Clinical signs and outcomes of beef cattle undergoing cesarean section because of dystocia

Mark W. H. Hiew Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

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Aubrey N. Baird Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

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Peter D. Constable Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, Illinois 61802.

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Abstract

OBJECTIVE To characterize signalment, clinical signs, reproductive history, surgical management, and outcomes of beef cattle undergoing cesarean section because of dystocia at a veterinary teaching hospital.

DESIGN Retrospective case series with nested cohort study.

ANIMALS 173 beef cattle admitted to a veterinary teaching hospital from 2001 through 2010 that underwent cesarean section because of dystocia.

PROCEDURES Medical records were reviewed and information collected on cattle signalment; reproductive history; cause of dystocia; anesthetic protocol; surgical management; number, sex, and body weight of calves delivered (alive or dead); perioperative treatment; duration of hospitalization; and discharge status. A questionnaire regarding postoperative fertility was mailed to all owners, and owners who did not respond were contacted via telephone.

RESULTS Overall mortality rate for calves was high, with 37.6% (62/165) of calves delivered dead or dying ≤ 24 hours after cesarean section. Mortality rate was higher for female versus male calves and for calves from dams with signs of labor for ≥ 3 hours versus < 3 hours before hospital admission. Overall mortality rate for dams was low, with only 10 of 161 (6.2%) dams failing to survive for ≥ 21 days after hospital discharge. Postoperative fertility rate was acceptable, with 75% (44/59) of dams that were rebred after cesarean section giving birth to ≥ 1 live calf.

CONCLUSIONS AND CLINICAL RELEVANCE Cesarean section was a clinically useful method for resolving dystocia in beef cattle, providing a high dam survival rate and an acceptable postoperative fertility rate. Beef cattle producers should seek veterinary assistance whenever clinical signs of dystocia are noticed, preferably within 6 hours after onset of parturition.

Abstract

OBJECTIVE To characterize signalment, clinical signs, reproductive history, surgical management, and outcomes of beef cattle undergoing cesarean section because of dystocia at a veterinary teaching hospital.

DESIGN Retrospective case series with nested cohort study.

ANIMALS 173 beef cattle admitted to a veterinary teaching hospital from 2001 through 2010 that underwent cesarean section because of dystocia.

PROCEDURES Medical records were reviewed and information collected on cattle signalment; reproductive history; cause of dystocia; anesthetic protocol; surgical management; number, sex, and body weight of calves delivered (alive or dead); perioperative treatment; duration of hospitalization; and discharge status. A questionnaire regarding postoperative fertility was mailed to all owners, and owners who did not respond were contacted via telephone.

RESULTS Overall mortality rate for calves was high, with 37.6% (62/165) of calves delivered dead or dying ≤ 24 hours after cesarean section. Mortality rate was higher for female versus male calves and for calves from dams with signs of labor for ≥ 3 hours versus < 3 hours before hospital admission. Overall mortality rate for dams was low, with only 10 of 161 (6.2%) dams failing to survive for ≥ 21 days after hospital discharge. Postoperative fertility rate was acceptable, with 75% (44/59) of dams that were rebred after cesarean section giving birth to ≥ 1 live calf.

CONCLUSIONS AND CLINICAL RELEVANCE Cesarean section was a clinically useful method for resolving dystocia in beef cattle, providing a high dam survival rate and an acceptable postoperative fertility rate. Beef cattle producers should seek veterinary assistance whenever clinical signs of dystocia are noticed, preferably within 6 hours after onset of parturition.

The reported incidence of dystocia requiring mechanical extraction or cesarean section in dairy heifers and cows in the United States is 6.8% and 3.5%, respectively.1 In comparison, fewer beef heifers and cows require such intervention (3.9% and 1.1%, respectively).2 Cesarean section is indicated for dystocic cows when assisted vaginal delivery is ineffective and fetotomy is not an option. The incidence of cesarean section is associated with several risk factors, including first parity, age at first calving < 24 months, single male calf, long gestation period, long interval between first service and conception, long nonlactating period, and previous cesarean section.3

Various surgical techniques have been described for performance of cesarean section in cattle.4–9 However, information regarding postoperative outcome in a teaching hospital setting has not been reported. The objective of the study reported here was to characterize the signalment, clinical signs, reproductive history, surgical management, and outcomes of beef cattle undergoing cesarean section for correction of dystocia at a teaching hospital. A secondary objective was to identify factors associated with an unfavorable outcome for the fetus or dam.

