Effect of reproductive disorders previous to conception on pregnancy attrition in dairy cows

This study was undertaken to determine whether reproductive disorders previous to conception influence pregnancy attrition in dairy cows. Reproductive disorders were registered and pregnancy diagnoses were performed as a part of a reproductive health program at 9 commercial dairy herds in northeastern Spain. Data from 3022 diagnosed pregnant lactating cows were used. Pregnancy diagnosis by palpation per rectum was performed from 33 to 70 d post insemination. Pregnancy attrition was registered when the pregnancy diagnosis was negative at the second palpation carried out between 120 and 150 d following insemination. Data analysis was performed by multiple logistic regression methods. Pregnancy attrition rates were 2.6 and 1.8 times higher in cows with previous pyometra and retained placenta, respectively, than in cows without these disorders. No effect of endometritis, ovarian cysts and repeat breeding was shown on pregnancy attrition. Our results suggest that additional efforts to reduce the risk of retained placenta and pyometra should decrease the incidence of pregnancy attrition in dairy cows.     

Risk factors for post partum ovarian dysfunction in high producing dairy cows in Belgium: a field study

An epidemiological study of risk factors for postpartal ovarian disturbances was carried out on 334 high-yielding dairy cows in 6 well-managed Belgian herds. Ovarian activity was closely monitored using progesterone profiles, based on twice weekly RIA-analysis for progesterone in milk fat, starting at 10 d after calving and continuing until the confirmation of a new pregnancy. Attention was focused on abnormal cyclicity during the preservice, postpartum period; cows were divided into 6 different categories. Three of these categories (normal profile, delayed cyclicity, and prolonged luteal phase) were of major importance and were analyzed using a multiple variable logistic regression model. Season of calving (stable vs pasture, odds ratio (OR)=5.7), an extended length of the previous dry period (> 77 vs < or = 63 d, OR=2.9), problem calvings (OR=3.6), abnormal vaginal discharge (OR=4.5), health problems during the first month of lactation (clinical disease, OR=5.4; ketosis, OR=11.3), and clinical parameters illustrating the appearance of a severe negative energy balance significantly increased the risk for delayed cyclicity before service. Parity (> or = 4 vs 1, OR=2.5), problem calvings (OR=2.9), occurrence of puerperal disturbances (OR ranged from 3.5 to 11.0), health problems during the first month of lactation (OR=3.1), and an early resumption of ovarian cyclicity after calving (< 19 d vs > 32 d, OR=2.8) increased the risk for prolonged luteal cycles before service.     

Genetic analysis of reproductive disorders in Israeli Holstein dairy cows

The heritability of common reproductive disorders was asessed in Israeli Holstein cows. Data were collected from 76,000 calvings on 102 collective farms (kibbuts) over a 36-mo period. The disorders considered were those of retained placenta, abnormal lochia, endometritis, anestrus, ovarian cysts with anestrus and ovarian cysts with nymphomania. The statistical model included fixed effects of herd-year, month of calving, duration of previous pregnancy, interaction between calving difficulty and sex of offspring, and the random effect of the sire. Herd-year effects consituted 0.68 of the explained variance of the incidence of retained placenta and approximately 0.89 of all the other disorders. Sire and calving-month effects were significant (P<0.05) for all the disorders. Heritability estimates of the disorders were 0.01 for retained placenta, abnormal lochia, and endometritis; 0.02 for anestrus; and 0.03 for all disorders. Correlations between any two disorders did not exceed 0.20. High genetic correlations were found between retained placenta and either abnormal lochia (0.90) or endometritis (0.70), while moderate genetic correlations were found among each of these and anestrus (0.30). Reproductive disorders occur as part of a complex which may be efficiently controlled by management measures. Nevertheless, breeding for resistance to reproductive disorders may also be feasible by using appropriate sires evaluated on a large number of daughters.     

