Reduced incidence of retained placenta with induction of parturition in the cow

Two experiments were designed to determine whether pretreatment with Opticortenol (OPT), a long-acting corticosteroid, prior to induction of parturition with 25 mg of dexamethasone (DEX) alone or in combination with 500 mug cloprostenol (CLO) would result in a reduced incidence of retained placenta. In Experiment 1, 70% of the cows pretreated with 25 mg OPT on Day 270 of gestation calved before or within 24 hours of the scheduled induction treatment on Day 277. Cows induced to calve with DEX plus CLO without OPT pretreatment had an increased rate of placental retention (P<0.05), whereas, cows that received OPT were not different from the controls. In Experiment 2, cows received either 1 mg/25 kg OPT (high dosage) or 1 mg/50 kg OPT (low dosage) on Day 270 of gestation and were induced with DEX plus CLO on either Day 274 (4 days) or Day 276 (6 days). Cows claved 29.0 to 31.8 hours after induction treatment with 95% beginning to calve between 0700 and 1900 hours. The interval from calving to placental release and the incidence of retained placenta was not different between the high dosage 6-day group (29.4+/-8.2 hours, 29%) and the non-induced control cows (16.1+/-10.7 hours, 5%). When three cows in the high dosage 6-day group that retained their placentas for 30 to 36 hours were considered as not retained, the incidence of placental retention for that group was reduced still further to 17%. First service conception rates and pregnancy rates were lower in cows with retained placentas. Differences were significant (P<0.01) in Experiment 1 but not in Experiment 2. It was concluded that pretreatment with 1 mg/25 kg OPT 6 days prior to induction of parturition with DEX plus CLO in combination results in a predictable calving time, high calf viability, and a low incidence of placental retention.     

Circulating PgF2alpha and nutritional parameters at parturition in dairy cows with and without retained placenta: Relation to prepartum diet

Reproductive and biochemical parameters were studied at parturition in multiparous single-carrying Holstein cows. These were compared in animals with (n=14) and without (n=40) a retained placenta and then according to 2 prepartum diets (corn silage/concentrate, n=44; grass silage/concentrate, n=10) in cows with and without retained placentas. Cows with retained placentas had a 4-day shorter gestation period and gave birth to 5 kg-lighter calves than cows without retained placentas. Furthermore, their plasma PGFM -PgF2alpha main metabolite- (3325 vs 5675 pg/ml; P<0.01) and glucose (79.2 vs 95.2 mg/100ml; P<0.05) levels were lower and their protein concentration was higher (85.7 vs 76.5 g/l; P<0.05) than those of cows without retained placentas. Retained placenta incidence in cows fed grass-silage was higher than in cows fed corn-silage (60% vs 18.2%; P<0.05). Cows with retained placentas and fed corn silage had shorter gestation lengths, gave birth to lighter calves, and had less circulating glucose at calving (77.6 vs 96.5 mg/100ml; P<0.05) than cows without retained placentas and fed the same forage. Cows with retained placentas and fed grass silage had less PGFM (2172 vs 4530 pg/ml; P<0.05) than cows without retained placentas and fed the same forage. Calving number, sex ratio and preceeding milk yield were not different between the two groups of cows whatever their prepartum diet. In the dairy cow, retained placenta could be due to a PgF2alpha or an energy deficiency at calving. Roles of the dietary polyunsaturated fatty acids toward the Pg synthesis and of the energy supply before calving in relation to retained placenta are discussed here.     