Materials and Methods

Case selection criteria

All medical records of female cattle admitted to the Veterinary Teaching Hospital of Purdue University from January 1, 2001, through December 31, 2010, for treatment of dystocia were reviewed. Of these cattle, only beef cattle with dystocia that underwent cesarean section were included in the study.

Medical record review

Information was retrieved from the medical records of included beef cattle regarding signalment; clinical signs; reproductive history; duration and cause of dystocia; fetal orientation; anesthetic protocol; surgical management; number, sex, and body weight of calves delivered (alive or dead); perioperative treatment; postoperative complications; and duration of hospitalization. When the number of calves born had not been recorded, the presumption was made that a singleton was born. Information related to dam and calf status at discharge from the hospital was also retrieved.

Obstetric examination

A standard method of obstetric examination had been used for all cattle. The dam was restrained in a chute and prepared for a vaginal examination to determine whether vaginal delivery was possible. The perineal and vulval regions were prepared aseptically with a warm povidone-iodine solution scrub. A vaginal examination was then performed by use of a lubricated sterile obstetric sleeve. For cattle that strained excessively, an epidural (3 to 5 mL of 2% lidocaine solution) was administered at the first intercoccygeal space. Examination included evaluation of the vaginal wall; extent of cervical dilation; size of the pelvis in relation to the fetus; orientation, position, and posture of the fetus; and viability of the fetus (retraction of limb or suckle reflex). Palpation per rectum was not typically performed.

Vaginal delivery was usually attempted unless elective cesarean section was requested by the owner or vaginal delivery had already been attempted by the referring veterinarian. When vaginal delivery was deemed impossible, the dam was prepared for a cesarean section by clipping the hair (over the paralumbar fossa and flank or ventral abdomen region, depending on surgical approach), followed by skin preparation with povidone-iodine solution scrub and 70% alcohol.

Follow-up information

Follow-up information was collected via questionnaire that was mailed to owners 2 to 11 years after cattle were discharged from the hospital (Supplementary Appendix S1, available at avmajournals.avma.org/doi/suppl/10.2460/javma.252.7.864). Attempts were made to contact owners via telephone when they failed to respond to the mailing. Owners were asked specifically about the period the dam had remained in the herd, reason for leaving the herd, whether breeding via natural mating or artificial insemination was performed, and whether any subsequent calf delivery required or did not require cesarean section.

Statistical analysis

Normality of data distribution was evaluated with the Shapiro-Wilk test. The primary outcomes of interest were calf mortality rate, calculated as the proportion of all calves that were delivered dead or died ≤ 24 hours after cesarean section, and dam mortality rate, calculated as the proportion of dams that died or were euthanized in the hospital or that died ≤ 3 weeks after returning to the farm of origin.

Because most continuous data had nonnormal distributions, values of all continuous variables hypothesized to differ between outcome statuses (died vs survived) were compared by means of a nonparametric method (Mann-Whitney U test). Distributions of categorical variables were compared between outcome statuses by use of the Fisher exact test given the small number of cattle (< 5) in > 20% of the categories.

Forward stepwise multivariable logistic regression was performed to characterize the relationship between all variables with a P value < 0.20 in preliminary analyses and calf or cow survival. For the prediction of survival, adjusted ORs and 95% confidence intervals were estimated simultaneously for predictors added in a forward stepwise fashion to the binary logistic regression equation on the basis of a value of P < 0.05 for the maximum likelihood estimate. Interaction terms were not considered because the maximum sample size was only 173 and data were missing for some evaluated variables. Adequacy of fit of the final logistic regression model was tested by evaluation of the Hosmer-Lemeshow goodness-of-fit statistic and plots of deviance influence statistics against the predicted values. Receiver operating characteristic curves were constructed for the final logistic regression model, and an optimal cutpoint for predicting cow and calf survival was identified. A software programa was used for statistical analysis. Values of P < 0.05 were considered significant for all comparisons.

Results

Animals

A total of 303 cattle were admitted to the teaching hospital for correction of dystocia over the 10-year study period. Of these 303 cattle, 173 (57.1%) were beef cattle that underwent cesarean section and were therefore included in the study. This group included beef cross-bred cattle (n = 62 [35.8%]), Aberdeen-Anguses (31 [17.9%]), Shorthorns (29 [16.8%]), Herefords (20 [11.6%]), Simmentals (13 [7.5%]), Maine-Anjous (12 [6.9%]), Charolais (3 [1.7%]), Chianinas (1 [0.6%]), Longhorns (1 [0.6%]), and Limousins (1 [0.6%]).