Mycoflora of cervicovaginal fluids in dairy cows with or without reproductive disorders

Fungal infection of reproduction system of dairy cattle have not been received much more attention. The aim of this study was to determine the fungal infection of Holstein dairy cows with reproductive disorders or healthy. Fungal isolates of cervicovaginal fluids of 176 Holstein dairy cows were collected by using the double rod swabs for cervix and the sterilized cotton swabs for discharges of vagina. They were evaluated for fungal infections. The treatment group included 70 dairy cows with reproductive diseases, such as abortion, repeat breeder, endometritis, metritis, retention of fetal membrane, dystocia, cervicitis, and vaginitis. The control groups were included 42 healthy non-pregnant cows and 64 pregnant cows. Isolates of fungi were obtained from cervix and vagina of 27.1% and 28.6% of treatment group, 26.7% and 31.2% of pregnant cows, and 33.3% and 21.4% of healthy non-pregnant cows, respectively, indicating no significant differences. It is showed that the cervix and vagina of the treatment group have been infected by six different mycotic isolates. However, the cervix and vagina of pregnant and non-pregnant healthy cows in control group were infected with 5, 6 and 5, 4 different fungal agents, respectively. Penicillium and yeast were the most common isolated agents. Regarding to the result of this study, it is concluded that fungal infections can occur in cervicovaginal cavity of Holstein dairy cows with or without reproductive diseases.     

Factors affecting reproductive performance in Ontario dairy herds

Data were collected on reproductive, health and production events in 45 dairy herds in southwestern and eastern Ontario, Canada, from July 1990 to July 1993. Mean and median days in milk at first estrus, at first service, and at conception were 85.1 and 83.9, 94.0 and 88.9, and 126.3 and 115.5 d, respectively. The mean estrus detection rate was 48.3%, with a minimum of 28.4% and a maximum of 64.2%. The mean overall conception rate was 46.7%, with a minimum of 29.8% and a maximum of 70.7%. The most commonly used used therapeutic agents were GnRH (11.5% lactational incidence risk) and PG (13.1% lactational incidence risk). Estrus management accounted for the largest portion of PG use in the herds studied (69.4%). Results of a two sample t-test indicated no significant difference in reproductive performance among herds housed in free-stall compared with those housed in tie-stall barns. Multivariate linear regression models of 3 reproductive performance measures indicated that cows with ovarian cysts and/or increased peak milk production had significantly longer calving-to-first estrus and calving-to-conception intervals as well as lower conception rates than average producing cows without cysts. Cows with metritis were found to have significantly shorter calving-to-conception intervals but no detectable difference in conception rate or calving-to-first estrus interval than their herdmates. As lactation number increased reproductive performance improved. Cows that were observed in estrus earlier conceived earlier. Animals receiving uterine infusions had significantly longer calving-to-conception intervals and lower conception rates than their herdmates. There was no detectable difference in reproductive performance for cows treated with GnRH or PG compared with the nontreated cows. An increased estrus detection rate was associated with shorter calving-to-conception intervals and lower conception rates. Based on the range of performance in the study herds, the factors with the greatest potential influence on calving-to-conception interval in the average herd were the estrus detection rate and conception rate.     

Population-based genetic epidemiologic analysis of Chlamydia trachomatis serotypes and lack of association between ompA polymorphisms and clinical phenotypes

Chlamydia trachomatis is the leading cause of bacterial sexually transmitted diseases worldwide. Urogenital strains are classified into serotypes and genotypes based on the major outer membrane protein and its gene, ompA, respectively. Studies of the association of serotypes with clinical signs and symptoms have produced conflicting results while no studies have evaluated associations with ompA polymorphisms. We designed a population-based cross-sectional study of 344 men and women with urogenital chlamydial infections (excluding co-pathogen infections) presenting to clinics serving five U.S. cities from 1995 to 1997. Signs, symptoms and sequelae of chlamydial infection (mucopurulent cervicitis, vaginal or urethral discharge; dysuria; lower abdominal pain; abnormal vaginal bleeding; and pelvic inflammatory disease) were analyzed for associations with serotype and ompA polymorphisms. One hundred and fifty-three (44.5%) of 344 patients had symptoms consistent with urogenital chlamydial infection. Gender, reason for visit and city were significant independent predictors of symptom status. Men were 2.2 times more likely than women to report any symptoms (P=0.03) and 2.8 times more likely to report a urethral discharge than women were to report a vaginal discharge in adjusted analyses (P=0.007). Differences in serotype or ompA were not predictive except for an association between serotype F and pelvic inflammatory disease (P=0.046); however, the number of these cases was small. While there was no clinically prognostic value associated with serotype or ompA polymorphism for urogenital chlamydial infections except for serotype F, future studies might utilize multilocus genomic typing to identify chlamydial strains associated with clinical phenotypes.     

