Estrous detection intensity and accuracy and optimal timing of insemination with automated activity monitors for dairy cows.

The objectives of this observational study were to assess the ability of automated activity monitoring (AAM) to detect estrus for first insemination, the accuracy of detection, and the optimum interval from the estrus alert from the AAM system to insemination. Four commercial farms using 1 of 2 commercial AAM systems were studied over 1 yr. Cows were inseminated between 55 and 80 d in milk (DIM) based on AAM only, then by a combination of AAM and timed artificial insemination (AI). Blood progesterone was measured in 1,014 cows at wk 5, 7, and 9 postpartum; purulent vaginal discharge (PVD) was assessed at wk 5; and lameness and BCS at wk 7. Overall, AAM detected 83% of cows in estrus by 80 DIM. Cows that had 3 serum progesterone <1 ng/mL, had PVD, or were both lame and had BCS ≤2.5 has lesser odds of being detected in estrus by 80 DIM (62, 68, and 53%, respectively). Blood samples were collected on the day of 445 AI based on AAM and 323 timed AI. The proportion of cows not in estrus (progesterone >1 ng/mL) on the day of AI was similar between AAM (4 ± 1.8%) and timed AI (3 ± 1.2%). Managers elected, based on subjective criteria, not to inseminate 17% of cows for which an AAM estrus alert was issued, of which 43% were not in estrus. Activity data were extracted from AAM software for 1,399 AI. Onset of estrus was calculated using the same or similar data processing criteria as the AAM system. Producers recorded the time of AI. The interval from onset of estrus to AI was categorized as 0 to 8, 8 to 16, or 16 to 24 h. We found no effect of AAM system on the probability of pregnancy per AI, but noted an interaction of interval with parity. For multiparous cows, the probability of pregnancy per AI was 31%, which did not differ with the interval to AI. For primiparous cows, the odds of pregnancy were greater if AI occurred 0 to 8 h (49%) than 8 to 16 (36%) or 16 to 24 h (31%) after the estrus alert from the AAM. Automated activity monitoring can detect estrus for first AI in just over the length of 1 estrous cycle for over 80% of cows, but the remainder would likely require intervention for timely insemination. For multiparous cows, performing AI based on AAM once per day would not affect pregnancy per AI, but for primiparous cows AI within 8 h of the onset of estrus may be advantageous.

Reproductive performance with an automated activity monitoring system versus a synchronized breeding program.

The objective was to compare reproductive performance with management programs based on an automated activity monitoring (AAM) system or a synchronized breeding program under field conditions. In total, 1,429 Holstein cows from 3 commercial herds in Ontario, Canada, were enrolled over 1 yr in a randomized controlled trial. At each farm, primiparous and multiparous animals were housed in separate pens. At the pen level, cows were assigned to reproductive management primarily using an AAM system based on monitoring activity levels (Heatime, SCR Engineers Ltd., Netanya, Israel) or a timed artificial insemination (TAI) program. A crossover occurred after 6 mo of the trial to avoid confounding treatment with parity. Insemination based on additional detection of estrus by visual observation was practiced in all pens. At the individual cow level, time to pregnancy throughout the study (n=1,985 cow-6 mo periods), time to first service, and time to second service were analyzed with a Cox proportional hazards models accounting for herd, and did not differ overall between the AAM and TAI treatment groups. However, we observed an interaction between herd and breeding program, such that association of AAM- or TAI-based program with these outcomes differed between farms. Time to pregnancy was not different in herd A [median=151 and 136 d; hazard ratio (HR) = 0.93] and herd C (median=99 and 124, HR = 1.24), whereas herd B had a median time to pregnancy of 119 d and 146 d (HR = 1.3) in the AAM and TAI groups, respectively. Under conditions in which 19 to 32% of artificial inseminations in both groups were based on visually detected estrus, herd pregnancy rate and cow-level time to pregnancy did not differ overall between TAI- and AAM-based programs, but the effect of reproductive management approach depended on herd. Considering 924 cow-6 mo periods with artificial inseminations only by the assigned program, we also found an interaction between herd and breeding program. Stratified analysis showed no difference in time to pregnancy in herd A (HR = 1.3), whereas in herds B (HR = 1.7) and C (HR = 2.8), cows in the AAM treatment group became pregnant sooner compared with those in the TAI group. Factors that influence the variability in relative performance of these management systems between herds require further investigation. Our study used one commercial activity monitoring system and the results cannot necessarily be generalized to other systems.

Risk factors and effects of postpartum anovulation in dairy cows.