Median age of included cattle was 29 months (2.4 years; range, 13 to 148 months). Parity, recorded for 113 (65.3%) cattle, was primiparous for 85 (75.2%) and multiparous for 28 (24.8%) cattle (7 [6.2%] second parity, 7 [6.2%] third parity, 4 [3.5%] fourth parity, 3 [2.7%] fifth parity, and 7 [6.2%] sixth parity or greater). Body condition score (9-point scale with 1 representing very thin and emaciated, 5 representing moderate, and 9 representing extremely obese) was recorded for 100 cattle, for a median value of 5 (range, 3 to 9).

Dystocia and treatment

Information related to the duration of dystocia before hospital admission was available for 64 dams, and 57 of these had information regarding to dam and calf survival. Reasons for cesarean section were summarized (Table 1). Most cesarean sections (92/173 [53.2%]) had been performed after regular hospital hours, between 5:00 pm and 8:00 am and on weekends. Fifty-nine of 138 (42.8%) dams with available data had received a 2% lidocaine epidural to reduce straining, whereas 79 (57.2%) received no epidural. Antimicrobial administration was reported for 136 dams and included ceftiofur sodium (90 dams before surgery and 42 dams after surgery; 1.1 to 2.2 mg/kg [0.5 to 1.0 mg/lb], IM or SC, q 24 h for 3 days), procaine penicillin G (2 dams before surgery and 3 dams after surgery; 6,600 U/kg [3,000 U/lb], IM, q 24 h for 4 to 7 days10), or ceftiofur crystalline-free acid (1 dam after surgery; 6.6 mg/kg [3.0 mg/lb], SC, once at base of the ear). Flunixin meglumine (1.1 mg/kg, IV) had been administered to 113 dams before or immediately after surgery.

Table 1—

Survival rates in various circumstances for dams during the 21-day period and for calves during the 24-hour period after dams underwent cesarean section at a veterinary teaching hospital because of dystocia.

CircumstanceNo. (%) of damsProportion (%) of dams that survived*Proportion (%) of calves that survived*
Duration of dystocia before admission (h; n = 64)
 < 332 (50)29/30 (97)23/31 (74)
 3–617 (27)16/17 (94)6/17 (35)
 > 6–92 (3)2/2 (100)2/2 (100)
 > 9–122 (3)2/2 (100)1/2 (50)
 > 1211 (17)11/11 (100)2/8 (20)
Reason for cesarean section (n = 155)
 Fetopelvic disproportion110 (71.0)97/101 (96)62/103 (60)
 Malpresentation or malposition26 (16.8)20/24 (83)12/25 (48)
 Uterine torsion7 (4.5)6/6 (100)3/6 (50)
 Undilated cervix3 (1.9)3/3 (100)2/3 (67)
 Elective3 (1.9)3/3 (100)2/3 (67)
 Schistosomus reflexus2 (1.3)2/2 (100)0/2 (0)
 Inadequate space due to twinning2 (1.3)1/2 (50)0/2 (0)
 Small vaginal tract1 (0.6)1/1 (100)0/1 (0)
 Late gestation with a terminal condition1 (0.6)0/1 (0)0/1 (0)
Surgical approach (n = 173)
 Left paralumbar fossa (standing)154 (89.0)137/144 (95)88/147 (60)
 Ventral midline11 (6.4)9/11 (82)3/11 (27)
 Right paramedian3 (1.7)3/3 (100)0/2 (0)
 Right paralumbar fossa (standing)3 (1.7)0/1 (0)1/3 (33.3)
 Unrecorded2 (1.2)2/2 (100)1/2 (50)
Uterine closure approach (n = 164)
 Single layer
  Utrecht36 (22.0)32/36 (89)24/35 (69)
  Lembert1 (0.6)1/1 (100)1/1 (100)
 2-layer appositional and inverting
  Simple continuous and Cushing5 (3.0)5/5 (100)4/5 (80)
  Simple interrupted and Cushing1 (0.6)1/1 (100)0/0 (0)
 2-layer inverting
  Lembert and Cushing98 (59.8)88/92 (96)50/95 (53)
  Utrecht and Cushing9 (5.5)5/7 (71)1/9 (11)
  Lembert and Utrecht7 (4.3)6/6 (100)6/7 (86)
  Lembert and simple continuous3 (1.8)3/3 (100)2/3 (67)
  Cushing and Lembert2 (1.2)2/2 (100)0/2 (0)
  Utrecht and Lembert1 (0.6)0/0 (0)1/1 (100)
  Cushing and Cushing1 (0.6)1/1 (100)1/1 (100)
Suture material (n = 163)
 Size-1 polydioxanone155 (95.1)137/146 (94)83/148 (56)
 Size-0 polydioxanone2 (1.2)1/1 (100)2/2 (100)
 Size-1 polyglactin 9102 (1.2)0/1 (0)0/1 (0)
 Size-2 polyglactin 910 or glycolide-lactide copolymer4 (2.5)3/3 (100)2/3 (67)

