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

From: Investigation of bovine abortion and stillbirth/perinatal mortality - similar diagnostic challenges, different approaches

Cause-of-death Sub-category Case definition Diagnostic criteria
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.
Dystociaa 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)
  1. aPolypathia may also occur, e.g. bradytraumotocia, bradytoxocia, bradytraumotoxocia, traumotoxocia; where known, clinical history can be combined with pathology to give a clinicopathological case definition, e.g. bradytocia-maldisposition