The objectives were to identify risk factors for and to quantify the effect of postpartum anovulation on reproductive performance in dairy cows. Data from 2,178 Holstein cows in 6 commercial herds enrolled in a randomized clinical trial were used. Data on periparturient disease incidence, calving history, and body condition score were collected. Cows were examined at wk 5 postpartum for reproductive tract disease; cytological endometritis was defined as ≥6% polymorphonuclear cells in endometrial cytology, and purulent vaginal discharge was defined as the presence of mucopurulent or purulent vaginal discharge. Cows were followed until 300 d in milk (DIM) for reproductive performance. Serum nonesterified fatty acids (NEFA) concentration was measured once during the week before expected calving. Serum ß-hydroxybutyrate, NEFA, and haptoglobin were measured at wk 1, 2, and 3 postpartum. Serum progesterone (P4) was measured at wk 3, 5, 7, and 9 postpartum. The end of the postpartum anovulation period was defined as the first sampling time at which P4 was >1 ng/mL. Statistical analyses were performed using logistic regression models and Cox proportional hazard models. The prevalence of anovulation was 72, 44, 26, and 17% at wk 3, 5, 7, and 9, respectively. Cows were classified according to their ovulatory status as having luteal function at 21 DIM (Cyc21), as having low P4 at 21 DIM but having luteal function at least once at 35 or 49 or 63 DIM (Cyc63), or being anovulatory at 63 DIM (Anov63; no samples with P4 >1 ng/mL). Factors associated with early ovulation (Cyc21) included season, parity, decreased haptoglobinemia, and decreased serum NEFA concentration before and after parturition. Risk factors for prolonged anovulation (Anov63) included cytological endometritis, increased haptoglobinemia, and greater serum NEFA concentrations before and after parturition. Cows classified as Anov63 had an increased median time to first breeding compared with Cyc63 (74.1 vs. 73.2 d). The effect of prolonged postpartum anovulation on median time to pregnancy was conditional on parity group; a detrimental effect was present in cows of parity ≥3 (129 d for Cyc21, 151 d for Cyc63, and 180 d for Anov63), but no effect was observed in cows of parity ≤2. Overall, these findings suggest that postpartum anovulation was associated with indicators of energy balance and uterine inflammation, and with detrimental effects on reproductive performance.

Randomized clinical trial of antibiotic and prostaglandin treatments for uterine health and reproductive performance in dairy cows.

The objectives of this study were to assess the efficacy of antibiotic treatment for preventing postpartum uterine disease among cows at high risk of uterine disease, and to assess the efficacy of PGF(2α) for treating cytological endometritis (CYTO) and purulent vaginal discharge (PVD). A total of 2,178 Holstein cows in 6 herds were enrolled in a randomized clinical trial. Within 24h after parturition, cows were classified at being at high risk of uterine disease (HRUD; n=1,017) if they had twins, dystocia, or retained placenta. All remaining cows were classified as being at low risk of uterine disease (LRUD; n=1,161). Cows in the HRUD group were randomly allocated in a factorial design to receive ceftiofur crystalline free acid (CCFA) at 24h after parturition or be untreated, and to receive dinoprost (PGF(2α)) at 35 and 49 (±3) days in milk (DIM) or to be untreated. Cows in LRUD were randomly allocated to receive PGF(2α) at 35 and 49 (±3) DIM or to be untreated. Serum progesterone was measured at 21, 35, 49, and 63 (±3) DIM. Cows were examined at 35 (±3; exam 1) and 56 (±3; exam 2) DIM for CYTO (by cytobrush device; ≥6% polymorphonuclear cells in endometrial cytology) and for PVD (by Metricheck device; mucopurulent or purulent vaginal discharge). Statistical analyses were performed using multivariable logistic regression models accounting for herd clustering. Treatment with CCFA in HRUD cows was not associated with the probability of metritis overall, but interactions occurred such that CCFA decreased the incidence of metritis among HRUD cows that did not have retained placenta and among cows of parity ≥2. Treatment with CCFA in HRUD cows decreased the probability of PVD at exam 1. Treatment with PGF(2α) did not affect the probability of cure of CYTO or PVD irrespective of progesterone concentration at the time of treatment. Among cows affected by CYTO or PVD at exam 1, 66 and 63%, respectively, had spontaneously cured at exam 2. Cows persistently affected at exam 2 had an increased time to pregnancy and were more likely to have both CYTO and PVD at exam 1. Administration of PGF(2α) at both 5 and 7 wk postpartum did not mitigate the effects of CYTO or PVD on reproductive performance. Clinical approaches to treatment of chronic postpartum reproductive tract infection and inflammation should be reassessed.

Effects of postpartum uterine diseases on milk production and culling in dairy cows.