The effect of interval from day of administration of bovine somatotropin (bST) to synchronization of ovulation and timed-insemination on conception rate of dairy cows with and without ovarian cysts

The objective of this study is to evaluate the effect of the interval from the day of administration of bovine somatotropin (bST) to the day of initiation of synchronization of ovulation (Day 0 and 7) and timed-insemination (TAI) on conception rate (CR) of dairy cows with and without ovarian cysts, respectively. Lactating dairy cows (n = 359) were divided into two groups. Cows in Group 1 (n = 238, without ovarian cysts) were treated with 100 microg, i.m. GnRH on Day 0; 25 mg, i.m. PGF2a on Day 8. 100 mirog. i.m. GnRH on Day 10; and inseminated 16 h later without detection of estrus. Cows in Group 2 (n = 121, with ovarian cysts) were treated with 100 microg, i.m. GnRH on Day 0; 100 microg, i.m. GnRH on Day 7; 25 mg, i.m. PGF2alpha on Day 14, 100 ug, i.m. GnRH on Day 16; and inseminated 16 h later without detection of estrus. Between 60 and 63 days postpartum, all cows in the herd were given bST every 14 days for the duration of the study. Logistic regression was used to assess the risk of nonpregnancy associated with interval from bST treatment to Day 0 for cows without ovarian cysts. and both Day 0 and 7 for cows with ovarian cysts adjusting for parity and days in milk. The CR for cows in Group 1 was significantly higher when the interval from last treatment with bST to Day 0 was between 1 and 3 days (28%) compared to 4-6 days (14%). In addition, the risk of nonpregnancy was 2.19 times greater in cows 4-6 days after bST treatment compared to 1-3 days after adjusting for parity and days in milk. The CR for cows in Group 2 was not significantly different when the interval from last treatment with bST to both Day 0 and 7 was between 1 and 3, 4 and 6, and 7 and 14 days. In conclusion, the results of this study suggested bST treatment closer to Day 0 had a positive effect on CR of cows without ovarian cysts, but bST treatment closer to both Day 0 and 7 had no effect on CR of cows with ovarian cysts. This was interpreted to mean that bST had a beneficial effect on either, or both, the preovulatory follicle and the oocyte in dairy cows without ovarian cysts, but not in dairy cows with ovarian cysts.     

Clinical analysis of reproductive failure among female buffaloes (Bubalus bubalis) under village management in Andhra Pradesh

Analysis of the clinical data of 20, 439 infertile graded Murrah female buffaloes (Bubalus bubalis ) of small and marginal farmers in Andhra Pradesh, examined over a period of two years, revealed that 2.50, 73.77 and 23.73 percent of the animals had reproductive disorders which were of anatomical, functional and non-specific infectious nature, respectively. Highest frequencies were of infantile tracts, ovarian quiescence and endometritis in each group, which together constituted 79.13 percent. The average gross incidence of various conditions encountered in order of frequency was: ovarian quiescence (56.36%), endometritis (20.68%), silent ovulations (5.3%), anovular heats (4.35%), sub-oestrus (3.48%), luteal persistency (3.37%), genital infantilism (2.09%), vaginitis (o.99%), salpingitis (0.98%), cystic ovarian degeneration (0.91%), bursal adhesions (0.75%), cervicitis (0.3%), hypoplasia of the ovaries and tracts (0.24%), paraovarian cysts (0.15%) and hydrosalpinx (0.03%). The incidence of quiescent ovaries followed seasonal trend with significant differences between seasons of the year both in heifers and cows. Between herds and between years, no marked difference in the incidence of different reproductive disorders was observed. It was estimated that 2.93 percent of the animals had disorders which rendered them unfit for breeding and, hence, sterile. Freemartinism was recorded in four cases. The comparative clinical features of freemartinism and cystic ovarian dgeneration in buffalo cows were described. The factors predisposing for higher incidence of endometritis in the species were also discussed.     

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.     

