Comparison of reproductive management programs for submission of Holstein heifers for first insemination with conventional or sexed semen based on expression of estrus, pregnancy outcomes, and cost per pregnancy.

Our objective was to evaluate reproductive management programs for submission of Holstein heifers for first insemination with conventional or sexed semen. In experiment 1, nulliparous Holstein heifers (n = 462) were submitted to a 5-d progesterone-releasing intravaginal device (PRID)-Synch protocol [d 0, GnRH + PRID; d 5, PGF2α - PRID; d 6, PGF2α; d 8, GnRH + TAI] and were randomly assigned for PRID removal on d 5 or 6 of the protocol followed by timed artificial insemination (TAI) with conventional semen. Delaying PRID removal decreased early expression of estrus before scheduled TAI (0.9 vs. 12.2%), and pregnancies per AI (P/AI) did not differ between treatments. In experiment 2, nulliparous Holstein heifers (n = 736) from 3 commercial farms were randomized within farm to 1 of 3 treatments for first AI with sexed semen: (1) CIDR5 [d -6, GnRH + controlled internal drug release (CIDR); d -1, PGF2α - CIDR; d 0, PGF2α; d 2, GnRH + TAI]; (2) CIDR6 (d -6, GnRH + CIDR; d -1, PGF2α; d 0, PGF2α - CIDR; d 2, GnRH + TAI); and (3) EDAI (PGF2α on d 0 followed by once-daily estrous detection and AI). Delaying CIDR removal decreased early expression of estrus before scheduled TAI (0.004 vs. 27.8%); however, CIDR5 heifers tended to have more P/AI at 35 (53 vs. 45 vs. 46%) and 64 (52 vs. 45 vs. 45%) days after AI than CIDR6 and EDAI heifers, respectively. Overall, CIDR5 and CIDR6 heifers had fewer days to first AI and pregnancy than EDAI heifers which resulted in less feed costs than EDAI heifers due to fewer days on feed until pregnancy. Despite greater hormonal treatment costs for CIDR5 heifers, costs per pregnancy were $16.66 less for CIDR5 than for EDAI heifers. In conclusion, delaying PRID removal by 24 h within a 5-d PRID-Synch protocol in experiment 1 suppressed early expression of estrus before TAI, and P/AI for heifers inseminated with conventional semen did not differ between treatments. By contrast, although delaying CIDR removal by 24 h within a 5-CIDR-Synch protocol in experiment 2 suppressed early expression of estrus before TAI, delaying CIDR removal by 24 h tended to decrease P/AI for heifers inseminated with sexed semen. Further, submission of heifers to a 5-d CIDR-Synch protocol for first AI tended to increase P/AI and decrease the cost per pregnancy compared with EDAI heifers.

Effect of manipulating progesterone before timed artificial insemination on reproductive and endocrine outcomes in high-producing multiparous Holstein cows.

Our objective was to evaluate the effect of manipulating progesterone (P4) concentrations before timed artificial insemination (TAI) on reproductive and endocrine outcomes in high-producing Holstein cows. Multiparous lactating Holstein cows (n = 80) were synchronized for first TAI using a Double-Ovsynch protocol and were randomly assigned to receive 25 mg of PGF2α 1 d after the first GnRH treatment of the Breeding-Ovsynch protocol that included a once-used P4 insert (low-P4 group) or to receive 2 new P4 inserts during the Breeding-Ovsynch protocol (high-P4 group). Blood samples were collected thrice weekly from -10 to 32 d relative to TAI for all cows and from 32 to 67 d after TAI for pregnant cows and were analyzed for P4 and pregnancy-specific protein B (PSPB) concentrations. Expression of IFNτ-stimulated gene 15 (ISG15) was assessed in blood leukocytes 18 and 20 d after TAI. As expected, P4 concentrations were greater for high-P4 cows than for low-P4 cows from 3 to 8 d before TAI. Incidence of double ovulation was 3-fold greater for low-P4 cows than for high-P4 cows (33 vs. 10%), which resulted in more twin pregnancies 32 d after TAI for low-P4 cows than for high-P4 cows (29 vs. 0%). Low-P4 cows had larger preovulatory follicles at the last GnRH treatment of the Double-Ovsynch protocol and greater P4 concentrations than high-P4 cows after TAI. Relative expression of ISG15 mRNA 18 and 20 d after TAI was greater for low-P4 cows than for high-P4 cows and for pregnant cows than for nonpregnant cows. Overall, PSPB concentrations tended to be greater for low-P4 cows than for high-P4 cows, and pregnant cows had greater P4 concentrations than nonpregnant cows. In summary, cows with low P4 before TAI had increased preovulatory follicle diameter, PSPB concentrations, relative expression of ISG15 mRNA 18 and 20 d after TAI, double ovulations, and twinning compared with cows with high P4 before TAI. Increasing P4 before TAI may effectively decrease double ovulation and twinning in high-producing multiparous Holstein cows.

