repeat breeder cows with low EGF concentrations on day 3. In study 1, we examined the effect of the deposition sites (the vagina and uterus) of SP on the endometrial EGF concentrations in repeat breeder cows. SP infusion into the vagina, but not uterus, on the first day of the estrus cycle (day 0) normalized the endometrial EGF concentrations (>= 4.7 ng/g tissue weight) on day 3. In study 2, the effect of SP volume (0.5 and 10 ml of SP and 0.5 ml of SP diluted to 10 ml) on EGF concentrations was examined. All groups with SP infusion had increased EGF concentrations on day 3, and cows with 10 ml of SP and 0.5 ml of SP diluted to 10 ml showed the highest levels of EGF concentrations. In study 3, we examined the effect of SP infusion on fertility. SP infusion normalized two peaks of endometrial EGF concentrations in about 60% of repeat breeder cows and produced more pregnancies than the controls (44.4 vs. 19.4%). Therefore, we concluded that SP may contain an activity to normalize the EGF profile and restore fertility in repeat breeder cows with altered EGF profiles.

The objective of the study was to compare the fertility after using sex-sorted or conventional semen either with oestrus detection (EST) or timed artificial insemination (TAI) in Holstein heifers. Holstein heifers were randomly assigned to one of the following treatments in a 2 × 2 factorial design. Heifers in the EST group were inseminated with sex-sorted (n = 114) or conventional semen (n = 100) after spontaneous or induced oestrus. Heifers in the TAI, subjected to the 5-day Cosynch+Progesterone protocol (GnRH+P4 insertion-5d-PGF2α +P4 removal-1d-PGF2α -2d-GnRH+TAI), were inseminated with sex-sorted (n = 113) or conventional semen (n = 88). Statistical analyses were performed using PROC GLIMMIX procedure of SAS 9.4 (SAS Institute Inc., Cary, NC). Overall P/AI was 60.7% for EST and 54.2% for TAI regardless of types of semen and 68.1% for conventional and 48.9% for sex-sorted semen regardless of insemination strategies. Fertility of heifers inseminated with either sex-sorted (53.5%; 44.2%) or conventional (69.0%; 67.0%) semen did not differ between EST and TAI respectively. Besides, the interaction between the semen type and the insemination strategy was not significant for P/AI. The embryonic loss was significantly greater with sex-sorted semen (17.1%) compared to conventional semen (1.6%). There was no sire effect with sex-sorted semen on P/AI (52.6% vs. 46.2%) and embryonic loss (16.4% vs. 18.0%). As expected, sex-sorted semen resulted in more female calves (89.8% vs. 51.6%) than conventional semen. Thus, sex-sorted semen can be used with 5-day Cosynch+Progesterone protocol to eliminate the inadequate oestrus detection and to increase female calves born in dairy heifers.

Litter size of commercial dam lines of pigs has seen a significant increase over the last 20 years. Although the current large litter size of gilts and sows can be attributed to improved genetic selection and nutrition, much of the increase in total number born has occurred through the continued increase in ovulation rate over the last four decades. Ovulation rate has increased from 14 in the 80’s to today’s average of 20–25 in commercial dam lines. However, high ovulation rate not only causes increased competition between embryos (uterine crowding), but the number of potential piglets born can out strip the number available teats. In addition, fetal crowding can reduce fetal growth and comprise health and survivability of lighter weight piglets at birth. Since there is usually minimal embryo loss observed up to blastocyst formation and hatching, the majority (20 to 30%) of embryonic loss occurs during Days 10 to 30 of gestation, which encompasses a critical period of conceptus development and differentiation, pregnancy recognition signaling, and onset of implantation. This period of early embryo loss is actually essential for establishing adequate uterine space to support fetal survival for a large litter. The period of rapid conceptus elongation on Day 12 of pregnancy provides a key “selection point” for regulating potential litter size in the pig. Establishing the fundamental roles of conceptus- and uterine-secreted factors is an essential step to develop strategies to increase placental and fetal growth to improve overall health and survivability of piglets before and after birth. During the peri-implantation period of pregnancy, porcine conceptuses produce interleukin-1B2, estrogens, prostaglandins and interferons. CRISPR/Cas9 genomic engineering technology has provided a direct method to evaluate the role of key pig conceptus genes. Loss-of-function studies have increased our understanding of the multiplicity of uterine/conceptus factors that are involved with maintenance of pregnancy.

The embryonic mortality in cows is a growing concern for an ever-expanding dairy industry. The current study was an attempt to shorten the open period of dairy cows having suffered embryonic loss by diagnosing them at an earlier stage. The blood samples were collected from the Karan Fries (KF) cows on days 0 (day of AI/estrus), 4, 8, 12, 14, 16, 18, 21, 24, 28, 35 and 42 post insemination. The experimental animals were then categorized into pregnant (P), conception failure/early embryonic mortality (EEM) and late embryonic mortality cows (LEM), based on progesterone assay, ultrasonography and per-rectal palpation. There were 6 animals in each group. The plasma progesterone was higher in pregnant than EEM and LEM cows. Plasma Interferon-tau concentration was significantly (p0.05) lower in LEM than pregnant cows where it could be detected from day 14-21 but was non-detectable in EEM cows. The mRNA expression of ISG15, OAS1, MX1 and MX2 in blood neutrophils was significantly (p 0.05) higher from day 8-42 as against day 0 in pregnant cows. The highest expression was observed around day 18-21 in pregnant cows. The ISG15, OAS1, MX1 and MX2 mRNA expression was significantly (p 0.05) higher from day 4-42 as compared to day 0 in LEM cows, whereas in EEM cows the expression stayed close to that of day 0 (1.00 ± 0.00). The mRNA expression of ISG15, OAS1, MX1 and MX2 started to decline from day 24 onwards. The degree of expression of Interferon-tau stimulated genes was higher in pregnant and LEM cows than EEM cows. The study reveals that the Interferon tau stimulated gene expression in neutrophils can act as peripheral biomarkers for detecting the embryonic mortality in dairy cows.