Bovine model for the study of reproductive aging in women: follicular, luteal, and endocrine characteristics

At present, there is no well-characterized animal model to study the effects of aging on fertility in women. The objectives of the study were to characterize age-related changes in ovarian and endocrine functions in old cows and to investigate the validity of a bovine model for the study of human reproductive aging. We tested the hypotheses that aging in cattle is associated with 1) elevated concentrations of gonadotropins and reduced concentrations of steroid hormones in systemic circulation and 2) increased recruitment of ovarian follicles during wave emergence. Daily ultrasonography was performed in 13- to 14-yr-old cows (n = 10) and their 1- to 4-yr-old daughters (n = 9) for one interovulatory interval to study ovarian function. Plasma samples were obtained every 12 h for determination of FSH, LH, progesterone, and estradiol concentrations. Circulating FSH concentrations were higher (P = 0.009) during follicular waves in old cows than in their daughters, but the number of 4- to 5-mm follicles recruited into a wave was lower (P = 0.04) in old cows. Plasma LH concentrations did not differ between groups (P = 0.4), but the ovulatory follicle in two-wave cycles was smaller in old cows (P = 0.04). Plasma estradiol concentrations were higher (P = 0.01) in old cows, and luteal phase progesterone tended to be lower (P = 0.1). We conclude that these changes are consistent with those reported for women approaching menopause transition. Therefore, our results validate the use of the bovine model to study reproductive aging in women.     

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.     

Risk factors for postpartum ovarian cysts and their spontaneous recovery or persistence in lactating dairy cows

Cystic ovarian disease is a major cause of reproductive failure and economic loss for the dairy industry. Many cysts that develop during the early postpartum period regress spontaneously. However, it is difficult to decide at what point it would be more cost effective to treat ovarian cysts than to wait for spontaneous recovery. The objective of this study was to analyze risk factors for the development of the ovarian cystic condition during early and late postpartum, and for its persistence or recovery during the pre-service period in lactating dairy cows. Using multiple logistic regression, we analyzed data derived from 873 lactating dairy cows from a single herd. An ovarian cyst was diagnosed if it was possible to observe a single follicular structure with an antrum diameter > or = 25 mm in the absence of a corpus luteum in three sonograms performed at 7-day intervals. The cystic condition was denoted as early if the cyst was diagnosed 43-49 days postpartum, and late if detected 57-63-day postpartum. Spontaneous cyst regression before 60-day postpartum was regarded as early cystic recovery. For the early cystic group, there were no significant effects of lactation number, body condition score on prepartum Day 60, at parturition or on postpartum Day 30, or of body condition loss from parturition to 30-day postpartum. Cows calving in summer were 2.6 times more likely to develop ovarian cysts than those giving birth in winter. The risk of having a cyst was 1.9 times higher in cows with an abnormal puerperium. A 1-kg increase in milk yield raised the risk of cysts by a factor of 1.05. A 1-unit increase in body condition score (scale from 1 to 5) from prepartum Day 60 to parturition increased the risk of cyst development 8.4 times. Milk production and lactation number were negatively correlated with spontaneous early cyst recovery. A 1-kg decrease in milk production increased the probability of cyst recovery by a factor of 1.06, and a 1-unit drop in lactation number was associated with a 1.4-fold increased probability of cyst recovery. For the late cystic group, there were no significant effects of abnormal puerperium and body score data, except for a prepartum change in body score. Calving season (Odds ratio: 2.3), lactation number (Odds ratio: 1.36), increased milk production (Odds ratio: 1.05) and increased body condition score during the prepartum period (Odds ratio: 4.3) were all related to an increased risk of ovarian cysts. The probability of having a late cyst was 36.6 times greater in cows with early cysts. These findings suggest that it would be profitable to treat multiparous cows having cysts very early in the postpartum period, while treatment of primiparous cows should be delayed, at least until the end of the pre-service period, to provide the opportunity for spontaneous recovery.     

Prevalence of urovagina and its effects on reproductive performance in Holstein cows

Two hundred fifty-eight Holstein cows (n = 344 lactations) from seven dairy herds were examined every month by vaginoscopy and transrectal palpation to determine the prevalence of urovagina, to investigate its effects on fertility, and to determine some risk factors for urovagina. Accumulation of urine in the vagina of a cow was diagnosed as urovagina and was classified into mild (urine only on the floor of vagina), moderate (urine covering less than or equal to half portion of the external cervical os), or severe (urine covering more than half or whole portion of the external cervical os). In total, 26.7% of lactations had urovagina (mild 11.3%, moderate 11.0%, and severe 4.4%). Survival analysis was used to derive the case definition of clinically relevant urovagina based on the factors associated with increased time to conception. Only moderate (hazard ratio [HR] = 0.39) and severe (HR = 0.20) degrees of urovagina were associated with reduction in pregnancy rate and thus defined as clinically relevant urovagina. Cows with clinically relevant urovagina had decreased AI submission rate (HR = 0.52) and pregnancy rate (HR = 0.35), required more inseminations per conception (5 vs. 2; P < 0.001), had more days open (370 vs. 136; P < 0.001), and were more likely not to get pregnant by 210 d postpartum (odds ratio [OR] = 6.62) and to be culled for any reasons (OR = 5.32) or for reproductive reasons (OR = 9.54) compared with those in cows with no urovagina. Cows with clinically relevant urovagina had a higher risk of endometritis (36.4% vs. 9.2%; P < 0.001) compared with that in cows without urovagina. Cow, low BCS at first postpartum examination (OR = 2.85), endometritis within 60 d (OR = 2.50), and horizontal vulva (OR = 9.30) were risk factors for urovagina. In conclusion, 15.4% of lactations had clinically relevant urovagina that increased the risk of endometritis and had detrimental effects on fertility. Individual susceptibility, low BCS, and horizontal vulva increased the risk of diagnosing urovagina in Holstein cows.     