Development of fertility programs to achieve high 21-day pregnancy rates in high-producing dairy cows.

Our objective is to overview the research that lead to the development of fertility programs for high-producing lactating dairy cows using only GnRH and Prostaglandin F2α (PGF2α), such as Ovsynch with a focus on the role of progesterone in fertility. A key factor affecting fertility to timed-AI is the response to each hormonal treatment of the Ovsynch protocol. Although not required for fertility, cows ovulating to the first GnRH treatment of the Ovsynch protocol (G1) have greater P/AI than cows failing to ovulate. The association between progesterone concentrations at each treatment during the Ovsynch protocol and fertility is reviewed, and data from 7792 cows from 14 studies are presented. Overall, medium P4 (between 0.5 and 6 ng/mL) at G1, high P4 concentrations (>1.0 ng/mL) at the PGF2α, and low P4 concentrations (<0.4 ng/mL) at final GnRH (G2) are associated with greater P/AI. The use of presynchronization treatments that increase the percentage of cows initiating the Ovsynch protocol during early diestrous increases the percentage of cows with medium P4 concentrations at G1 and with high P4 concentration at PGF2α. Some cows, however, fail to completely undergo luteal regression after a single PGF2α treatment, particularly cows that initiate the Ovsynch protocol in a low P4 environment and cows with a young (d 6) CL at the time of treatment with PGF2α. Addition of a second PGF2α treatment increased the percentage of cows with complete luteal regression and P/AI. The use of fertility programs that include the concepts described in this review have resulted in more P/AI than inseminating cows after an induced estrus at first insemination. In addition, extending these concepts to strategies for resynchronization of ovulation and the implementation of an aggressive reproductive management program for first and subsequent inseminations results in reproductive performance that is unprecedented for high-producing Holstein dairy cows.

Descriptive analysis of rabies in wild animals in the state of Sergipe, Brazil / Análise descritiva da raiva em animais silvestres no estado de Sergipe, Brasil

The wild cycle of rabies constitutes a serious challenge to epidemiological surveillance for disease control in domestic, companion or production animals, and in humans. The understanding of rabies virus circulation in the natural environment is increasingly important due to the constancy of natural reservoirs of the disease and the presence of potential vectors of the infection to humans and domestic animals. Aiming to evaluate the occurrence of rabies in the State of Sergipe a total of 935 hematophagous bats (Desmodus rotundus), 46 wild dogs (Cerdocyon thous) and 24 primates (Callithrix spp.) were analyzed from 1987 to 2014, of which 1 bat, 17 crab-eating foxes and no primates were positive. Due to the lack of positive results in hematophagous bats, the main vector of herbivorous rabies, more studies are needed to monitor cases, because from an epidemiological point of view, Sergipe is endemic for herbivorous rabies. Epidemiological surveillance of rabies virus in wild animals is primordial for the success of disease control programs in herds of domestic animals and humans.(AU)

O ciclo silvestre da raiva constitui um sério desafio para a vigilância epidemiológica no controle da doença nos animais domésticos, de companhia ou de produção, e nos seres humanos. O entendimento sobre a circulação do vírus rábico no ambiente natural é cada vez mais importante, em razão da constância de reservatórios naturais da doença e da presença de vetores potenciais da infecção aos humanos e aos animais domésticos. Com o objetivo de avaliar a ocorrência da raiva no estado de Sergipe, foram analisados 935 morcegos hematófagos (Desmodus rotundus), 46 cachorros-do-mato (Cerdocyon thous) e 24 primatas (Callithrix spp.) no período de 1987 a 2014, dos quais resultaram positivos um morcego, 17 cachorros-do-mato e nenhum primata. Em que pese a contundente falta de resultados positivos em morcegos hematófagos, principal vetor da raiva dos herbívoros, mais estudos são necessários no monitoramento dos casos, pois o estado, do ponto de vista epidemiológico, é endêmico para a raiva dos herbívoros. A vigilância epidemiológica do vírus da raiva nos animais silvestres é primordial para o sucesso dos programas de controle da doença em rebanhos de animais domésticos e em seres humanos.(AU)

Effect of dose and timing of prostaglandin F2α treatments during a Resynch protocol on luteal regression and fertility to timed artificial insemination in lactating Holstein cows.

