Treatment with an elevated dose of the GnRH analogue dephereline in the early luteal phase improves pregnancy rates in repeat-breeder dairy cows.

This study sought to establish whether treatment with the GnRH analog dephereline in the early luteal phase could be useful to improve fertility in repeat-breeder cows (>3 inseminations). Dephereline was given 5-7 days after insemination, and effects of both a single and elevated (2.5 times) dephereline dose on pregnancy and subsequent embryo survival determined in repeat-breeder lactating dairy cows. The study population comprised 810 cows: 399 repeat-breeder cows and 411 non repeat breeders. To determine the effects of treatment on the pregnancy rate, three study groups were established: Control, no treatment (n = 269), DEPH, single dephereline dose (100 µg) (n = 270), or 2.5DEPH, 2.5 dephereline doses (250 µg) (n = 271). Recorded pregnancy rates in these groups were 28.6% (77/269), 31.9% (86/270) and 39.1% (106/271), respectively. Binary logistic regression analysis revealed a significant effect of the interaction treatment x repeat breeder on the pregnancy rate. This meant that the single dose and control treatments led to a pregnancy likelihood of repeat-breeder cows reduced by factors of 0.47 and 0.34, respectively, when compared to the 2.5 dose treatment as reference. Treatment had no effects on non repeat breeders. Based on odds ratios, treatment given either as a single or 2.5 dose increased the probability of an additional corpus luteum (more corpora lutea than embryos) in pregnant cows by factors of 5 or 5.4, respectively. Treatment had no effect on embryo survival. Our findings support the hypothesis that dephereline treatment in the early luteal phase after AI improves fertility in repeat-breeder cows. A dephereline dose 2.5 times higher than normal led to improved pregnancy rates, thus overcoming the impacts of repeat-breeder syndrome. Importantly, both the single and 2.5 dephereline doses increased the chances of pregnant cows having an additional corpus luteum, likely favoring embryo survival.

The GnRH analogue dephereline given in a fixed-time AI protocol improves ovulation and embryo survival in dairy cows.

This study compares the fertility effects of inducing ovulation using the GnRH analogue, dephereline, versus natural GnRH at the end of a 5-day progesterone(P4)-based protocol for fixed-time artificial insemination (FTAI) in in heat-stressed and non-heat stressed lactating dairy cows. Cows were given GnRH (GnRH group, n = 369) or dephereline (DEPH group, n = 379) and were inseminated 14-20 h later. Dephereline treatment increased corpus luteum (CL) size on Day 7 post-AI compared with GnRH (P < .0001) while a one-mm increase in CL size was found to give rise to a 1.1-fold increase in the pregnancy rate at FTAI (P = .001). Based on odds ratios, the interaction between treatment and heat stress had a significant effect on the ovulation failure rate (P < .01). This meant that relative to non-heat-stressed GnRH-treated cows, ovulation failure was 2.9 times more likely in heat-stressed GnRH-treated cows (P = .001), 0.3 times less likely in non-heat-stressed DEPH-treated cows (P = .04) and was similar in heat-stressed DEPH-treated cows. Further, non-heat-stressed DEPH-treated cows were more likely to conceive by a factor of 1.6 than the remaining cows (P = .03). Finally, GnRH-treated multiparous cows were 9.9 times more likely to suffer pregnancy loss than the remaining cows (P = .03). Our results indicate that, compared to treatment with GnRH, dephereline reduced the risk of ovulation failure and consequently increased the pregnancy rate under heat stress conditions. In multiparous cows, dephereline treatment also reduced the negative age effect on pregnancy maintenance.

Inducing ovulation with hCG in a five-day progesterone-based fixed-time AI protocol improves the fertility of anestrous dairy cows under heat stress conditions.