For some variables, survival data were not available for all dams or calves.

The left paralumbar fossa approach to cesarean section with the cow in a standing position had been used for cesarean section in most dams (154/173 [89.0%]). Other approaches to cesarean section included ventral midline, right paramedian, and standing right paralumbar fossa (Table 1).

Three main methods of uterine closure had been used, depending on surgeon preference: single layer, 2-layer appositional and inverting pattern, and 2-layer inverting pattern (Table 1). Suture materials (on swaged needles), recorded for 163 dams, included size-0 or −1 polydioxanone,b size-1 polyglactin 910,c or size-2 polyglactin 910 or glycolide-lactide copolymer.d

In all instances, the uterus had been stabilized for closure by holding it with wet 4 × 4 gauze pads. After uterine closure, the uterine surface was lavaged with approximately 3 L of warmed sterile saline (0.9% NaCl) solution to remove any blood clots and debris. Postoperative complications were not documented because most (97/165 [58.8%]) dams were sent home immediately after surgery.

Calves

A total of 178 calves were delivered from the 173 dams via cesarean section, including 5 pairs of twins, yielding a dam twinning rate of 2.9%. Uterine location of the pregnancy was recorded for 84 (48.6%) dams and was the right horn for 49 (58.3%) of these dams and left horn for 35 (41.7%). Sex was recorded for 115 (64.6%) calves, of which 88 (76.5%) were male and 27 (23.5%) were female. Body weight was recorded for 99 (55.6%) calves, for a mean ± SD value of 48.1 ± 9.0 kg (105.9 ± 19.9 lb; range, 25.9 to 77.3 kg [57 to 170 lb]). Mean recorded birth weight of 64 male calves (48.5 ± 8.6 kg [106.7 ± 19.0 lb]; range, 29.1 to 77.3 kg [64 to 170 lb]) was similar (P = 0.45) to that of 18 female calves (47.5 ± 9.6 kg [104.4 ± 21.2 lb]; range, 25.9 to 62.3 kg [57 to 137 lb]).

Calf survival

Survival information was available for 165 (92.7%) calves, of which 62 (37.6%) were born dead or died ≤ 24 hours after birth. No association was identified between dam parity and body condition score and calf survival (Table 2). A significantly (P = 0.008) greater percentage of female calves were recorded as having been born dead or having died ≤ 24 hours after cesarean section (14/26 [54%]), compared with the percentage of male calves (22/89 [25%]). No difference (P = 0.96) in mortality rate was identified between calves born to primiparous cattle (32/85 [38%]) and those born to multiparous cattle (10/27 [37%]), although dam age was generally but not significantly (P = 0.08) lower for calves that survived versus those that did not survive. No differences in calf mortality rate were identified between right and left uterine horn pregnancies (P = 0.49), cesarean section performed during versus outside regular hospital hours (P = 0.75), and cesarean sections performed by a board-certified versus non–board-certified veterinary surgeon (P = 0.48).

Table 2—

Comparison of values (Mann-Whitney U test) of various factors between the surviving and nonsurviving calves and dams of Table 1.

 SurvivingNonsurviving 
FactorNo. of cattle with dataValueNo. of cattle with dataValueP value
Calf survival
 Dam parity701 (1–11)421 (1–12)0.96
 Dam age (mo)9127 (14–145)6737 (17–148)0.08
 Dam body condition score*605.6 (3–9)395.4 (4–8)0.52
 Duration of dystocia (h)322 (1–24)256 (1–24)< 0.001
 Calf body weight (kg)6447.3 (29.1–66.4)3346.4 (25.9–77.3)0.95
Dam survival
 Dam parity1011 (1–11)62 (1–12)0.12
 Dam age (mo)14528 (13–148)960 (25–120)0.11
 Dam body condition score*875.4 (3–9)56.7 (5–7)0.46
 Duration of dystocia (h)563 (1, 24)14 (4–4)0.76
 Calf body weight (kg)9146.4 (25.9–77.3)351.8 (30.5–66.4)0.69

Body condition was scored on a 9-point scale, with 1 representing very thin and emaciated, 5 representing moderate, and 9 representing extremely obese.