Our objective was to evaluate the effect of a second PGF2α treatment (25 mg of dinoprost) or a double dose of PGF2α (50 mg of dinoprost) during a Resynch protocol on luteal regression and pregnancies per artificial insemination (P/AI) in lactating dairy cows. Lactating Holstein cows (n = 1,100) were randomly assigned at a nonpregnancy diagnosis to receive (1) Ovsynch (control: 100 µg of GnRH; 7 d, 25 mg of PGF2α; 56 h, 100 µg of GnRH), (2) Ovsynch with a second PGF2α treatment (GPPG: 100 µg of GnRH; 7 d, 25 mg of PGF2α; 24 h, 25 mg of PGF2α; 32 h, 100 µg of GnRH), or (3) Ovsynch with a double dose of PGF2α (GDDP: 100 µg of GnRH; 7 d, 50 mg of PGF2α; 56 h, 100 µg of GnRH). All cows received timed artificial insemination (TAI) approximately 16 h after the second GnRH treatment (G2). Pregnancy diagnosis was performed by transrectal palpation 39 ± 3 d after TAI, and pregnancy status was reconfirmed 66 d after TAI. Blood samples collected from a subset of cows in each treatment at the first PGF2α treatment (n = 394) and at G2 (n = 367) were assayed for progesterone (P4). Data were analyzed by logistic regression using the GLIMMIX procedure of SAS (SAS Institute Inc., Cary, NC). At 39 d after TAI, GPPG cows tended to have more P/AI than control cows [35% (137/387) vs. 31% (107/349)], whereas P/AI for GDDP cows [32% (118/364)] did not differ from that for control cows. Pregnancy loss from 38 to 66 d did not differ among treatments and was 8% (30/362). The percentage of cows with complete luteal regression (P4 <0.4 ng/mL at G2) tended to differ among treatments and was greater for GPPG cows than for GDDP and control cows (94% vs. 88% vs. 88%, respectively). Overall, cows with P4 <1 ng/mL at the first PGF2α treatment had fewer P/AI than cows with P4 ≥1 ng/mL (27% vs. 38%), whereas cows with P4 ≥0.4 ng/mL at G2 had fewer P/AI than cows with P4 <0.4 ng/mL (15% vs. 38%). We conclude that adding a second PGF2α treatment 24 h after the first within a Resynch protocol tended to increase the proportion of cows undergoing complete luteal regression and P/AI, whereas treatment with a double dose of PGF2α at a single time did not.

Fertility of lactating Holstein cows submitted to a Double-Ovsynch protocol and timed artificial insemination versus artificial insemination after synchronization of estrus at a similar day in milk range.

Our objective was to compare the AI submission rate and pregnancies per artificial insemination (P/AI) at first service of lactating Holstein cows submitted to a Double-Ovsynch protocol and timed artificial insemination (TAI) versus artificial insemination (AI) to a detected estrus after synchronization of estrus at a similar day in milk range. Lactating Holstein cows were randomly assigned to receive their first TAI after a Double-Ovsynch protocol (DO; n = 294) or to receive their first AI after a synchronized estrus (EST; n = 284). Pregnancy status was determined 33 ± 3 d after insemination and was reconfirmed 63 ± 3 d after insemination. Data were analyzed by ANOVA and logistic regression using the MIXED and GLIMMIX procedures of SAS (SAS Institute Inc., Cary, NC). By design, days in milk at first insemination did not differ between treatments (76.9 ± 0.2 vs. 76.7 ± 0.3 for DO vs. EST cows, respectively), but more DO cows were inseminated within 7 d after the end of the voluntary waiting period than EST cows (100.0 vs. 77.5%). Overall, DO cows had more P/AI than EST cows at both 33 d (49.0 vs. 38.6%) and 63 d (44.6 vs. 36.4%) after insemination, but pregnancy loss from 33 to 63 d after insemination did not differ between treatments. Primiparous cows had more P/AI than multiparous cows 33 and 63 d after insemination, but the treatment by parity interaction was not significant. Synchronization rate to the hormonal protocols was 85.3%, which did not differ between treatments; however, synchronized DO cows had more P/AI 33 d after insemination than synchronized EST cows (54.7 vs. 44.5%). In summary, submission of lactating Holstein cows to a Double-Ovsynch protocol and TAI for first insemination increased the percentage of cows inseminated within 7 d after the end of the voluntary waiting period and increased P/AI at 33 and 63 d after first insemination resulting in 64 and 58% more pregnant cows, respectively, than submission of cows for first AI after detection of estrus at a similar day in milk range. We conclude that, because the proportion of synchronized cows did not differ between treatments, DO cows had more P/AI than EST cows because of an intrinsic increase in fertility after submission to a fertility program.

MALDI MS imaging investigation of the host response to visceral leishmaniasis.