This study compares the fertility effects of inducing ovulation using human chorionic gonadotropin (hCG) versus gonadotropin releasing hormone (GnRH) at the end of a 5-day progesterone(P4)-based protocol for fixed-time artificial insemination (FTAI) in heat-stressed and non-heat stressed anestrous lactating dairy cows. Heat stress (HS) was defined as an environmental temperature-humidity index (THI) > 72. A P4 intravaginal device (CIDR) was fitted for five days and GnRH administered upon CIDR insertion and a double dose (24 h apart) of prostaglandin F2α upon CIDR removal. Cows then received either GnRH (GnRH group; n = 506), or hCG (hCG group; n = 493) 36 h after CIDR removal and were inseminated 50-56 h after CIDR removal. Ovulation failure was investigated in a subset of 425 cows: 223 and 202 receiving GnRH and hCG, respectively. Based on odds ratios, the interaction between treatment and HS had a significant effect on the ovulation failure rate (P = 0.01). This meant that compared to the rates recorded in non-heat-stressed, GnRH-treated cows (13%), ovulation failure in heat-stressed GnRH-treated cows (25.3%) was more likely by a factor of 2.3 (P = 0.04), in non-heat-stressed hCG-treated cows (2.3%) was less likely by a factor of 0.16 (P = 0.02) and was not significantly different in heat-stressed hCG-treated cows (7%). Interactions between treatment and HS and between treatment and parity had a significant effect on the pregnancy rate (P = 0.0001 and P = 0.001, respectively). The treatment-HS interaction determined that compared to the rates recorded in non-heat-stressed, GnRH-treated cows (30.5%), pregnancy in heat-stressed GnRH-treated cows (17.6%) was less likely by a factor of 0.48 than the remaining cows (P = 0.001), whereas because of the treatment-parity interaction, compared to the rates recorded in primiparous, GnRH-treated cows (31.4%), pregnancy in GnRH-treated multiparous cows (18.9%) was less likely to conceive by a factor of 0.51 than the remaining cows (P = 0.002). No significant effects of treatment on the rates of pregnancy loss or twin pregnancy were identified by binary logistic regression. In conclusion, hCG treatment given at the end of a 5-day P4-based protocol for FTAI improved ovulation and pregnancy rates in anestrous cows under conditions of HS and also had a beneficial impact on the pregnancy rate in anestrous multiparous cows throughout the year.

The presence of two ovulatory follicles at timed artificial insemination influences the ovulatory response to GnRH in high-producing dairy cows.

This study sought to examine the impact of the presence of two co-dominant (ovulatory) follicles at the time of artificial insemination (AI) on the ovulatory response to GnRH given in a fixed-time AI protocol. The study population comprised 622 lactating dairy cows: 306 (49.2%) with a single follicle, 198 (31.8%) with two bilateral follicles (one follicle per ovary) and 118 (19%) with two unilateral follicles (same ovary). Based on odds ratios, cows with two bilateral or unilateral follicles were less likely (by factors of 0.09 and 0.11, respectively) to undergo ovulation failure compared with cows with one follicle (P = 0.01 and P = 0.02, respectively); the likelihood of ovulation failure decreased 0.75 times with every one-mm increase in follicle diameter for cows with a single follicle, whereas individual follicle diameter was not related to ovulation failure in cows with two bilateral follicles (P = 0.001). The likelihood of double ovulation decreased 0.7 times with every one-mm diameter difference between the larger and smaller follicle for all cows with two follicles (P = 0.001), whereas cows with two unilateral follicles showed a higher (P < 0.05) double ovulation rate than cows with two bilateral follicles. In 116 (58.6%) of the cows with two bilateral follicles, only the larger follicle ovulated in 59.5% cows, whereas only the smaller one ovulated in the remaining 40.5% cows. In these cows, a one-mm size difference between the larger and the smaller follicle gave rise to a 1.12-fold increase in the ovulation failure rate for the larger follicles (P = 0.0001). Cows with two bilateral follicles were more likely (by a factor of 1.5) to conceive than cows with one follicle (P = 0.001). Significant right-left differences were not found in cows with two bilateral follicles, whereas the right ovary was more active than the left in the remaining cows. Our results indicate that cows with two co-dominant follicles at AI show different ovulation patterns to those with one dominant follicle. A higher rate of ovulation failure was observed among cows with one follicle than cows with two follicles, whereas the conception rate was higher for cows with two bilateral follicles than for the remaining cows. In cows with two follicles, double ovulations along with ovulation of the smaller follicle were related to the least size difference between the larger and smaller follicle.

Reproductive performance of lactating dairy cows after inducing ovulation using hCG in a five-day progesterone-based fixed-time AI protocol.