Incidence of retained placenta following induction of parturition with corticoids or prostaglandins

Three trials involving 214 cows were conducted to 1) compare the timing of events during normal parturition with parturition induced with a corticoid or a prostaglandin; 2) determine if synchrony could be improved by injection of steroids either concurrently or after injection of a corticoid or a prostaglandin; 3) determine if the incidence of retained placenta could be reduced; and 4) explore methods of treating retained placenta. The timing of events following induction of parturition was compared with that following a normal parturition in 76 heifers. The time from onset of labor to appearance of the placenta, abdominal press, appearance of feet and expulsion of the fetus did not differ between normal and induced parturition. The time from onset of labor to calf standing was increased from 2.3 +/- 2.0 hours in normal parturition to 5.8 +/- 5.5 hours in cows receiving 10 mg of flumethazone (P<0.05). The interval from onset of labor to calf nursing also tended to be longer (P>0.05<0.01). All control cows expelled fetal membranes by 48 hours after onset of labor, but the proportion expelled by the treatment groups varied from 24 to 76%. None of the treatments used in this study significantly increased placental expulsion over that noted when flumethazone or prostaglandins were used alone. No difference in placental expulsion time was noted in cows douched with nolvasan or injected with 30 cc oxytetracycline. None of the treatments used in the three trials reported in this study improved synchrony of parturition over that noted in the cows receiving only an injection of flumethazone or prostaglandins.     

Induction of parturition with prostaglandin F2α in cows with hydrallantois. A case report

Two cows with hydrallantois were treated with single intramuscular injection of 30 mg (cow number 1) and 25 mg (cow number 2) prostaglandin F_2α (PGF_2α). At about 82 hours post-injection, most of the fluids were expelled and a dead calf was delivered by forced extraction from cow number 1. Cow number 2 delivered twin calves (1 live, 1 dead) without assistance. The cow lost 225 Kg body weight (162.7 Kg fluid and 62.2 Kg weight of fetuses). Plasma progesterone was 4.45 ng/ml before PGF_2α injection and 0.79 ng/ml 24 hours post-injection. No abnormal lesions or pathogens were found at necropsy of the dead calves. Fetal membranes were retained in both cows and were removed manually four days post-calving.     

Effect of route of dexamethasone administration on parturition,fertility and calf performance in beef cattle

Three trials (A, B and C) were conducted using 162 beef cows and heifers from a fall calving herd to determine the effect of route of administration of dexamethasone on induced parturition and retained placenta. Each trial contained a control group, a treated group receiving dexamethasone intramuscularly and a treated group receiving all or part of the dexamethasone intravenously. Dexamethasone treatment ranged between 20 and 50 mg and resulted in 81 to 100% induced parturition and in an increased incidence (P<.01 and P<.05 in trials A and C, respectively) of retained placenta compared to nontreated controls. Incidence of retained placenta in dexamethasone treated groups ranged between 23 and 78%, and in control groups between 0 and 6%. Route of dexamethasone injection did not affect either the incidence of cows responding with parturition or the incidence of retained placenta. Neither subsequent reproduction of cows nor growth performance of calves was significantly affected by induced parturition or route of dexamethasone injection.     

Effect of prepartum injection of vitamin E and selenium on postpartum reproductive function of dairy cattle

A total of 198 cows were randomly assigned to treatment with a single intramuscular injection of 10 ml of a preparation containing vitamin E and selenium or placebo 3 wk before expected parturition. Incidence of retained fetal membranes was 3.0% for the treated group and 10.1% for the control group (P=0.06). Administration of MU-SE also increased the percentage of cows pregnant to the first service (41.2 vs 25.3%; P=0.02), reduced the number of services per conception (2.3 vs 2.8; P=0.03), and reduced the interval from calving to conception (121 vs 141 days; P=0.06). The effect of MU-SE on fertility was apparent in cows with and without retained fetal membranes. There was no effect of MU-SE on the interval from calving to the first estrus. In conclusion, prepartum supplementation with vitamin E and selenium can decrease the incidence of retained fetal membranes, increase pregnancy rates and, thereby, reduce the interval from calving to conception in lactating dairy cows.     