Analysis of fertility indices of cows with reproductive disorders and of normal cows in herds with low and normal fertility

Semiannual computer printouts of reproductive disorders diagnosed in high producing Israeli dairy herds were evaluated for a comparison of fertility indices of diseased and normal cows in low (LFH) and normal fertility herds (NFH). In 16,910 cows, conception rates to first AI in cows with reproductive disorder were >50% below those in normal cows (P<0.001). For both groups of cows, conception rates were lower in LFH (P<0.0001). A comparison of fertility indices between LFH (5, 171 cows) and NFH (14,573 cows) revealed, in addition a higher overall conception rate and a lower percentage of cows still open on Day 150 post partum (problem cows, (P<0.0001), as well as a higher pregnancy rate for NFH (P<0.001), for cows with reproductive disorder and for normal cows in these herds. In herds with predominantly uterine-related reproductive disorder, a high incidence of postpartum anestrus was seen infrequently; while in herds with a high incidence of postpartum anestrus, postbreeding anestrus was equally high (P<0.05 - 0.001). In general reproductive disorder have been shown to have long-term negative effects on fertility indices in both LFH and NFH, but with more serious consequences in LFH. Since a sizeable percentage of normal cows can be identified, reproducing normally under identical management conditions, cows in both kinds of herds with reproductive disorder must be less resistant to environmental stress. Thus, while cows with reproductive disorders maintained their general health and their high level of productivity, they responded either immediately with uterine disturbances or they refused to cycle properly, and they conceived later. A case can be made that all reproductive disorders represent disease entities influenced by management factors.     

Is fertility declining in dairy cattle? A retrospective study in northeastern Spain

The past few decades have seen a dramatic increase in infertility and reproductive disorders associated with a rising milk yield. Herein, we present a 10-year (from 1991 to 2000) retrospective survey of these factors using data from a reproductive management program performed on high-yielding dairy herds in north-east Spain. The data series included 12,711 lactations. The year was divided into warm and cool periods. Data were obtained from cows first inseminated or examined 45-70 days postpartum. The reproductive tract of each animal was examined by palpation per rectum within 43-48 days postpartum. Cows were then weekly examined until insemination or until postpartum Day 70. Cows with a corpus luteum were synchronized for estrus and timed AI. Cows showing natural estrus in the same period were also inseminated. All inseminations were pooled as a single group and inseminated cows were considered cyclic. Inactive ovaries and ovarian cysts were recorded as ovarian disorders. Incomplete uterine involution, endometritis and pyometra were grouped as uterine disorders.Overall cyclicity and pregnancy rates of all AI cows, and cyclicity and pregnancy rates corresponding to the warm period significantly decreased over the 10-year period, yet remained practically constant during the cool period. The incidence of inactive ovaries in the entire population and that corresponding only to cows examined during the warm period significantly increased with time but was similar during the cool period. Ovarian cysts were more frequent during the warm (12.3%) than during the cool (2.4%) period, though these proportions were maintained throughout the study. The incidence of uterine disorders significantly decreased with time and did not differ between cool and warm periods. Milk yield per cow and year increased from 7800 kg in 1991 to 10,200 kg in 2000. Regression analysis revealed that, for all cows and those inseminated or examined in the warm period respectively, each 1000 kg increase in average milk yield was related to decreases of 3.2 and 6% in pregnancy rate, 4.4 and 7.6% in cyclicity, and to increase of 4.6 and 8% in the incidence of inactive ovaries. The rate of uterine disorders decreased 1.1% regardless of season. Our overall results clearly reflect the increased infertility and incidence of reproductive disorders over the study period. This occurred simultaneous to increasing average milk yield. Nevertheless, under our study conditions, a cool environment appears to preserve fertility and reduce the risk of reproductive disorders irrespective of the milk yield. These findings prompt the need to improve management practices by attempting to reduce the effects of factors provoking stress.     