This study compares the effects of inducing ovulation using human chorionic gonadotropin (hCG) or gonadotropin releasing hormone (GnRH) at the end of a 5-day progesterone(P4)-based protocol for fixed-time artificial insemination (FTAI) in lactating dairy cows on ovarian dynamics and fertility. A P4 intravaginal device (PRID) was fitted for five days and GnRH administered upon PRID insertion and a double dose (24 h apart) of prostaglandin F2α upon PRID removal. Cows received either GnRH (GnRH group; n = 98), 1000 IU hCG (hCG-1 group; n = 97), or 3000 IU hCG (hCG-2 group; n = 104) 36 h after PRID removal and were inseminated 50-56 h after PRID removal. Based on Tukey-Kramer tests, cows in hCG-1 and hCG-2 showed a larger follicle diameter at AI than cows in GnRH (P < 0.05). HCG-2 treatment increased corpus luteum (CL) size on Day 7 post-AI compared with the GnRH and hCG-1 treatments (P < 0.05). Based on odds ratios, the likelihood of ovulation failure decreased with increasing follicle diameter at AI (P = 0.002). Cows in hCG-1 or hCG-2 that did not become pregnant were more likely to return to estrus than cows in GnRH (P < 0.01). A larger CL size post-AI was related to an increased conception rate at FTAI (P = 0.003). Cows given hCG-2 treatment showed a 1.9-fold cumulative pregnancy rate after two rounds of AI compared to cows receiving GnRH. Our results indicate that hCG treatment hCG treatment used to induce ovulation at the end of a short protocol for FTAI improves follicular/luteal dynamics compared to GnRH treatment. Of the two hCG treatments tested, better results were obtained with the 3000 IU dose.

Progesterone supplementation in the early luteal phase after artificial insemination improves conception rates in high-producing dairy cows.

This study examines the possible effects on the reproductive performance of high-producing dairy cows of progesterone (P4) given in the early luteal phase (1.55 g of P4), from Days 3 to 5 post-artificial insemination (AI) as compared with the time of pregnancy recognition, from Days 15 to 17 post-AI. Cows in their third day post-AI were alternately assigned on a weekly rotational basis to the following groups: control, no treatment (C: n = 351), P4 treatment started 15 days after AI (P4-D15: n = 261), or P4 treatment started 3 days after AI (P4-D3: n = 203). Based on odds ratios, cows in P4-D3 were 1.71 times more likely to conceive than control cows (P = 0.004), whereas cows in P4-D15 showed a 1.4-fold greater risk approaching significance of becoming pregnant compared with control cows (P = 0.06). Differences were not observed between treatments. In nonpregnant cows, the given treatment (D3 vs. D15) had no effect on subsequent return to estrus or AI interval and neither were any effects of treatment observed on early fetal loss rates. In contrast, in pregnant cows, the relative risk of twin pregnancy was 2.5 times higher for those in P4-D15 (P = 0.02) than the remaining cows. These findings indicate the efficacy of P4 supplementation after AI. However, when given at the time of pregnancy recognition rather than in the early luteal phase, this treatment increases the twin pregnancy rate.

Factors associated with ovarian structures and intrauterine fluid in the postpartum period in dairy cows.

The objective was to examine risk factors for the interval to resumption of ovarian cyclicity (ROC), multiple ovulations (MCL), ovarian follicular cysts (OC), and presence of intrauterine fluid (IUF) at 22 to 28 [visit (V) 1] and 36 to 42 (V2) days in milk (DIM) in dairy cows. The study was conducted retrospectively by evaluating records from 1,155 Holstein cows from 3 herds. Ovaries and uteri were examined at V1 and V2 by transrectal ultrasonography to determine ovarian structures and IUF. Based on the odds ratio, multiparous cows were more likely to have ROC at V1 by a factor of 1.79 compared with primiparous cows. The likelihood of ROC at V1 was lower in cows with higher milk production, in cows with retained fetal membranes (RFM) or cows with IUF at V1 by factors of 0.98 (for each kg of milk increased), 0.52, and 0.61, respectively. Based on the odds ratio, cows diagnosed with IUF at V2 were 2.85 times more likely to have attained ROC at V2. Multiparous cows and cows that delivered twins were 2.73 and 2.16 times, respectively, more likely to have MCL at V1, whereas cows with RFM were 0.38 times less likely to have MCL at V1. The likelihood of MCL at V2 was higher in cows with MCL and OC at V1 by factors of 2.67 and 1.91, respectively. Multiparous cows were 8.51 times more likely to have OC at V1 than primiparous cows. Higher producing cows were more likely to have OC at V2 by a factor of 1.04 compared with lower producing cows. Parity, stillbirth, RFM, and ROC at V1 were all identified as risk factors for IUF at V1. Cows with RFM and delivering twins were more likely to be diagnosed with IUF at V2 by a factor of 3.43 and 4.07, respectively. In summary, parity, twinning, RFM, metritis, IUF, and milk production were all associated with altered ovarian structures, and the presence of IUF was related to parity, twinning, RFM, and ROC in postpartum dairy cows.

Progesterone supplementation during the time of pregnancy recognition after artificial insemination improves conception rates in high-producing dairy cows.