Induction of parturition in conjunction with antibiotic treatments

Parturicion was induced in pregnant beef cows and heifers with 15 mg of flumethasone to test: 1) the effects of an orally active antibiotic on flumethasone induction of parturition success rate and incidence of retained placenta and 2) the effects of injectable long acting and orally active antibiotics on subsequent fertility and offspring performance. Gestation length and birth weight were not significantly changed. There were no significant differences among calving ease scores even though induction significantly improved vigor. Induction caused a significant increase in the incidence of retained placental membranes. Pregnancy rate (P<.01) and conceptions per service (P<.05) were lower for those animals affected with retained placentas. There were no significant differences among actual weaning weights for the three treatment groups or between adjusted weaning weights for the control and the orally active antibiotic groups, however, the adjusted weaning weights of calves from cows receiving an orally active antibiotic were significantly greater than those receiving an injectable long acting antibiotic (P<.10).     

Dexamethasone and estradiol benzoate induced parturition in dairy cattle

Fifteen 2-year-old Holstein cows and 21 mature Holstein cows were assigned to one of three groups. Cows in Group I calved spontaneously. Cows in Groups II and III received single intramuscular injections of 20 mg dexamethasone and 25 mg estradiol benzoate to induce parturition prematurely. In addition, cows in Group III received a single intramuscular injection of 12.5 mg estradiol benzoate 48 hr prior to dexamethasone and estradiol benzoate. The objective of the experiment was to determine the effectiveness of estradiol benzoate in combination with dexamethasone on traits at parturition and on productive and reproductive characteristics following parturition. Induction of parturition shortened gestation length and increased the incidence of retained placentas (both P < .01). All induced cows calved between 21 and 59 hr postinjection with less (P < .05) udder edema when compared to control cows. Mean plasma estrogen concentrations, using an assay system which does not measure estradiol benzoate, were not different among groups following injections of estradiol benzoate. Mean estradiol-17β concentrations in induced cows, however, using an assay system which does recognize estradiol benzoate (70.8% crossreactivity), were higher (P < .01) following estradiol benzoate injection, tended to be higher through parturition, and remained elevated (P < .01) at 12 and 24 hr following parturition when compared to cows calving spontaneously. Mean monthly milk production and the 2x, 305-ME records for milk, fat and FCM were not different among groups.     

The effect of a monensin controlled-release capsule on the incidence of retained fetal membranes, milk yield and reproductive responses in Holstein cows

The objective of this study was to determine the effect of a monensin controlled-release capsule on the incidence of retained fetal membranes (RFM), milk yield and conception rate at first service (CRFS). The study was conducted during May to August 2004 in a large dairy herd in Chihuahua, Mexico. Cows (n = 2,025) from 20 to 30 d before expected parturition were randomly assigned to either a treatment or a control group. The treated group (n = 1,010) received orally a capsule of monensin that released 335 mg/d for 95 d. Control cows (no capsule, n = 1,015) were randomly assigned and matched by parity. Outcome variables were the incidence of RFM, first three test day milk and CRFS. Monensin decreased the incidence of RFM by 3.9% only in multiparous cows. Therefore, multiparous cows treated with monensin were 0.78 times (95% C.I. = 0.71-0.86) as likely as control multiparous cows to develop RFM. Overall, milk yield was negatively affected by the RFM condition, but it was improved by monensin only in multiparous cows with RFM at test day 1. Conception rate at first service was depressed by 10.6% in multiparous cows with RFM. However, in RFM cows treated with monensin, CRFS improved to the level of treated cows without RFM.     

In vivo oxytocin release from microdialyzed bovine corpora lutea during spontaneous and prostaglandin-induced regression