Mass spectrometry imaging (MSI) of animal tissues has become an important tool for in situ molecular analyses and biomarker studies in several clinical areas, but there are few applications in parasitological studies. Leishmaniasis is a neglected tropical disease, and experimental mouse models have been essential to evaluate pathological and immunological processes and to develop diagnostic methods. Herein we have employed MALDI MSI to examine peptides and low molecular weight proteins (2 to 20 kDa) differentially expressed in the liver during visceral leishmaniasis in mice models. We analyzed liver sections of Balb/c mice infected with Leishmania infantum using the SCiLS Lab software for statistical analysis, which facilitated data interpretation and thus highlighted several key proteins and/or peptides. We proposed a decision tree classification for visceral leishmaniasis with distinct phases of the disease, which are named here as healthy, acute infection and chronic infection. Among others, the ion of m/z 4963 was the most important to identify acute infection and was tentatively identified as Thymosin ß4. This peptide was previously established as a recovery factor in the human liver and might participate in the response of mice to Leishmania infection. This preliminary investigation shows the potential of MALDI MSI to complement classical compound selective imaging techniques and to explore new features not yet recognized by these approaches.

Matrix-assisted laser desorption/ionization imaging mass spectrometry for the spatial location of feline oviductal proteins.

With the purpose of identifying factors involved in early stages of embryo development in the domestic cat, matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) was used for the first time to describe the spatial localization of proteins in the oviducts of queens. Oviducts were obtained from two 2 and 4 years old cross-bred queens, divided into three segments, snap-frozen in liquid nitrogen and then stored at -80°C until use. Next, they were sectioned in a cryostat, fixed on ITO (indium tin oxide) conductive glass slides for MALDI-IMS and serial sections were collected on microscope slides for histology. As confirmed by histology, MALDI-IMS was able to show contrasting protein distributions in the oviductal infundibulum, ampulla and isthmus. Mass spectra were characterized by abundant ions of m/z 1,259, 4,939, 4,960 and 10,626, which have been tentatively attributed to keratin, thymosin ß10, thymosin ß4 and S100, respectively. Keratin and thymosins are involved in the biological response to tissue damage. S100 proteins are calcium-modulated proteins implicated in a variety of cellular activities, including cell differentiation and regulation of cell motility. These results suggest that protein composition differs between segments of the cat oviduct, which corresponds to morphological changes within these sections. Further functional studies could elucidate the effects of these proteins on feline reproductive physiology.

Impaired CD23 and CD62L expression and tissue inhibitors of metalloproteinases secretion by eosinophils in adults with atopic dermatitis.

BACKGROUND: Eosinophils are multifunctional, polymorphonuclear leucocytes that secrete proteins within cytoplasmic granules, such as cytokines, chemokines, metalloproteinases (MMPs) and metalloproteinases tissue inhibitors (TIMPs). Although eosinophilia is a hallmark of atopic dermatitis (AD), several functional aspects of eosinophils remain unknown. OBJECTIVE: We aimed to evaluate the phenotype and functional response of eosinophils under staphylococcal enterotoxin B (SEB) and Toll-like receptor (TLR)-2/6 (FSL-1) stimulation in the secretion of CCL5, MMPs and TIMPs in adults with AD. METHODS: Forty-one adult patients with AD and 45 healthy controls enrolled for the study. Phenotype of eosinophils from granulocytes of peripheral blood was analysed by flow cytometry. We performed evaluation of CCL5 (cytometric bead array), MMP and TIMP (ELISA) secretion, in culture supernatants of purified eosinophils stimulated with SEB or TLR2/6 agonist (FSL-1). RESULTS: We found a higher frequency of LIN1- CCR3+ eosinophils, and decreased expression of CD23 and CD62L receptors in eosinophils of AD patients. There was no difference in MMP and TIMP serum levels between the evaluated groups. However, we detected decreased basal levels of TIMP-1, TIMP-2 and CCL5 in culture supernatants from purified, unstimulated eosinophils from AD patients. CONCLUSION: In adults with AD, phenotypical features of eosinophils reveal decreased expression of early activation and L-selectin receptors. Regarding the functional profile of purified eosinophils related to tissue remodelling in atopic dermatitis, innate immune stimulation (TLR2/6 agonist and SEB) did not affect the ratio of MMP/TIMPs secretion in AD. Our findings reinforce the potential breakdown in tissue remodelling process mediated by eosinophils in AD.

Adding a second prostaglandin F2α treatment to but not reducing the duration of a PRID-Synch protocol increases fertility after resynchronization of ovulation in lactating Holstein cows.