The objective of this study was to elucidate the impact of parity on the efficiency of three different protocols to synchronize time of ovulation in Holstein cows. All cows enrolled in this trial were categorized into primiparous and multiparous (M 1 = 2–3 and M 2 ≥3 parities). Conception (P/AI at Day 28) and pregnancy (P/AI at Day 75) rates in the Presynch and CIDRsynch (31.7% and 35.5%; 26.3% and 28.4%, respectively) groups were significantly greater than that in spontaneous estrus (SE; 24.7 and 20.4%, respectively) group (P = 0.048 and 0.024; 0.041 and 0.011, respectively); however, no significant differences were detected between the SE and Ovsynch group for conception, pregnancy, and embryonic loss rates. Conception and pregnancy rates in the Presynch group decreased from 37.8% and 33.5%, respectively in primiparous cows to 29.6% and 23.1%, respectively in M 1 cows (P = 0.022 and 0.007, respectively). However, conception and pregnancy rates using the CIDRsynch regimen were increased from 31.1% and 23.8% in primiparous cows to 41.4% and 34.7% in M 1 cows (P = 0.017 and 0.008, respectively), and 40.9% and 33.6% in M 2 cows (P = 0.021 and 0.019, respectively). Embryonic loss rate using the CIDRsynch protocol was decreased from 22.9% in primiparous cows to 15.1% and 18.2% in M 1 and M 2 cows (P = 0.013 and 0.130, respectively). On the contrary, embryonic loss rate using the Ovsynch protocol was increased from 11.5% in primiparous cows to 22.1% and 21.8% in M 1 and M 2 cows (P = 0.001 and 0.003, respectively). The Cox proportional-hazards model of embryonic loss showed significant associations for parity and season of calving with the hazard of embryonic loss (P = 0.001 and 0.016, respectively). Multiparous cows (M1 and M2) had a higher risk of embryonic loss than primiparous cows (Hazard ratio = 1.32 and 1.89, respectively). Our results indicate that use of the CIDRsynch regimen may achieve satisfactory conception and pregnancy rates in multiparous Holstein cows. However, synchronizing time of ovulation in primiparous cows with use of the Presynch treatment increases the fertility indices.

Lymphocytic foci (also known as lymphoid aggregates or tertiary lymphoid structures) form within the bovine endometrium after antigenic challenge. Their presence in the pregnant uterus provides evidence for a chronic inflammatory condition perhaps arising from an early postpartum uterine infection. The chronic inflammation that includes the foci could explain greater embryonic loss in dairy cows with early postpartum uterine disease. The objectives were to characterize the size and location of the foci in the pregnant uterus, determine their composition using immunohistochemistry, and associate their presence with the development of the pregnancy and embryonic loss. Pregnant cows (n = 43) were slaughtered on days 28, 35, or 42 of pregnancy. Uterine tissue was collected and processed for histologic and immunohistochemical analysis. The number of small (100 micron diameter), intermediate (100-250 micron diameter), and large (250 micron diameter) foci was counted. The number of cows averaging 0, 0.1 to 1, 1.1 to 2, and more than 2 foci per section (small, intermediate, and large; combined) was 7 (16%), 14 (33%), 11 (26%), and 11 (26%), respectively. The average number of small and intermediate foci found in the histologic sections was greater in cows with evidence of uterine infection postpartum (P 0.05). Lymphocytic foci were distributed within the caruncle and the intercaruncular tissue and comprised a core of CD3-positive cells (T cells) surrounding CD79-positive cells (B cells). The number of lymphocytic foci was correlated with a total inflammation score (on the basis of the total number of inflammatory cells in the endometrium; r(2) = 0.49; P 0.001) and a fibrosis score (based on the extent of fibrosis in the endometrium; r(2) = 0.33; P 0.001). Cows with a high foci count (averaging more than 0.5 foci per section) had lesser (P 0.01) placental weight on Day 42 of pregnancy. There was no effect of foci count on placental weight on Day 28 or 35. Two cows with embryonic loss were in the highest quartile for foci count. In conclusion, cows with chronic inflammation as evidenced by a large number of lymphocytic foci had reduced placental weight during pregnancy. The number of foci in pregnant cows was associated with early postpartum uterine disease. Whether the foci themselves are inhibitory to pregnancy development or are associated with other bacteriological, morphological, or biochemical changes to the uterus that lead to infertility will need to be investigated.

This study evaluated the influence of artificial insemination (AI) by cervical retraction (CRI) on serum levels of interferon gamma (IFNγ) and interleukin-10 (IL-10) in ewes. Synchronized pluriparous Santa Ines ewes were subjected to natural mating (NM, n = 8) and AI, which was performed for a fixed time (55 ± 1 hour) by CRI (n = 8) or laparoscopy (n = 8). Ewes were classified as pregnant, with return to estrus (RE) or with embryonic loss (EL). Blood samples were collected on Day 0, Day 3, Day 5, Day 12, and Day 17 (Day 0 = AI/NM) for progesterone dosage and cytokines were quantified from Day 0 to Day 12. Progesterone levels were constant, except for a decrease in ewes with RE at Day 17 (P

Fixed timed-AI (TAI) pregnancy rates were compared in suckled beef cows (n = 883; 5 replications) synchronized using the 5-d CO-Synch protocol with (CDR) or without (NCDR) the inclusion of exogenous progesterone (EAZI-BREED CIDR insert; CIDR). Cows were assigned to either the CDR (n = 445) or NCDR (n = 438) treatment by breed, parity, and days postpartum. Blood samples were collected 10 d before and immediately before CIDR insertion (d 0) to determine cyclic status. On d 0 all cows received gonadotropin-releasing hormone (100 μg), and cows in the CDR treatment received a CIDR. On d 5, CIDR were removed in CDR treatment and all cows received 2 separate doses of prostaglandin F 2α (25 mg/dose). Cows were TAI 72 h after CIDR removal (d 8), concurrent with gonadotropin-releasing hormone (100 μg). The proportion of females determined to be cyclic before estrous synchronization was 87.1% (757/869). Timed-AI pregnancy rates were greater ( P = 0.05) in CDR (62.3%, n = 438) than NCDR (50.7%, n = 436) treatment. However, a treatment × parity interaction ( P = 0.08) was noted relative to TAI. Although CDR obtained greater ( P ≤ 0.01) TAI pregnancy rates than NCDR in both primiparous and multiparous groups, difference between treatments was greater in primiparous females (69.0 vs. 46.3% for CDR and NCDR, respectively) than multiparous females (60.7 vs. 51.7% for CDR and NCDR, respectively). To optimize TAI pregnancy rates in beef cows synchronized with the 5-d CO-Synch protocol, inclusion of a CIDR is recommended.

To investigate the effect of uterine space on timing of embryonic mortality, multiparous sows were left intact (CTR; n=42) or subjected to unilateral oviduct ligation (LIG; n=23), after their first post wean oestrus. Intact sows were killed at day 9 (n=10), day 21 (n=15), or day 35 (n=17), and LIG sows were killed at day 21 (n=11) or day 35 (n=12) of gestation. At day 9, 92% of ovulations were represented by an embryo. At day 21, embryonic mortality was 24% and was not altered by increasing uterine space. At day 35, space per embryo was twice as large in LIG sows (30±3 v. 16±0.8 cm), and implantation length tended to be larger (19.0±1.2 v. 15.5±1.3 cm). Between day 21 and day 35, CTR sows lost another 8% to 14% of their embryos, whereas LIG sows lost none. Embryos tended to be heavier (4.9±0.2 v. 4.3±0.3 g) in LIG sows. In conclusion, embryonic loss in multiparous sows is 24% by day 21 and is not related to space, whereas after day 21 limited space causes additional 8% to 14% embryonic mortality in intact sows only.

