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.

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.

Factors affecting the response to the specific treatment of several forms of clinical anestrus in high producing dairy cows.

This study was designed to examine estrous response rates to the therapeutic treatment of clinical anestrus in high producing dairy cows and to identify the factors that could affect these rates. Cows with silent ovulation (Subestrus group), cystic ovarian disease (Cyst group) or ovarian hypofunction (OH group) were given specific treatment for their disorder. Data were derived from 1764 treatments in cows producing a mean of 45.4 kg of milk upon treatment including: 889 subestrous cows, 367 cystic cows and 508 cows with ovarian hypofunction. Cows showing estrus following treatment exhibited a similar pregnancy rate to cows attaining natural estrus used as reference: 33% (337/1006) and 35% (626/1796), respectively. No significant differences in pregnancy rates were observed among the Subestrus, Cyst and OH groups (34% (196/571), 34% (44/130), 32% (97/305), respectively. Based on the odds ratio, an estrous response for all groups was less likely to occur in cows that had suffered previous anestrus, compared to cows that were anestrous for the first time, whereas the likelihood of an estrous response increased in cows treated after 90 days in milk. Our results indicate that previous anestrus and a late stage of lactation can have a negative and positive effect, respectively, on the estrous response to the specific treatment of clinical anestrus shown by high producing dairy cows. Treatment targeted at each type of clinical anestrus can render similar pregnancy rates to those shown by cows in natural estrus.

Progesterone supplementation during mid-gestation increases the risk of abortion in Neospora-infected dairy cows with high antibody titres.

Progesterone has been reported to reduce Th1 responses during pregnancy. Thus, given that an excessive Th1 response could lead to abortion in Neospora-infected dairy cows, we hypothesized a reduction in abortion risk following progesterone supplementation during the mid-gestation period in these animals. Seropositive animals were assigned on day 120 of gestation to a Control (n=33) or Treatment (n=34) group. Treatment consisted of progesterone supplementation by fitting a progesterone releasing intravaginal device containing 1.55g of progesterone for 28 days. Mean Neospora caninum antibody titres tested by ELISA on days 40, 90 and 120 of gestation were used to classify the cows as showing high (> or =30 units) or low (<30 units) titration. Abortion rate showed a significant increase (P<0.01) in the Treatment group (35%) compared to the Control (9%). Using logistic regression procedures, there was a significant (P<0.0001) interaction between progesterone treatment and antibody titration. Progesterone-treated cows with a high antibody titre showed a likelihood of abortion 14.3 times higher than those not treated, while in cows with low antibody titres, exogenous progesterone had not effect. Our results do not support our starting hypothesis and suggest that progesterone supplementation in cows with high N. caninum antibody titres increases the risk of abortion possibly by affecting cell-mediated immune responses.

Screening for high fertility in high-producing dairy cows.

A retrospective study involving 2756 pregnancies from two commercial dairy herds in northeastern Spain determined relationships between management, production and reproductive data, and high fertility (conception before 90 days in milk) in high-producing dairy cows. High fertility was registered in 989 (35.9%) cows. The following data were recorded for each animal: herd, repeated animal (cows included two or more times within the study in which data were obtained from different lactational periods), parity (primiparous versus multiparous), previous twinning, reproductive disorders following calving (retained placenta, primary metritis) and at postpartum gynecological examination (incomplete uterine involution, pyometra and ovarian cysts), days in milk at conception, previous estrous synchronization and season of calving and conception. In order to evaluate the possible effect of high production during the peak milk yield on subsequent fertility, daily milk production at Day 50 postpartum was also recorded and cows were classified as high (> or = 50 kg) and low (< 50 kg) producers. Logistic regression analysis indicated no significant effects of herd, repeated animal, previous twinning, reproductive disorders such as primary metritis, incomplete uterine involution, pyometra and ovarian cysts, previous estrous synchronization and season of calving and insemination. Based on the odds ratio, the likelihood of high fertility increased in high-producer cows by a factor of 6.8. High fertility was less likely for multiparous cows (by a factor of 0.35) and for cows suffering placenta retention (by a factor of 0.65). High fertile cows produced a mean of 49.5 kg milk at Day 50 postpartum, in contrast to that 43.2 kg milk of the remainder cows. These findings question the negative effect of high production on fertility. Our results indicated that high individual cow milk production can be positively related to high fertility.