Our objective was to evaluate the effect of a second PGF2α treatment and duration of an Ovsynch protocol that included a progesterone-releasing intravaginal device (PRID) on progesterone (P4) concentrations and pregnancies per artificial insemination (P/AI) after resynchronization of ovulation and timed artificial insemination (TAI). Lactating Holstein cows (n=821) were assigned randomly at a nonpregnancy diagnosis (d 0) to 3 resynchronization protocols: (1) GnRH, d 0; PGF2α, d 7; GnRH, d 9.5 (7D1PGF); (2) GnRH, d 0; PGF2α, d 7; PGF2α, d 8; GnRH, d 9.5); (7D2PGF); or (3) GnRH, d 2; PGF2α, d 7; PGF2α, d 8; GnRH, d 9.5 (5D2PGF). All cows received a PRID at the first GnRH treatment of the resynchronization protocol, which was removed at the first PGF2α treatment, and all cows received TAI approximately 16h after the second GnRH treatment. Blood samples were collected from a subgroup of cows at each treatment of the resynchronization protocols. At 32 d after TAI, cows receiving a second PGF2α treatment (7D2PGF + 5D2PGF cows) had more P/AI (42.6 vs. 35.7%) than cows receiving a single PGF2α treatment (7D1PGF cows). For cows treated with a second PGF2α treatment, decreasing the duration of the protocol did not increase P/AI (41.4 vs. 43.8% for 7D2PGF vs. 5D2PGF cows). At 60 d after TAI, P/AI did not differ between cows treated with the 1 PGF2α (7D1PGF cows) or 2 PGF2α (7D2PGF + 5D1PGF cows) treatments (32.5 vs. 37.9%, respectively). In addition, reducing the duration of the protocol did not increase P/AI at 60 d after TAI (37.8 vs. 38.5% for 7D2PGF vs. 5D2PGF cows). Pregnancy loss from 32 to 60 d after TAI was not affected by the number of PGF2α treatments (8.5 vs. 10.6%, for 7D1PGF vs. 7D2PGF + 5D2PGF cows) or the duration of the protocol (9.1 vs. 12.1%, for 7D2PGF vs. 5D2PGF cows). The percentage of cows with incomplete luteal regression at the second GnRH treatment tended to differ among treatments and was lowest for 7D2PGF cows, intermediate for 5D2PGF cows, and greatest for 7D1PGF cows (1.9 vs. 6.9 vs. 11.0%, respectively). In conclusion, addition of a second PGF2α treatment tended to decrease the percentage of cows with incomplete luteal regression and increased P/AI 32 d after AI, whereas decreasing the duration of the Ovsynch protocol did not increase P/AI.

Defective secretion of Prostaglandin F2α during development of idiopathic persistent corpus luteum in mares.

Five mares that developed idiopathic persistent corpus luteum (PCL) were compared with 5 mares with apparently normal interovulatory intervals (IOIs). Progesterone (P4) and a metabolite of prostaglandin F2α (PGFM) were assayed daily beginning on the day of ovulation (Day 0). Transition between the end of an initial progressive P4 increase and the beginning of a gradual decrease in P4 occurred on mean Day 6. The gradual decrease in P4 between Days 6 and 12 was less (approached significance, P < 0.06) in the PCL group than in the IOI group. The P4 concentration on Day 12 (before luteolysis in IOI group) was greater (P < 0.05) in the PCL group than in the IOI group. In a post hoc comparison, an interaction (P < 0.04) of group by day for Days 4 to 7 indicated that the end of the progressive increase in P4 was temporally associated with a transient increase in concentration of PGFM in IOI mares but not in PCL mares. Complete luteolysis (P4 < 1 ng/mL) occurred in the IOI mares on Days 13 to 15. Partial luteolysis (mean P4 decrease, 62%) occurred in 3 of the 5 PCL mares. Normalization to the day at the end of the most pronounced P4 decrease in the IOI mares and in the 3 PCL mares with partial luteolysis resulted in a day-by-group interaction (P < 0.05) for PGFM concentration. The interaction was partly from lower PGFM concentration on the day at the end of the pronounced P4 decrease in the 3 PCL mares than in the IOI mares. The peak of a transient PGFM increase and the day at the end of the most pronounced decrease in P4 were synchronized in each IOI mare but not in any of the 3 PCL mares. In the other 2 PCL mares, partial luteolysis did not occur, and a transient increase in PGFM was not apparent. Results tentatively indicated that the relationship between P4 and PGFM may be altered as early as Day 6 in PCL mares and supported the hypothesis that prostaglandin F2α secretion is defective in mares with idiopathic PCL.

Concentrations of progesterone, a metabolite of PGF2α, prolactin, and luteinizing hormone during development of idiopathic persistent corpus luteum in mares.