Five sets of twins were delivered for a total of 178 calves from 173 dams, but summary data from the second recorded calf were omitted from analysis of calf survival data. Data were not consistently available for all variables for all 173 calves and dams.

A significant (P < 0.001) association was identified between duration of dystocia and calf survival, with the percentage of surviving calves decreasing as this duration increased (Table 2). Calf survival rates differed significantly between dystocia durations < 3 hours and 3 to 6 hours (P = 0.008) as well as between durations < 3 hours and > 6 hours (P = 0.01). Calves were also more likely to survive if the dam had received epidural analgesia prior to cesarean section (P < 0.001).

Variables included in the final multivariable logistic regression model to predict calf survival to 24 hours after cesarean section were duration of dystocia (continuous variable logarithmically transformed to improve model fit), administration of epidural analgesia to the dam, calf sex, and dam age. Results indicated that duration of dystocia (as logarithmically transformed) provided the best predictor of calf survival (OR, 0.85; 95% confidence interval, 0.75 to 0.97; Hosmer-Lemeshow goodness-of-fit test, P = 0.24). The β coefficient for the intercept in the model was 2.22 (SE, 0.68; P = 0.001), and that for the logarithmically transformed duration of dystocia was −1.44 (SE, 0.46; P = 0.002). Area under the receiver-operating characteristic curve for the logistic regression equation was 0.80. At the optimal cutpoint for this equation to predict calf survival (duration of dystocia, < 6 hours), the sensitivity and specificity were 0.53 and 0.96, respectively. The positive likelihood ratio (sensitivity/[1 – specificity]) was 13.3.

Dam survival

The medical records indicated that 151 of 161 (93.8%) dams that underwent cesarean section survived for ≥ 3 weeks surgery, whereas 10 (6.2%) had died or were euthanized during this period. No association was identified between dam survival and dam age, parity, body condition score, or duration of dystocia or calf body weight. There was also no association (P = 1.00) between dam survival and whether (yes vs no) cesarean section had been performed during regular hospital hours or by a board-certified veterinary surgeon or whether the pregnancy had been in the right versus left uterine horn. Although the percentage of surviving dams was greater when dams had received (vs had not received) epidural analgesia, this difference was not significant (P = 0.08). The percentage of dams that received ≥ 1 dose of oxytocin (20 to 100 U, IM; median dose, 20 U) after cesarean section was similar (P = 0.52) for survivors and nonsurvivors. Dams stayed for a median of 0 days (range, 0 to 19 days) in the hospital before discharge.

Variables examined during logistic regression modeling to predict dam survival for ≥ 3 weeks after cesarean section included administration of epidural analgesia and dam age. Parity was not examined because of its collinearity with age. No variables were significant in this analysis.

Follow-up data

Follow-up information was obtained for 95 of the 173 (54.9%) dams. For 48 (51%) dams, this was achieved via mail, and for the other 47 (49%), it was achieved via telephone contact with owners. Fifty-nine of the 95 (62%) dams had been bred at least once after the cesarean section, and 44 (75%) of these had delivered 1 live calf. Forty-two (95%) calves had been delivered vaginally, and 2 (5%) had been delivered via cesarean section. Forty-five (47%) dams had been sold ≤ 1 year after surgery (including 9 that had been bred at least once after surgery), and the most common reason reported for culling was poor rebreeding performance (n = 10; 22%). Additional information was available for 26 dams that became pregnant, of which 9 (35%) had been artificially inseminated, 9 (35%) had received embryo transfer, and 8 (31%) had received natural service.

Discussion

The most important findings of the present study involving beef cattle with dystocia treated by cesarean section included the high overall mortality rate for calves, 37.6% of which were born dead or died ≤ 24 hours after cesarean section. This mortality rate was higher when the dam had had dystocia for ≥ 3 hours before hospital admission. On the other hand, the overall mortality rate for dams within the 21-day period after hospital discharge was low at 6.2% and postoperative fertility was acceptable, in that 75% of dams that were rebred gave birth to ≥ 1 live calf and only 22% of dams were culled because of infertility ≤ 12 months after surgery.