The objective was to quantify the effect of postpartum uterine diseases on milk production and culling. Data from 2,178 Holstein cows in 6 herds enrolled in a randomized clinical trial were used. Milk production data from the first 4 Dairy Herd Improvement Association (DHIA) test-days and culling data from farm records were collected. Retained placenta (RP; ≥24 h after parturition) and metritis [≤20 d in milk (DIM)] were diagnosed by farm managers using standardized definitions. Farms were visited weekly and cows were examined at 35 and 56 (±3) DIM using endometrial cytology (cytobrush device), vaginal discharge scoring (Metricheck device), and measurement of cervical diameter by transrectal palpation. Diagnostic criteria for cytological endometritis (CYTO) and purulent vaginal discharge (PVD) were established based on a detrimental effect on subsequent reproduction. Statistical analyses were performed using linear mixed models, logistic regression models, and Cox proportional hazard models, accounting for the effects of experimental treatments and herd clustering. Milk production and culling were the outcomes. Primiparous and multiparous cows were modeled separately for milk production. Milk production of primiparous cows was unaffected by uterine diseases. The effect of metritis on milk production was variable over time in multiparous cows: it decreased production per cow by 3.7 kg at the first DHIA test, but was not different at later tests. Retained placenta decreased milk production by 2.6 kg/d in multiparous cows through the first 4 DHIA tests. The projected effects of metritis and RP in multiparous cows were reductions of 259 kg and 753 kg over 305 DIM, respectively; these effects were additive. Neither CYTO nor PVD affected milk production. Culling risks at 30 and 63 DIM were unaffected by RP and metritis. Culling hazard up to 300 DIM was unaffected by RP, metritis, CYTO, or PVD, whether or not pregnancy status, milk production, and displaced abomasum were accounted for. Uterine disease decreased pregnancy rate, which was a substantial risk factor for culling; however, if affected cows became pregnant they were not at greater risk of culling.

Risk factors for postpartum uterine diseases in dairy cows.

The objective of this observational study was to investigate the risk factors for metritis, purulent vaginal discharge, and cytological endometritis. The hypothesis was that purulent vaginal discharge and cytological endometritis would have different risk factors because they represent distinct manifestations of uterine disease. Data generated from 1,363 Holstein cows (3 herds) enrolled in a randomized clinical trial were used. Calving history, periparturient disease incidence, and body condition score at calving and at 63 d in milk (DIM) were recorded. Serum nonesterified fatty acid concentration was measured once during the week before expected calving. Serum nonesterified fatty acid, ß-hydroxybutyric acid, and haptoglobin (Hapto) concentrations were measured at 4 ± 3, 11 ± 3, and 18 ± 3 DIM. Serum progesterone concentration was measured at 21 ± 3, 35 ± 3, 49 ± 3, and 63 ± 3 DIM. Metritis was diagnosed by farm managers within the first 20 DIM using a standardized definition. Cows were examined at 35 ± 3 DIM by a veterinarian for purulent vaginal discharge (mucopurulent or worse vaginal discharge; Metricheck device) and cytological endometritis (≥ 6% polymorphonuclear cells on endometrial cytology; cytobrush device). Statistical analyses were performed using multivariable logistic regression models for each disease, accounting for the random effect of herd. Risk factors for metritis included increased nonesterified fatty acid prepartum (≥ 0.6 mmol/L), dystocia, retained placenta, and increased Hapto in the first week postpartum (≥ 0.8 g/L). Risk factors for purulent vaginal discharge included twinning, dystocia, metritis, and increased Hapto (≥ 0.8 g/L) in the first week postpartum. Risk factors for cytological endometritis included low body condition score at parturition (≤ 2.75), hyperketonemia (≥ 1,100 µmol/L), and increased Hapto (≥ 0.8 g/L) in the first week postpartum. These results support the hypothesis that some of the risk factors for purulent vaginal discharge and cytological endometritis are different, which supports that they are distinct manifestations of uterine disease.

Definitions and diagnosis of postpartum endometritis in dairy cows.