Embryonic loss in cattle may be related to a hormonal imbalance resulting in alterations in timing of prostaglandin F2α (PGF2α) secretion around the time of maternal recognition of pregnancy. The objective of this study was to examine effects of aspirin (a PGF2α inhibitor) on pregnancy per AI (P/AI), and progesterone (P4), and pregnancy specific protein B (PSPB) concentrations in lactating dairy cows inseminated more than once after parturition. Fourteen days after second or subsequent AI (Day 0 = Day of AI), 556 cows were assigned randomly to aspirin (187.2 g total; n = 277) or control (n = 279) groups. Aspirin was administered orally on Day 14 and 15, and control cows were subjected to sham bolus administration. On Day 25, blood samples were collected from a subset of cows (n = 194) to quantify P4 and PSPB, whereas pregnancy was determined in all cows at 35–42 days post-AI. Maximum daily ambient temperature ranged from 38-41 °C during the experiment. Mean parity, days in milk, and times bred before treatment (TBRD) did not differ between groups. There were no differences in P/AI between treatments (aspirin 21.6 % compared with control 27.5 %). Neither treatment, parity, TBRD, or any two-way interactions with treatment affected concentrations of P4. Moreover, there were no effects (P > 0.50) of treatment, or treatment by TBRD interaction on serum PSPB concentrations. A tendency (P = 0.07) occurred for multiparous cows to have greater serum PSPB concentrations compared with primiparous cows. Mean serum PSPB concentrations tended (P = 0.07) to be greater for second or third TBRD compared to fourth and greater TBRD. These results provide evidence that aspirin administered during periods of heat stress after the second and subsequent AI post-partum during the summer months does not improve P/AI or alter P4 and PSPB in lactating dairy cows.

Objectives were to determine relative ovary location of follicles, GnRH-induced corpora lutea (CL), and older CL present in ovaries as part of ovulation synchronization and their associations with progesterone concentration and risk for luteolysis, ovulation, and pregnancy. Cows were exposed to a timed artificial insemination (AI) program [GnRH-1-7 d-PGF2α (1 dose or 2 doses 24 h apart)-56 h after first or only dose of PGF2α-GnRH-2-16 h-timed AI at 72 ± 3 d in milk]. Blood was collected to assess progesterone when ovarian structures were mapped in 694 cows before GnRH-1 and before and 48 h after PGF2α and, in a subset of cows, size of CL (n = 599) and progesterone (n = 380) at 6 d after AI. Dominant follicles and CL in single-ovulating cows were detected more often in right than left ovaries (follicles before GnRH-1: 60.6% right and GnRH-2: 61.2% right; and CL before GnRH-1: 58.6% right and GnRH-2: 66.4% right). Dominant follicles in single-ovulating cows before GnRH-1 tended to be ipsilateral to the CL more often than contralateral (54.8 vs. 45.2%) with co-dominant follicles identified in both ovaries (19.3%). In response to GnRH-1 or GnRH-2, more left-ovary follicles ovulated contralateral to CL (left to right, 54.7%; right to left, 34.7%) than right-ovary follicles, but fewer left-ovary follicles ovulated ipsilateral to CL (left to left: 45.3%) than right-ovary follicles ovulated ipsilateral (right to right: 65.3%). Preovulatory follicles in single-ovulating cows before PGF2α tended to be detected more often ipsilateral than contralateral to CL induced by GnRH-1 (younger CL; 56.5 vs. 43.6%), but were of equal frequency ipsilateral or contralateral to older CL present before GnRH-1. Luteolytic risk was less in cows bearing co-dominant follicles in both ovaries compared with those in either right or left ovaries. Luteolytic risk in single-ovulating cows did not differ between ovaries. Luteolytic risk was greater for cows bearing older CL (86.5%) than for cows bearing younger GnRH-1-induced CL (65.3%) or both (79.6%). Pregnancy risk at 60 d after AI was or tended to be greater in cows having both CL types compared with either younger or older CL, respectively, partly because of greater embryonic loss in the latter 2 cases. More female calves tended to be carried in right horns when conception occurred after first service, whereas the opposite greater female frequency occurred in left horns after repeat services. Right-ovary dominance is evident before and after GnRH treatment.

Equine embryos tolerate an unusually large degree of negative uterine asynchrony (recipient mare up to 5 days behind the donor mare). By contrast, positive asynchrony of more than 2 days results in a high incidence of early embryonic loss (EEL). Day 8 embryos range in diameter from approximately 130-1300 μm, with embryos smaller than 300 μm reported to suffer an increased incidence of EEL. However, it is not known whether this reduced viability is due to intrinsically poor embryo quality, or to inadvertent recipient uterine stage-embryo (positive) asynchrony. To examine whether small embryos survive better in Day 4-5 recipients than in recipients with a more advanced uterine stage, the likelihood of pregnancy (PR) and EEL for 62 small ( 0.1). The EEL for small embryos transferred into Day 4-5, 6-7 and 8-9 recipients was 20.8, 18.7 and 25.0%, respectively. We conclude that embryos recovered on Day 8 with a diameter

The main objective of the present study was to compare milk production in pregnant versus nonpregnant dromedary camels. In addition, we described the effect of embryonic mortality on lactation and measured serum progesterone levels until d 60 to 90 of gestation. Twenty-five multiparous camels were selected in midlactation for 2 studies in consecutive years. Camels were mated naturally when the size of the dominant follicle reached 1.2 to 1.5cm. Pregnancy was diagnosed by ultrasonography and progesterone determination. In the first experiment (Exp 1), 8 of 11 animals conceived at 284±21.5d postpartum. Three pregnant dromedaries were given PGF2α to induce luteolysis and pregnancy loss on d 62 and spontaneous embryonic loss was detected in 2 camels (on d 27 and 60). Animals were allotted to 3 groups retrospectively: nonpregnant camels (group 1, n=4), pregnant camels (group 2; n=3), and camels with embryonic loss after d 55 (group 3; n=4). In the second study (Exp 2), 14 dromedaries were mated during midlactation. Seven of them failed to conceive (group 1) and 7 became pregnant (group 2). No embryonic loss was detected in Exp 2. Turning points in milk production were identified by change point analysis. In nonpregnant dromedaries (group 1), milk decreased slowly over time without significant change point. In pregnant camels (group 2), a gradual decline until 4 wk after mating was followed by a sudden drop, and the change point model resulted in one breakpoint at d 28±7 and 35±3 of gestation in Exp 1 and Exp 2, respectively. In camels with embryonic mortality (group 3, Exp 1), milk yield started to decline similarly as in pregnant animals, but milk production increased gradually after embryonic loss and reached similar levels as in their nonpregnant herdmates. Change point analysis for group 3 resulted in 2 turning points at 30±4 and 48±4d after conception. Mean length of lactation was shorter by 230 (34.2%) and by 249d (37.6%) and mean total lactation production was decreased by 1,532 (31.6%) and 2,151 kg (44.3%) in pregnant compared with nonpregnant camels in Exp 1 and Exp 2, respectively. We concluded that the calving interval can be shortened by mating during midlactation. However, pregnancy has a strong negative effect on milk production as dromedaries stop lactating by the fourth month of gestation. Following embryonic mortality within 3mo of conception, milk production is restored.