In the study reported here, only 50% of cattle were admitted to the hospital ≤ 3 hours after onset of parturition and the calf mortality rate was much higher when this period was ≥ 3 hours. Delay in dam admission was therefore highly influential on fetal survival. It is essential that farm personnel be able to determine whether, when, and how to intervene and when to seek veterinary assistance for dams with signs of labor.11,12 The recommendation is that dairy producers assist dairy cattle 70 minutes after the appearance of the amniotic sac or 65 minutes after feet appear outside the vulva,12 regardless of the dam's parity, and it is reasonable to assume that these guidelines for dairy cattle are applicable to beef cattle. It is also imperative that earlier obstetric intervention be provided when an abnormal fetal position or posture is identified immediately after the amniotic sac appears.12

No difference in survival rates was identified between calves born to primiparous versus multiparous dams in the present study, which differs from the findings of other studies.13,14 This finding suggested that duration of dystocia played a dominant role in calf survival, given that fetopelvic disproportion can be addressed with cesarean section.1,2,15,16 The value of the positive likelihood ratio at the optimal cutpoint for predicting calf survival (duration of dystocia, < 6 hours) was > 10 in the present study, suggesting that this variable would be very good at ruling in a diagnosis, such as calf survival.17 Knowledge that the duration of dystocia was < 6 hours would therefore be clinically helpful in supporting a decision for cesarean section in beef cattle with dystocia, despite the low test sensitivity of 0.53. Calf birth weight is an important contributor to dystocia, and the odds of dystocia in Holstein-Friesian cattle increase by 13% per 1-kg increase in calf birth weight.18 Heavier birth weights can also contribute to a greater likelihood of calving difficulties, which may ultimately lead to higher perinatal mortality rates.13,18 Consequently, it is important that primiparous beef cattle be bred to bulls that have a low expected-progeny difference with respect to birth weight to reduce the incidence of fetopelvic disproportion.

The incidence of cesarean section in beef cattle admitted to the teaching hospital for dystocia in the present study was 57.1%. Dairy cattle were excluded because of the small numbers that underwent surgery. Primiparous cattle were overrepresented, which is consistent with many observations that primiparous cattle are more likely to need assistance at calving.19,20 Holstein-Friesian heifers are reportedly 3.1 times as likely to undergo cesarean section as their multiparous counterparts,3 and a smaller (versus larger) pelvic area increases the risk of dystocia at parturition for dairy and beef cattle.21–24

The main reason for cesarean section in beef cattle in the present study was fetopelvic disproportion. The discrepancy between a large fetus and small pelvic size leading to dystocia has been studied by various groups, and inadequate pelvic area is associated with dystocia in cattle.22,25,26 Fetal malpresentation or malposition was the second most common reason for cesarean section, and this included fetuses that had a posterior or transverse orientation, dorsopubic position, malpositioned limbs, or retroflexed head or were breeched. Fetal malpresentation has been ascribed various degrees of importance (from 0.9% to 20%) as a cause of dystocia.15,27

Uterine torsion was the third most common indication for cesarean section (4.5%) in the present study, although the prevalence in other cattle populations is reportedly 5% to 10%.28,29 Uterine torsion has been suspected of being underdiagnosed given that palpation per rectum is infrequently performed when cattle are treated for dystocia because some cases of vaginal involvement are not evident even on speculum examination.28 Clinicians at the Purdue University Veterinary Teaching Hospital routinely perform a vaginal examination for cattle with dystocia and rarely perform palpation per rectum. Generally, correction of torsions via rolling is not attempted. Approximately 62% of cattle with uterine torsion reportedly require a cesarean section,28 indicating that the likelihood of surgical intervention is moderate for cattle with a torsed uterus. In contrast, a UK study28 showed that only 9% of complicated dystocia cases caused by uterine torsion require cesarean section. In a study29 involving 55 dairy cattle, multiparous cattle were at greater risk of uterine torsion than primiparous cattle, and that finding may explain the relatively low incidence of uterine torsion in the study reported here, in which the prevalence of primiparous cattle was relatively high.