The objectives of this observational study were to determine and compare diagnostic criteria for postpartum endometritis in dairy cows. Data generated from 1,044 Holstein cows (6 herds) enrolled in a randomized clinical trial were used. Cows were examined for endometritis at 35±3 d (exam 1) and 56±3 d (exam 2) after parturition, using endometrial cytology (cytobrush technique), vaginal discharge scoring (Metricheck device; Simcrotech, Hamilton, New Zealand), and cervical diameter measurement (transrectal palpation). Reproductive data were recorded until 200 d after parturition. Diagnostic criteria for cytological and clinical endometritis were determined based on detrimental effect on subsequent reproductive performance, using logistic regression and Cox proportional hazard models accounting for the effect of herd clustering. Comparison of diagnostic criteria was performed using endometrial cytology as reference test or by quantifying the agreement between diagnostic approaches. At exam 1, diagnostic criteria were ≥6% polymorphonuclear cells and mucopurulent or worse (purulent or foul) vaginal discharge for cytological and clinical endometritis, respectively. At exam 2, diagnostic criteria were ≥4% polymorphonuclear cells and mucopurulent or worse vaginal discharge for cytological and clinical endometritis, respectively. Cows were classified as having cytological endometritis only, clinical endometritis only, or both cytological and clinical endometritis. Prevalence at exam 1 was 13.5, 9.4, and 5.8% for cytological endometritis only, clinical endometritis only, and both cytological and clinical endometritis, respectively. The detrimental effects of cytological and clinical endometritis on reproductive performance were additive. Among cows with clinical endometritis, only 38 and 36% had cytological endometritis at exam 1 and exam 2, respectively. Combination of diagnostic criteria improved neither the accuracy for predicting cytological endometritis nor the agreement between cytological and clinical endometritis. Overall, these results suggested that cytological and clinical endometritis may represent different manifestations of reproductive tract disease. They also suggested that use of the terminology clinical endometritis may not be accurate and that purulent vaginal discharge may be more descriptive.

The effect of subclinical ketosis in early lactation on reproductive performance of postpartum dairy cows.

Data generated from 796 Holstein cows enrolled in a clinical trial to investigate the health effect of a monensin controlled release capsule were analyzed to investigate the association between circulating serum beta-hydroxybutyrate (BHBA) concentration in the peri-parturient period and subsequent reproductive performance. Overall, accounting for both repeated measures within cow and clustering at the herd level, non-pregnant cows after first insemination tended to have increased circulating BHBA concentrations from 3 wk before calving to 9 wk after calving relative to pregnant cows. Including the interaction between the week of sample collection and pregnancy outcome, non-pregnant cows had higher circulating BHBA concentrations in the second week after calving than cows diagnosed pregnant after first artificial insemination. Within individual weeks, cows with circulating BHBA concentrations > or =1,000 micromol/L in the first week postpartum were less likely to be diagnosed pregnant after first insemination. In the second week postpartum, the cows with circulating BHBA concentrations > or =1,400 micromol/L were significantly less likely to be pregnant after first artificial insemination. A dose response relationship was found when a comparison of the probability of pregnancy after first insemination and duration of elevated circulating ketone bodies was investigated. The probability of pregnancy was reduced by 20% in cows diagnosed subclinically ketotic in either the first or second week postpartum. Nevertheless, cows above the subclinical ketosis threshold in both the first and second week postpartum were 50% less likely to be pregnant after first insemination. Similarly, the median time to pregnancy increased in cows experiencing elevated BHBA concentrations in either (124 d) or both (130 d) the first and second week postpartum relative to cows never experiencing elevated BHBA concentrations (108 d). To further investigate this, the effect of elevated circulating BHBA was permitted to vary with time. The effect decreased with time, such that the daily probability of pregnancy increased similar to nonsubclinically ketotic cows by approximately 160 d in milk. From this analysis, both the relative circulating concentration of BHBA and the duration of elevated circulating BHBA were negatively associated with the probability of pregnancy at first service.

Synchronization of estrus and pregnancy risk in anestrous dairy cows after treatment with a progesterone-releasing intravaginal device.

Lactating Holstein cows (located in 4 dairy herds) that had failed to display estrus as defined by increased pedometer activity by 63 +/- 3 d in milk, were enrolled to investigate the effect of a progesterone-releasing intravaginal device (PRID, n = 268) relative to a placebo intravaginal device (PID, control, n = 266) on days from device removal to artificial insemination (AI), the probability of pregnancy at first AI, and days from device removal to pregnancy. Cows were assigned randomly to receive a PRID or PID for 7 d and an injection of PGF2alpha at device removal. Upon device removal, a vaginitis score was assigned and AI occurred at observed estrus. Cows failing to display estrus within 14 d of device removal were subjected to a subsequent reproductive exam and were treated with PGF2alpha. Two percent of PRID-treated cows and 11% of control cows displayed estrus during the 7-d exposure period. Among the remaining cows, 93% of the devices were present at the scheduled removal. Cows treated with the PRID were 60% less likely to have purulent debris on the device than control cows. Vaginal reaction, however, was not associated with any of the reproductive outcomes. Investigation of the reproductive outcomes revealed a treatment x parity interaction. Progesterone-treated primiparous cows were inseminated 17 d earlier, with no significant change in the probability of pregnancy at first AI (30.3 vs. 42.0%), and no difference in median time from device removal to pregnancy (52 vs. 53 d) relative to control primiparous cows. Conversely, PRID-treated multiparous cows were inseminated 8 d earlier, with no change in probability of pregnancy at first AI (24.6 vs. 18.8%); however, median time from device removal to pregnancy was reduced by 20 d (67 vs. 87 d). These results support the efficacy of a PRID to induce estrus in previously anestrous cows. The reason, however, for the variable response between primiparous and multiparous cows was not clear.

