Bovine Dystocia Study Guide

Overview and Clinical Importance

Dystocia (Greek: dys = difficult, tokos = birth) is defined as abnormal or difficult birth requiring assistance for delivery. It represents one of the most common emergency presentations in bovine practice and is a high-yield topic on the NAVLE. The incidence ranges from 1.5-6.6% in dairy cows and 4.1-8.7% in beef cows, with primiparous heifers experiencing dystocia in 17-40% of calvings.

Dystocia significantly impacts both maternal and fetal health, causing economic losses estimated at $145-$400 per case. Understanding the causes, diagnosis, and management of dystocia is essential for effective bovine practice and successful NAVLE performance.

Stages of Normal Parturition

Understanding normal parturition is essential for recognizing when intervention is required. Parturition in cattle is divided into three distinct stages:

Fetal Disposition Terminology

Accurate assessment of fetal disposition is critical for determining the appropriate intervention. Fetal disposition is described using three parameters:

Presentation

The relationship of the fetal spinal axis to that of the dam:

• Longitudinal: Anterior (cranial - head first, NORMAL) or Posterior (caudal - tail first)
• Transverse: Dorsal or ventral (requires conversion to longitudinal)

Position

The relationship of the fetal dorsum to the maternal pelvis quadrants:

• Dorso-sacral: Fetal back toward maternal sacrum (NORMAL - right side up)
• Dorso-pubic: Fetal back toward maternal pubis (upside down)
• Dorso-ilial: Fetal back toward right or left ilium (sideways)

Posture

The relationship of fetal extremities (head, neck, limbs) to its own body:

• Extended: Normal - head resting on extended forelimbs
• Flexed: Carpal, shoulder, hock, hip, or head/neck flexion

Causes of Dystocia

Dystocia causes are broadly classified as maternal (14.5%) or fetal (85.5%) in origin. In heifers, fetopelvic disproportion is most common, while in mature cows, malpresentation predominates.

Uterine Torsion

Uterine torsion is the rotation of the gravid uterine horn over its broad ligament and represents a unique form of maternal dystocia commonly tested on the NAVLE. It occurs most frequently near term and is more common in certain breeds (Brown Swiss at higher risk; Jersey, Hereford, Angus at lower risk).

Clinical Findings

• Tachycardia (93%), tachypnea (94%), mild colic signs, straining (23%)
• Vaginal examination: Spiral folds (corkscrew pattern) in vaginal wall
• Direction determination: Run palm along vaginal roof toward cervix - fingers guided by direction of spiral folds
• Rectal palpation: Broad ligament feels like tight band; ventral crossing from right to left = counterclockwise torsion
• Degree: Usually 180-270 degrees (57%); counterclockwise direction in 63% of cases

Correction Methods

Management of Dystocia

Management decisions depend on fetal viability, duration of dystocia, maternal condition, and the specific cause. The primary goals are delivery of a viable calf and preservation of maternal health and future fertility.

Initial Assessment

• History: Duration of labor, breeding date, previous dystocias, parity
• Physical examination: Vital signs, mucous membrane color, hydration status
• Vaginal examination: Cervical dilation, fetal presentation/position/posture, fetal viability, lubrication status
• Rectal examination: Assess broad ligaments (torsion), fetal size estimation

Mutation and Correction Techniques

Mutation refers to manipulation of the fetus to achieve normal disposition for delivery:

• Repulsion (retropulsion): Push fetus back into uterus to create space for correction
• Rotation: Turn fetus on its long axis to correct malposition
• Version: Turn fetus on its transverse axis to convert presentation
• Extension: Straighten flexed limbs or head/neck

Common Malposture Corrections

Cesarean Section

Cesarean section (C-section) is indicated when vaginal delivery is not possible or poses excessive risk to dam or calf. The standing left paralumbar approach is most commonly used.

Indications

• Irreducible fetopelvic disproportion
• Uncorrectable malpresentation or fetal monsters
• Incomplete cervical dilation (especially post-torsion correction)
• Uterine torsion that cannot be corrected
• Prolonged dystocia with live calf when vaginal delivery would cause excessive trauma

Surgical Approaches

Fetotomy

Fetotomy is the surgical dissection and removal of a dead fetus in utero. It is applicable primarily to cattle due to uterine size and instrument accessibility.

Indications

• Dead fetus confirmed
• Emphysematous fetus (decreases survival after C-section)
• Fetopelvic disproportion where C-section is not feasible
• Fetal abnormalities preventing vaginal delivery (schistosomus reflexus, severe arthrogryposis)

Procedure (Anterior Presentation)

Complete fetotomy in anterior presentation requires maximum of 6-7 cuts:

• Decapitation: Remove head and neck to collapse shoulders
• Forelimb amputation: Remove one or both forelimbs
• Thoracic transection: Cut through thorax to allow evisceration
• Evisceration: Remove thoracic and abdominal contents
• Abdominal transection: Cut through lumbar region
• Pelvic bisection: Split pelvis between ischial arch to remove hindquarters

Complications and Sequelae

Maternal Complications

Prevention Strategies

Target dystocia rates: less than 15% for heifers and less than 5% for multiparous cows.

Genetic Selection

• Use Expected Progeny Differences (EPDs) for calving ease and birth weight
• Select calving ease bulls for heifers
• Consider sexed semen (female calves have 28% lower dystocia in heifers)

Heifer Development

• Breed heifers to reach 65% of mature body weight at breeding
• Pelvimetry for selection (cull heifers with narrow pelvic width)
• Do NOT restrict nutrition during late pregnancy (increases dystocia)

Pharmacological Considerations