This study examines the possible effects of progesterone (P4) supplementation during the time of pregnancy recognition, from Days 15 to 17 post-artificial insemination (AI), on reproductive performance in high-producing dairy cows. Cows in their 15th day post-AI were alternately assigned to a control, no-treatment group (C: n = 257) or treatment group (P4: n = 287) on a weekly rotational basis according to the chronologic order of their gynecologic visit. On the basis of the odds ratio, the interaction treatment × previous placenta retention had a significant effect (P = 0.02) on conception rate. Thus, cows in P4 that had not suffered a retained placenta were 1.6 times more likely to conceive 28 to 34 days post-AI than the remaining cows. In nonpregnant cows, treatment had no effect on subsequent return to estrus or AI interval and neither were any effects of treatment observed on twin pregnancy and early fetal loss rates. The results of this study demonstrate the efficacy of P4 supplementations during the time of pregnancy recognition after AI in cows without a clinical history of placenta retention.

Effects of crossbreeding on endocrine patterns determined in pregnant beef/dairy cows naturally infected with Neospora caninum.

Neospora caninum is an intracellular coccidian parasite causing abortion worldwide in dairy cattle. Studies have shown that N caninum infection modifies endocrine patterns and that beef cows or cows with a crossbreed pregnancy, especially for a greater maternal-paternal genetic distance, show a reduced risk of abortion when naturally infected compared with pure-breed Holstein Friesian (HF) pregnancies. This study examined the effects of crossbreeding on plasma progesterone (P4), pregnancy-associated glycoprotein (PAG)-1 and -2, and prolactin patterns produced during gestation in N caninum-infected beef/dairy cows. We analyzed 74 pregnancies in nonaborting cows carrying a single fetus established in 26 lactating HF cows bred with Holstein bulls (H-H), 13 HF cows bred with Limousin bulls (H-L), 12 HF cows used as recipients of transferred in vivo-produced frozen-thawed Rubia Gallega (beef breed; RG) embryos (H-RG-ET), and 23 RG suckling cows bred with RG bulls (RG-RG). Of the cows, 29 (39%) were seropositive for N caninum. Blood samples for hormone and placental protein determinations were collected on Days 30, 60, 90, 120, 150, and 180 of gestation. Procedures of repeated measures analysis of variance throughout gestation revealed higher PAG-1 levels in the H-L and H-RG-ET groups compared with H-H and RG-RG. Higher prolactin levels were detected in RG-RG than in the remaining groups. N caninum seropositivity and fetal genotype had a significant effect on PAG-2 concentrations, such that highest levels of PAG-2 occurred in RG-RG seropositive cows and lowest in H-H seropositive cows, whereas Neospora-seropositive cows showed lower P4 concentrations than their seronegative partners. In conclusion, chronic N caninum infection modifies endocrine patterns of PAG-2 and P4 during pregnancy, whereas PAG-1 and prolactin concentrations are affected by breed and fetal genotype, irrespective of Neospora infection status.

Photoperiod length and the estrus synchronization protocol used before AI affect the twin pregnancy rate in dairy cattle.

This study addresses potential management risk factors affecting the incidence of twin pregnancies in high-producing dairy cows. Special attention was paid to the estrus synchronization protocol used before the AI resulting in pregnancy. Possible factors affecting the twin pregnancy rate were analyzed through binary logistic regression procedures on 2015 pregnant cows from July 2010 to July 2011. Twin pregnancy was recorded in 361 of the 2015 pregnancy diagnoses made (17.9%). Twin pregnancy rates differed among herds (P < 0.001) and ranged from 12.4% to 23.9%. Based on the odds ratios, the risk of twin pregnancy was reduced by factors of 0.65 or 0.71 when AI was performed during the warm season or an increasing photoperiod, respectively and increased by a factor of 1.11 for each unit increase in lactation number; by factors of 4.57 or 6.33 in cows that received a progesterone-releasing intravaginal device (PRID) plus 500 or 750 IU of equine chorionic gonadotropin (eCG) 28 days before the pregnancy AI, respectively; by a factor of 2.39 in cows with an ovarian cyst diagnosed in the 14 days prior to AI and treated with prostaglandins (PG); by factors of 1.94 or 3.91 in cows that received two PG doses during the 14 days prior to AI or cows that following failed PRID treatment had received PG started over the 28 days prior to AI, respectively; and by a factor of 2.58 in cows that had previously delivered twins compared to cows delivering singletons. Our results indicate that cow factors, such as lactation number and previous twining, as well as environmental factors, such as photoperiod and season and management related to synchronization protocols affect significantly the incidence of twin pregnancies.

The influence of genital tract status in postpartum period on the subsequent reproductive performance in high producing dairy cows.