The objective of this study was to elucidate the efficiency of Ovsynch protocol, new (N-CIDRsynch) and once-used (U-CIDRsynch) controlled internal drug-release (CIDR) devices to synchronize the ovulation time of primiparous and multiparous Holstein cows. The current study was performed on a total of 2207 cows using three different synchronized groups. Conception [pregnancy per AI (P/AI) at day 28] and pregnancy (P/AI at day 75) rates using the N-CIDRsynch and U-CIDRsynch regimens (35.9% and 29.6%; 29.2% and 25.1%, respectively) were significantly greater than those in the Ovsynch group [Odds ratio (OR)=1.88 and 1.44; 1.92 and 1.52, respectively]. Embryonic loss rate did not differ significantly (P>0.05) among the Ovsynch, N-CIDRsynch and U-CIDRsynch regimens. In primiparous cows, no significant differences were found in conception and pregnancy rates between the U-CIDRsynch and N-CIDRsynch groups (OR=0.95 and 1.12; p=0.693 and 0.451, respectively). In multiparous cows, conception and pregnancy rates in the N-CIDRsynch group were significantly greater than those observed in the U-CIDRsynch group (OR=0.66 and 0.71; p=0.016 and 0.027, respectively) and embryonic loss rate in multiparous cows was lower for the U-CIDRsynch treatment than for the N-CIDRsynch treated cows (COR=0.58; p=0.048). The present study indicates that the use of a progesterone device in a synchronization protocol may improve fertility in dairy cows compared to the Ovsynch treatment. The use of U-CIDRsynch regimen may achieve satisfactory fertility results compared to those reported with N-CIDRsynch in primiparous Holstein cows.

Contents Over a 25-month period 8118 blood samples were assayed for the presence of the serum pregnancy specific-protein B (PSPB) and progesteron (P4) concentrations on three Hungarian large-scale dairy farms. Pregnancy (n = 4085) was checked by BioPRYN assay at 30–36 days post-insemination (PI). Samples from all cows that tested not pregnant and from cows with an optical density (OD) reading in the BioPRYN test that was between 0% and 30% above the cutoff OD value were tested for serum P4 concentration. According to serum P4 concentration, cows were assigned to three categories: high (>4 ng/ml), medium (2–4 ng/ml) and low (

In buffalo species embryonic mortality is considered one of the major causes of fertility loss, especially in the animals that are not mated during their reproductive period. Embryonic loss in animals mated by artificial insemination (AI) is 20-40% during seasons characterized by high number of light hours. Also in buffalo naturally mated the incidence of embryonic mortality is about 20% and a higher incidence is observed between 28- 60 days of gestation in buffaloes that conceive during increasing daylight length. A reduced capacity to secrete progesterone seems to explain in part this embryonic mortality but other as yet unidentified factors contribute between 40-50% to the embryonic losses. Treatments with hCG, GnRH agonist or progesterone on Days 5 after AI not always reduce embryonic mortality in buffalo species. Embryonic mortality in buffaloes appears to occur later (Day 25-40) than in cattle and P4 treatments should perhaps be applied later in buffaloes.

The objective of this study was to evaluate the impact of thermal stress on the efficiency of three different protocols to synchronize time of ovulation in purebred Holstein cows under subtropical Egyptian conditions. The influence of temperature humidity index (THI) on the conception, pregnancy, embryonic loss and early abortion rates were investigated. Conception and pregnancy rates using the CIDRsynch and Presynch (37.5% and 33.9%; 29.5 and 29. 6%, respectively) were significantly greater than that for cows expressing spontaneous estrus (SE) and with use of the Ovsynch (28.5% and 24.3%; 21.6% and 24.6%, respectively) treatment regimen. Conception and pregnancy rates using the Ovsynch protocol were significantly decreased from 31.6% and 26.3% at the lesser THI to 11.5% and 9.9%, respectively than at the greater THI [crude odds ratio (COR) = 0.28 and 0.32; P = 0.001 and 0.004, respectively]. However, conception (P/AI at 28 days) and pregnancy (P/AI at 75 days) rates using the Presynch protocol were significantly reduced at either the lesser or greater THI (COR = 0.47 and 0.42; 0.48 and 0.34, respectively). Embryonic loss rate with the Presynch group was significantly increased from 11.5% at the lesser THI to 22.2% at the greater THI (COR = 2.28; P = 0.039). In contrast, conception, pregnancy and embryonic loss rates did not differ significantly (P > 0.05) with the CIDRsynch protocol at the different THI. Results from the present study indicate that use of the CIDRsynch protocol may provide consistent and satisfactory conception and pregnancy rates in Holstein cows under subtropical environmental conditions.

Alpha-fetoprotein has proved to be a good indicator of fetal well-being in human medicine for decades. Although this molecule is present in most of the mammalian species including horses, reference values in healthy and high-risk pregnant mares have not yet been published. The aim of the present study was to determine whether equine alpha-fetoprotein (eqAFP) is a good indicator of complicated pregnancies in Lipizzaner mares. A total of 111 serum samples from 30 mares have been analyzed for eqAFP levels throughout gestation (Days 60-325). After the pregnancy was confirmed, 23 mares had normal pregnancies with viable foals, six had late embryonic loss, and one of the mares aborted in the ninth gestational month. Equine alpha-fetoprotein concentrations significantly differed in the normal group (72.93 ± 49.25 pg/mL; mean ± standard deviation) and in the complicated pregnancy loss group (152 ± 36.48 pg/mL; mean ± standard deviation). The mares' age, gestational age, and the conception rate significantly affected the alpha-fetoprotein concentrations in the normal group. Furthermore, notable individual differences occurred in eqAFP concentrations between mares. Equine alpha-fetoprotein seems to be an important indicator of fetal well-being in horses, but there are still some unanswered questions (levels in foals of different age, ponies, and draft horses) regarding this serum protein. Large-scale studies are needed to assess the specificity, sensitivity, and reliability of this test as a possible future diagnostic tool for fetal well-being in horses.

Embryonic loss occurring in the first week of the incubation is termed early embryonic mortality. Environmental, technological and genetic factors can be responsible for its appearance. The examina...