In experiment 1, daily blood samples were available from Days 0 to 20 (Day 0 = ovulation) in mares with an interovulatory interval (IOI, n = 5) and in mares that developed idiopathic persistent corpus luteum (PCL, n = 5). The PCL was confirmed by maintenance of progesterone (P4) concentration until end of the experiment (Day 20). Significant interactions of group and day revealed the novel findings that luteinizing hormone (LH) was lower (P < 0.05) in the PCL group than that in the IOI group on Days 0 to 4, and prolactin was lower (P < 0.05) on Days 1, 4, 6, and 7. In experiment 2, treatment with a gonadotropin-releasing hormone antagonist (n = 6) significantly reduced LH on Days 1 to 6 compared with the controls (n = 6) but did not support the hypothesis that low LH during the postovulatory period increases the frequency of PCL. In experiment 3, P4, PGFM (a PGF2α metabolite), and prolactin concentrations on Days 12 to 20 from 2 reported experiments were combined to increase the number of mares with an IOI (n = 11) or a PCL (n = 11). An abrupt and complete decrease in P4 (luteolysis) began on Day 13 in the IOI group compared with a gradual and partial P4 decline after Day 12 in the PCL group. Concentrations of PGFM and prolactin were lower (P < 0.05) in the PCL group than those in the IOI group on the day at the end of the most pronounced decrease in P4. The PCL mares were subgrouped into those with an abrupt but incomplete P4 decrease (partial luteolysis; n = 5) at the expected time and those without partial luteolysis (n = 6). There were no significant differences between the 2 subgroups in concentrations of PGFM and prolactin, but on a tentative basis (P < 0.10), the concentration of PGFM seemed more focused on the day of the most pronounced decrease in P4 in the subgroup with partial luteolysis. Results for PCL compared with IOI indicated (1) postovulatory LH and prolactin were lower, (2) treatment to reduce postovulatory LH did not increase the incidence, and (3) both PGFM and prolactin were lower on the day of the most pronounced decrease in P4.

Long-term characteristics of idiopathic persistent corpus luteum in the mare.

Persistent CL (PCL; n = 10) in mares was studied daily from Day 20 (Day 0 = ovulation) to the ending ovulation. In addition, the 10 days before ovulation at the end of a PCL were compared with the end of an interovulatory interval (IOI; n = 28) during the same months. Concentration of P4, cross-sectional area of CL, and percentage of CL with Doppler signals of blood flow during PCLs remained constant from 64 to about 33 days before the end of luteolysis and then decreased linearly. Concentration of LH between Day 20 and beginning of the ovulatory LH surge increased linearly. A dominant follicle developed on average every 15 days throughout each PCL. Novel transient P4 depressions were detected with the P4 nadir at a day of maximal diameter of a dominant follicle. At the apparent beginning of luteolysis before the ending ovulation, P4 concentration in PCLs (5.0 ± 0.5 ng/mL) was less (P < 0.0001) than that in IOIs (9.3 ± 0.6 ng/mL). Concentration of LH began to increase 2 days before the end of luteolysis in each group, but concentration on the day of the ending ovulation in PCLs (3.7 ± 0.3 ng/mL) was less (P < 0.005) than that in IOIs (8.9 ± 1.8 ng/mL). In a separate survey of PCLs (n = 23) and IOIs (n = 352), frequency of PCL (6.1%) differed significantly among mares indicating repeatability. These original and critical comparisons between PCLs and IOIs should provide hypotheses for further study.

Oxytocin induction of pulses of a prostaglandin metabolite and luteolysis in mares.

A procedure for oxytocin (OT) administration on Day 13 postovulation was developed in mares for stimulation of a pulse of PGFM (a PGF2α metabolite) that mimics a natural PGFM pulse during luteolysis. Bolus treatment with each of five OT doses (1-10 IU/mare, n = 3) stimulated a burst of PGFM that was maximum in 4 minutes and was unlike a natural pulse. A 2-hour OT infusion of 1.25, 2.5, or 5 IU/100 kg (n = 4) induced a PGFM pulse similar to reported pulses; lower doses did not. The peak of an induced pulse (approximately 260-380 pg/mL) seemed similar to reported natural peaks (approximately 200-300 pg/mL), using the same assay system. The interval from nadir to nadir was 6.6 ± 0.2 hours. Percentage decrease in progesterone (P4) within 8 hours was greater (P < 0.05) for doses of 1.25, 2.5, or 5 IU/100 kg (43%-50%) than that for a vehicle group (11%). Treatment with flunixin meglumine (1.0 mg/kg), a cyclooxygenase inhibitor, decreased (P < 0.008) P4 concentration, but treatment 2 hours before the beginning of OT infusion (2.5 IU/100 kg) did not prevent the OT-induced PGFM pulses and the decrease in P4. In conclusion, a PGFM pulse was simulated by infusion of OT during 2 hours but not by a single OT bolus, and an OT-simulated PGFM pulse stimulated a decrease in P4 that was not prevented by a cyclooxygenase inhibitor. These are the first firm demonstrations that OT in mares as in other species has a role in luteolysis.

Hormonal, luteal, and follicular changes during initiation of persistent corpus luteum in mares.