The effect of a progesterone releasing intravaginal device (PRID) on pregnancy risk to fixed-time insemination following diagnosis of non-pregnancy in dairy cows.

The objective was to compare the probability of pregnancy after fixed-time insemination in cows diagnosed as non-pregnant and re-inseminated following the Ovsynch protocol, with or without exogenous progesterone. Cows (n=415) used in this study originated from 25 farms. Upon diagnosis of non-pregnancy between 30 and 60 days after AI, cows were randomly assigned to receive either a progesterone releasing intravaginal device (PRID; n=208) or a placebo intravaginal device (PID; n=207). All cows received GnRH at enrollment (Day 0), PGF(2alpha) concurrent with intravaginal device removal 7 days later, GnRH on Day 9 and fixed-time insemination 16h later (Day 10). Cows observed in estrus prior to Day 7, had the device removed and were inseminated. Ovaries were examined by transrectal palpation at the time of enrollment and the prominent structures were assessed and recorded. Body condition score, lameness status, interval from previous insemination, and times bred at enrollment were recorded. At intravaginal device removal, the occurrence and intensity of vaginitis was determined according to the amount of debris on the device. Overall, the intravaginal device retention rate was 91%. A total of 5.2% of PID-treated cows and 2.9% of PRID-treated cows were detected in estrus within the 7 days treatment period. Pregnancy status was diagnosed between 30 and 56 days after insemination and all cows were followed for a minimum of 150 days after enrollment. Approximately 28% of cows had evidence of mild vaginitis in response to the intravaginal device, whereas 6% of cows had copious debris associated with the intravaginal device at removal. The probability of pregnancy after fixed-time insemination was 43.8% versus 34.9% in PRID-treated versus PID-treated animals. Exogenous progesterone provided through an intravaginal device to non-pregnant cows that had not displayed estrus improved the probability of pregnancy after fixed-time AI.

Prevalence and risk factors for postpartum anovulatory condition in dairy cows.

The objectives of this research were to determine the prevalence of the anovulatory condition within a temperate region of North America and identify cow-level and herd-level risk factors for this condition. A total of 1,341 cows from 18 herds were classified as cycling or anovular based on skim milk progesterone concentration determined at 46 and 60 +/- 7 d in milk. Calving history, periparturient disease incidence, body condition score, milk ketone concentration in the first 2 wk of lactation, and first 305-d mature-equivalent milk projections were recorded. Reproductive and culling information was retrieved monthly from the Dairy Herd Improvement Association. The cow-level prevalence of anovulation was 19.5%, with a herd-specific range from 5 to 45%. Accounting for the effect of clustering at the herd level, cows experiencing a difficult calving, cows with twin calvings, displaced abomasum, and cows with subclinical ketosis in the first week after calving were at greater risk for diagnosis of anovulation. Anovular cows within herds using ovulation synchronization programs were inseminated at the same time postpartum with a 6-percentage point reduction in the probability of pregnancy relative to cycling herdmates (29.7 vs. 35.9%, respectively), whereas anovular cows in herds breeding based on observed estrus were inseminated 8 d later and suffered a 10-percentage point reduction in the probability of pregnancy at first insemination (20.3 vs. 30.5). Time to pregnancy was delayed in anovular cows by 30 d (156 vs. 126 d). Using survival analysis, the impact of anovulation decreased with time. The daily probability of pregnancy (hazard ratio) was similar to cycling cows by 165 d in milk. The results underline the important associations of peripartum health with reproductive function and performance.

Effect of presynchronization using prostaglandin F2alpha and a milk-ejection test on pregnancy rate after the timed artificial insemination protocol, Ovsynch.