The aim of the present study was to characterize the early postpartum period in clinically healthy dairy cows by ultrasonography (US), endometrial cytology (EC), and white blood cell counts, and determine possible relationships between postpartum findings and subsequent reproductive performance. Fifty-three dairy cows were examined on Days 15 to 21 (Visit 1), 22 to 28 (Visit 2), and 29 to 35 (Visit 3) postpartum. The clinical examination included: examination of vaginal fluid, EC, transrectal palpation and ultrasonography of the genital tract (cervical diameter, endometrial thickness, presence of a corpus luteum [CL] or intrauterine fluid [IUF] and its echogenicity). Luteal activity (presence of a CL in a single visit), return to cyclicity (presence of a CL in 2 consecutive visits), and conception rate at 70 and 120 days postpartum were considered as the dependent variables in four consecutive binary logistic regression analyses. Factors affecting leukocyte counts were established by general linear model (GLM) repeated measures analysis of variance. Based on the odds ratio (OR), the likelihood of luteal activity was higher in multiparous than primiparous cows (OR = 3.75) and tended to diminish in cows showing increased endometrial thickness in Visit 1 (V1) (OR = 0.06). The likelihood of returning to cyclicity decreased for each centimeter increase in cervical diameter in V1 (OR = 0.14) and that of conception on Day 70 was lower in cows showing the presence of echogenic or anechogenic IUF in V1 (OR = 0.09 or OR = 0.13, respectively) compared with cows lacking IUF. Effects of parity and IUF were observed on neutrophil counts. Positive EC results were unrelated to the cumulative conception rate at 70 and 120 days in milk, whereas cows returning a positive EC result in V1 showed a greater likelihood of increased endometrial thickness. In conclusion, measuring cervical diameter, endometrial thickness, and detecting the echogenicity of IUF by ultrasonography from Days 15 to 21 postpartum in clinically normal cows is an appropriate tool to predict subsequent reproductive performance. Vaginal examination and transrectal palpation alone did not emerge as valuable predictors.

Reproductive performance of anoestrous high-producing dairy cows improved by adding equine chorionic gonadotrophin to a progesterone-based oestrous synchronizing protocol.

This study sought to improve the reproductive performance of anoestrous high-producing dairy cows by including equine chorionic gonadotrophin (eCG) after progesterone-releasing intravaginal device (PRID) removal. In Experiment I, 806 cows at 51-57 days post-partum were randomly assigned to a PRID (treated with PRID), PRID-500 (treated with PRID plus 500 IU of eCG) or PRID-750 (treated with PRID plus 750 IU of eCG) group. In Experiment II, 422 cows showing a long anoestrus period (animals with no oestrus signs nor luteal tissue 35 days before treatment) were randomly assigned to the PRID, PRID-500 or PRID-750 groups. The dependent variables considered in binary logistic regression analyses for both experiments were the rates of oestrus, ovulation and conception after treatment, the cumulative conception rate on Day 120 post-partum and pregnancy loss. In Experiment I, interaction between treatment and season showed a significant effect on the oestrous response. Thus, during the warm season, PRID group cows were 8.9 times more likely to express oestrus than the remaining cows. Moreover, inseminated cows with two or more corpora lutea 8-14 days after treatment were more likely to become pregnant (by a factor of 2.4) than cows with a single corpus luteum. Finally, cows without luteal structures treated with PRID were 0.4 less likely to be pregnant on Day 120 post-partum, compared with the remaining cows. In Experiment II, cows in the PRID group treated during the warm or cool season were less likely to exhibit oestrus (by a factor of 0.06 or 0.2, respectively) or ovulate (by a factor of 0.004 or 0.14, respectively) than the remaining cows. In conclusion, in anoestrous cows in both experiments, the addition of eCG to the use of an intravaginal progesterone device to induce oestrus was beneficial. The recommended dose of eCG is 500 IU.

Effects of GnRH or progesterone treatment on day 5 post-AI on plasma progesterone, luteal blood flow and leucocyte counts during the luteal phase in dairy cows.