Ceftiofur and procaine penicillin G were the most commonly administered antimicrobials during the perioperative period of cattle in the present study, with most dams receiving ceftiofur sodium. Ceftiofur had been selected on the basis of clinician preference and its fairly brief preslaughter withdrawal period for food-producing cattle (4 days; 0 days for milk).30,31 Procaine penicillin G also has a preslaughter withdrawal period of 4 days (48 hours for milk). Antimicrobials are routinely recommended when cesarean sections are performed in ruminants because peritonitis, incisional infection, and endometritis associated with a retained placenta are common in sheep and goats that receive no antimicrobials after cesarean section.32 Oxytetracycline is another antimicrobial administered perioperatively to cattle undergoing abdominal surgery.33 However, this drug has a preslaughter withdrawal period of 28 days (96 hours for milk), rendering it a suboptimal choice.

Antimicrobial selection for ruminants undergoing cesarean section is empirically based owing to the lack of randomized clinical trials regarding efficacy. Clinicians should consider administration of antimicrobials other than the third-generation cephalosporin ceftiofur to cattle undergoing cesarean section because ceftiofur has no label claim for this purpose and because of the theoretical potential for ceftiofur administration to promote transmissible antimicrobial resistance. The prophylactic use of cephalosporins for the prevention of extralabel conditions such as peritonitis in cattle was legal during the observation period of the study reported here (which concluded December 1, 2010), but such use has been prohibited in the United States since January 4, 2012, in that cephalosporins cannot be used for disease prevention unless such use is approved by the FDA.

Most clinicians prefer to administer antimicrobials after rather than before surgery, although limited evidence exists of better antimicrobial efficacy in adult cattle undergoing laparotomy that receive antimicrobials after rather than before surgery.33,34 Protection against infection is deemed optimal when antimicrobials are present in tissues before microbial inoculation happens.35 Even so, no justification exists for antimicrobial use when clean surgeries are performed in optimal aseptic conditions36 and antimicrobials should not be used as prophylaxis against poor aseptic technique.

Postoperative IM administration of oxytocin had been performed for cattle in the present study to aid uterine involution and placental passage.37 An oxytocin dose as low as 30 U, given immediately after calving and again 2 to 4 hours later, reportedly reduces the likelihood of retained placenta in cattle,38 thereby negating the need for a higher dose. Not all dams in our study were given oxytocin because they had live, suckling calves, which stimulated endogenous oxytocin release. A high proportion of dams (58.8%) were immediately discharged from the hospital after cesarean section because the clinician determined that there was no need for further postoperative monitoring.

The most common regional anesthesia technique used for cattle in the study reported here was the inverted L block which requires a large amount of anesthesia. Although to our knowledge no reports exist of any toxic effects of systemic lidocaine absorption in cattle undergoing cesarean section,39 an estimated maximum lidocaine dose of 10 mg/kg (4.5 mg/lb) has been proposed.40 The paravertebral and line block were the second most common regional blocks used. The line block involves infusion of local anesthetic into the incision site,41 and in our teaching hospital some technicians and clinicians place this block behind the last rib to supplement a paravertebral block, particularly when a left paralumbar flank approach to cesarean section involves incision more ventrally.

A caudal epidural block with 2% lidocaine solution was administered to 42.8% of cattle in the present study for which such information was recorded. This block is recommended for cesarean sections because it eliminates straining42 and tenesmus.43 A 2% lidocaine dose of 3 to 5 mL was used because doses > 10 mL (in 450-kg [990-lb] cattle) reportedly cause hind limb incoordination and recumbency.44

The most common surgical approach in the study reported here was via the left paralumbar fossa with the dam standing. This method requires minimal restraint and assistance when used for cattle restrained in a chute with a head catch. A halter should be placed on the cattle and fastened to the left side of the head catch to ensure that the left flank incision stays uppermost if cattle attempt to become recumbent during surgery. With this approach, the rumen prevents evisceration of the intestines during surgery45 and the mammary veins are avoided. This is a good method to use when the fetus is of reasonable size and is alive or just died recently.45 In the authors' experience, most cattle admitted for dystocia are in good condition and have the demeanor to allow a standing surgery. In the present study, the recumbent approach (ventral midline and right paramedian) was not commonly used and only considered when the dam was recumbent, the fetus was dead, or the uterus was contaminated. For 1 cow, a recumbent midline approach, involving 2% lidocaine solution for a line block, was chosen by the owner, who had had a bad experience with another cow that had a flank incision performed at another veterinary practice. This ventral approach enables evacuation of fetal and uterine debris and minimizes spillage into the peritoneal cavity.45 Before the uterine incision is closed, the entire uterus should be thoroughly examined to avoid overlooking a twin fetus.42

The most common uterine closure method used in the study reported here was a Lembert pattern oversewn with a Cushing pattern, which ensured adequate inverting closure.42 Two-layer closures such as this are indicated whenever a risk exists of leakage or excessively contaminated uterine fluid.46 The Utrecht pattern was the second most common closure method and was typically used when uterine tissue did not appear compromised and a 1-layer pattern was deemed sufficient. Use of this pattern for uterine closure has been associated with improved fertility of the dam,47 supporting the need to bury all knots8,46 within the suture line.