The objective of the study was to determine the effect of flunixin meglumine (FM; a non-steroid antiflammatory drug) on the length of the estrous cycle and luteal phase, with the aim of increasing lambing rate and prolificacy in Pelibuey ewes. Two groups of females under a natural mating system were allotted to two groups: a FM-2 group, with ewes (n = 46) treated with 2.2 mg/kg of FM twice a day (06:00 and 18:00 h); a control group, with ewes (n = 50) given a placebo once a day (06:00 h). Both groups were treated for 8 days, starting at day 11 following mating. Blood samples from 10 ewes per group were collected every 3rd day, and from day 15 (mating = day 0) blood samples were taken daily, until ewes showed estrus or until day 21, whichever was first. The lambing rate was 58.0% and 56.5% for the control and FM-2 group respectively, while the length of the estrous cycle (19.4 ± 0.8 days) and luteal phase (15.3 ± 0.4 days) was longer (P

For the embryo to successfully complete development it must be capable of executing its developmental program within a microenvironment largely established by the mother. Mortality results either because of intrinsic defects within the embryo, an inadequate maternal environment, asynchrony between embryo and mother, or failure of the mother to respond appropriately to embryonic signals. To some extent, the embryo’s fate is dictated by events before fertilization: embryos formed from incompetent oocytes have a low probability of successful development. For example, embryos have reduced developmental competence when formed from oocytes from persistent ovarian follicles or from cows during the summer in Florida. Chromosomal abnormalities, caused by incompetent gametes or other causes, and homozygous recessive genes, exacerbated by inbreeding, represent additional types of intrinsic errors responsible for embryonic loss. Alterations in the maternal environment can cause embryonic mortality, as has been shown for heat stress and feeding diets high

Reproductive tracts were collected from 870 ewes slaughtered at an abattoir in County Dublin over a 9-mo period from September 1993 to June 1994. Ovarian activity was evident in 59.3% of the tracts examined. The mean ovulation rate was 1.26 ± 0.045 (mean ± SEM). The spatial relationship between corpora lutea (CL) and dominant follicles was established. Ten percent of the ewes examined were pregnant. Embryonic transuterine migration was observed in 12% of the single ovulating ewes and in all ewes pregnant with twins which had double ovulations on one ovary. Based on the observation of tracts with contemporaneous double ovulations and a single fetus, the prevalence of embryonic loss was 17.2%. Overall, 9.4% of the tracts showed evidence of pathological change, and 5.5% of the tracts had abnormalities likely to impair fertility.

Poor reproductive efficiency is a worldwide problem that has affected the dairy industry during the last several decades. In an attempt to explain the changes in reproductive physiology caused by high milk production, a model of elevated steroid metabolism in lactating dairy cows has been proposed. A slow increase in levels and low peak levels of estradiol (E2) and progesterone (P4) characterize endocrine changes in high producing cows. Similar changes have been reported in the repeat breeder cows. The abnormal changes in E2 and P4 concentrations of these cows may cause an improper uterine environment due to disturbed expression of growth factors and cytokines in the endometrium. This review focuses on the alteration in epidermal growth factor (EGF) profile in the endometrium during the estrous cycle. The normal cow has two peaks of EGF concentrations on days 2–4 and 13–14. Low concentrations of EGF on these days distinguished both high-producing and repeat breeder cows from normal cows. Alteration of the EGF profile could be found in 70 and 40% of the repeat breeder and high-producing cows, respectively. Treatment with a high dose of estradiol benzoate and an intravaginal progesterone-releasing device restored the normal EGF profile in about 70% of the affected cows. The cows having a normal EGF profile after treatment showed a higher pregnancy rate than the cows with the altered profile. Further studies to understand the etiology of the alteration in the EGF profile are needed to develop another treatment option and preventive management for this problem.

Early pregnancy factor (EPF) is detectable in sera of pregnant cattle within 24 to 48 h after fertilization. It has been considered that the repeat breeder is relatively sterile as a result of fertilization failure and the early embryonic loss. This study used the rossete inhibition test to clarify whether repeat breeding is a result of early embyronic loss. We measured serum EPF in cattle that were diagnosed as repeat breeders to examine the incidence of early embryonic losses after artificial insemination (AI) (n=20). There were no significant differences in the presence of EPF on day 3 after AI for 20 repeat breeders and controls. Furthermore, EPF-positive rates decreased about 60% by day 21 after AI for both repeat breeders and a control group. It is suggested that a high incidence of early embryonic losses takes place in cattle, and we attempted embryo transfer (ET) as the treatment of choice.

The aim of this study was to evaluate the efficiency of presynchronization with GnRH and PGF(2 alpha) or with progesterone on overall Ovsynch (OVS) outcomes in noncyclic dairy cows. Cows were scanned 7 d apart with ultrasonography to determine cyclicity. Noncyclic cows (n = 281; no corpus luteum on ovaries at both examinations) were randomly divided into 3 groups. In the GP group (n = 108), the cows received GnRH and PGF(2 alpha) (PGF) administrations 7 d apart, and OVS was started 11 d after PGF (GnRH-7 d-PGF-11 d-OVS). In the P4 group (n = 90), the cows were treated for 7 d with an intravaginal progesterone (P4) implant (PRID), and then OVS was started 11 d after removal of the implant (7 d PRID-11 d-OVS). The control group (CON, n = 83) did not receive any presynchronization, and OVS was started at the same time as in the other groups (18 d-OVS). The percentage of cows that became cyclic at the beginning of OVS was lower in the CON group (38.6%; 32/83) than in the presynchronization groups (66.7%, 72/108 in GP; 71.1%, 64/90 in P4). The response to the first GnRH of OVS did not differ among groups (63.9%, 53/83 in CON; 67.6%, 73/108 in GP; 63.3%; 57/90 in P4), and synchronization rates were similar among the groups (74-82%). The cows that responded to presynchronization treatments (GP or P4) had higher pregnancy per artificial insemination (P/AI) than did nonresponding cows. Pregnancy per AI at 31 d did not differ between groups (30.1%, 25/83 in CON; 43.5%, 47/108 in GP; and 35.6%, 32/90 in P4). However, CON cows (24.1%, 20/83) had lower P/AI at 62 d than GP cows (41.7%, 45/108). Embryonic loss was higher in CON (20%, 5/25) compared with the P4 group (3%, 1/32). The administration of GnRH followed by PGF or exogenous progesterone (PRID) similarly increased the percentage of cows that became cyclic before Ovsynch in noncyclic cows, but fertility did not improve. However, the cows that responded to presynchronization had higher fertility rates than the nonresponding cows.

A study was done to evaluate the effect of using progesterone (P4) intravaginal device (CIDR: controlled internal drug-releasing dispenser) to synchronise the return to oestrus of previously timed inseminated (TAI) dairy heifers, and to evaluate embryo survival and pregnancy rate (PR) in the return to oestrus heifers. At the onset of the artificial insemination (AI) breeding period (day −9), heifers were randomly assigned into two groups (treated group CGPG, n = 79) and (control group GPG, n = 83). Every heifer in both groups was injected with gonadotropin-releasing hormone (GnRH) agonist and prostaglandin F2-alpha (PGF2α) as follows: GnRH on day −9; PGF2α on day −2; GnRH and TAI on day 0. Heifers in both groups received TAI within 30 min after the second GnRH injection. Artificial insemination at first breeding was conducted for all heifers during 55 days from day 0. On day 14 after timed insemination, every heifer in the CGPG group received CIDR device for 6 days. Within 3 days after CIDR removal, more heifers in CGPG group showed oestrus within 1.9 days compared to heifers that showed oestrus within 2.9 days in the control. Within 10 days after CIDR removal, more heifers in the CGPG group showed oestrus within 2.4 days compared to heifers that showed oestrus within 6.7 days in the control. PRs on days 30 and 55 were not different between both groups, while PR on day 55 during September were higher (P = 0.032) in CGPG group (58.0%) than GPG group (37.0%). In addition, PR from first to second AI was higher (P = 0.037) for CGPG group (79.8%) than for GPG group (65.1%) but it was similar after that. Pregnancy losses between days 30 and 55 tended to be lower (P = 0.089) for the CGPG group (12.7%) compared to 25.1% for the GPG group. Interval between first and second AI was lower (P = 0.052) for the CGPG group (27.5 ± 1.6 days) compared to 31.6 ± 1.3 days for heifers in the GPG group but no differences were detected for intervals from second to third AI and from third to fourth AI between the two groups. Number of services per pregnancy was not different between CGPG and GPG groups. Results indicate that the CIDR device improved synchronisation to return to oestrus and increased PR to first AI during high temperature months by reducing embryonic losses.