Mares with persistent CL (PCL) with no known etiology (idiopathic) were matched with mares with an interovulatory interval (IOI) of apparent physiological length, so that ovulation at the beginning of each PCL and IOI occurred during the same month (n = 6/group). Blood samples were collected daily from Days 12 to 22 (Day 0 = ovulation). Mean progesterone (P4) decreased in both groups on Days 14 and 15 and then diverged with a continued decrease in the IOI group and the beginning of constant and greater (P < 0.05) P4 concentration on each day in the PCL group. Before P4 divergence between groups, P4 in the PCL group decreased either abruptly (apparent incomplete luteolysis) or gradually. Concentration of PGFM (a metabolite of PGF2α) was not different between groups and reached maximum on mean Day 15 in each group. After the divergence in P4 between groups, LH and estradiol (E2) remained low in the PCL group. There was no indication that an increase in a luteotropic effect of LH in the PCL group accounted for the divergence in P4. Differences in prolactin between the groups were inconclusive. The hypothesis that secretion of PGF2α at the time of expected luteolysis is defective in mares with idiopathic PCL was not supported. The hypothesis that E2 concentration before expected luteolysis is greater in mares with PCL than those without PCL was not supported; however, a difference on Day 12 approached significance (P < 0.06) and tentatively indicated greater E2 in the PCL group before the beginning of luteolysis.

Role of PGF2α in luteolysis based on inhibition of PGF2α synthesis in the mare.

The effects of inhibition of PGF2α synthesis on luteolysis in mares and on the incidence of prolonged luteal activity were studied in controls and in a group treated with flunixin meglumine (FM), a PGF2α inhibitor (n = 6/group). The FM was given every 8 hours (1.0 mg/kg) on each of Days 14.0 to 16.7. Concentration (pg/mL) of PGF2α metabolite averaged over 8 hours of hourly blood sampling at the beginning of each day, was lower in the FM group than in the controls on Day 14 after ovulation (6.7 ± 1.3 vs. 13.8 ± 2.9, P < 0.05), Day 15 (15.0 ± 3.9 vs. 35.2 ± 10.4, P < 0.10), and Day 16 (21.9 ± 5.7 vs. 54.7 ± 11.4, P < 0.03). Concentration (ng/mL) of progesterone (P4) was greater in the FM group than in the controls on Day 14 (10.1 ± 0.9 vs. 7.7 ± 0.9, P < 0.08), Day 15 (9.2 ± 1.0 vs. 4.3 ± 1.0, P < 0.008), and Day 16 (5.6 ± 1.6 vs. 1.2 ± 0.4, P < 0.02). The interval from ovulation to the beginning of a decrease in P4 and to the end of luteolysis (P4 < 1 ng/mL) was each delayed (P < 0.03) by ~1 day in the FM group. Intervals involving the luteal phase were long (statistical outliers, P < 0.05) in two mares in the FM group, indicating prolonged luteal activity. Results supported the hypotheses that (1) inhibition of PGF2α synthesis interferes with luteolysis in mares and (2) inhibition of PGF2α at the expected time of luteolysis may lead to prolonged luteal activity.

Interrelationships among progesterone, LH, and luteal blood flow during a pulse of a PGF2α metabolite and functional role of LH in the progesterone rebound in heifers.

On Day 16 (Day 0 = ovulation) or before the expected transition into the luteolytic period, heifers were not treated (control group, N = 7) or were treated with a single 0.1-mg dose of estradiol (E2) (E2 group, N = 6) or E2 combined with the GnRH antagonist acyline (E2/Ac group, N = 5). Hourly blood samples were collected from hour of treatment (Hour 0) to Hour 20. Estradiol induced a pulse of PGFM, but the peak of the pulse occurred 2 hours later (P < 0.05) and mean PGFM concentrations during the descending portion of the pulse were lower (P < 0.05) in the E2/Ac group than in the E2 group. In the E2 group, concentration of progesterone (P4) decreased (P < 0.05) during the ascending portion of the PGFM pulse, and increased (rebounded; P < 0.05) along with an LH increase during the descending portion. In the E2/Ac group, a rebound in P4 and an increase in LH were not detected during the descending portion of the PGFM pulse. The percentage of CL with color Doppler signals of blood flow increased (P < 0.04) concurrently with the PGFM increase during Hours 0 to 5 and during the ascending portion of the PGFM pulse. Blood flow and PGFM decreased concurrently. The following hypotheses were supported: (1) LH has a positive effect on PGFM pulses; (2) the rebound in P4 and the increase in LH during the descending portion of a PGFM pulse are functionally related; and (3) the increase in luteal blood flow in association with a PGFM pulse represents a direct effect of PGF2α rather than an effect of P4 or LH.

Contralateral ovarian location between the future ovulatory follicle and extant corpus luteum increases the length of the luteal phase and number of follicular waves in heifers.

