Table 5 Cause-of-death and diagnostic case definitions for non-infectious causes of bovine perinatal mortality

Accident

Colostrum aspiration (iatrogenic)

Administration of colostrum by oro-oesophageal feeder or bottle into the trachea with subsequent calf clinical signs (e.g. bawling, dyspnoea, weakness, depression, recumbence).

History and presence of colostrum in the trachea, bronchial tree and lungs, pulmonary oedema/congestion/consolidation/pneumonia and foreign basophilic deposit in airways and alveoli

Non-parturient trauma

Trauma independent of calving such as stood on or laid on by cow or attacked by cow (assault injury) or otherwise fatally injured, e.g. by automatic scraper in cubicle house, other machinery.

History and/or fatal traumatic lesions (e.g. antemortem fractured ribs and/or legs, hepatic rupture) usually in the absence of subcutaneous bruising.

Oesophageal rupture (iatrogenic)

Rupture of oesophagus while administering colostrum using an oro-oesophageal feeder with subsequent calf clinical signs (e.g. bawling, dyspnoea, weakness, depression, recumbence, cervical oedema).

History and traumatic tear in oesophagus with discharge of colostrum and cellulitis if in cervical region resulting in a swollen neck.

Co-mortality

Presence of more than one cause-of-death

Listed for each cause-of-death

Congenital defect

Lethal congenital defect

Defect present at birth incompatible with life. Where the cause of the defect/s is diagnosed, e.g. BVDv, both an ultimate and proximate COD can be reported.

Most diagnosed defects are grossly visible structural defects. Examples include hydranencephaly, hydrocephalus, schistosomus reflexus and multiple defects. Some defects are economically lethal – the calf may survive following remediation but this is economically prohibitive hence euthanasia follows.

Economically-lethal congenital defect

Grossly visible structural defect incompatible with independent life and with economic viability of the calf (e.g. surgery may be possible but cost-prohibitive and poor prognosis) necessitating euthanasia

Examples include intestinal atresia, vestigial limbs, palatoschisis and arthrogryposis.

Dystocia^a

Bradytocia

Prolonged stage one or two of calving

History of prolonged stage one (e.g. milk fever, ‘slow calving syndrome’, disturbance during calving, uterine torsion) and/or prolonged stage two (e.g. foetal oversize) with moderate/severe peripheral subcutaneous antemortem oedema (e.g. lower legs, tongue, submandibular, head, neck)

Dystoxia

Dystocia with anoxia/asphyxia lesions

Moderate/severe calving assistance with atelectasis and moderate/severe meconium staining/aspiration (hair, trachea, lungs, abomasum), mucosal/serosal haemorrhages (e.g. trachea, heart, pleura, thymus, abomasum, adrenals, sclera, conjuctiva), organ congestion and thoracic/abdominal serous transudate.

Maldistoxia

Maldisposition with anoxia/asphyxia lesions

Malpresentation or malposition with moderate/severe meconium staining/aspiration (hair, trachea, lungs, abomasum), mucosal/serosal haemorrhages (e.g. trachea, heart, pleura, thymus, abomasum, adrenals, sclera, conjuctiva), organ congestion, thoracic/abdominal serous transudate and atelectasis.

Traumotocia

Fatal trauma to the calf at assisted calving

Severe antemortem (haemorrhage at the site) acute lesions consistent with history of iatrogenic parturient trauma (e.g. fractured/dislocated spine, ribs, limbs, moderate/severe subcutaneous thoracic and lower limb haemorrhage/bruising, traumatic diaphragmatic hernia, hepatic rupture, moderate/severe haemothorax, haemoperitoneum, haemarthrosis, or polytrauma)

Eutoxia

Eutocia with anoxia/asphyxia lesions, e.g. umbilical cord accidents, placental insufficiency, placentitis, ‘non-clinical dystocia’.

History of no (or slight) calving assistance with some or all of the following: moderate/severe amniotic fluid or meconium staining/aspiration [e.g. lungs (multifocal keratinocytes, exfoliated epithelia, yellow/brown granular material, eosinophilic material in alveoli and bronchioles, incipient inflammatory reaction), hair, trachea, abomasum], mucosal/serosal petechial haemorrhages (e.g. trachea, heart, pleura, thymus, abomasum, adrenals, sclera, conjuctiva), organ congestion, thoracic/abdominal serous transudate and atelectasis (dark purple, moist, congested, heavy fluid-filled, round-bordered lungs; negative on floatation test)

Haemorrhage/ anaemia

Anaemia

Generalised pallor in the absence of visible haemorrhage

Diffuse severe pallor (e.g. conjunctiva, gingiva, skeletal muscles, thymus, trachea, liver, heart, lungs, brain, adrenals, kidneys)

Omphallorhagia

Haemorrhage from the umbilical arteries

Severe, acute peri-umbilical haematoma or moderate/severe hemoperitoneum (up to > 1 l free blood and coagulum) with one or more unsealed umbilical arteries (internal omphallorhagia) and diffuse pallor with/without blood stained hair coat (external omphallorhagia)

Hypothermia

Cold-stress induced mortality

History of extreme cold weather stress (~ < 0 °C, high wind speed, rain/sleet/snow; wind chill), unobserved calving, not born into a straw bed (e.g. cubicle house, outdoors), not dried off (wet/faeces covered coat, abandoned by dam), no colostrum consumption (FPT), low rectal temperature (< 37 °C) and limb/ventral sternum lesions (yellow subcutaneous oedema and haemorrhage, esp. hind legs)

Micronutrient disorder

Iodine/selenium imbalance

Abnormal thyroid gland

Thyroid histopathological lesions: hyper- (current imbalance: columnar epithelium-lined microfollicles +/− epithelia invaginations) or hypoplasia (historic imbalance: moderately/markedly enlarged colloid-filled follicles lined by flat columnar epithelium; ‘colloid goitre’) and atelectasis with/without low thyroid iodine (< 1200 ppm DM), low tissue selenium content, absolute (thyroid > 30 g) or relative (thyroid/body weight ratio > 0.80) goitre

Selenium/Vitamin E deficiency

Cardiomyopathy with low selenium/vitamin E status (white muscle disease)

Gross/histological lesions (cardiomyopathy - streaks of myocardial pallor with hyaline necrosis +/− calcification; Zenkers’ necrosis) plus low tissue (e.g. liver, kidney) or blood selenium and/or vitamin E concentrations

Premature placental separation (PPS)

Separation and expulsion of the placenta before/with the calf

History of placenta expelled before/with the fresh foetus and/or placenta attached to fresh carcass, Grossly the placenta may be normal. On histology there may be acute, multifocal haemorrhage into the interstitium of the cotyledonary villi.

Prematurity or dysmaturity

Calf born before physiological maturity

Premature characteristics [e.g. small size (IUGR), short light hair, partial incisor eruption, domed skull, respiratory distress syndrome (RDS)] in fullterm (dysmature) or pre-term [(premature; <mean-2SD gestation for single (< 270 days) or twin (< 265 days)] foetuses (e.g. sudden unexpected calving, poor udder swelling and pelvic ligament relaxation)

Twin-to-twin transfusion

Transfusion of blood from one twin to the other resulting in one anaemic and one congested twin with fatal sequelae

Foetal plurality with asymmetrical body weights if chronic (IUGR and normosomia) and asymmetrical carcass lividity (pallor and congestion)

Unexplained

Idiopathic stillbirth

None of the diagnostic criteria of causes-of-death apply; no visible/no significant lesions (NVL/NSL) or diagnosis not reached (DNR)