The release of luteal oxytocin during spontaneous and prostaglandin-induced luteolysis was investigated in cows. A continuous-flow microdialysis system was used in 11 cows to collect dialysates of the luteal extracellular space between Days 12 and 24 postestrus. Seven cows were untreated and were expected to exhibit spontaneous luteolysis during sampling, whereas 4 cows received prostaglandin F(2alpha) (PGF(2alpha)) systemically between Days 13 and 15 to induce luteolysis during sampling. Oxytocin was detectable in the dialysate of all cows before Day 16 postestrus and occurred as 2 or 3 discrete pulses per 12-h sampling period. For non-PGF(2alpha)-treated cows, dialysate oxytocin content began to decline spontaneously on Day 15 postestrus and was undetectable by Day 17 postestrus. Oxytocin decay curves preceded onset of serum progesterone decline by at least 72 h and were not related temporally with onset of progesterone decline within cow. Exogenous PGF(2alpha) (25 mg, i.m.) produced a 10-fold increase in dialysate oxytocin within 1 h (1.9 +/- 0.3 pg/ml to 20.8 +/- 3.0 pg/ml; P < 0. 01). Dialysate oxytocin then declined to pretreatment concentrations within 2 h and was undetectable within 8 h posttreatment. A second PGF(2alpha) injection given 20 h after the first did not result in a measurable increase in dialysate oxytocin, probably because luteolysis was underway. Although robust luteal oxytocin release was observed after treatment with a pharmacological dose of PGF(2alpha), the lack of detectable oxytocin secretion during spontaneous luteolysis suggests that the contribution of luteal oxytocin in the cow may be less than that proposed for the ewe.     

The use of dimenhydrinate in conjunction with dexamethasone for induction of parturition in beef cattle

Forty-eight crossbred Chianina cows (3 to 5 years of age), with an expected gestation length of 288 days, were randomly divided into four treatment groups to evaluate the use of dimenhydrinate (an antihistamine agent) in conjunction with dexamethasone (DEX) for inducing parturition in beef cattle. Group (A) received a 20 mg dose of DEX (im) on day 282 of gestation and a carrier vehicle (iv) 24 hours later (day 283); Group (B) was given a carrier vehicle (im) on day 282 and 500 mg of dimenhy-drinate (DMH) diluted in 200 ml of 2.5% dextrose-0.9% saline solution given (iv) on day 283 and Group (C) received 20 mg of DEX (im) on day 282 and 500 mg of DMH in solution (iv) on day 283 of gestation. The remaining 12 cows assigned to Group (D) were not handled and were allowed to calve under natural conditions. The number of cows calving and percent calving within 60 hours after the first injection were: 10(91%), none(0%) and 12(100%) for the DEX, DMH and DEX plus DMH groups, respectively. The mean gestation length of the control cows in Group (D) was 288.6 days. Frequency of dystocia was: 18.2, 8.3, 0 and 0% and retained placentae (>/=24 hours) was: 72.8, 16.6, 33.3 and 0% for DEX, DMH, DEX plus DMH and control groups, respectively. In this study, a 20 mg dose of DEX (im) followed 24 hours later with 500 mg of DMH (iv) was more successful for calving induction than when DEX or DMH was used alone. The combination DEX and DMH treatment induced calving in a shorter interval from treatment (P<.05) and decreased the incidence of retained placentae (P<.01) when compared with those induced following DEX treatment.     

Synchronization of parturition in beef cattle with prostaglandin and dexamethasone

The effectiveness of dexamethasone and prostaglandin in combination for induction and synchronization of parturition in cattle was evaluated in 100 pregnant Angus, Hereford, Charolais and Simmental cows. Cows were distributed equally by breed, day of gestation and cow age to one of three treatments: 1) Control, 2) Dexamethasone (25 mg) plus prostaglandin F(2alpha) (25 mg) or 3) Dexamethasone (25 mg) plus fenprostalene (1 mg). Hormones were administered simultaneously from 275 to 283 d of gestation. Gestation length at calving for control cows differed significantly (P < 0.01) among breeds: Angus, 278.5 +/- 0.9; Hereford, 283.1 +/- 1.1; Charolais, 283.2 +/- 1.5; and Simmental, 285.4 +/- 1.2 d. For hormone-treated cows, 80% of the calves were born between 30 and 46 h after the hormone injections; overall mean was 37.6 +/- 1.1 h. Calving response did not differ (P >0.1) between cows treated with prostaglandin F(2alpha) versus fenprostalene (36.5 +/- 1.6 vs 38.6 +/- 1.6 h) or among cow age, day of gestation, or breed. Also, duration of labor, calving difficulty and calf viability did not differ between calves born at an induced or spontaneous parturition. The incidence of placenta retained for >24 h was higher for induced than spontaneous parturition (21.0 vs 0.0%), but it did not differ (P >0.1) between cows treated with prostaglandin F(2alpha) or fenprostalene (19.2 vs 22.6%). An acceptable degree of synchrony of parturition was attained by the administration of prostaglandin F(2alpha) or fenprostalene in combination with dexamethasone. The higher incidence of retained placenta in treated than control cows did not affect subsequent fertility. The longer biological half-life for fenprostalene than for prostaglandin F(2alpha) provided no improvement in increasing synchrony of parturition or decreasing frequency of retained placenta.     