The objective of this research was to determine if PGF2alpha-induced milk letdown (ML) is an accurate indicator of luteolysis, allowing cows to be synchronized to begin the Ovsynch protocol (GnRH-7d-PGF2alpha-2d-GnRH-24h-AI) at the most beneficial time of the estrous cycle (days 5-9), and determine if this would improve pregnancy rate (PR). Lactating Holstein cows between 55 and 70 days in milk were used to evaluate the ML test and PR after the Ovsynch protocol, when initiated on the basis of the test result (PROSYNCH). PROSYNCH cows (n = 60) had one teat cannulated to test for ML and were treated with 500 microg cloprostenol, PGF2alpha analogue (PG). Cows with ML were started on Ovsynch 10 days later, and those without started 3 days later. Cows in the control group (OVSYNCH, n = 64) were injected with physiological saline and observed for ML. This group was started on Ovsynch 10 days after saline treatment. Milk samples were collected thrice weekly to determine progesterone concentrations. ML indicated luteolysis with a sensitivity of 98% and a specificity of 60%. The positive and negative predictive values were 83 and 92%, respectively. Pregnancy rates were 48% for PROSYNCH and 52% for OVSYNCH (P = 0.72). When data from both groups were combined, PR was greater in cows that started the Ovsynch protocol in stage 2 of the estrous cycle (days 5-9, 67%) than all other stages (stage 1: days 1-4, 35%; stage 3: days 10-16, 45%; stage 4: days 17-21, 42%; P < 0.01). The proportion of animals with ovulation after GnRH#1, luteolysis after PGF2alpha, and ovulation after GnRH#2 were all greater in the PROSYNCH group (77% versus 55%, P < 0.02; 83% versus 66%, P < 0.03; 97% versus 84%, P < 0.03, respectively). Therefore, the ML test indicated luteolysis with sufficient precision to time the initiation of the Ovsynch protocol between days 5 and 9 of the cycle, however, this did not alter PR compared to starting the protocol randomly throughout the cycle. Initiating the Ovsynch protocol between days 5 and 9 of the cycle increased PR, and improved the efficacy of each injection.

The effect of a single administration of cephapirin or cloprostenol on the reproductive performance of dairy cows with subclinical endometritis.

This study examined the effect of a single administration of cephapirin iu or cloprostenol im on the reproductive performance of dairy cows with subclinical endometritis. Cows (n = 228) at 20-33 days in milk (DIM) from two commercial dairy farms, determined to be normal for clinical endometritis (based on absence of abnormal uterine discharge on vaginoscopic examination) were enrolled. At enrollment, a thorough reproductive examination was performed, including rectal palpation, ultrasonography (US) and endometrial cytology (EC). The case definition for subclinical endometritis was the presence of >18% neutrophils on EC examination or fluid in uterus (FIU) on US examination. All cows were randomly assigned to receive one of three treatments: 500 mg benzathine cephapirin iu, 500 microg cloprostenol im, or control (no treatment). Reproductive performance was monitored for a minimum of 8 months after treatment. Cows with subclinical endometritis treated with cephapirin or cloprostenol had a significantly increased relative pregnancy rate compared to control [hazard ratios 1.89 (P = 0.01) and 1.70 (P = 0.05), respectively]. In conclusion, a single treatment with cephapirin or cloprostenol at 20-33 DIM significantly improved the reproductive performance of cows with subclinical endometritis.

Endometrial cytology and ultrasonography for the detection of subclinical endometritis in postpartum dairy cows.

The objectives of the study were to validate the use of endometrial cytology (EC) and ultrasonography (US) to diagnose subclinical endometritis in clinically normal postpartum dairy cows, and to measure the impact of subclinical endometritis on reproductive performance. Holstein cows from two dairy farms were examined at Visit 1 (V1) at 20-33 days in milk (DIM), and clinically normal cows (n = 228), based on the absence of abnormal discharge on external inspection and vaginoscopy, were selected. The reproductive tract of selected cows was evaluated by transrectal palpation, US and EC. All cows in the study were re-examined at Visit 2 (V2) at 34-47 DIM (2 weeks after V1) and were subsequently followed for a minimum of 8 months (until pregnant or culled). Survival analysis was used to derive a case definition of subclinical endometritis, based on factors associated with decreased relative pregnancy rate. Positive EC at V1 (>18% polymorphonuclear leukocytes; PMN) or fluid in uterus at V1 (FIU1) were associated with a significant reduction in the relative pregnancy rate and identified cows with subclinical endometritis. Similarly, a positive EC (>10% PMN) at V2 or fluid in the uterus at V2 (FIU2), identified cows with subclinical endometritis. Cows with subclinical endometritis at V1 and at V2 had a relative pregnancy rate of 41 and 51% (hazard ratio for pregnancy of 0.59 and 0.49), respectively, compared to cows without subclinical endometritis. Given EC or US findings, no diagnostic criteria based on transrectal palpation of the uterus had predictive value for risk of pregnancy. In conclusion, subclinical endometritis, diagnosed by EC or US, was associated with reduced relative pregnancy rate.

Ovarian follicular activity in lactating Holstein cows supplemented with monensin.