The effects of grazing endophyte-infected tall fescue on luteal function, pregnancy rates, and embryonic loss rates were compared between treated mares (n=18) and untreated controls (endophyte-free, n=12). Mares grazing endophyte-infected fescue demonstrated significantly (P0.01) prolonged luteal function (22.9 vs 15.8 d) than those grazing endophyte-free fescue. Continuous grazing of endophyte-infected fescue resulted in a decreased (P=0.30) per cycle 14-d viable pregnancy rate (14/31, 45.2%) compared with that of endophyte-free grazing (12/16, 75.0%). Early embryonic death rates were higher (P=0.20) in the endophyte-infected group (6/20, 30.0%) than the endophyte-free group (1/13, 7.7%). Cumulative pregnancy rates after a 60-d breeding period did not differ between the 2 groups. Embryonic development based on mean vesicle height at 14-d was not significantly different between treatment groups for embryos that maintained viability. Embryos that underwent early embryonic death were smaller (P0.10) at Day-14 than embryos that maintained viability. Mean plasma progesterone concentrations were significantly (P0.01) greater at Day-21 postovulation in endophyte-infected mares in which the embryo remained viable (15.8 ng/ml) than in endophyte-free mares that experienced early embryonic death (9.8 ng/ml) or that demonstrated prolongation of luteal function (11.2 ng/ml). The results of this study suggest that grazing endophyte-infected tall fescue can have a detrimental effect on reproductive efficiency in the mare due to an increase in cycles bred per pregnancy rate, increased early embryonic death rate and prolongation of luteal function.

A total of 240 pregnant genitalia of Iraqi goats consisting of 193 single, 46 twin and one triplet pregnancies were studied. Distribution of 288 fetuses in the right and left horns was in the ratio of 54 t0 46, respectively. Volume of allantoic and amniotic fluids increased with advancing pregnancy. Consistency of allantoic fluid was watery throughout gestation, and colour changed from colourless to yellow and turbid as pregnancy advanced. The amniotic fluid was watery until crown rump length (CRL) was 20 cm, subsequently becoming mucoid and gelatinous. Incidence of early embryonic loss was 8.3% in single pregnancies. Trans-uterine migration was 37.8% in single and 19.6% in twin pregnancies. Mean (±SD) length, width, thickness and weight of the right ovary were 2.2±0.5 cm, 1.6±0.3 cm, 1.0±0.2 cm and 2.3±0.9 g, respectively; and those of the left ovary were 2.2±0.4 cm, 1.5±0.3 cm, 0.9±0.9 cm and 2.1±0.9 g, respectively. Mean diameter and weight of corpora lutea in the right ovary were 1.5±0.3 cm and 1.1±0.2 g, respectively, and 1.4±0.3 cm and 1.1±0.3 g for the left ovary. This study indicated that the right ovary was more active than the left, whereas fetal migration was toward the left horn. Low twinning percentage was also observed.

Ultrasonographic observations were carried out at 10-day intervals from 27 to 107 days of gestation, to monitor embryonic losses in Japanese Black cows which received two or three embryos that had been transferred nonsurgically on Day 7 (Day 0 = estrus). Group I cows (n=60) received two embryos, one in each uterine horn. Group II cows (n=31) received three embryos, two embryos in the uterine horn ipsilateral to the corpus luteum and one embryo in the uterine horn contralateral to the corpus luteum. The Group II pregnancy rate was maintained above 83.9% until Day 37, but it decreased significantly (P

Two levels of energy and protein fed to gilts from days 3 to 15 of gestation had no effect on plasma progesterone in early pregnancy or embryo survival to day 28. However, overall, day 3 progesterone concentrations were positively related to embryo survival (P

Information is lacking as to the timing and cause of sows that repeatedly have low litter size over several parities. Sows evaluated for the present study had at least two parities either smallor=7 (SL) or normalor=12 (NL) litter size. Following breeding of sows with contemporary boars, reproductive tracts were obtained on day 30 of gestation. There was no difference (p0.10) between SL and NL sows in the number of CL, embryo weight or placental length. The total number of embryos and embryonic survival tended to be lower (p0.10) in SL sows compared with NL sows, but there were 5.1 less viable embryos (p0.03) in SL. Results indicate that time of conceptus loss in SL sows was variable throughout gestation.

A study on postpartum dairy cows was done to evaluate the effect of using progesterone intravaginal device (CIDR) to synchronize return to oestrus of previously timed inseminated (TAI) cows and to evaluate embryo survival and pregnancy rate in the return to oestrus cows. All cows were subjected to TAI program. On Day 14 after AI, cows were assigned randomly into two groups: treated group (CTAI; n=126) and control group (TAI; n=172). Every cow in the CTAI group received CIDR device for 7 days. Cows were observed for oestrus after CIDR removal in the first period (Days 21-28). Cows, which did not show oestrus, were retreated with CIDR on Day 28 for 7 days and they were observed for oestrus after CIDR removal in the second period (Days 35-42). Pregnancy was diagnosed on Days 28, 45 and 90 after AI. In the first period, more cows in the CTAI group showed oestrus within 2.4 days after CIDR removal compared to cows within 4 days in the control. In the second period, more cows in the CTAI group showed oestrus within 4.5 days compared to cows within 3.7 days in the control. Pregnancy rates on Day 28 were not different between both groups. Pregnancy rates on Days 45 and 90 were higher for cows in the CTAI (42.1+/-5.3%, P=0.028 and 38.9+/-5.2%, P=0.020) compared to that in the TAI group (35.5+/-3.9% and 31.9+/-3.8%). Moreover, pregnancy rates were lower for multiparous cows (34.2+/-4.1, P=0.017 and 30.2+/-3.9%, P=0.008) compared to primiparous cows (42.7+/-5.2% and 39.9+/-5.1%) on Days 45 and 90, respectively. Pregnancy losses between Days 28-45 and 45-90 tended to be lower for the CTAI group and primiparous cows compared to the TAI group and multiparous cows. Pregnancy rates of first (P=0.020), second, third and up to fourth AI were higher (P=0.001) for the CTAI group (38.9+/-0.05%, 78.6+/-0.05%, 92.1+/-0.04%, 93.6+/-3.71%) compared to that for the TAI group (31.9+/-0.03%, 54.1+/-0.04%, 68.0+/-0.03%, 81.4+/-2.75%, respectively). Days open for pregnant cows were similar in both groups, but lower (P=0.025) for primiparous cows (81.6+/-4 day) compared to multiparous cows (93.8+/-3 day). Number of services for pregnant cows was lower (P=0.002) for the CTAI group (1.70+/-0.10) compared to that for the TAI group (2.14+/-0.09), whereas it was similar for primiparous and multiparous cows. Results indicate that the CIDR device improved synchronization to return to oestrus and increased pregnancy rate to first, second, third and fourth AI by reducing embryonic and fetal losses.