A note on the effect of controlling stable flies (Stomoxys calcitrans) in the resting activity and pen distribution of dairy cows

This study investigated the effect of controlling stable flies (Stomoxys calcitrans) on the number of dairy cows lying down and their pen distribution. The study randomly assigned 80 Holstein cows to 1 of 2 groups. The treated group (T) included cows individually sprayed with insecticide when found with an average of 10 stable flies per cow; in the control group (C), cows received no application of insecticide. The pen had 4 equal-size areas: (a) feeding, (b) drinking and sunny, (c) covered, and (d) manure. The study recorded the number of cows lying and the area of the pen where the nonhuman animal was located. The study found no difference (p > .05) between the proportion of T and C cows lying. However, cows preferred to lie down in pen area 3 when fewer than 10 stable flies per cow were found. Area 4 was the most avoided section of the pen, except when a high incidence of flies was present. The study concluded that high populations of S. calcitrans (> 10 flies per cow) did not affect the number of dairy cows lying down. However, it modified site preferences for lying.     

A Note on the Effect of Controlling Stable Flies (Stomoxys Calcitrans) in the Resting Activity and Pen Distribution of Dairy Cows

This study investigated the effect of controlling stable flies (Stomoxys calcitrans) on the number of dairy cows lying down and their pen distribution. The study randomly assigned 80 Holstein cows to 1 of 2 groups. The treated group (T) included cows individually sprayed with insecticide when found with an average of 10 stable flies per cow; in the control group (C), cows received no application of insecticide. The pen had 4 equal-size areas: (a) feeding, (b) drinking and sunny, (c) covered, and (d) manure. The study recorded the number of cows lying and the area of the pen where the nonhuman animal was located. The study found no difference (p > .05) between the proportion of T and C cows lying. However, cows preferred to lie down in pen area 3 when fewer than 10 stable flies per cow were found. Area 4 was the most avoided section of the pen, except when a high incidence of flies was present. The study concluded that high populations of S. calcitrans (> 10 flies per cow) did not affect the number of dairy cows lying down. However, it modified site preferences for lying.     

The effects of Ureplasma diversum inoculated into the amniotic cavity in cows

Ureaplasma diversum was inoculated into the amniotic cavity in four cows. Two calves were aborted and two were born alive. One of the latter died shortly after birth and the other was killed. The cows remained clinically normal except that three retained their placenta. On microscopic examination there was a severe placentitis and an alveolitis was present in the lungs of all calves. Ureaplasma was recovered from four placentas and three lungs. Cows remained infected for a maximum of 132 days following inoculation and the organism was recovered in urine and vulvar swabs for a maximum of 17 and 60 days respectively following expulsion of the calf. Ureaplasma diversum has been isolated from natural cases of abortion with similar lesions. This experiment strongly supports a causal relationship between abortion, birth of calves with pneumonia and U. diversum infection.     