Prevalence of antibodies to IBR and BVD viruses in dairy cows with reproductive disorders

We determined the prevalence of antibodies to infectious bovine rhinotracheitis virus (IBRV) and bovine viral diarrhea virus (BVDV) in sera of dairy cows on 4 different farms in the Republic of Croatia. A high percentage (60.8%) of cows had various reproductive disorders. The results showed that seroprevalence of infectious bovine rhinotracheitis (IBR) was 85.8% and that of bovine viral diarrhea (BVD) was 79.2% in tested cows. Antibodies to both viruses were found in 80.8% of cows with reproductive disorders but in only 46.8% of cows without reproductive disorders. This difference was statistically significant (P<0.01), and indicated a connection between reproductive disorders and simultaneous infections with IBR and BVD viruses in dairy cows.     

Relationships between cytology, bacteriology and vaginal discharge scores and reproductive performance in dairy cattle

The objective was to compare three diagnostic approaches for intrauterine infection and inflammation: scoring of vaginal contents; quantification of percentage of nucleated cells that were polymorphonuclear leukocytes (PMN) following endometrial cytology; and intra-uterine bacteriology. Dairy cows (n = 303) were examined twice, Days 28 (D28) and 42 (D42), where Day 0 = day of calving. Associations between gross vaginal inflammation scores, uterine cytology, and bacteriology, and subsequent reproductive performance were examined using multivariable models. There was fair agreement at D28 (Kappa = 0.29), but only slight agreement at D42 (Kappa < 0.15), between PMN% and gross vaginal inflammation score. Cows were categorized as having PMN% in the highest quartile (H), or not (L), at both D28 and D42; therefore, cows were categorized as PMNLL, PMNLH, PMNHL, or PMNHH. Cows in the highest PMN% quartile at both time periods were slower to conceive (P < 0.001) than those in all other quartiles (mean ± SEM 32.2 ± 2.3, 37.0 ± 5.3, 40.8 ± 4.1, and 55.3 ± 7.3 d from start of breeding to conception for PMNLL, PMNLH, PMNHL, and PMNHH PMN% cows, respectively). Milk yield was greater (P = 0.001) in cows in the lower quartiles for PMN% at D28 and D42 (i.e., PMNLL) than those in the PMNHH and PMNHL categories, with PMNLH intermediate (P = 0.001). We concluded that PMN% was a better predictor of reproductive performance than either intra-uterine bacteriology or gross vaginal inflammation score. Cows in the highest quartile for PMN% at both D28 and D42 had lower pregnancy rates, took longer to conceive, and had a lower milk yield than those in the lower PMN% categories.     

Defining delayed resumption of ovarian activity postpartum and its impact on subsequent reproductive performance in Holstein cows

The objectives of this study were to derive a useful case definition of delayed resumption of ovarian activity, based on factors associated with reduced fertility, and to assess its impact on subsequent reproductive performance in Holstein cows (Bos taurus). Milk samples were collected twice weekly from 219 cows from four commercial herds, and whole-milk progesterone concentrations were determined with an enzyme-linked immunosorbent assay. Ovulation was considered to have occurred 5 d before the first rise of milk progesterone concentration above the basal level. Survival analysis was used to derive a case definition of delayed resumption of ovarian activity postpartum based on factors that were predictive of reduced pregnancy rate. First postpartum ovulation occurring beyond 35 d postpartum was associated with a reduced pregnancy rate (hazard ratio [HR] = 0.50; P < 0.001) and was defined as delayed resumption of ovarian activity; overall, 75 (34.9%) cows were in this category. These cows were more likely not to conceive on first artificial insemination (odds ratio [OR] = 2.85; P = 0.01) and more likely not to become pregnant within 100 d (OR = 3.30; P = 0.001) and 210 d (OR = 3.20; P < 0.001) postpartum compared with cows with normal resumption of ovarian activity. Furthermore, 13 (6%) cows that ovulated within 35 d postpartum had a prolonged (≥14 d) interval between either first and second or second and third luteal phases postpartum. A prolonged interluteal interval was also associated with a reduced pregnancy rate (HR = 0.35; P = 0.02). Days open (mean ± SEM) were greater (P = 0.0002) in cows with delayed resumption of ovarian activity (213 ± 13 d) and in cows with prolonged interluteal interval (220 ± 37 d) than in cows with normal resumption of ovarian activity (152 ± 9 d). In conclusion, first ovulation occurring beyond 35 d postpartum was defined as delayed resumption of ovarian activity, and the first ovulation occurring within 35 d postpartum but the absence of luteal activity ≥14 d between two consecutive luteal phases was defined as a prolonged interluteal interval; both abnormalities adversely affected the subsequent reproductive performance of Holstein cows.     