Lactating Holstein cows (n = 711) on a commercial dairy farm in Wisconsin received a hormonal synchronization protocol to initiate first timed artificial insemination (TAI) on the following postpartum schedule: two injections of 25 mg PGF2alpha at 32 +/- 3 d and 46 +/- 3 d (Presynch); 100 microg GnRH at 60 +/- 3 d; 25 mg PGF2alpha at 67 +/- 3 d; and 100 microg GnRH + TAI at 69 +/- 3 d (Ovsynch). At first TAI, cows were randomly assigned to initiate the first GnRH injection of a hormonal protocol for resynchronization of ovulation (Resynch; 100 microg GnRH, d 0, 25 mg PGF2alpha, d 7, 100 microg GnRH + TAI, d 9) at 19 (D19), 26 (D26), or 33 d (D33) after first TAI to set up a second TAI service for cows failing to conceive to Ovsynch. Overall pregnancy rate per artificial insemination (PR/AI) to Ovsynch assessed 68 d after TAI was 31% and did not differ among treatment groups. For Resynch, PR/AI was assessed 26 d after TAI for D19 and D26 cows and 33 d after TAI for D33 cows. Overall PR/AI to Resynch was 32%. However, the PR/AI for D26 (34%) and D33 (38%) cows to Resynch was greater than for D19 cows (23%). Cows with a CL at the PGF2alpha injection (D19 cows) or at the first GnRH injection (D26 + D33 cows) of Resynch exhibited greater PR/AI to Resynch compared with cows without a CL. Survival analysis (failure time) of cows in the D26 and D33 treatment groups across the first three TAI services did not differ statistically. Although administration of GnRH to pregnant cows 19 d after first TAI service did not appear to induce iatrogenic embryonic loss, initiation of Resynch 19 d after first TAI service resulted in a lower PR/AI compared with initiation of Resynch 26 or 33 d after first TAI service.

To test the hypothesis that an abnormal uterine environment was a cause of early embryonic loss in subfertile mares, morphologically normal embryos were transferred to normal mares (n = 20) and subfertile mares (n = 20), and embryo survival rates were compared. Embryos were recovered nonsurgically at Days 7 to 8 postovulation and transferred surgically to normal and subfertile mares that had ovulated on the same day or within 2 d after a donor. Survival of transferred embryos was monitored by ultrasonography of the recipient mare's uterus from Day 9 through Day 28 postovulation. There were no significant differences (P > 0.5) in the embryo survival rates at Day 12 ( 11 20 vs 9 20 ) or Day 28 ( 10 20 vs 8 20 ) for normal or subfertile mares, respectively. The uterine environment of subfertile mares was apparently adequate to support the development of transferred embryos from Days 7 or 8 through Day 28 postovulation.

Early embryonic death (EED) was studied in 354 pregnant mares during two breeding seasons. Pregnant mares from six independent research projects were examined at 15, 20, 25, 30, 35, 40 and 50 days post-ovulation using a real-time ultrasound scanner. Mares that had previously been treated with anabolic steroids tended (P 0.05) in the incidence of EED between mares inseminated with frozen-thawed and fresh semen (16.7% vs 12.5%). Further, combined over both years, there was no difference (P>0.10) in the incidence of EED (24.2% vs 14.4%). There was a 38.9% incidence of EED in infertile mares. Of the 354 pregnant mares, the overall incidence in EED through day 50 postovulation was 17.3%. The majority of EED (77.1%) occurred prior to day 35 post-ovulation. During the period 15 to 35 days post-ovulation, a greater (P

Plasma levels of LH and FSH before and after ovulation were measured in two rabbit strains (New Zealand A 1077 and Californian A 1066) having a different number of ovulations and rate of embryonic loss. Maximal concentrations and total secreted amounts before ovulation were slightly higher in New Zealand, but the difference was not significant. No relationship between the number of ovulations and the increase in plasma LH or FSH level was found in either strain. In most cases, there was no relationship between gonadotropic surge and early embryonic loss.

Serum samples were collected from pigs ( n = 28) immediately before flushing the uteri on days 2–6 after mating or insemination and investigated for the presence of early pregnancy factor (EPF) activity by the rosette inhibition test. Embryos from 15 of these animals were additionally cultured and observed for further development in vitro. With the exception of one sow, EPF-positive rosette inhibition titres (RIT) were detected only in pregnant animals. The degree of rosette inhibition was found to be positively correlated to the number of fertilized and viable ova. Regression analysis indicated that detection of EPF activity in the pig usually depends upon the presence of at least three or four live embryos. At 24 h after removal of ova an EPF-positive titre was detected in serum of only one of 13 pigs. Following the transfer of 14 and 15 embryos into two sows an increase in serum RIT occurred within 2–4 h. Disappearance of EPF activity was later confirmed to be associated with embryonic loss in both animals.

Two closed lines of sheep selected for high and low prolificacy were established in 1969. Rams within each line were selected on the basis of their dams' lambing records. Foundation ewes were assigned at random to selected rams, and no ewe selection was practiced until replacement yearlings were selected for mating. Selection of the rams used to mate the foundation ewes resulted in more lambs born per 100 ewes exposed to the ram (P Seven rams from each line were then used to estimate fertilization rate and embryonic survival rate when mated to an unrelated group of ewes. There was no difference in ovulation rate or fertilization rate of ewes mated to low and high line rams. Percent eggs recovered per CL was 80 and 92 (P

SummaryIn two separate experiments, ewes of the Scottish Blackface breed were subjected to management stresses in the first or second 10-day period after mating or were treated with daily injections of 60 i.u. ACTH for the whole 20-day period. Embryonic loss is defined as the number of corpora lutea not represented by viable embryos at slaughter. Examinations were carried out between 26 and 32 days post-mating. In the two experiments combined, losses were 29·9, 29·0, 37·7 and 17·2%, respectively, for ewes subjected to environmental stress during days 1–10, during days 11–20, treated with ACTH or kept as unstressed control. Expressed as the percentage of ewes in which partial or complete loss of shed ova occurred, the results were 49·0, 46·0, 54·3 and 25·5%, respectively. Losses were significantly higher in all treated groups than in the unstressed control.