Prevention of retained placenta by injection of collagenase into umbilical arteries of calves delivered by cesarean section: a tolerance study

In the cow, cesarean section delivery is often followed by retention of fetal membranes. Hypothetically, the retention of fetal membranes could be prevented by intraplacental injections of the enzyme collagenase. However, the infusion of this potent proteolytic enzyme into a uterus traumatized by surgery can lead to uterine damage, including perforation. Thus, the objective of this research was to evaluate tolerance of intraplacental treatment of bacterial collagenase. A cesarean section was performed on 10 experimental cows undergoing induced delivery or diagnosed with dystocia. During the surgical procedure, 200,000 units of bacterial collagenase in 1 L of saline were infused via the umbilical arteries. A cesarean section was also performed on control cows (n = 25) affected by dystocia, but these received no collagenase. The collagenase-treated cows showed no clinical or laboratory signs of abnormality over a 3- to 4-wk observation period post treatment. When membrane retention time was set at 36 h post surgery, 20% of the experimental cows and 60% of the control cows had retained the fetal membranes. It was concluded that intraplacental administration of collagenase during cesarean section is safe. However, treatment effectiveness and economic benefits for commercial application need further study.     

Subclinical hypocalcaemia follows specific time-related and severity patterns in post-partum Holstein cows

Hypocalcaemia is a common metabolic disorder of post-parturient dairy cows; enhancement of our knowledge regarding Ca dynamics would improve cow health and welfare. This study investigated the presence of time- and severity-related subclinical hypocalcaemia (SCHCa) patterns in Holstein cows after calving and their association with diseases during the first week of lactation. A total of 938 cows from nine herds were blood sampled on days 1, 2, 4 and 8 post-partum, and serum Ca concentration was measured with atomic absorption. Subclinical ketosis (serum β-hydroxybutyrate≥1.2 mmol/L) and cases of retained foetal membranes, metritis (MET), mastitis, ketosis and displaced abomasum (DA) were recorded. Using receiver operating characteristic (ROC) analysis, the SCHCa cut-off was identified at serum Ca ≤ 2.09 mmol/L. Hierarchical and two-step cluster analysis classified cows to seven clusters based on test day cow Ca records and overall SCHCa status. Two clusters (NORM and HIGH) included 318 normocalcaemic cows and five clusters (SCH-1 to −5) those that were at least once subclinically hypocalcaemic (n = 620). A second ROC analysis was performed in order to distinguish mild from severe cases of SCHCa in these 620 cows; this cut-off was identified at 1.93 mmol/L. The associated risk of disease with Ca clustership was assessed with generalized linear mixed models. Overall incidence of SCHCa was 66.1%. Clusters SCH-1 and SCH-2 included cows with short-term SCHCa of day 1 and day 2, respectively, while SCH-3 included cows with severe and prolonged SCHCa extending to day 4 and beyond. Clusters SCH-4 and SCH-5 included cows with delayed SCHCa, which culminated on days 4 and 8, respectively. Compared to NORM cows in HIGH had lower risk of MET and no cases of DA. Cows in SCH-3 had higher risk of being diagnosed with retained foetal membranes, DA or any disease during the study period. Cows in SCH-5 had higher risk of being diagnosed with ketosis, subclinical ketosis or any disease. In conclusion, there are multiple normocalcaemic and hypocalcaemic patterns that are differently associated with disease risk.     

Luteal competency during the resumption of ovarian cyclicity in postpartum Brahman cows

Twenty pluriparous, spring-calving Brahman cows were used to determine luteal competency, as measured by serum progesterone concentrations, during the first and the second postpartum estrous cycles. Prior to and after calving, all cows were maintained in good body condition on Coastal bermudagrass pasture (IFN 1-00-703). The calves were allowed to suckle ad libitum, and sterile marker bulls were maintained with the cow herd as an aid in estrus detection throughout the trial. Cow weight and body condition score were recorded within 24 hours after calving and again at the first behavioral estrus observed. From day 1 through day 14 (day 0 = estrus) of both the first and the second postpartum estrous cycles, blood samples were collected from each cow, processed to yield serum and analyzed by radioimmunoassay for progesterone concentrations. There was a higher incidence of abnormal estrous cycles following the first postpartum estrus (35%) than following the second (5%) postpartum estrus (P<0.05). The abnormal first estrous cycles were characterized by either a short luteal phase (four cows) or by standing estrus behavior without luteal tissue formation (three cows). When serum progesterone concentrations were compared for all cows during the first estrous cycle with those during the second estrous cycle, there was less progesterone released during the cycle (P<0.05) and lower peak progesterone concentrations (P<0.10) during the first estrous cycle. However, if the abnormal cows were excluded from the analyses, there was no difference (P>0.10) in either progesterone concentrations through the 14 days measured or in peak progesterone concentrations between the first and the second postpartum estrous cycles. It can be concluded from this study that the higher incidence of abnormal luteal function following the first postpartum estrus may contribute to the decreased conception rates observed when cows are bred at their first postpartum estrus.     

