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 ifferences 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

Climate factors affecting conception rate of high producing dairy cows in northeastern Spain.

Abstract Summer heat stress is a main factor related to low conception rate in high producing dairy herds in warm areas worldwide. We assessed the impact of several climate variables on conception rate in high producing dairy cows in northeastern Spain by examining 10,964 inseminations. The temperature-humidity index (THI) was compared with maximum temperature in terms of its efficiency at predicting conception rate. The following data were recorded for each animal: herd, lactation number, insemination number, insemination date, inseminating bull, and AI technician along with climate variables such as mean and maximum temperatures, rainfall, mean and maximum THI for individual time points Days 7 to 1 before insemination, the day of insemination and 1, 2 and 3 days after insemination. Averages were also established for the following periods: from 7 days before insemination to the insemination day, from 3 days before insemination to the insemination day and from the insemination day to 3 days postinsemination. Based on the odds ratios, the likelihood of conception rate increased significantly by factors of 1.48, 1.47, 1.5, and 1.1 for the respective maximum THI classes <70, 71-75, 76-80, and 81-85 only on Day 3 before AI, while on the insemination day, it increased by factors of 1.73, 1.53, 1.11, and 1.3 for the respective maximum THI classes <70, 71-75, 76-80, and 81-85. In a subsequent logistic regression excluding mean and maximum THI, the effectiveness of temperature at predicting conception rate was evaluated. Although high, the fit of the second logistic regression model was slightly lower than that of the full model (P=0.88 versus P=0.98, respectively) and the information provided by the THI model. The likelihood of conception rate increased significantly by factors of 1.5, 1.2, 1.0, 1.0 for the respective maximum temperature classes <20, 21-25, 26-30, 31-35 degrees C on Day 1 after AI. The choice of the THI or temperature to monitor the farm environment would have to depend on the particular farm and situation. In our study conditions, the use of maximum temperature alone gives a new point of view regarding the information provided by the THI variables

Factors affecting plasma progesterone in the early fetal period in high producing dairy cows.

The aim of the present study was to determine whether certain animal- or management related factors could affect plasma progesterone concentrations on Day 42 of gestation in high producing dairy cows. Factors affecting early fetal loss were also analyzed. The study population was comprised of 199 pregnant cows classified as having high (> or =9 ng/ml) or low (4 ng/ml) of pregnancy associated glycoprotein-1 (PAG-1) were 2.73 times more likely to have high progesterone concentrations than the remaining cows. Of the 199 pregnancies, 25 (12.6%) suffered early fetal loss: 22/136 (16.2%) during the warm season and 3/63 (4.8%) during the cool season, all in cows without additional corpora lutea. Based upon the odds ratio, cows without an additional corpus luteum were 3.67 times more likely to suffer fetal loss during the warm season than during the cool season. Our results indicate that milk production, the presence of two or more corpora lutea and plasma PAG-1 concentrations can affect plasma progesterone concentrations at the onset of the fetal period. The presence of an additional corpus luteum strongly diminished the risk of early fetal loss during the warm 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

Protection against abortion linked to gamma interferon production in pregnant dairy cows naturally infected with Neospora caninum

Many immunological aspects of pregnancy, such as the role played by gamma interferon (IFN-gamma) in abortion, are not well understood. Neospora caninum is an intracellular protozoan considered to be among the main causes of abortion in cattle worldwide. The present study analyzes the interaction between IFN-gamma production and N. caninum infection in naturally infected pregnant cows. Data were obtained from 126 pregnant cows: 86 seropositive and 40 seronegative for the parasite. Pregnancy diagnosis and blood sample collection were performed on days 40, 90, 120, 150, 180 and 210 post-insemination or until the time of abortion detection. Plasma was tested for antibodies against N. caninum and IFN-gamma. Interferon-garmna was detected at some point along the pregnancy in 16 (19%) of the 86 Neospora-seropositive cows yet was undetectable in the 40 seronegative animals. Of the 126 pregnancies examined, 22 (17.5%) ended in abortion. Abortion occurred in 24.4% of seropositive cows (21/86) and in 2.5% of seronegative animals (1/40). Significant (P < 0.0001) interaction was observed between Neospora-seropositivity and IFN-gamma production. Based on the odds ratio, the risk of abortion was 15.6 times higher in seropositive cows not producing IFN-gamma than in seronegative animals, whereas neosporosis had no effect in seropositive cows with IFN-gamma production. A significant (P = 0.001) negative effect of IFN-gamma production on the Neospora titer was furthermore observed in the 65 non-aborting seropositive animals. These results indicate that IFN-gamma production affords protection against abortion in Neospora-infected cows and also point to a reduced humoral immune response to N. caninum during gestation in cows producing IFN-gamma

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