Pregnancy rates at Days 2 and 14 postovulation were determined for 15 normal mares and 15 subfertile mares. Embryonic loss rates were estimated by the difference in the Day 2 and Day 14 pregnancy rates. Mares were artificially inseminated with the pooled ejaculates from three stallions, and the embryonic vesicle was detected with ultrasonography at Days 9, 10, 12 and 14. Mares were short-cycled with prostaglandin F(2) alpha (PGF(2alpha)) and rebred to the same stallions, and the Day 2 pregnancy rates were determined by recovery of cleaved ova (embryos) from the surgically excised oviducts. Significantly more (P0.01) normal versus subfertile mares were pregnant at Day 14 (12 15 vs 3 15 ). There was no significant difference in the Day 2 pregnancy rate for normal versus subfertile mares (10 14 vs 11 14 ). There were no significant differences (P0.5) in the mean number of blastomeres per embryo or in the mean diameter of embryos recovered at Day 2 from normal or subfertile mares. The estimated embryonic loss rate was significantly lower (P0.01) for normal verusus subfertile mares (0 10 vs 8 11 ). Fertilization rates were similar for normal and subfertile mares; however, subfertile mares had a higher embryonic loss rate prior to Day 14 postovulation.

Pregnancy rates, length of interovulatory intervals, and progesterone concentrations were examined in mares which had ultrasonically detected collections of fluid in the uterine lumen and in mares which lost the embryonic vesicle during Days 11 to 15 and did not become pseudopregnant. In mares with embryonic loss, the loss rate for mares with re-established pregnancies (9 18 ) was greater (P0.05) than the loss rate for all pregnancies (38 154 ), indicating repeatability. Pregnancy rates were higher (P0.01) in controls (100 177 ) than in mares with intrauterine fluid collections (2 34 ) or mares with embryonic loss (10 33 ), excluding the pregnancy associated with embryonic loss. The mean length (days) of the interovulatory interval was reduced (P0.05) in mares with intrauterine fluid collections (20.4 +/-0.9) and in mares with embryonic loss both for the intervals in which loss occurred (19.6 +/-0.7) and for intervals in which pregnancy was not detected (21.0 +/-1.0; controls, 23.5 +/-0.6). Mean progesterone concentration (ng/ml) on Day 7 was lower (P0.05) in mares with intrauterine fluid collections (8.8 +/-1.8) and in mares with embryonic loss (12.1 +/-1.1) than in pregnant controls (17.2 +/-0.9) and nonpregnant controls (17.5 +/-0.1). The embryonic loss seemed attributable to uterine-induced luteolysis in association with uterine inflammation, but the possibility of involvement of a primary luteal inadequacy or other factors in at least some of the mares was not eliminated.

The fertilization rate and incidence of embryonic loss in virgin Brahman crossbred heifers between d 3 and 35 postinsemination (d 0 = first day of estrus) were determined. One hundred fifty-five virgin heifers, maintained in a dry lot, received approximately 22 Mcal.head-1.d-1 and were allotted to one of three groups (d 3, 16 or 35) according to body weight at the time of estrous detection. Seven empty ruptured zona pellucidae (ERZP) were recovered from five heifers in the d 3 group. It was impossible to determine whether the ERZP originated from fertilized or unfertilized ova and whether they were ovulated at the estrus immediately preceding or during a previous cycle. Consequently, the fertilization rate (d 3) was calculated to be 80 or 93% depending upon whether the ERZP were included or deleted from the calculations, respectively. Because of the large number of ERZP recovered, a second study was conducted with an additional 21 virgin Brahman crossbred heifers from which ova were recovered on d 3 postinsemination. The results of the two studies were similar. The percentage of heifers with an embryo on d 16 was 78 (10% had degenerating embryos and 12% no embryos), and the percentage pregnant at d 35 was 72. The conclusions suggested from this study depend upon the classification of the ERZP. If the ERZP are designated as ova ovulated during a previous cycle or ova damage in the collection process and are deleted from the calculations, the fertilization rate is high (93%), and embryonic loss apparently occurs between d 3 and 35 (P less than .95). However, if the ERZP are classified as ova ovulated at the immediately preceding estrus, unavailable for further embryonic development, and are included in the calculations, the fertilization rate is comparatively low (80%). In the latter case, the primary loss of potential embryos occurs before d 3, and the loss after d 3 is negligible (P greater than .05).

Synopsis An experiment is reported in which hatching eggs were stored in a room at 12.7° ± 1.1° C. for up to 3 weeks after storage on the farm for 2 to 5 days. The eggs were stored in the room on keyes trays in part open‐sided wooden boxes or in sealed Cryovac bags or in sealed Cryovac bags flushed out with nitrogen before sealing. It was found that the normal decline in hatchability with storage time was reduced by storage in bags. There was no difference in hatchability between bags with or without nitrogen though there was an indication that the proportion of cull chicks at hatching was reduced by storage in bags flushed out with nitrogen for eggs stored more than 8 days. The effect on hatchability of the storage in bags is pinpointed as resulting from reduced embryonic loss between fertilisation and the 2nd day of incubation. This disagrees with a previous result and it is suggested that differences in genetic origin of eggs may account for differences in time of effect of storage treatment.

1. Twenty-four Merino ewes acclimatized to a hot environment were compared with twenty-four kept at normal temperatures, with respect to ovulation rate and embryonic loss by 25 days' pregnancy. Possible modifying effects of the three subsidiary factors, thyroxine level, vitamin A intake and progesterone level, were sought. The design of the experiment was a balanced factorial one.2. While the differences between the hot-room and yard groups as a whole were not significant, in the former there were fewer ovulations, a smaller proportion of the potential embryos actually began to develop and, of these, a larger proportion had died by 25 days' pregnancy. Consequently only thirteen hot-room ewes contained live embryos compared to twenty in the yard; the total numbers of live embryos were fourteen and twenty-seven, respectively.3. Of the subsidiary factors only thyroxine produced any marked effect. Both in the hot-room and in the yard the proportion of potential embryos developing and the proportion of actual embryos surviving at 25 days' pregnancy were greater where thyroxine injections were given. There appeared, however, to be no effect on ovulation rate. There was a significant increase in the proportion of hot-room ewes with live embryos due to thyroxine. Grouping hot-room and yard ewes together, thyroxine injections were associated with a significant increase in the proportion of potential embryos developing and in the proportion of actual embryos surviving; also, consequently, in the proportion of ewes with live embryos.4. The results are discussed in relation to published work on the effects of high temperatures on reproduction.

Summary A total of 837 services were analyzed for the effects of sire and system of mating on estimated embryonic mortality by 150 days of gestation. The sire had a highly significant effect on the rate of embryonic death in the females to which he was bred. Outbred embryos had an estimated death rate of 19.8% by 150 days as compared-to 22.3% for inbred embryos. Outbred dams had 19.2% embryonic death by 150 days, whereas embryonic mortality in inbred dams was 28.4%. Although the difference between outbreds and inbreds was not statistically significant in either case, the trend was for inbreeding of either embryos or dams, particularly the latter, to increase embryonic mortality.