Location of the future ovulatory follicle and CL in the same ovary (ipsilateral) or opposite ovaries (contralateral) and number of major follicular waves (two or three) per interovulatory interval (IOI) was studied in 14 heifers. Follicle diameter and a blood sample for progesterone (P4) assay were obtained each day throughout an IOI. Heifers were partitioned into three groups: ipsilateral follicle/CL relationship and two follicular waves (Ipsi-2W, N = 5), contralateral relationship and two follicular waves (Contra-2W, N = 5), and contralateral relationship and three waves (Contra-3W, N = 4). Only one heifer had an ipsilateral relationship and three waves and was not included in the analyses. An unexpected observation was slower growth of the dominant follicle of Wave 1 in the Ipsi-2W group than in the Contra-2W and Contra-3W groups. Increased P4 production in the Contra-3W group compared with the Ipsi-2W and Contra-2W groups was indicated by significantly greater P4 concentration averaged over Days 0 to 20 (Day 0 = ovulation), longer interval from ovulation to the beginning of a decrease in P4 and to the beginning of postluteolysis (P4 <1 ng/mL), and longer IOI. The interval from the beginning of postluteolysis to ovulation was not different among groups, indicating that the prolonged IOI reflected the prolonged luteal phase. An effect of the follicle/CL relationship on length of the IOI was not detected in mares. Results supported the hypothesis that the prolonged luteal phase of the contralateral follicle/CL relationship favors the development of three follicular waves/IOI in heifers.

Progesterone concentration when the future ovulatory follicle and corpus luteum are located in ipsilateral or contralateral ovaries in heifers.

Three studies were done on the effects of ipsilateral location (same ovary) versus contralateral location (opposite ovaries) of the future ovulatory follicle and CL in heifers. The numbers of heifers for the ipsilateral and contralateral groups, respectively, were: experiment (Exp) 1 (N = 4 and 4), Exp 2 (N = 6 and 4), and Exp 3 (N = 5 and 10). In the Exps with available data (Exp 2 and 3), the interval between ovulation and the end of luteolysis was significantly shorter in the ipsilateral group than in the contralateral group (Exp 2: 16.8 ± 0.3 vs. 19.8 ± 1.7 days; Exp 3: 16.9 ± 0.2 vs. 19.7 ± 0.9 days). In Exp 3, the interovulatory interval was shorter (P < 0.01) in the ipsilateral group (20.1 ± 0.4 days) than in the contralateral group (22.7 ± 0.7 days), but the interval from the end of luteolysis to ovulation was not altered significantly. Circulating progesterone (P4) concentration for 33 hours normalized to the beginning of luteolysis (Exp 1) and on Days 16 to 20 (Day 0 = ovulation; Exp 3) was significantly lower in the ipsilateral group than in the contralateral group (Exp 1: 3.7 ± 0.2 vs. 4.8 ± 0.3 ng/mL; Exp 3: 1.7 ± 0.4 vs. 5.9 ± 0.4 ng/mL). Area (cm(2)) of the CL and percentage of CL with color Doppler signals of blood flow were lower and resistance index for a CL arteriole was greater in the ipsilateral group (Exp 3). The decreased P4 concentration in the ipsilateral group began by Day 16, but the decreased luteal area and vascular perfusion were not detected until Days 17 or 18. Results supported the hypothesis that the ipsilateral location of the future ovulatory follicle and CL was associated with lower P4 production and a shorter interovulatory interval.

Role of LH in the progesterone increase during the bromocriptine-induced prolactin decrease in heifers.

The luteotrophic effect of bromocriptine in heifers was studied to determine if the reported posttreatment increase in progesterone (P4) just before or at the beginning of luteolysis was attributable to loss of a luteolytic effect of prolactin (PRL) or to the stimulation of LH, a known luteotropin. Four treatment groups (n = 7) were used: control (Ct), bromocriptine (Bc; 16 mg/heifer), acyline (Ac; 3 µg/kg), and bromocriptine and acyline combined (BcAc). Bromocriptine (inhibitor of PRL) and acyline (antagonist of GnRH and therefore blocker of LH) were given at Hour 0 on Day 16 postovulation, and blood samples were taken hourly at Hours 0 to 8. Concentration of P4 was greater (P < 0.05) in the Bc group than in the Ct group at each of Hours 1 to 8. Concentration of LH increased (P < 0.05) between Hours 0 to 2 in the Bc group but not in the other three groups. The peak of the first posttreatment LH pulse occurred earlier in the Bc group than in the Ct group. Average concentration of PRL was lower (P < 0.05) and number of PRL pulses was less (P < 0.05) in the Bc group than in the Ct group. Acyline inhibited LH in the Ac and BcAc groups as indicated by a decrease (P < 0.05) in concentration between Hours 0 and 2 and a decrease (P < 0.001) in number of pulses/heifer during the 8 h. A decrease in PRL but not an increase in P4 and LH occurred in the BcAc group. Results supported the hypothesis that the P4 increase associated with PRL suppression by bromocriptine treatment is attributable to an increase in LH.