Haughey K G
J S Afr Vet Assoc. 1991 Jun;62(2):78-91.
Methods of investigating perinatal loss in grazing sheep flocks are reviewed and evaluated. The "wet-dry" method is the simplest method for assessing minimal prevalence, whereas the differences between the numbers of single and twin foetuses present at ultrasonic determination of litter size during pregnancy, and the numbers of single and twin lambs present at lamb-marking, is the most precise. The veterinary investigation of field mortality involves full autopsy of a representative sample of dead lambs, a history of prenatal nutrition, disease and husbandry, as well as a qualitative estimate of weather conditions over the period of lamb collection. Pathological processes may be identified in over 95% of deaths and the specific cause determined in about 75% of deaths. The identification of the specific causes in the remainder of deaths, all classified as the starvation-mismothering-exposure (SME) complex, requires intensive, costly, on-site observation, and physiological and biochemical assessment. The probable causes of these deaths include prenatal physiological handicaps resulting from placental insufficiency, aberrant parent-offspring behaviour, management-induced mismothering, misadventure, inadequate milk supply or teat and udder abnormalities, and cold-induced starvation. The gross pathology and pathophysiology of birth stress and the SME complex, which are associated with at least 80% of mortality, are summarised. Birth injury to the foetal central nervous system, characterised by cranial and spinal meningeal haemorrhage is exclusive to parturient deaths and the SME complex. Observed flock prevalences range from 81% to 100% in parturient deaths, and 20% to 57% in the SME complex. The high total prevalence and experimental evidence, indicate the major causal role of birth stress in the pathogenesis of these entities. Lethal congenital malformations, infections (both congenital and acquired after birth), trace element deficiencies and predation are reviewed as minor causes. The new understanding of the pathogenesis of perinatal lamb mortality, recognises the heritable nature of birth mass, maternal pelvic dimensions, parent-offspring behaviour, and the resistance of neonates to cold. Control measures need to incorporate selection for maternal rearing ability, further refinement of prenatal nutritional management of twin-bearing ewes, disease control, provision of shelter for lambing flocks, and avoidance of husbandry practices which frustrate innate parent-offspring behaviour. A selection programme is summarised.
对放牧羊群围产期损失的调查方法进行了综述和评估。“湿-干”法是评估最低患病率的最简单方法，而在孕期通过超声测定产仔数时单胎和双胎胎儿数量，与羔羊标记时单胎和双胎羔羊数量之间的差异，则是最精确的方法。对野外死亡情况的兽医调查包括对代表性死羔样本进行全面尸检、产前营养、疾病和饲养管理的病史，以及对收集羔羊期间天气状况的定性评估。在超过95%的死亡病例中可识别出病理过程，约75%的死亡病例可确定具体病因。其余所有归类为饥饿-错母-暴露（SME）综合征的死亡病例，要确定其具体病因，需要进行密集、昂贵的现场观察以及生理和生化评估。这些死亡的可能原因包括胎盘功能不全导致的产前生理缺陷、亲子行为异常、管理导致的错母、意外事故、乳汁供应不足或乳头及乳房异常，以及寒冷导致的饥饿。总结了与至少80%的死亡率相关的出生应激和SME综合征的大体病理和病理生理学。胎儿中枢神经系统的出生损伤，以颅骨和脊髓脑膜出血为特征，是分娩死亡和SME综合征所特有的。观察到的分娩死亡羊群患病率为81%至100%，SME综合征为20%至57%。高总患病率和实验证据表明，出生应激在这些疾病的发病机制中起主要因果作用。对致死性先天性畸形、感染（先天性和出生后获得性）、微量元素缺乏和捕食等次要原因进行了综述。对围产期羔羊死亡率发病机制的新认识，认识到出生体重、母体骨盆尺寸、亲子行为以及新生儿对寒冷的抵抗力的遗传性。控制措施需要包括选择母羊的育羔能力、进一步完善怀双羔母羊的产前营养管理、疾病控制、为产羔羊群提供庇护所，以及避免采用阻碍先天亲子行为的饲养管理方法。总结了一个选择方案。