Recombinant bovine somatotropin: association with reproductive performance in dairy cows

A clinical trial was performed to determine the effect of bST on reproductive performance in dairy cows on 4 Michigan dairy farms when bST was used according to labeled directions. Holstein cows (n = 555) at 4 Michigan dairy farms were randomly assigned to receive bovine somatotropin (bST) or to serve as untreated controls. Bovine somatotropin (500 mg, s.c.) was administered every 14 d beginning at 63 to 69 d of lactation and continuing until approximately 21 d prior to the end of lactation or until the producer removed the animal from the herd. A total of 229 (42.57%) animals consisting of 112 (48.91%) controls and 117 (51.09%) bST-treated cows were not diagnosed pregnant and were considered as having reproductive failure by 150 d of lactation and 92 (17.10%) of the animals consisting of 45 (48.91%) controls and 47 (51.09%) bST-treated cows had reproductive failure at the end of their lactation. No significant difference in the incidence of reproductive failure existed between the study treatment groups during either time frame. Cows with cystic ovarian disease had more instances of reproductive failure at 150 d of lactation than cows without this disease. Cows with dystocia, twin births, metritis, displaced abomasum and cystic ovarian disease had more instances of reproductive failure by the end of lactation than cows without these diseases. The bST-treated cows developed more nonspecific off feed conditions during the study lactation and had more twin births at the calving following bST administration compared to control cows. No differences were found between the study treatment groups in calculations of reproductive parameters. Logistic regression analysis found no significant effect of bST on reproductive failure; the odds ratios for the bST treatment effect on reproductive failure at 150 d of lactation and reproductive failure at the end of lactation were 0.95 (95% CI 0.67 to 1.36) and 0.95 (95% CI 0.59 to 1.54), respectively. Overall, bST was not found to have a significant impact on reproductive performance in the herds studied.     

Effects of diagnostic low-volume uterine lavage shortly before first service on reproductive performance, culling and milk production

The objective was to evaluate if uterine sampling by low-volume uterine lavage, done shortly before the end of the voluntary waiting period, affected reproductive performance, milk production, or culling. Approximately 20 cows (40 and 60 d postpartum) were sampled in each of 38 herds (total, 752 cows), whereas all remaining cows concurrently between 40 and 60 d were a non-sampled reference cohort (n = 2,252 cows). There was an interaction between parity and sampling for first-service conception, calving to conception interval, and milk production. When stratified by parity, there was a tendency for impaired reproductive performance in sampled primiparous cows compared with non-sampled primiparous cows (Odds Ratio for pregnancy to first-service = 0.78 (95% C.I. 0.58-1.04). The Hazard Ratio for pregnancy in sampled primiparous cows was 0.89 (95% C.I. 0.77-1.04) compared to non-sampled primiparous cows. Sampling did not affect first-service conception rate (Odds Ratio for pregnancy Odds ratio (OR) for pregnancy = 1.03; 95% C.I. 0.80-1.33) or calving-to conception interval in multiparous cows (Hazard Ratio = 1.04; 95% C.I. 0.91-1.18). Sampling did not affect culling risk (Hazard Ratio HR = 0.92; 95% C.I. 0.77-1.11) after accounting for covariates. After stratification by parity, milk production was not affected by sampling except in fourth- and fifth-parity cows where sampled cows produced more milk than non-sampled cows after controlling for first test-day milk production and days-postpartum at first test-day. In conclusion, sampling by low-volume uterine lavage did not have significant detrimental effects on reproduction, culling, or milk production. However, there was a tendency for lower first-service conception in sampled primiparous cows, but the procedure appeared to be benign in multiparous cows.