This study was designed to test the effects of progesterone or GnRH treatment on day 5 post-AI on fertility and luteal function in dairy cows and heifers. Five days after AI, 32 animals were randomly assigned to a control, intravaginal progesterone for 14 days progesterone releasing intravaginal device (PRID) or GnRH treatment group. On days 5, 7, 12, 14, 17 and 19 post-AI, each animal underwent colour Doppler ultrasonography of the corpus luteum and blood samples were collected for cell counts and plasma progesterone determination. Through general linear model repeated measures analysis of variance, significant effects were observed of treatment, parity, inseminating bull, reduced vascularization of the CL and pregnancy on plasma progesterone concentrations, whereas mean plasma progesterone and time luteal phase day, and treatment and plasma progesterone concentration on day 5 post-AI were found to, respectively, affect neutrophil and lymphocyte counts throughout the luteal phase. Moreover, two binary logistic regression analyses were performed. Based on the odds ratio, the likelihood of pregnancy by days 26-32 post-AI was 23.4 times higher in animals with high mean progesterone levels throughout the study period, compared with animals with low mean progesterone. The likelihood of reduced CL vascularization was 14 times higher in animals treated with PRID, compared with control and GnRH-treated animals. In conclusion, our results indicate that treatment on day 5 post-AI with PRID reduced subsequent CL vascularization, whereas GnRH treatment increased plasma progesterone concentrations on day 12 post-AI, although an effect was identified of the inseminating bull on plasma progesterone levels. Pregnant animals showed higher mean plasma progesterone concentrations than in nonpregnant ones and heifers higher than in lactating cows, whereas blood cell counts differed depending on the treatment and on the mean plasma progesterone concentration on day 5 post-AI.

Clinical implications of induced twin reduction in dairy cattle.

Embryo reduction may prevent the negative effects of twinning in dairy cattle; however, the technique may carry an additional risk of pregnancy loss. The aim of this study was to evaluate the effect on pregnancy maintenance of embryo reduction by manual amnion rupture in unilateral and bilateral twin pregnant cows. A secondary objective was to examine the dynamics of endocrine factors following the treatment. On Day 35-41 of gestation 55 cows bearing two live twin embryos (28 bilateral, 27 unilateral) were randomly assigned to a twin reduction group (n = 27; cows fitted with a progesterone releasing intra-vaginal device for 21 days after manual amnion rupture) or control group (n = 28; untreated cows). Pregnancy loss before Day 90 was recorded in nine control and eleven twin reduction cows (32.1% vs 40.7%, respectively, p = 0.508). Logistic regression models indicated that laterality was the only variable significantly affecting pregnancy loss. The pregnancy loss risk was 8.7 times higher for unilateral than for bilateral twin pregnancies (59.3% vs 14.3%, respectively, P < 0.001) yet was similar in the unilateral control and unilateral twin reduction cows (62.3% vs 53.8%, respectively, P = 0.581). In contrast, four of 14 cows with bilateral twin pregnancies undergoing twin reduction lost their pregnancies while no losses were recorded in control cows with bilateral pregnancies (P = 0.049). A rise in plasma progesterone concentration was detected on the day following treatment in the twin reduction group and concentrations remained high within the first week of treatment. Plasma pregnancy-associated glycoprotein-1 (PAG-1) concentrations fell between Day 35-41 and Day 42-48, regardless of treatment. Our findings indicate that embryo reduction by manual amnion rupture did not carry an additional risk of pregnancy loss for unilateral twin pregnancies, whereas it increased the risk of pregnancy failure in bilateral twin pregnancies. However, benefits of preventing cows from delivering twins might also be considered when assessing the success of embryo reduction in bilateral twin pregnancies.

Neospora caninum and coxiella burnetii seropositivity are related to endocrine pattern changes during gestation in lactating dairy cows.

Q fever is a zoonotic infection caused by Coxiella burnetii that is endemic worldwide. Domestic ruminants are a source of infection for humans. Given the suggestion that the bacterium recrudesces during pregnancy in cattle, this study was designed to determine whether C. burnetii infection affects hormonal patterns, such as progesterone, cortisol, pregnancy associated glycoproteins (PAG), and prolactin during gestation in lactating cows. Possible interactions with Neospora caninum were also explored. The study was performed on 58 gestating non-aborting cows. Blood samples for hormone determinations were collected on Days 40, 90, 120, 150, 180, and 210 of gestation. For antibody determinations, blood was collected at day 40 postinsemination and postpartum. By GLM repeated measures analysis of variance, we established the effects of production and reproductive variables as well as Coxiella and Neospora seropositivity related to changes on cortisol, PAG, progesterone, and prolactin levels. Coxiella antibody levels were significantly related to cortisol, PAG, and plasma progesterone concentrations, whereas Neospora seropositivity was linked to plasma progesterone concentrations. The interaction between Coxiella and Neospora seropositivity was correlated with cortisol and plasma progesterone levels, whereas the interaction seropositivity against C. burnetii-plasma cortisol concentration was related to plasma PAG levels. Finally, an effect of lactation number only was observed on plasma prolactin. Our findings suggest that both the N. caninum and C. burnetii infection or the presence of both modify endocrine patterns throughout gestation. Cows seropositive to both, Neospora and Coxiella, showed higher plasma progesterone levels than the remaining animals examined. Seropositivity to C. burnetii was associated with placental damage and diminishing PAG levels throughout the second half of gestation, along with increased plasma cortisol levels on Day 180 of gestation.