The most commonly used suture material was polydioxanone, whereas polyglactin 910 and glycolide-lactide copolymer (both composed of polyglycolic acid) were also used. Chromic catgut is commonly used for uterine closure in cattle,8,42,48 but in the present study, synthetic suture material was preferred owing to availability and surgeon preference. Synthetic absorbable monofilament sutures are recommended for cesarean section to avoid periuterine adhesions and reduce the potential risk of transmissible spongiform encephalopathy associated with chromic catgut.46 Compared with chromic catgut, polyglycolic acid suture material produces a milder inflammatory reaction but is more expensive and causes more tissue drag because of its braided structure. However, no difference has been identified between these 2 materials in the incidence of adhesions.49

Surgical skills and technique are also important in cesarean sections involving cattle, given that calf mortality rate increases with prolonged surgeries.47 The present study involved 2 senior surgeons and 12 surgery residents; however, no effect of surgeon experience (ie, board certification) on calf or cow survival was identified.

Generally, beef herds have a lower twinning rate than dairy herds.50 The twinning rate in the present study (2.9%) was within the range that is typically reported for beef cattle (0.4% to 4.6%).51,52 Male calves, considered a risk factor for cesarean section,3 were more prevalent than female calves, but their mean body weights were similar. Given that calf sex and body weight are related, both of these factors influence the incidence of dystocia53 and subsequently the number of cesarean sections performed. Right uterine horn pregnancies were considerably more common than left uterine horn pregnancies, and this is consistent with observations that the right ovary of cattle is functionally more active than the left ovary for unknown reasons.54 On the other hand, the results of another study55 suggested that pregnancy rates are similar between the left and right uterine horns.

A high percentage (93.8%) of dams that underwent cesarean section in the present study remained alive 21 days after discharge from the hospital, suggesting that cesarean section performed at a teaching hospital is an effective method of dealing with dystocia. This overall survival rate was higher than previously reported survival rates of 86% for dams with a live calf, 79% for dams with nonsurviving calves, and 33% for dams with an emphysematous fetus when cesarean section is performed on the farm.56 The high survival rate in the present study may have been influenced by the availability of technically skilled staff and ease of implementation of aseptic surgical principles, compared with conditions in field settings. Prognostic factors associated with dam survival for 14 days after cesarean section include exteriorization of the uterus and removal of abdominal blood clots, female (vs male) calf, absence of fetopelvic disproportion, and absence of retained placenta at 24 to 48 hours after surgery.47

Most dams in the present study were rebred following cesarean section, and a substantial number were able to deliver live calves with no recurrence of dystocia. Given that dystocia is most common in primiparous cattle14,15 and all primiparous cattle at the time of cesarean section were no longer so after rebreeding, the cattle in the present study would have had time to mature and have larger pelvic areas in their subsequent pregnancies, reducing the likelihood of fetopelvic disproportion.

Weaknesses of the study reported here included inconsistent record keeping that prevented full investigation of all variables for all cattle and the number and experience level of veterinarians performing the surgery. Although the high survival rate of dams undergoing cesarean section at our teaching hospital was an encouraging finding, this high rate resulted in low statistical power to identify factors associated with survival or mortality rate.

Early intervention for dystocic cattle is recommended to decrease the incidence of perinatal death and reduce injury to the dam.12 Results of the study reported here suggested that beef producers should seek veterinary assistance whenever clinical signs of dystocia are evident, preferably within 6 hours after the onset of parturition. Cesarean section was a useful method for resolution of dystocia in beef cattle, as indicated by the low dam mortality rate and acceptable postoperative dam fertility.

Footnotes

a.

SPSS, version 22, SPSS Inc, Chicago, Ill.

b.

PDS II, Ethicon, Sommerville, NJ.

c.

Vicryl, Ethicon, Sommerville, NJ.

d.

Polysorb, Covidien, North Haven, Conn.

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