The objective of this study was to determine effects of monensin on ovarian follicular development and reproductive performance in postpartum dairy cows. Forty-eight multiparous Holstein cows were randomly assigned to receive either a control total mixed ration (n = 24) or the same diet plus 22 mg of monensin/kg (n = 24) from 21 d before anticipated calving until cows were either confirmed pregnant or were >180 d postpartum. Monensin had no effect on development of the first dominant follicle postpartum or the numbers of class 1 (3 to 5 mm), 2 (6 to 9 mm), or 3 (10 to 15 mm) follicles. Control cows had more class 4 (>15 mm) follicles at 10 to 13 d postpartum than cows in the monensin group. The first dominant follicle postpartum ovulated, regressed, or became cystic unrelated to differences between diets. However, the first ovulation postpartum occurred earlier in monensin-fed cows than in the control group (27.2 +/- 2.1 d vs. 32.4 +/- 1.5 d), with no dietary effects on the diameter of the ovulating follicle. Similarly, treatments did not differ in the proportion of cows with 2 or 3 waves of ovarian follicular development per cycle, nor in the number of follicles of all classes during the breeding period. Times of ovulation following treatment with prostaglandin F2alpha were not different between dietary groups. Pregnancy rates after timed artificial insemination were similar between diets. Supplementation with monensin resulted in a shorter postpartum interval to first ovulation but did not affect other reproductive measures in healthy, lactating dairy cows.

Defining and diagnosing postpartum clinical endometritis and its impact on reproductive performance in dairy cows.

The objectives of this study were to validate diagnostic criteria for clinical endometritis in postpartum dairy cows and to measure the impact of endometritis on reproductive performance. Data were collected from 1865 cows in 27 herds, including history of dystocia, twins, retained placenta, or metritis. All cows were examined once between 20 and 33 d in milk (DIM) including external inspection, vaginoscopy, and transrectal palpation of the cervix, uterus, and ovaries. All cows were followed for a minimum of 7 mo or until pregnancy or culling. Survival analysis was used to derive a case definition of endometritis based on factors associated with increased time to pregnancy. The significance of clinical findings depended on the interval postpartum when examination took place. The presence of purulent uterine discharge or cervical diameter > 7.5 cm after 20 DIM, or mucopurulent discharge after 26 DIM identified cows with clinical endometritis. Given vaginoscopy, no diagnostic criteria based on palpation of the uterus had predictive value for time to pregnancy. The prevalence of clinical endometritis was 16.9%. Vaginoscopy was required to identify 44% of these cases. Accounting for parity, herd, and ovarian status, cows with clinical endometritis between 20 and 33 DIM had a hazard ratio of 0.73 for pregnancy (took 27% longer to become pregnant), and were 1.7 times more likely to be culled for reproductive failure than cows without endometritis.

The effect of treatment of clinical endometritis on reproductive performance in dairy cows.

The objective of this field trial was to compare the effect of intrauterine (i.u.) antibiotic or intramuscular (i.m.) prostaglandin F2 alpha (PGF2 alpha) on time to pregnancy in dairy cows diagnosed with clinical endometritis between 20 and 33 days in milk (DIM). The case definition of endometritis was the presence of purulent uterine discharge or cervical diameter > 7.5 cm, or the presence of muco-purulent discharge after 26 DIM. There were 316 cows with endometritis from 27 farms assigned randomly within herd to receive 500 mg of cephapirin benzathine intrauterine (i.u.), 500 micrograms of cloprostenol i.m., or no treatment. The rate of resolution of clinical signs 14 d after treatment was 77% and was not affected by treatment. Reproductive performance was monitored for a minimum of 7 mo after treatment. Survival analysis (multivariable proportional hazards regression) was used to measure the effect of treatment on time to pregnancy. There was no benefit of treatment of endometritis before 4 wk postpartum. Administration of PGF2 alpha between 20 and 26 DIM to cows with endometritis that did not have a palpable corpus luteum was associated with a significant reduction in pregnancy rate. Between 27 and 33 DIM, cows with endometritis treated with cephapirin i.u. had a significantly shorter time to pregnancy than untreated cows (hazard ratio = 1.63). In this time period, there was no difference in pregnancy rate between PGF2 alpha and untreated cows, but the difference in pregnancy rate between cows treated with cephapirin i.u. and with PGF2 alpha was not statistically significant. Treatment of postpartum endometritis should be reserved for cases diagnosed after 26 DIM, based on criteria that are associated with subsequent pregnancy rate.

Expression of luteinizing hormone genes in bovine conceptuses.