Naloxone cannot abolish the lack of oxytocin release during unexperienced suckling of dairy cows

To evaluate the role of opioids for the regulation of oxytocin release in response to teat stimulation, 10 brown-Swiss dairy cows were randomized to two experiments during mid of lactation. In the first experiment, four cows without previous suckling experience were suckled by an alien calf between two normal milkings. Before and during milking or suckling, frequent blood samples were collected via a jugular cannula for determination of oxytocin and beta-endorphin. In the second experiment, six cows were treated with naloxone or saline, 10min before the start of the first or second suckling, respectively. The collected blood samples were assayed for oxytocin.In the first experiment, the plasma levels of beta-endorphin were elevated during and after the unexperienced suckling in three cows, but not in the fourth cow, and the release of oxytocin during suckling was markedly reduced, suggesting no release of alveolar milk. In the second experiment, the release of oxytocin during suckling was again significantly reduced. Pretreatment with naloxone before suckling did not completely abolish the adverse effect of suckling and the oxytocin plasma level did not increase to levels comparable with control milking.In emotional stress situations, the release of oxytocin from the pituitary is inhibited with simultaneously elevated beta-endorphin plasma levels. Although there is some evidence for a regulatory role of opioids for the release of oxytocin, other mediators are suggested to be more potent in regulating oxytocin under stress conditions.     

Pathology of brucellosis in bison from Yellowstone National Park

Between February 1995 and June 1999, specimens from seven aborted bison (Bison bison) fetuses or stillborn calves and their placentas, two additional placentas, three dead neonates, one 2-wk-old calf, and 35 juvenile and adult female bison from Yellowstone National Park (USA) were submitted for bacteriologic and histopathologic examination. One adult animal with a retained placenta had recently aborted. Serum samples from the 35 juvenile and adult bison were tested for Brucella spp. antibodies. Twenty-six bison, including the cow with the retained placenta, were seropositive, one was suspect, and eight were seronegative. Brucella abortus biovar 1 was isolated from three aborted fetuses and associated placentas, an additional placenta, the 2-wk-old calf, and 11 of the seropositive female bison including the animal that had recently aborted. Brucella abortus biovar 2 was isolated from one additional seropositive adult female bison. Brucella abortus was recovered from numerous tissue sites from the aborted fetuses, placentas and 2-wk-old calf. In the juvenile and adult bison, the organism was more frequently isolated from supramammary (83%), retropharyngeal (67%), and iliac (58%) lymph nodes than from other tissues cultured. Cultures from the seronegative and suspect bison were negative for B. abortus. Lesions in the B. abortus-infected, aborted placentas and fetuses consisted of necropurulent placentitis and mild bronchointerstitial pneumonia. The infected 2-wk-old calf had bronchointerstitial pneumonia, focal splenic infarction, and purulent nephritis. The recently-aborting bison cow had purulent endometritis and necropurulent placentitis. Immunohistochemical staining of tissues from the culture-positive aborted fetuses, placentas, 2-wk-old calf, and recently-aborting cow disclosed large numbers of B. abortus in placental trophoblasts and exudate, and fetal and calf lung. A similar study with the same tissue collection and culture protocol was done using six seropositive cattle from a B. abortus-infected herd in July and August, 1997. Results of the bison and cattle studies were similar.