Effects of a progesterone-based oestrous synchronization protocol in 51- to 57-day postpartum high-producing dairy cows.

The aim of this study was to investigate the effect of applying a progesterone-based oestrous synchronization protocol at 51-57 days postpartum in high-producing dairy cows. The data analysed were derived from 1345 lactating cows. Cows between 51 and 57 days postpartum were assigned to the groups: control, PRID (receiving a progesterone-releasing intravaginal device for 9 days, and prostaglandin F(2α) 24 h before PRID removal) or GnRH-PRID (the same as the PRID group plus GnRH at PRID insertion). Oestrus was detected by using pedometers and confirmed by examination of the genital tract at AI. Oestrous and conception rates before days 71-77 postpartum, pregnancy loss in early pregnant cows or the cumulative conception rate registered on day 120 postpartum were considered as the dependent variables in four consecutive logistic regression analyses. Based on the odds ratios, the oestrous rate increased by a factor of 1.73 in cows showing oestrus before treatment for each unit increase in the number of previous oestruses; decreased by a factor of 0.44 in the control group with respect to the treatment groups; and by a factor of 0.61 in cows without luteal structures at treatment with respect to cows with corpora lutea. The conception rates of cows inseminated before days 71-77 postpartum remained similar across the groups, whereas the likelihood of pregnancy loss for cows becoming pregnant during this period was 0.11 times lower in the PRID group than in the control. Based on the odds ratio, the likelihood of a higher cumulative conception rate on day 120 postpartum: increased in cows showing oestrus before treatment by a factor of 1.41 for each unit increase in the number of previous oestruses, was reduced 0.56-fold in control cows compared with treated cows, and was also reduced by a factor of 0.98 for each kilogram of milk production increase recorded at treatment. In conclusion, although oestrous synchronization programmes performed in this study did not improve fertility, cows treated with progesterone could be inseminated earlier than untreated cows, such that the treatments increased the cumulative pregnancy rates determined on day 120 postpartum. In addition, fewer pregnancy losses were observed in early pregnant cows in the PRID group than the GnRH-PRID group.

Factors affecting plasma pregnancy-associated glycoprotein 1 concentrations throughout gestation in high-producing dairy cows.

This study was designed to establish the factors, if any, which could affect plasma pregnancy-associated glycoprotein-1 (PAG-1) expression in a study population of 87 pregnant, high-producing dairy cows. The factors examined were: semen providing breed (Holstein-Friesian vs Limousin), outcome of gestation (male vs female newborn, and singleton vs twin pregnancies), lactation number, milk production at pregnancy diagnosis, plasma progesterone concentration, season of gestation (warm period, March-November vs cool period, December-February), and day of gestation (40, 90, 120, 150, 180 and 210). Pregnancy was diagnosed by transrectal ultrasound on day 40 post-insemination and by palpation per rectum on days 90, 120, 150, 180 and 210. Blood samples were collected from each animal immediately before each pregnancy diagnosis. The relative contributions of the different factors on PAG-1 concentrations were evaluated by GLM repeated measures analysis of variance. No significant effects of the herd, foetal sex, milk production, lactation number and plasma progesterone concentrations were observed. In contrast, twin pregnancy, the use of Limousin semen and conception during the cool period were correlated with significantly increased plasma PAG-1 concentrations throughout gestation. Our data indicate that both cow well-being during early placental development, determined in our conditions by reduced heat stress when conception occurred in the cool season, and crossbreed pregnancies lead to improved PAG-1 production throughout the gestation period.

Pregnancy patterns during the early fetal period in high producing dairy cows treated with GnRH or progesterone.

