An Overview of Developmental Disorders Leading to Dystocia in Cattle

Abstract

Dystocia due to developmental disorders causing foetal malformation is a significant challenge in bovine obstetrics, often resulting in severe birth complications. This narrative review provides an updated overview of the most common congenital syndromes associated with dystocia in cattle, emphasising both their clinical implications and underlying causes. Congenital disorders such as schistosoma reflexum, perosomus elumbis, arthrogryposis, hydrocephalus, anasarca and embryonic duplication are reviewed in detail, along with their impact on the course of calving. While the management of dystocia due to foetal malformations has remained relatively constant over time-mainly involving assisted delivery, foetotomy or caesarean section-our understanding of their aetiologies has advanced considerably. In addition to environmental factors, such as viral infections during gestation, genetic causes may also be implicated. Genetic aetiologies, including dominant de novo mutations and recessively inherited alleles, such as single nucleotide variants, larger structural variants or aneuploidies, have been identified as the cause of some of these congenital defects. This review provides a comprehensive resource on dystocia due to developmental disorders, offering veterinarians updated knowledge to guide clinical decision making and improve outcomes for both the dam and the calf.

Keywords: anasarca; arthrogryposis; embryonic duplication; foetal malformation; hydrallantois; hydramnion; hydrocephalus; meningocele; perosomus elumbis; schistosoma reflexum.

FIGURE 1

Historical illustration of a bovine schistosoma reflexum case. Throughout the history of veterinary obstetrics, schistosoma reflexum has been an important cause of dystocia in cattle. Adapted from Harms' Lehrbuch der tierärztlichen Geburtshilfe published in 1912 (Richter et al. 1912).

FIGURE 2

Schistosoma reflexum. (a) This syndrome is mainly characterised by U‐shaped dorsal retroflexion of the spine and thoracoabdominoschisis. (b) Foetal intestinal loops protrude from the vulva if the foetus is presented with its visceral pole. Courtesy (b): E Andersen.

FIGURE 3

Congenital arthrogryposis. These four cases illustrate that congenital arthrogryposis has a wide morphological expression. The posture of the limbs is abnormal and, in some cases, the deviation of the head also causes dystocia. Ankylosis of one or more joints may hinder the correction of the abnormal posture. The cause of (a) and (b) was not determined, while (c) was due to a missense mutation in the gene CHRNB1 (Agerholm et al. 2016) and (d) due to foetal exposure to Schmallenberg virus (Agerholm and Wernike 2022).

FIGURE 4

Congenital syndromic Chiari‐like malformation (CSCM). (a) Typical case of CSCM, characterised by bilateral symmetrical pelvic limb arthrogryposis with flexion and ankylosis of the tarsal joints. Such foetuses are usually in breech presentation. (b) Spina bifida in the posterior lumbar spine is present as a sulcus. Palpation of this can facilitate the diagnosis of CSCM. Bar = 2 cm.

FIGURE 5

Acute fracture of the left tibia associated with extensive haemorrhage. There is an increased risk of fracturing the long bones in cases of arthrogryposis. Arthrogryposis causes joint rigidity and bones may be fragile due to reduced limbic activity during foetal development. Transvaginal manipulation and attempts to correct the malposture must therefore be done with care.

FIGURE 6

Perosomus elumbis. The anterior half of the foetus appears normally developed, while the posterior half consists of an abdominal skin “sac” that encloses the abdominal organs. The spine and spinal cord posterior to the thorax is not developed, and the pelvis and pelvic limbs are hypoplastic. Cases are often in breech presentation, but correction of the malpresentation may be achievable due to the high flexibility of the hind part.

FIGURE 7

Pulmonary Hypoplasia and Anasarca (PHA). The extensive subcutaneous oedema characteristic of this lethal syndrome prevents foetal entrance into the pelvic canal. Some cases may die prematurely. Adapted from Agerholm and Arnbjerg (2011).

FIGURE 8

Abdominal distension in a pregnant cow due to excessive accumulation of fluid in the amniotic and/or allantoic cavities.

FIGURE 9

Supernumerary limbs. (a) Notomelia: A supernumerary thoracic limb is attached near the dorsal midline. (b) Pygomelia: Two supernumerary pelvic limbs are attached to the pelvis. Supernumerary limbs may interfere with the progression of the foetus through the birth canal. Pygomelia is of particular significance if the foetus is in posterior presentation.

FIGURE 10

Craniofacial duplication (diprosopia). The level of duplication varies among cases, as illustrated by the three cases shown (a–c). The risk of dystocia increases with an increased level of duplication as the size of the head also increases.

FIGURE 11

Embryonic duplication. Symmetrical conjoined twinning is invariably associated with dystocia in cattle. While a condition like dicephalus with two necks (derodymus; a) may be managed by foetotomy, embryonic duplication involving larger body parts usually requires caesarean section; (b) Thoracopagus: The foetuses are conjoined at the sternal region; (c) Parapagus: There are two separate spines, two heads and four thoracic limbs. The foetuses are joined in the abdominal region and only two pelvic limbs are present; (d) Omphalopagus: The twins are conjoined in the abdominal region with two heads, two spines and two sets of thoracic and pelvic limbs.

FIGURE 12

Hydrocephalus. Severe hydrocephalus may increase the size of the foetal calvarium or present as a cerebrospinal fluid‐filled sac protruding from the forehead. (a) External appearance of a case of severe hydrocephalus. (b) Longitudinal mid‐plane section of a frozen specimen. The frontal bones (arrowheads) are included in the lower part of the structure as flat, partly cartilaginous bone plates. Evacuation of the cerebrospinal fluid through an incision will cause collapse of the structure to the level indicated by the dotted line.

FIGURE 13

Meningocele. Like hydrocephalus, meningocele may cause dystocia if the saccular structure is of a size that interferes with the posture of the head or the foetus' progression through the birth canal.