RT-PCR analysis demonstrated that bovine conceptuses at days 16, 23 and 30 expressed LH-beta-like and glycoprotein hormone alpha-like transcript sequences; adult kidney, liver and brain produced predominantly unspliced products. Sequencing of the LH-beta-like fragment (from conceptuses at day 30) indicated complete homology with the published sequence. In addition, ribonuclease protection assay of RNA samples from bovine conceptuses at day 30 with a bovine LH-beta probe revealed the presence of protected molecules that appeared to be full length. Northern blot analysis of total RNA from conceptuses at day 30 failed to demonstrate the presence of LH-beta or glycoprotein alpha subunit transcripts, whereas both transcripts were readily detected in adult pituitary RNA. Administration of hCG into the uterus of heifers from day 14 to day 16 of the oestrous cycle did not affect circulating progesterone concentrations, whereas the same dose increased progesterone concentrations (P < 0.05) when administered intravenously. These results indicate that the early bovine conceptus transcribes genes encoding LH-alpha and -beta subunits, but at a level unlikely to be of physiological consequence.

Reproductive performance of postpartum dairy cows under a highly intervenient breeding program involving timed insemination and combinations of GnRH, prostaglandin F2alpha and human chorionic gonadotropin.

Lactating Holstein cows (n=288) were grouped as pairs at parturition and randomly assigned to two treatments (control, C vs intervenient treatment, T). The reproductive management of the Group C cows (n=130) consisted of the intramuscular administration of 500 microg PGF2alpha analogue (PG) on Days 28 and 63 postpartum and breeding on the basis of estrus signs with the a.m.-p.m. rule after Day 63. Cows that were not bred by 77 d postpartum received another injection of PG and were bred at estrus or 84 h after PG treatment. Pregnancy diagnoses were perfomed by palpation of the uterus per rectum 42 to 48 d after AI. Cows in the T group (n=139) received intramuscular injections of 100 microg GnRH 14 d and PG 28 d after calving. On Day 56 postpartum, cows were given a second dose of GnRH followed by PG on Day 63 postpartum and a third GnRH injection 48 h after PG (OvSynch). Cows were inseminated at a fixed time (22+/-1 h) after GnRH. Five days after the fixed-time insemination cows were given 1500 IU hCG i.m.. Group C and T cows that returned to service or were diagnosed as non-pregnant continued to receive PG at intervals of 14 d with breeding at estrus or 84 h after the second PGF2alpha dose. A sustained increase in milk progesterone concentration was observed in 59.0% of T cows after GnRH administration on Day 14. A similar rise in milk progesterone concentrations was observed in 53.8% of C cows. The PG on Day 28 induced luteolysis more in Group T cows (53.2%) than in Group C cows (36.9%). The PG on Day 63 reduced milk progesterone concentrations to basal levels in 50.7% of T and 49.2% of Group C animals. The first service pregnancy rates (T, 40.3% vs C, 36.2%) and the overall pregnancy rates (all services, T, 83.5% vs C, 86.9%) were not different between the two groups. The two treatments did not differ in the interval from first service to pregnancy, calving to pregnancy or in calving interval, number of services per pregnancy or culling rates.

Relationships between milk urea concentrations and nutritional management, production, and economic variables in Ontario dairy herds.

The objectives of this study were to describe the relationships between milk urea concentrations and nutritional management, production, and economic variables in commercial dairy herds. Dairy Herd Improvement (DHI) test-day milk urea data, production data, and information on ration nutrient composition and feeding management programs were collected over a 13-mo period from 53 commercial Ontario dairy herds. Economic variables included gross milk revenue, feed costs, and income over feed costs. Herd mean milk urea concentrations had a positive relationship with dietary levels of crude protein (CP), rumen degradable protein (RDP), and rumen undegradable protein (RUP) and a negative relationship with dietary levels of nonfiber carbohydrates (NFC), forage:concentrate (F:C) ratio, NFC:CP ratio, and NFC:RDP ratio. These findings are consistent with experimental studies that used chemical methods of milk urea analysis. Herd mean milk urea concentration was not associated with feeding management (e.g., total mixed rations, component feeding, feeding frequency, or synchrony of forage and concentrate feeding). Herd mean milk urea was not associated with either mean milk yield or linear score. Herd mean milk urea had a positive relationship with feed costs per cow per day but was not associated with gross milk revenue per cow per day. Herds with a high mean milk urea concentration tended to have lower income over feed costs per cow per day. High herd mean milk urea concentrations were associated with higher feed costs per kilogram of milk fat but lower gross milk revenue and lower income over feed costs per kilogram of milk fat. The results of this study demonstrate that DHI milk urea measurements produced by an infrared test method offer a useful tool for monitoring the efficiency of nitrogen utilization in commercial dairy herds. The results also suggest that diets may be balanced to achieve greater efficiency of nitrogen utilization, lower milk urea concentrations, and lower feed costs, while still achieving high milk production. This may lead to improved income over feed costs.