In order to explore pregnancy patterns in high producing dairy cows treated with GnRH or progesterone at pregnancy diagnosis (Days 28-34), two consecutive experiments were designed. In Experiment 1, cows bearing a single embryo were randomly assigned to a PRID (n=40; cows fitted with a progesterone releasing intra-vaginal device for 28 days), GnRH (n=40; cows receiving GnRH) or Control (n=26; untreated cows) group. PRID treatment led to a rise in plasma progesterone concentrations in the 7 days following the onset of treatment compared to the other two groups. In Experiment 2, in which we also examined twin pregnancies, animals were randomly assigned to PRID (n=312) or GnRH (n=294) treatment groups. Treatments were the same as described for Experiment 1. Logistic regression procedures revealed that in cows with a single corpus luteum, the probability of pregnancy loss between the first (Days 28-34) and second (Days 65-62) pregnancy diagnosis decreased by a factor of 0.51 in the PRID group compared to the GnRH group. However, in cows with two or more corpora lutea, PRID treatment increased the likelihood of pregnancy loss by a factor of three, compared to GnRH treatment. In cows carrying twins, the conceptus reduction rate was higher (P=0.02) for the GnRH (36%) than for the PRID (16.4%) group. Formation of a new corpus luteum was recorded in 17.7% of cows in the GnRH group. Our results indicate that compared to GnRH treatment, progesterone treatment given at pregnancy diagnosis in high producing dairy cows, reduced by a factor of 0.51 and increased by a factor of 3 the probability of pregnancy loss in cows with a single or with two or more corpora lutea, respectively, and reduced the conceptus reduction rate in cows carrying twins. The practical implications of our findings are that in herds with a high incidence of early fetal loss of a non-infectious nature, treatment at the time of pregnancy diagnosis with PRID in cows with one corpus luteum and with GnRH in cows with two or more corpora lutea should offer considerable benefits.

Factors affecting plasma prolactin concentrations throughout gestation in high producing dairy cows.

The aim of the present study was to investigate possible relationships between plasma concentrations of prolactin and the following factors throughout gestation in lactating dairy cows: photoperiod, season, milk production, Neospora caninum-seropositivity, twin pregnancy, and plasma concentrations of pregnancy associated glycoproteins-1 (PAG-1), progesterone and cortisol. Pregnancy was diagnosed by trans-rectal ultrasonography on Day 40 post-insemination and by palpation per rectum on Days 90, 120, 150, 180 and 210 or until abortion in aborting cows. Blood samples were collected from each animal immediately before each pregnancy diagnosis. The study population was comprised of 73 non-aborting (54 Neospora-seropositive cows) and 20 aborting cows (all Neospora-seropositive) cows. In non-aborting cows, GLM repeated measures of analysis of variance revealed that lactation number and days in milk had no effect on plasma prolactin concentrations throughout gestation, whereas high plasma prolactin concentrations were significantly associated with high plasma levels of cortisol and PAG-1, with Neospora-seropositivity, positive photoperiod (increasing day length), twin pregnancy, and with low plasma progesterone concentrations. An interaction among plasma prolactin, plasma cortisol and milk production was observed in that plasma prolactin concentrations differed significantly throughout gestation and were highest in high-producing cows with high cortisol levels. In Neospora-seropositive non-aborting versus aborting cows, mean prolactin concentrations failed to differ on Days 40, 90, 120, 150 and 180 of pregnancy, whereas prolactin values were significantly lower (P=0.03) in aborting animals on Day 210 of pregnancy. Our results indicate that a positive photoperiod and Neospora-infection lead to increased plasma prolactin concentrations throughout gestation. Reduced prolactin concentrations detected in Neospora-seropositive aborting cows compared to non-aborting animals suggests a protective effect of prolactin in N. caninum infection.

Anomalous pregnancies during late embryonic/early foetal period in high producing dairy cows.

This study analyses anomalous cases of gestation ending in pregnancy loss during the early foetal period and their effect on progesterone and plasma pregnancy-associated glycoprotein-1 (PAG-1) concentrations. Data derived from a large-scale ultrasound pregnancy diagnosis programme in high producing dairy cows. Over a 3-year period (2004-2007), a very low incidence (0.5%: 15 of 3094) of anomalous pregnancies was recorded. The results revealed that the following anomalies were detected on days 35-41 of gestation in cows carrying singletons with one single corpus luteum: embryo death in eight cows (0.3%); and embryo in the uterine horn contralateral to the corpus luteum in seven cows (0.2%). All these animals suffered pregnancy loss during the early foetal period. In cows carrying dead embryos, no signs of conceptus degeneration were observed on pregnancy diagnosis. Amnion size (approximately 25 mm diameter) and uterine horn fluid contents were estimated to be similar to those of the normal pregnant cows in this period. In the contralateral gestations, live embryos were observed in all ultrasound checks before pregnancy loss. Uterine fluid contents increased in the two cows in which gestation continued for more than a week. In the cases of embryo death but not in those of contralateral gestation, a drop in PAG-1 levels was noted prior to pregnancy loss. Two cows carrying dead embryos increased with time allantoic fluid contents. The PAG-1 values increased with time in one cow bearing a dead embryo (from 2.31 to 6.79 ng/ml) and in two of the contralateral gestations (from 1.66 to 2.33 ng/ml and from 0.39 to 6.79 ng/ml, respectively). Results of this study indicate that the foetal membranes continue to undergo some activity following embryo death, and that contralateral pregnancy may determine failure of the gestation process.